Skip to main content
PLOS One logoLink to PLOS One
. 2023 Jan 26;18(1):e0280925. doi: 10.1371/journal.pone.0280925

Effect of quitting immediately vs progressively on smoking cessation for smokers at emergency department in Hong Kong: A posteriori analysis of a randomized controlled trial

William Ho Cheung Li 1,*, Wei Xia 2, Man Ping Wang 3, Derek Yee Tak Cheung 3, Kai Yeung Cheung 4, Carlos King Ho Wong 5, Tai Hing Lam 3
Editor: Yann Benetreau6
PMCID: PMC9879435  PMID: 36701401

Abstract

Background

A progressive approach to quitting smoking has been a popular strategy for motivating smokers who are reluctant to quit. However, whether this strategy can effectively achieve complete cessation or is as successful as quitting immediately remains unresolved. This study aimed to determine whether quitting immediately or progressively was more effective in achieving complete cessation among smokers in Hong Kong who presented at emergency departments.

Methods and findings

A posteriori analysis of a single-blinded, multicenter, randomized controlled trial was performed. The original trials was conducted at emergency departments of four major acute hospitals in different districts of Hong Kong. In total, 1571 smokers 18 years or older who presented at 4 major emergency departments between July 4, 2015 and March 17, 2017 were randomized into an intervention group (n = 787) and a control group (n = 784). The intervention group received brief advice (about 1 minute) and could choose their own quit schedules (immediate or progressive, labeled QI and QP, respectively). The control group received a smoking cessation leaflet. Follow-ups were conducted at 1, 3, 6 and 12 months. The primary outcomes, by intention-to-treat, were biochemically validated abstinence between the QI subgroup and control group; between the QP subgroup and control group, and between the QI subgroup and QP subgroup at 6 months. After the propensity sore matching, the biochemically validated abstinence was statistically significantly higher in the QI subgroup than the control group at 6 months (12.1% vs 3.4%, P = 0.003; adjusted odds ratio [aOR] 4.34, 95% CI 1.63–11.52) and higher in the QP subgroup than the control group at 6 months (9.8% vs 3.4%, P = 0.02; aORs 2.95, 95% CI: 1.04–8.39). No statistically significant differences of biochemically validated abstinence at both 6 month (12.1% vs 9.8%, P = 0.49; aORs 1.50, 95% CI: 0.71–3.19) were found in the comparison between QI and QP subgroups.

Conclusions

This study demonstrates that the strategy of quitting progressively is effective, especially for smokers who lack motivation or find it difficult to quit. If adopted routinely, such an approach can help achieve a greater level of smoking abstinence in the community.

Trial registration

ClinicalTrials.gov: NCT02660957.

Introduction

Cigarette smoking is addictive, and quitting the practice is very difficult [1, 2]. Our previous studies have found that many smokers recruited from outpatient clinics and the community were reluctant to quit, but showed an interest in reducing the number of cigarettes smoked per day [35]. Therefore, a potential strategy would be to allow or motivate smokers to quit progressively, with the ultimate goal of complete cessation of smoking. The progressive approach to quitting smoking has been used for a long time, following the assumption that smokers who reduce cigarette consumption and nicotine dependence will find it easier to further reduce the number of cigarettes smoked or quit smoking altogether [6, 7]. Nevertheless, whether the progressive approach can eventually lead to complete cessation or is as effective as abruptly quitting smoking remains controversial. Many previous studies have incorporated the strategy of quitting progressively in addition to nicotine replacement therapy, and their findings support the effectiveness of this strategy in achieving complete cessation in smokers who initially lacked the motivation to quit [3, 8]. However, not all smokers opt for pharmacotherapy to manage nicotine dependence. It has been reported that adherence to nicotine replacement therapy is low among Chinese smokers [9, 10]. It remains unclear whether using the progressive quitting strategy in such a population will help achieve long-term cessation [5, 7]. A previous trial conducted by our research group showed that quitting immediately was more effective than quitting progressively, although nicotine replacement therapy was not used. The outcomes of smokers were assessed at the 6-month medical follow-up in an outpatient clinic [4]. Another trial on smokers recruited from community settings showed that both the immediate and progressive approaches had similar 7-day point prevalence abstinence rates when assessed at the 6-month follow-up [5]. A Cochrane systematic review from 2019, which analyzed data from 22 randomized controlled trials (9219 participants) on quitting smoking immediately vs. progressively, found that neither approach was superior to the other in terms of long-term quitting rates [8]. Our previous trial examined the effectiveness of a brief self-determination theory-based smoking cessation intervention adopted for 1571 smokers who presented at emergency departments. We found that giving the smokers the option to either quit immediately or gradually doubled the quitting rates, compared to a control group that only received a smoking cessation pamphlet [11]. In this study, we aimed to conduct a posteriori analysis of the data from this published randomized controlled trial to determine whether the smokers who chose to quit immediately or progressively had higher quitting rates than the smokers in the control group. In addition, the analysis aimed to determine which option (immediate or progressive) was more effective in achieving complete cessation.

Materials and methods

Study design and intervention

We analyzed the archived data from our previously published randomized controlled trial of a brief self-determination theory-based smoking cessation intervention adopted for smokers recruited from emergency departments [11]. Ethical approval was obtained from the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster (UW14-528). The trial protocol has been published elsewhere [11]. Participants provided written informed consent.

Participants who presented at the emergency departments of four major acute care hospitals in different districts of Hong Kong were considered eligible if they were current smokers (occasional or daily) aged 18 years or older and triaged as either semi-urgent (level 4) or non-urgent (level 5) [12]. Exclusion criteria included an impaired mental status, cognitive impairment, communication barriers, or enrollment in other smoking cessation projects.

The sample size was calculated according to a previous trial [3] of a smoking reduction plus nicotine replacement therapy intervention involving 1154 Chinese adult smokers unwilling to quit smoking (biochemically validated quit rate of 4.4% [10 of 226] in the control group and 8.0% [74 of 928] in the intervention group at 6months). To detect a two-sided significant difference between groups by a chi-square test for comparing proportions with a power of 80% and significance level of 5%, the required sample size was estimated to be 1088 participants (544 in each group). Given an expected attrition rate of approximately 30% at the 6-month follow-up, the target was at least 1554 individuals (777 in each group). Between July 4, 2015 and March 17, 2017, 1571 smokers who presented at 4 major emergency departments consented to participate in this randomized controlled trial and were randomized into an intervention group (n = 787) and a control group (n = 784). Participants in the intervention group received brief advice and were given the option to either quit immediately (QI) or progressively (QP). Participants in the control group received a smoking cessation leaflet. Other details of the trial have been reported elsewhere [11]. Table 1 shows the characteristics of participants in the QI, QP, and the control groups. A Consolidated Standards of Reporting Trials (CONSORT) flowchart is presented in Fig 1.

Table 1. Baseline characteristics of subjects in the Quit Immediately (QI) group, Quit Progressively (QP) group, and Control group in the original unmatched sample.

