Impacts of revised smoke-free regulations under the 2020 Japan Health Promotion Act on cigarette smoking and heated tobacco product use in indoor public places and homes: findings from 2018 to 2021 International Tobacco Control (ITC) Japan Surveys

Abstract

Background

In April 2020, Japan’s revised Health Promotion Act (HPA) banned cigarette smoking and heated tobacco products (HTP) use in indoor public places but exempted small establishments and permitted smoking-designated/HTP-designated rooms. This pre–post study evaluated the effectiveness of the HPA.

Methods

Data were from waves 1 to 4 (2018–2021) of the International Tobacco Control Japan Surveys among a national cohort of adults who smoke cigarettes, use HTPs and do not use any tobacco products. The sample sizes in the respective surveys were 4615, 4222, 4387 and 4254. Multivariable logistic regression models employing generalised estimating equations estimated the prevalence of observed and self-reported indoor smoking/HTP use in key public venues (restaurants/cafés, bars/pubs and workplaces), smoke-free places, and homes, and smoke-free/HTP aerosol-free home policies (model 1). The models were additionally adjusted for waves 1–4 to estimate the impacts of the HPA (model 2).

Results

The implementation of the HPA significantly reduced observed indoor smoking in bars/pubs (model 1: 82.2% (pre) to 55.5% (post), model 2: p=0.04) but not in restaurants/cafés (model 1: 53.0%–24.9%, model 2: p=0.15) or workplaces (model 1: 35.3%–30.1%, model 2: p=0.62). Observed indoor HTP use was also common postimplementation (restaurants/cafés: 19.6%, bars/pubs: 53.9%, workplaces: 36.4%). The implementation of the HPA was associated with a significant increase in observed HTP use in smoke-free places (model 1: 26.3%–33.3%, model 2: p=0.001) and a suggestive increase in homes without HTP aerosol-free policies among adults who smoke (model 1: 64.0%–77.0%, model 2: p=0.09).

Conclusions

The implementation of the HPA was limited in its effectiveness. Comprehensive regulations with no exemptions are needed in Japan.

WHAT IS ALREADY KNOWN ON THIS TOPIC

• Comprehensive smoke-free regulations are effective in protecting people from the harmful effects of secondhand smoke and are required by the WHO Framework Convention on Tobacco Control (FCTC) Article 8.

• Smoke-free policies in Japan have been historically challenging due to persistent tobacco industry interference and the instilled concept of ‘smoking manners’ which facilitated social acceptability of smoking.

• After a long period of adopting voluntary smoke-free measures, the amended Health Promotion Act (HPA) restricting indoor cigarette smoking and heated tobacco product (HTP) use was implemented in April 2020.

WHAT THIS STUDY ADDS

• The implementation of the revised HPA only partially reduced smoking and HTP use in indoor public places and increased exposure to HTP aerosols in cigarette smoke-free places.

• Our findings may be explained by the substantial exemptions for the existing smaller food and beverage establishments and the distinction made between cigarettes and HTPs.

• The implementation of the revised HPA did not increase the prevalence of cigarette smoke-free or HTP aerosol-free homes among those who use tobacco.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• The study highlights the urgent need to implement comprehensive smoke-free regulations that conform to the WHO FCTC to eliminate secondhand smoke in Japan.

• Governments should consider regulating indoor HTP use in accordance with the scientific evidence regarding the harmfulness of HTP aerosols.

• It is also important to encourage people to adopt smoke-free or HTP aerosol-free policies in homes in accordance with the scientific evidence.

Background

Globally, secondhand smoke (SHS) exposure is a preventable cause of serious health problems and an estimated 1.3 million premature deaths each year, including 51 000 children and adolescents.^{1 2} A key provision of the WHO Framework Convention on Tobacco Control (FCTC) is Article 8, which calls on the 183 Parties to implement ‘effective measures …to create a 100% smoke-free environment,’ explicitly stating that ‘there is no safe level of exposure to tobacco smoke’ and thus ‘approaches other than 100% smoke-free environments…have been repeatedly shown to be ineffective.’³ Since the FCTC came into force in 2005, smoke-free (SF) regulations have been implemented at a best-practice level in 74 countries.²

Japan, the world’s ninth largest tobacco market,⁴ ratified the FCTC in 2004. However, Japan’s action on protection from exposure to SHS was weak with legally non-binding provisions and was left to the discretion of property owners, managers and employers. Although the prevalence of exposure to SHS in public places has been decreasing steadily in Japan,⁵ the International Tobacco Control (ITC) Japan Survey conducted in 2018 reported high prevalences of smoking in indoor public places (96.7% among those who smoke) and indoor smoking observed by those who do not smoke in restaurants (53%), bars (82%) and workplaces (48%).^{6 7} Adding complexity to the situation, heated tobacco products (HTPs), which entered the Japanese tobacco market in December 2013,⁸ have increasingly gained popularity, with the prevalence of HTP use in 2022 being 11.8%.⁹ Previous studies found that HTP use in indoor public spaces was common (80.1% of those who used HTPs in 2018),⁶ and the exposure to secondhand HTP aerosols has increased rapidly in recent years.¹⁰

In July 2018, Japan’s Health Promotion Act (HPA) was amended to include enhanced SF regulations with fines, restricting both cigarette smoking (referred to as smoking here) and HTP use in indoor public places.^{11 12} The revised regulations were implemented first in schools, hospitals, child welfare facilities and government facilities in July 2019 and then in restaurants, bars and offices in April 2020. The revised HPA is considered a major advance for tobacco control in Japan where tobacco control has been challenging due to the Japan government’s partial ownership of Japan Tobacco. However, the revised HPA includes several substantial exemptions. First, it allows smoking and HTP use in existing small food and beverage establishments (seating area ≤100m² or total capital/investment ≤50 million yen), thus exempting nearly half of such establishments. Second, it allows smoking-designated and HTP-designated rooms to be allocated or built-in larger-sized food and beverage establishments. While no food and drinks are allowed to be served in smoking-designated rooms, they can be served in HTP-designated rooms or establishments. Although HTPs have been reported to generate toxicants at lower levels compared with cigarettes, this does not eliminate potential harm since HTP aerosols contain toxic chemicals, including potential carcinogens, and some toxicants found in HTP aerosols exceed the levels found in cigarette smoke although these are found in minuscule quantities in both.13,16

Given these exemptions in the revised HPA in Japan, how effective the enhanced regulations were