Standardized differences
QI (n = 242) QP (n = 545) Control (n = 784) P value Post-hoc analysis QI vs QP QI vs Control QP vs Control
Age, mean(SD), y 46.4(15.8) 47.7(15.2) 48.0(16.8) 0.42 0.084 0.098 0.019
Gender 0.04 QI>Con*# 0.122 0.135 0.013
    Male 202(83.5) 484(88.8) 700(89.3)
    Female 40(16.5) 61(11.2) 84(10.7)
Marital status 0.05 QI>Con*## 0.040 0.125 0.086
    Single/Divorce/Separate/Widowed 104(43.0) 221(40.6) 278(35.5)
    Married/Cohabit 138(57.0) 324(59.4) 506(64.5)
Employment status 0.36 0.017 0.048 0.065
    Unemployed/Retired 63(26.0) 137(25.1) 224(28.6)
    Employed 179(74.0) 408(74.9) 560(71.4)
Educational level 0.11 0.115 0.048 0.074
    Tertiary 21(8.7) 27(5.0) 56(7.1)
    Secondary or below 221(91.3) 518(95.0) 728(92.9)
Monthly household income, US $ 0.09 0.115 0.142 0.026
    ≥3825 (HKD 30000) 22(9.1) 73(13.4) 114(14.5)
    <3825 (HKD 29999) 220(90.9) 472(86.6) 670(85.5)
Smoking-related chronic disease 0.18 0.050 0.110 0.058
    Yes 12(5.0) 35(6.4) 64(8.2)
    No 230(95) 510(93.6) 720(91.8)
Health utility score by SF-6Da 0.59(0.1) 0.57(0.1) 0.57(0.1) 0.08 0.200 0.200 0.000
Daily cigarette consumption 12.8(7.5) 15.0(7.9) 13.5(7.6) 0.001 QI>QP*# 0.286 0.093 0.195
Nicotine dependence by Heaviness of Smoking Index (HIS)b <0.001 QI< QP*# 0.271 0.168 0.102
    Moderate to heavy(3–6) 95(39.3) 303(55.6) 387(49.4) QI< Con*#
    Light(≤2) 147(60.7) 242(44.4) 397(50.6)
Age at starting smoking weekly 17.4(6.2) 17.2(5.7) 17.6(6.5) 0.52 0.034 0.031 0.067
Tried to quit smoking for more than 24 hours <0.001 QI>QP*# 0.262 0.257 0.005
    Yes 192(79.3) 357(65.5) 516(65.8) QI>Con*#
    No 50(20.7) 188(34.5) 268(34.2)
Tried to reduce smoking for more than 24 hours 0.77 0.000 0.029 0.029
    Yes 119(49.2) 268(49.2) 400(51.0)
    No 123(50.8) 277(50.8) 384(49.0)
Readiness to quit 0.34 0.084 0.022 0.063
    Quit ≤ 30 days 71(29.3) 133(24.7) 218(28.1)
    Quit > 30 days 171(70.7) 405(75.3) 557(71.9)
Self-efficacy against tobacco by SEQ-12c 29.8(12.3) 29.1(10.8) 28.2(11.3) 0.14 0.060 0.135 0.078

Continuous variables are reported as mean ± standard deviation. Dichotomous variables are reported as N (Percent).

Abbreviations: SF-6D, Shot-Form Six-Dimension; SEQ-12, Smoking Self-Efficacy Questionnaire.

aThe SF-6D is composed of 6 multilevel dimensions. The SF-6D scores were weighted from a sample of the general population, which ranged from 0 to 1.

bThe Heaviness of Smoking Index, a 2-item index from multiple-choice response options (0–3), was determined by assessing cigarettes smoked per day and time to smoke after waking; the higher the indexes, the greater smoking nicotine dependence.

cOn a 12-item 5-point Likert-type scale in the SEQ-12, responses ranged from “not at all sure” to“absolutely sure.” A summary score of the SEQ-12 ranged from 12 to 60, with higher scores indicating higher self-efficacy.

*: P< 0.05.

#: Using the Tukey’s honestly significant difference post-hoc test as equal Variances assumed.

##: Using the Games -Howell post-hoc test as equal Variances not assumed.

Fig 1. CONSORT flowchart.

Fig 1

Measures

Primary outcomes

The primary outcome measures of this posterior analysis consisted of biochemically validated abstinence comparisons between the QI subgroup and control group, between the QP subgroup and control group, and between the QI and QP subgroups as assessed at the 6-month follow-up.

Secondary outcomes

The secondary outcomes included differences in biochemically validated abstinence as assessed at the 12-month follow-up, the self-reported 7-day point prevalence of abstinence as assessed at the 6- and 12-month follow-ups, and a self-reported reduction of at least 50% in daily cigarette consumption as assessed at the 6- and 12-month follow-ups between the QI subgroup and control group, between the QP subgroup and control group, and between the QI and QP subgroups.

Statistical analysis

Data analysis was performed using the IBM Statistical Package for Social Sciences (SPSS) for Windows (version 25.0; IBM). To minimize the effects of potential confounding factors (demographic characteristics and smoking history of participants) on the primary and secondary outcome measures, a three-way propensity matched analysis was performed. To estimate the propensity scores, all demographic and smoking variables were included in the multinomial regression to maximally inform the propensity of the dependent variables [13]. The QI subgroup vs. control group and QP subgroup vs. control group were matched 1:1 using a nearest-neighbor approach with caliper restrictions [14]. A three-way matched data set was then created without replacement by extracting participants from the QI or QP subgroup who had common matches with participants in the control group [14, 15]. The standardized differences in demographic and smoking variables were compared to diagnose the balancing of the matched groups [16]. For continuous and dichotomous variables, the standardized difference used is shown in the S1 and S2 Figs, respectively [17].

The baseline characteristics of the participants in the QI, QP, and control groups were compared using an analysis of variance (ANOVA) for continuous variables, the chi-square test for categorical variables, and the two-tailed Fisher’s exact test based on the group cell size. For the variables showing significant difference in ANOVA, the Tukey’s honestly significant difference post-hoc test the Games -Howell post-hoc test and were performed when the assumption of equal variances was met and not met, respectively. All analyses were performed based on intention-to-treat, in which participants lost to follow-up were assumed to be active smokers with no changes with respect to the baseline. For primary analysis, the differences in biochemically validated quit rates, as assessed at the 6-month follow-up, between the QI, QP, and control groups were analyzed using the propensity score matched samples. A similar approach was used to analyze the differences in secondary outcomes.

Univariate logistic regression was performed to examine the crude odds ratios (ORs) for primary and secondary outcomes using both the original unmatched and matched samples. A Generalized Logistic Mixed Model (GLMM) was then used to calculate the adjusted odds ratios (aORs) for primary and secondary outcomes after adjusting for characteristics at baseline and the random effect of hospitals using the matched sample. A P value < 0.05 was considered to be statistically significant.

In addition, a posteriori analysis was performed to examine the association between the quantity of smoking reduction across all follow-ups and abstinence at the final follow-up. The percentage reduction was calculated by dividing the difference in daily cigarette consumption between the baseline and a given follow-up by the number of cigarettes consumed at baseline. Multiple logistic regression models were used to examine the predictive power of the absolute and percentage reductions on 12-month abstinence in participants who had not quit by the time of the follow-ups. Each model examined the reduction quantity at a given follow-up as either the absolute or percentage reduction to predict the 12-month abstinence. All models were adjusted for the treatment condition (QI, QP, and control group), demographic and smoking characteristics at the baseline, and the random effect of hospitals. The observed power (1-β) of quitting immediately and quitting progressively on the biochemically validated quit rate, the self-reported quit rate, and self-reported reduction of cigarette consumption were then calculated using G*power. A scatterplot and fitted line analysis were then used to demonstrate the linear association between the absolute or percentage cigarette reduction at 1-, 3-, and 6-month follow-ups and biochemically validated abstinence as assessed at the 12-month follow-up. Given the discrepancies in smoking profiles between the QI and QP subgroups, a two-group propensity matching between the QP and control group was conducted to provide more information on the outcomes in smokers who chose to quit smoking progressively. Similar analyses as described above were also additionally performed.

Results

Fig 1 shows that in the intervention group, 242 participants (30.7%) chose to quit smoking immediately and 545 participants (69.3%) chose to quit smoking progressively. Compared with the QI subgroup, the QP subgroup had a significantly higher mean rate of daily cigarette consumption (QP vs. QI: 15.0 vs. 12.8), more moderate to heavy nicotine dependence (QP vs. QI: 55.6% vs. 39.3%), and a higher number of participants who had not previously attempted to quit smoking (QP vs. QI: 34.5% vs. 20.7%). After propensity score matching, 174 pairs of subjects in the QI, QP, and control groups were matched and analyzed. In the matched sample shown in Table 2, the absolute standardized differences in all covariates were less than 0.10, and the means and prevalence of baseline covariates were similar in the two matched samples, indicating good balance between the groups [18].

Table 2. Baseline characteristics of subjects in the Quit Immediately (QI) group, Quit Progressively (QP) group, and Control group in the propensity-score matched sample.

Standardized differences
QI (n = 174) QP (n = 174) Con (n = 174) P value QI vs QP QI vs Con QP vs Con

Age, mean(SD), y

46.6(15.6) 47.0(16.2) 47.1(15.6) 0.96 0.025 0.045 0.019
Gender 0.71 0.067 0.067 0.000
    Male 147(84.5) 152(87.4) 151(86.8)
    Female 27(15.5) 22(12.6) 23(13.2)
Marital status 0.95 0.010 0.018 0.008
    Single/Divorce/Separate/Widowed 72(41.4) 73(42.0) 75(43.1)
    Married/Cohabit 102(58.6) 101(58.0) 100(56.9)
Employment status 0.26 0.012 0.076 0.064
    Unemployed/Retired 40(23) 41(23.6) 52(29.9)
    Employed 134(77) 133(76.4) 122(70.1)
Educational level 0.13 0.000 0.089 0.089
    Tertiary 14(8.0) 14(8.0) 9(5.2)
    Secondary or below 160(92.0) 160(92.0) 165(97.1)
Monthly household income, US $ 0.79 0.061 0.014 0.046
    ≥3825 (HKD 30000) 17(9.8) 21(12.1) 19(10.9)
    <3825 (HKD 29999) 157(90.2) 153(87.9) 155(89.2)
Smoking-related chronic disease 0.96 0.000 0.022 0.022
    Yes 9(5.2) 9(5.2) 8(4.6)
    No 165(94.8) 165(94.8) 166(95.4)
Health utility score by SF-6Da 0.58(0.1) 0.58(0.1) 0.59(0.1) 0.47 0.000 0.090 0.090
Daily cigarette consumption 13.8(7.8) 13.9(7.4) 13.9(7.6) 0.99 0.013 0.013 0.000
Nicotine dependence by Heaviness of Smoking Index (HIS)b 0.55 0.067 0.095 0.028
    Moderate to heavy(3–6) 78(44.8) 85(48.9) 88(50.6)
    Light(≤2) 96(55.2) 89(51.1) 86(49.4)
Age at starting smoking weekly 17.6(6.4) 17.2(5.5) 17.6(6.2) 0.84 0.067 0.000 0.067
Tried to quit smoking for more than 24 hours 0.73 0.066 0.000 0.066
    Yes 132(75.9) 126(72.4) 132(75.9)
    No 42(24.1) 48(27.6) 42(24.1)
Tried to reduce smoking for more than 24 hours 0.95 0.010 0.028 0.018
    Yes 80(46.0) 81(46.6) 83(47.7)
    No 94(54.0) 93(53.4) 91(52.3)
Readiness to quit 0.93 0.022 0.009 0.032
    Quit ≤ 30 days 45(25.9) 43(24.7) 46(26.4)
    Quit > 30 days 129(74.1) 131(75.3) 128(73.6)
Self-efficacy against tobacco by SEQ-12c 29.3(12.0) 29.0(10.4) 28.4(10.5) 0.73 0.027 0.078 0.053

Continuous variables are reported as mean ± standard deviation. Dichotomous variables are reported as N (Percent).

Abbreviations: SF-6D, Shot-Form Six-Dimension; SEQ-12, Smoking Self-Efficacy Questionnaire.

aThe SF-6D is composed of 6 multilevel dimensions. The SF-6D scores were weighted from a sample of the general population, which ranged from 0 to 1.

bThe Heaviness of Smoking Index, a 2-item index from multiple-choice response options (0–3), was determined by assessing cigarettes smoked per day and time to smoke after waking; the higher the indexes, the greater smoking nicotine dependence.

cOn a 12-item 5-point Likert-type scale in the SEQ-12, responses ranged from “not at all sure” to“absolutely sure.” A summary score of the SEQ-12 ranged from 12 to 60, with higher scores indicating higher self-efficacy.

Tables 3 and 4 showed that after propensity score matching, the biochemically validated abstinence was significantly higher in the QI subgroup than in the control group as assessed at the 6-month (12.1% vs. 3.4%, P = 0.003; aOR = 4.34, 95% CI: 1.63–11.52) and 12-month follow-ups (10.9% vs. 4.0%, P = 0.01; aOR = 3.23, 95% CI: 1.24–8.43). The number needed to treat (NNT) for the QI subgroup was 11.5 [1/(0.121–0.034)]. Compared with the control group, the QI subgroup showed a significantly higher self-reported 7-day point prevalence of abstinence as assessed at the 6-month (21.8% vs. 7.5%, P < 0.001; aOR: 4.34, 95% CI: 1.63–11.52) and 12-month follow-ups (20.7% vs 6.3%, P < 0.001; aOR: 3.23, 95% CI: 1.24–8.43). After excluding those participants who completely ceased smoking, the number of participants who self-reported a reduction in smoking of at least 50% was found to be significantly higher in the QI subgroup than control group at both the 6-month (19.9% vs. 10.6%, P = 0.03; aOR = 2.15, 95% CI: 1.10–4.24), and 12-month follow-ups (18.8% vs. 10.4%, P = 0.04; aOR = 1.95, 95% CI: 0.96–3.93). However, after adjusting for demographics and smoking characteristics at the baseline and the random effect of hospitals, the aOR as assessed at the 12-month follow-up was no longer significantly different between the two groups (P = 0.07; aOR = 1.95, 95% CI: 0.96–3.93).

Table 3. Cessation outcomes of subjects in the Quit Immediately (QI) group, Quit Progressively group and control group in the original unmatched sample and the propensity-score matched sample.

Original unmatched sample Propensity-score matched sample
N (%) N (%) P value Post-hoc analysis
QI (n = 242) QP (n = 545) Con (n = 787) P value Post-hoc analysis QI (n = 174) QP (n = 174) Con (n = 174)
Biochemically validated abstinence
6 months 34 (14.0) 19 (3.5) 22 (2.8) <0.001 QI>QP***# 21 (12.1) 17 (9.8) 6 (3.4) 0.01 QI>Com**#
QI>Con***# QP>Con*#
12 months 31 (12.8) 24 (4.4) 33 (4.2) <0.001 QI>QP***# 19 (10.9) 18 (10.3) 7 (4.0) 0.04 QI>Com**#
QI>Con***# QP>Con*#
Self-reported 7-day point prevalence of abstinence
6 months 53 (21.9) 43 (7.9) 73 (9.3) <0.001 QI>QP***# 38 (21.8) 25 (14.4) 13 (7.5) 0.001 QI>Com**#
QI>Con***# QP>Con*#
12 months 54 (22.3) 48 (8.8) 67 (8.5) <0.001 QI>QP***# 36 (20.7) 33 (19.0) 11(6.3) 0.001 QI>Com**#
QI>Con***# QP>Con**#
Self-reported reduction of ≥ 50% in cigarette consumptiona
6 months 34 (18.0) 89 (17.7) 127 (17.9) 0.99 27 (19.9) 36 (24.2) 17(10.6) 0.006 QI>Com**#
QP>Con**#
12 months 34 (18.1) 96 (19.3) 105 (14.6) 0.09 26 (18.8) 42 (29.8) 17(10.4) <0.001 QI>QP*#
QI>Com*#
QP>Con***#

Subjects lost to follow-up were assumed to be active smokers with no changes from baseline.

a The quitters were excluded in both numerators and denominators.

*: P<0.05

**: P<0.01

***: P<0.001

#: Using the Tukey’s honestly significant difference post-hoc test as equal Variances assumed.

##: Using the Games -Howell post-hoc test as equal Variances not assumed.

Table 4. Logistic regression for validated abstinence, self-report abstinence, and reduction of cigarette consumption among the QI group (n = 174), QP group (n = 174) and control group (n = 174) in the propensity-score matched sample.

QI group vs QP group QI group vs Control group QP group vs Control group
Crude ORa P value Adjusted ORb P value Crude ORa P value Adjusted ORb P value Crude ORa P value Adjusted ORb P value
Biochemically validated abstinence
    6 months 1.40(0.70, 2.83) 0.29 1.50(0.71, 3.19) 0.29 2.88(1.13, 7.32) 0.005 4.34(1.63, 11.52) 0.003 3.03(1.17, 7.89) 0.02 2.95(1.04, 8.39) 0.02
    12 months 1.19(0.59, 2.39) 0.59 1.22(0.57, 2.59) 0.59 2.34(1.16, 5.72) 0.019 3.23(1.24, 8.43) 0.01 2.75(1.12, 6.77) 0.03 2.85(1.11, 7.33) 0.03
Self-reported 7-day point prevalence of abstinence
    6 months 1.52(0.88, 2.65) 0.07 1.67(0.93, 2.99) 0.07 2.29(1.17, 4.48) <0.001 3.65(1.80, 7.43) <0.001 2.08(1.03, 4.21) 0.04 1.96(1.12, 4.08) 0.04
    12 months 1.10(0.65, 1.85) 0.69 1.08(0.62, 1.87) 0.69 2.17(1.09, 4.34) <0.001 3.85(1.82, 8.16) <0.001 3.47(1.69, 7.12) 0.001 3.10(1.52, 6.79) 0.002
Self-reported reduction of ≥ 50% in cigarette consumption
    6 months 0.78(0.44, 1.37) 0.38 0.77(0.42, 1.39) 0.38 2.10(1.09, 4.04) 0.027 2.15(1.10, 4.24) 0.03 2.70(1.44, 5.05) <0.002 2.70(1.40, 5.23) 0.001
    12 months 0.55(0.31, 0.96) 0.03 0.60(0.31, 0.98) 0.03 1.99 (1.03, 3.85) 0.040 1.95(0.96, 3.93) 0.07 3.64(1.96, 6.76) <0.001 3.42(1.76, 6.64) <0.001

Subjects lost to follow-up were assumed to be active smokers with no changes from baseline.

a Crude RR = Crude Relative Risks. Crude estimates from the univariable logistic regression

b Adjusted RR = Adjusted Relative Risks. Adjusted estimates from Generalized Logistic Mixed Model adjusted for age, sex, employment status, health utility score, daily cigarette consumption, nicotine dependence level, readiness to quit, and smoking efficacy against tobacco at baseline, and random effect of hospitals.

The biochemically validated abstinence was also significantly higher in the QP subgroup than the control group when it was measured at the 6-month (9.8% vs. 3.4%, P = 0.02; aOR = 2.95, 95% CI: 1.04–8.39) and 12-month follow-ups (10.3% vs. 4.0%, P = 0.02; aOR = 2.85, 95% CI: 1.11–7.33). The NNT for the QP subgroup was 15.6 [1/(0.098–0.034)]. Compared with the control group, the QP subgroup showed a significantly higher self-reported 7-day point prevalence of abstinence when measured at the 6-month (14.4% vs. 7.5%, P = 0.04; aOR = 1.96, 95% CI: 1.12–4.08) and 12-month follow-ups (19.0% vs. 6.3%, P < 0.001; aOR = 3.10, 95% CI: 1.52–6.79). After excluding those participants who completely ceased smoking, the number of participants who self-reported a reduction in smoking of at least 50% was significantly higher in the QP subgroup than in the control group as measured at the 6-month (24.2% vs. 10.6%, P = 0.001; aOR = 2.70, 95% CI: 1.40–5.23) and 12-month follow-ups (29.8% vs. 10.4%, P < 0.001; aOR = 3.42, 95% CI: 1.76–6.64). A comparison of the baseline characteristics and smoking profiles between the QP and control groups after two-group propensity score matching is presented in the S1 Table. The cessation outcomes showed that the biochemically validated and self-reported abstinence rates among subjects in the matched QP group were significantly higher than those in the matched control group as assessed at both the 6- and 12-month follow-ups (S2 Table). After excluding those participants who completely ceased smoking, participants who self-reported a reduction in smoking of at least 50% was higher in the QP subgroup than in the control group. This increase was significantly different when measured at the 12-month follow-up, but not at the 6-month follow-up.

There were no significant differences in biochemically validated abstinence between the QI and QP subgroups at when assessed at the either 6-month (12.1% vs. 9.8%, P = 0.49; aOR = 1.50, 95% CI: 0.71–3.19) or 12-month follow-up (10.9% vs. 10.3%, P = 0.86; aOR = 1.22, 95% CI: 0.57–2.59). Higher self-reported abstinence was reported in the QI subgroup than in the QP subgroup, but this difference was not significant as assessed at either the 6-month (21.8% vs. 14.4%, P = 0.07; aOR = 1.67, 95% CI: 0.93–2.99) or 12-month follow-up (20.7% vs. 19.0%, P = 0.69; aOR = 1.08, 95% CI: 0.62–1.87). Excluding those participants who completely ceased smoking, the number of participants who self-reported a reduction in smoking of at least 50% was lower in the QI subgroup than in the QP subgroup. This reduction was significantly different between the two groups when assessed at the 12-month follow-up (18.8% vs. 29.8%, P = 0.03; aOR = 0.60, 95% CI: 0.31–3.98), but not at the 6-month follow-up (19.9% vs. 24.2%, P = 0.38; aOR = 0.77, 95% CI: 0.42–1.39). Table 5 presented that the powers of the quitting immediately had a and quitting progressively on the biochemically validated quit rate, the self-reported quit rate, and self-reported reduction of cigarette consumption were acceptable (all larger than 0.80) to detect the hypothesis in this study.

Table 5. Posterior power calculation for quitting immediately (QI) and quitting progressively (QP) compared to smoking cessation leaflet (Control group).

Observed power (1-β)
Quitting Immediately Quitting Progressively
Biochemically validated abstinence
    6 months 0.91 0.84
    12 months 0.85 0.82
Self-reported 7-day point prevalence of abstinence
    6 months 0.96 0.81
    12 months 0.97 0.95
Self-reported reduction of ≥ 50% in cigarette consumption
    6 months 0.82 0.92
    12 months 0.80 0.98

The scatterplot and fitted line analysis showed that the values of both the absolute and percent cigarette reduction at the 1-, 3-, and 6-month follow-ups were associated with the biochemically validated abstinence as assessed at the 12-month follow-up (Fig 2). The R2 showed that the percent cigarette reduction (a-2, b-2, c-2) could better predict the 12-month abstinence than the absolute cigarette reduction (a-1, b-1, c-1).

Fig 2. Scatterplot of the predicted probability of 12-month abstinence against the reduction of cigarette consumption at 1-month, 3-month, and 6-month.

Fig 2

Discussion

The results of this a posteriori analysis showed that the number of smokers in the intervention group who chose to quit smoking progressively outnumbered that of smokers who chose to quit smoking immediately by more than two folds (progressive vs. immediate: 69.3% vs. 30.7%). The results also indicated that smokers in the QP subgroup had significantly higher rates of daily cigarette consumption and nicotine dependency and had made fewer attempts to quit previously than those in the QI subgroup. The findings of this study provide support to existing reports in the literature which show that many heavy smokers are reluctant to quit smoking immediately. Therefore, smoking and the quitting histories of smokers should be considered when recommending different types of smoking cessation interventions. For heavy or hard-core smokers who are reluctant to quit, intervention strategies that enforce immediate quitting may be perceived as being too harsh and be ineffective in helping them to cease smoking. In contrast, those who smoke a few cigarettes a day with mild nicotine dependence may deem the progressive quitting approach unnecessary or superfluous and consequently undermine the effectiveness of the approach.

The subgroup analyses showed that smokers in both the QI and QP subgroups had significantly higher biochemically validated abstinence and self-reported 7-day point prevalence of abstinence rates at the 6- and 12-month follow-ups than those in the control group. The results demonstrated that offering a brief smoking cessation intervention to smokers and allowing them to choose the quitting schedules effectively promoted the cessation of smoking. In addition, a significantly higher proportion of smokers who had not quit in the QP subgroup achieved at least 50% reduction in cigarette consumption by the 12-month follow-up, compared to those in the QI subgroup. Though the ultimate goal of quitting progressively is the complete cessation of smoking, it is anticipated that these smokers will find it much easier to gradually reduce their cigarette consumption or quit smoking altogether in the near future, given that they have already initiated the process and reduced their nicotine dependence [6, 7]. The fitted line analysis supported the potential of using the rates of reduction in cigarette consumption to predict future abstinence from smoking. These findings imply that progressive quitting is a useful alternative approach for smokers who lack motivation and experience difficulty in quitting smoking [19].

Limitations

Given the discrepancies in the smoking profiles of smokers who choose to quit either immediately or progressively, it is difficult to compare the smoking cessation outcomes between the QI and QP groups. Therefore, three-group and two-group propensity score matching analyses were conducted. This study conducted a posteriori analysis of data from a previous trial, which could not provide sufficient evidence for a causal relationship between a reduction in smoking and abstinence from smoking. In future, a randomized controlled trial should be conducted in which smokers with similar smoking profiles should be recruited to test the differences in reduction and abstinence for longer follow-up periods.

Implications for clinical practice

This study addresses the important question of whether the approach to quitting smoking in a progressive manner is or is not effective. Our findings also addressed existing gaps in the field by demonstrating that quitting progressively is effective, especially for chronic smokers who lack motivation or find it difficult to quit. A measured application of these results can help achieve a greater level of abstinence from smoking and make important contributions to evidence-based practice. Most importantly, the outcomes of this original study can inform future researchers and policymakers on designing effective smoking cessation interventions and policies for smokers who are reluctant to quit smoking immediately. Thus, the study has important implications for clinical practice and the improvement of public health. In future, we will explore the means to retain smokers in gradual cessation programs as they reduce their frequency of smoking, develop more successful methods to encourage reduction in smoking, and find ways to prevent a perception of failure by participants, which usually causes them abandon their attempts to reduce the number of cigarettes smoked and quit smoking. Finally, in Hong Kong, which is a region with a low prevalence of smoking yet has many hard-core smokers, our results can guide future strategies toward a total ban on tobacco sales.

Conclusions

This secondary analysis of a randomized controlled trial provides further support to a previous study that allowed smokers to choose their quitting schedules, which was essential in motivating them to quit smoking. This study supplements the previous trial by determining that the progressive quitting approach is effective, especially for smokers who lack motivation or find it difficult to quit.

Supporting information

S1 Checklist. CONSORT 2010 checklist of information to include when reporting a randomized triala.

(PDF)

S1 Fig. Calculation formula of the standardized difference for continuous variables.

(TIF)

S2 Fig. Calculation formula of the standardized difference for dichotomous variables.

(TIF)

S1 Table. Comparison of baseline characteristics and smoking profiles among subjects in the QP group and control group in the original unmatched sample and the propensity-score matched sample.

(DOCX)

S2 Table. Cessation outcomes of subjects in the QP group vs. control group original trial protocol and statistical analysis plan.

(DOCX)

S1 File. Trial protocol with statistical analysis plan.

(PDF)

Data Availability

All data belong to the funder (Health and Medical Research Fund, Food and Health Bureau, Hong Kong Special Administrative Region). The data can be accessed only with the permission by the Bureau (https://rfs2.fhb.gov.hk/english/welcome/welcome.html). The authors did not have any special access privileges that others would not have.

Funding Statement

This research was funded by Health and Medical Research Fund, Food and Health Bureau, Hong Kong Special Administrative Region (Dr Li: grant No. 12133111). The funder sources had no role in the design and conduct of the study; collection; management; analysis; and interpretation of the data; preparation; review; or approval of the manuscript; and decision to submit the manuscript for publication.

References

  • 1.Darville A, Hahn EJ. Hardcore smokers: what do we know? Addict Behav. 2014; 39(12): 1706–1712. doi: 10.1016/j.addbeh.2014.07.020 [DOI] [PubMed] [Google Scholar]
  • 2.Warner KE, Mendez D. Tobacco control policy in developed countries: yesterday, today, and tomorrow. Nicotine Tob Res. 2010; 12 (9):876–887. doi: 10.1093/ntr/ntq125 [DOI] [PubMed] [Google Scholar]
  • 3.Chan SS, Leung DY, Abdullah AS, Wong VT, Hedley AJ, Lam TH. A randomized controlled trial of a smoking reduction plus nicotine replacement therapy intervention for smokers not willing to quit smoking. Addiction. 2011; 106(6):1155–63. doi: 10.1111/j.1360-0443.2011.03363.x [DOI] [PubMed] [Google Scholar]
  • 4.Ho KY, Li WH, Wang MP, Lam KK, Lam TH, Chan SS. Comparison of two approaches in achieving smoking abstinence among patients in an outpatient clinic: a phase 2 randomized controlled trial. Patient education and counseling. 2018; 101(5):885–93. doi: 10.1016/j.pec.2018.02.003 [DOI] [PubMed] [Google Scholar]
  • 5.Wang MP, Li WHC, Cheung YT, et al. Brief advice on smoking reduction versus abrupt quitting for smoking cessation in Chinese smokers: a cluster randomized controlled trial. Nicotine Tob Res. 2017; 20(1):67–72. doi: 10.1093/ntr/ntx026 [DOI] [PubMed] [Google Scholar]
  • 6.Mooney ME, Johnson EO, Breslau N, Bierut LJ, Hatsukami DK. Cigarette smoking reduction and changes in nicotine dependence. Nicotine Tob Res. 2011; 13(6):426–30. doi: 10.1093/ntr/ntr019 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7.Wu L, Sun S, He Y, Zeng J. Effect of smoking reduction therapy on smoking cessation for smokers without an intention to quit: an updated systematic review and meta-analysis of randomized controlled. Int. J. Environ. Res. Public Health. 2015; 12(9):10235–53. doi: 10.3390/ijerph120910235 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Lindson N, Klemperer E, Hong B, Ordóñez‐Mena JM, Aveyard P. Smoking reduction interventions for smoking cessation. Cochrane Database Syst Rev 2019; 9: CD013183. doi: 10.1002/14651858.CD013183.pub2 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9.Jiang Y, Elton-Marshall T, Fong GT, Li Q. Quitting smoking in China: findings from the ITC China Survey. Tob Control. 2010;19(Suppl 2):i12–7. doi: 10.1136/tc.2009.031179 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Lam TH, Abdullah AS, Chan SS, Hedley AJ. Adherence to nicotine replacement therapy versus quitting smoking among Chinese smokers: a preliminary investigation. Psychopharmacology. 2005;177(4):400–8. doi: 10.1007/s00213-004-1971-y [DOI] [PubMed] [Google Scholar]
  • 11.Li WH, Ho KY, Wang MP, Cheung DY, Lam KK, Xia W, et al. Effectiveness of a Brief Self-determination Theory–Based Smoking Cessation Intervention for Smokers at Emergency Departments in Hong Kong: A Randomized Clinical Trial. JAMA Intern Med 2019. Dec 2. doi: 10.1001/jamainternmed.2019.5176 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12.Hospital Authority. Accident & Emergency (A&E). https://www.ha.org.hk/visitor/ha_serviceguide_details.asp?Content_ID=10051&IndexPage=200066&Lang=ENG&Ver=HTML. Accessed August 7, 2019.
  • 13.Morgan CJ. Reducing bias using propensity score matching. 2018. [DOI] [PubMed] [Google Scholar]
  • 14.Rassen JA, Shelat AA, Franklin JM, Glynn RJ, Solomon DH, Schneeweiss S. Matching by propensity score in cohort studies with three treatment groups. Epidemiology. 2013; 401–9. doi: 10.1097/EDE.0b013e318289dedf [DOI] [PubMed] [Google Scholar]
  • 15.Wang LG, Rginwood JV. Control-informed ballast and geometric optimisation of a three-body hinge-barge wave energy converter using two-layer optimization. Renewable Energy. 2021; 171:1159–70. doi: 10.1016/j.renene.2021.02.125 [DOI] [Google Scholar]
  • 16.Austin PC. Using the standardized difference to compare the prevalence of a binary variable between two groups in observational research. Commun Stat-Simul Comput. 2009; 38(6):1228–34. doi: 10.1080/03610910902859574 [DOI] [Google Scholar]
  • 17.Austin PC. Balance diagnostics for comparing the distribution of baseline covariates between treatment groups in propensity-score matched samples. Statist Med. 2009; 28(25): 3083–3107. doi: 10.1002/sim.3697 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Zhang Z., Kim H. J., Lonjon G., & Zhu Y. (2019). Balance diagnostics after propensity score matching. Ann Transl Med. 7(1):16. doi: 10.21037/atm.2018.12.10 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.Begh R, Lindson-Hawley N, Aveyard P. Does reduced smoking if you can’t stop make any difference? BMC med. 2015;13(1):257. doi: 10.1186/s12916-015-0505-2 [DOI] [PMC free article] [PubMed] [Google Scholar]

Decision Letter 0

Hao Xue

Transfer Alert

This paper was transferred from another journal. As a result, its full editorial history (including decision letters, peer reviews and author responses) may not be present.

26 Apr 2022

PONE-D-21-03778

Effect of Quitting Immediately vs Progressively on Smoking Cessation for Smokers at Emergency Department in Hong Kong: A Posteriori Analysis of a Randomized Controlled Trial

PLOS ONE

Dear Dr. Li,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Jun 10 2022 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Hao Xue

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at 

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and 

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. We note that the grant information you provided in the ‘Funding Information’ and ‘Financial Disclosure’ sections do not match. 

When you resubmit, please ensure that you provide the correct grant numbers for the awards you received for your study in the ‘Funding Information’ section.

3. We note that you have indicated that data from this study are available upon request. PLOS only allows data to be available upon request if there are legal or ethical restrictions on sharing data publicly. For more information on unacceptable data access restrictions, please see http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions. 

In your revised cover letter, please address the following prompts:

a) If there are ethical or legal restrictions on sharing a de-identified data set, please explain them in detail (e.g., data contain potentially sensitive information, data are owned by a third-party organization, etc.) and who has imposed them (e.g., an ethics committee). Please also provide contact information for a data access committee, ethics committee, or other institutional body to which data requests may be sent.

b) If there are no restrictions, please upload the minimal anonymized data set necessary to replicate your study findings as either Supporting Information files or to a stable, public repository and provide us with the relevant URLs, DOIs, or accession numbers. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories.

We will update your Data Availability statement on your behalf to reflect the information you provide.

4. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

********** 

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

********** 

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

********** 

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

********** 

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: A two-arm randomized controlled study aimed to determine which method of quitting smoking is more effective: suddenly or progressively. In a propensity score matched analysis, the 6-month abstinence rate was statistically significantly higher in the intervention group who chose to quit smoking immediately compared to controls. At 6-months, the cessation of smoking rate was also higher in the intervention group who chose to quit smoking progressively compared to controls. The smoking cessation rates were not statistically significantly different in the two intervention groups.

Minor revisions:

1- Tables 1 to 3: For each baseline characteristic, provide only one p-value for comparing all three groups. If the p-value is significant, perform step-down tests to determine pairwise differences.

2-Page 9: Explain the rationale for using a GEE model when adjusting for baseline characteristics rather than applying multivariate logistic regression models.

3- Page 10, Line 1: The figure number had been omitted.

4- Provide a post-hoc power calculation.

5- Explain the graphical results in figure 2.

********** 

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2023 Jan 26;18(1):e0280925. doi: 10.1371/journal.pone.0280925.r002

Author response to Decision Letter 0


19 May 2022

Dear Editor,

Re: "Effect of Quitting Immediately vs Progressively on Smoking Cessation for Smokers at Emergency Department in Hong Kong: A Posteriori Analysis of a Randomized Controlled Trial" (PONE-D-21-03778)

We sincerely thank the editor and reviewer’s very useful and constructive comments. We have made changes accordingly. Please also refer to the following point-by-point responses to the comments from the reviewer and editor.

Please kindly let me know in case any responses are not clear or the information is not adequate to clarify concerns. Thanks for giving us an opportunity to revise the manuscript.

Please also note that all data are belong to the funder (Health and Medical Research Fund, Food and Health Bureau, Hong Kong Special Administrative Region). The data can be accessed only with the permission by the Bureau (https://rfs2.fhb.gov.hk/english/welcome/welcome.html.)

Sincerely,

Authors

Response to the Journal requirements

Comment 1 1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id= wjVg/ PLOSOne_formatting_sample_ main_body.pdf and https://journals.plos. org/ plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_ affiliations.pdf

Response 1 We have changed the format of the manuscript and ensured that the manuscript meets the requirement of PLOS ONE.

Comment 2 2. We note that the grant information you provided in the ‘Funding Information’ and ‘Financial Disclosure’ sections do not match.

When you resubmit, please ensure that you provide the correct grant numbers for the awards you received for your study in the ‘Funding Information’ section.

Response 2 Thank you for pointing out the inconsistent information. We have corrected the Funding information in the manuscript (Page 23, line 13).

Comment 3 3. We note that you have indicated that data from this study are available upon request. PLOS only allows data to be available upon request if there are legal or ethical restrictions on sharing data publicly. For more information on unacceptable data access restrictions, please see http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions.

In your revised cover letter, please address the following prompts:

a) If there are ethical or legal restrictions on sharing a de-identified data set, please explain them in detail (e.g., data contain potentially sensitive information, data are owned by a third-party organization, etc.) and who has imposed them (e.g., an ethics committee). Please also provide contact information for a data access committee, ethics committee, or other institutional body to which data requests may be sent.

b) If there are no restrictions, please upload the minimal anonymized data set necessary to replicate your study findings as either Supporting Information files or to a stable, public repository and provide us with the relevant URLs, DOIs, or accession numbers. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories.

We will update your Data Availability statement on your behalf to reflect the information you provide.

Response 3 Thanks for the comment. We have contacted with the Funder and then update our Data Availability statement as below:

All data are belong to the funder (Health and Medical Research Fund, Food and Health Bureau, Hong Kong Special Administrative Region). The data can be accessed only with the permission by the Bureau (https://rfs2.fhb.gov.hk/english/welcome/welcome.html.)

Comment 4 4. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

Response 4 We have checked the reference list and ensure that it is complete and correct.

Response to comments from Reviewer

Comment 1 1- Tables 1 to 3: For each baseline characteristic, provide only one p-value for comparing all three groups. If the p-value is significant, perform step-down tests to determine pairwise differences.

Response 1 Following the reviewer’s suggestion, the one-way ANOVA analysis was used to compare the differences of baseline variables among the three groups, and then a Tukey's honestly significant difference (HSD) post hoc test was performed to specific groups difference for the variables showing significant difference in the one-way ANOVA analysis. Please find the results in the table 1 to 3. The description of the statistical analysis method was revised accordingly as below (Page 9, line 8):

“For the variables showing significant difference in ANOVA, the Tukey's honestly significant difference post-hoc test the Games -Howell post-hoc test and were performed when the assumption of equal variances was met and not met, respectively.”

In addition, we will keep the standardized differences in table 1 and table 2 as they may allow the readers to well understand that demographic and smoking profiles among the three groups were well balanced after the PSM.

Comment 2 2-Page 9: Explain the rationale for using a GEE model when adjusting for baseline characteristics rather than applying multivariate logistic regression models.

Response 2 We are apologized for the mistake of the description. Actually we used a Generalized Logistic Mixed Model (GLMM) to calculate the odds ratios as the data in this study were collected in multiple research center and the GLMM allowed us to adjust the random effect of the hospitals in the model. We have corrected the description in the manuscript as below (Page 9, line 20) and the notes under the table 4 accordingly:

“A Generalized Logistic Mixed Model (GLMM) was then used to calculate the adjusted odds ratios (aORs) for primary and secondary outcomes after adjusting for characteristics at baseline and the random effect of hospitals using the matched sample.”

Comment 3 3- Page 10, Line 1: The figure number had been omitted.

Response 3 Thank you for pointing out the mistake, we have revised it as “Figure 1” in Page 10, line 1.

Comment 4 4- Provide a post-hoc power calculation.

Response 4 Thank you for your suggestion, the results of power calculations have been added in the manuscript, please find it in table 5 and page 18, lines 1-4 as below:

“The observed power (1-β) of quitting immediately and quitting progressively on the biochemically validated quit rate, the self-reported quit rate, and self-reported reduction of cigarette consumption were then calculated using G*power.”

Comment 5 5- Explain the graphical results in figure 2.

Response 5 The explanation of the results in figure 2 has been added in the results section as below (Page 19, line 1-5):

“The scatterplot and fitted line analysis showed that the values of both the absolute and percent cigarette reduction at the 1-, 3-, and 6-month follow-ups were associated with the biochemically validated abstinence as assessed at the 12-month follow-up (Fig 2). The R2 showed that the percent cigarette reduction (a-2, b-2, c-2) could better predict the 12-month abstinence than the absolute cigarette reduction (a-1, b-1, c-1).”

Attachment

Submitted filename: Responses to the comments-2.docx

Decision Letter 1

Hao Xue

4 Jul 2022

PONE-D-21-03778R1Effect of Quitting Immediately vs Progressively on Smoking Cessation for Smokers at Emergency Department in Hong Kong: A Posteriori Analysis of a Randomized Controlled TrialPLOS ONE

Dear Dr. Li,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Aug 18 2022 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Hao Xue

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Minor Revision:

Include the full details of the power calculation. The power calculation should include: sample size, alpha level (indicating one or two-sided), minimal detectable difference (plus the standard deviation when appropriate) and statistical testing method.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2023 Jan 26;18(1):e0280925. doi: 10.1371/journal.pone.0280925.r004

Author response to Decision Letter 1


5 Jul 2022

Dear Editor,

Re: "Effect of Quitting Immediately vs Progressively on Smoking Cessation for Smokers at Emergency Department in Hong Kong: A Posteriori Analysis of a Randomized Controlled Trial" (PONE-D-21-03778R1)

We sincerely thank the editor and reviewer’s very useful and constructive comments. We have made changes accordingly. Please also refer to the following point-by-point responses to the comments from the reviewer and editor.

Please kindly let me know in case any responses are not clear or the information is not adequate to clarify concerns. Thanks for giving us an opportunity to revise the manuscript.

Please also note that all data are belong to the funder (Health and Medical Research Fund, Food and Health Bureau, Hong Kong Special Administrative Region). The data can be accessed only with the permission by the Bureau (https://rfs2.fhb.gov.hk/english/welcome/welcome.html.)

Sincerely,

Authors

Response to comments from Reviewer

Comment 1 Minor Revision required:

Include the full details of the power calculation. The power calculation should include: sample size, alpha level (indicating one or two-sided), minimal detectable difference (plus the standard deviation when appropriate) and statistical testing method.

Response 1 Thanks for the reviewer’s suggestion. We have added the following information related to sample size calculation in the text:

“The sample size was calculated according to a previous trial [3] of a smoking reduction plus nicotine replacement therapy intervention involving 1154 Chinese adult smokers unwilling to quit smoking (biochemically validated quit rate of 4.4% [10 of 226] in the control group and 8.0% [74 of 928] in the intervention group at 6months). To detect a two-sided significant difference between groups with a power of 80% and significance level of 5%, the required sample size was estimated to be 1088 participants (544 in each group). Given an expected attrition rate of approximately 30% at the 6-month follow-up, the target was at least 1554 individuals (777 in each group). Between July 4, 2015 and March 17, 2017, 1571 smokers who presented at 4 major emergency departments consented to participate in this randomized controlled trial and were randomized into an intervention group (n = 787) and a control group (n = 784).”

Attachment

Submitted filename: Responses to Reviewers.docx

Decision Letter 2

Katrien Janin

15 Nov 2022

PONE-D-21-03778R2Effect of Quitting Immediately vs Progressively on Smoking Cessation for Smokers at Emergency Department in Hong Kong: A Posteriori Analysis of a Randomized Controlled TrialPLOS ONE

Dear Dr. LI,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Your manuscript has been reassessed by two reviewers, whose reports can be found below. As you will see from the comments, there remain some minor additions to your sample size/power justification which should be addressed before your manuscript is suitable for publication.

Please submit your revised manuscript by Dec 29 2022 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Katrien Janin

Staff Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Minor revision:

Sample Size/Power justification: State the statistical testing method which attains 80% power. Perhaps the method is a chi-square test for comparing proportions.

Reviewer #2: This is a well written articles and novel approach to smoking cessation, building on the authors previous works. Findings are clearly described and presented.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2023 Jan 26;18(1):e0280925. doi: 10.1371/journal.pone.0280925.r006

Author response to Decision Letter 2


18 Nov 2022

Thanks for your suggestion. We have added the following information to justify the sample size calculation in the text:

“The sample size was calculated according to a previous trial [3] of a smoking reduction plus nicotine replacement therapy intervention involving 1154 Chinese adult smokers unwilling to quit smoking (biochemically validated quit rate of 4.4% [10 of 226] in the control group and 8.0% [74 of 928] in the intervention group at 6months). To detect a two-sided significant difference between groups by a chi-square test for comparing proportions with a power of 80% and significance level of 5%, the required sample size was estimated to be 1088 participants (544 in each group). Given an expected attrition rate of approximately 30% at the 6-month follow-up, the target was at least 1554 individuals (777 in each group). Between July 4, 2015 and March 17, 2017, 1571 smokers who presented at 4 major emergency departments consented to participate in this randomized controlled trial and were randomized into an intervention group (n = 787) and a control group (n = 784).”

Attachment

Submitted filename: Responses to Reviewers.docx

Decision Letter 3

Yann Benetreau

12 Jan 2023

Effect of Quitting Immediately vs Progressively on Smoking Cessation for Smokers at Emergency Department in Hong Kong: A Posteriori Analysis of a Randomized Controlled Trial

PONE-D-21-03778R3

Dear Dr. Li,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Yann Benetreau

Staff Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********

Acceptance letter

Yann Benetreau

17 Jan 2023

PONE-D-21-03778R3

Effect of Quitting Immediately vs Progressively on Smoking Cessation for Smokers at Emergency Department in Hong Kong: A Posteriori Analysis of a Randomized Controlled Trial

Dear Dr. Li:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Katrien Janin

Staff Editor

PLOS ONE

Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 Checklist. CONSORT 2010 checklist of information to include when reporting a randomized triala.

    (PDF)

    S1 Fig. Calculation formula of the standardized difference for continuous variables.

    (TIF)

    S2 Fig. Calculation formula of the standardized difference for dichotomous variables.

    (TIF)

    S1 Table. Comparison of baseline characteristics and smoking profiles among subjects in the QP group and control group in the original unmatched sample and the propensity-score matched sample.

    (DOCX)

    S2 Table. Cessation outcomes of subjects in the QP group vs. control group original trial protocol and statistical analysis plan.

    (DOCX)

    S1 File. Trial protocol with statistical analysis plan.

    (PDF)

    Attachment

    Submitted filename: Responses to the comments-2.docx

    Attachment

    Submitted filename: Responses to Reviewers.docx

    Attachment

    Submitted filename: Responses to Reviewers.docx

    Data Availability Statement

    All data belong to the funder (Health and Medical Research Fund, Food and Health Bureau, Hong Kong Special Administrative Region). The data can be accessed only with the permission by the Bureau (https://rfs2.fhb.gov.hk/english/welcome/welcome.html). The authors did not have any special access privileges that others would not have.


    Articles from PLOS ONE are provided here courtesy of PLOS

    RESOURCES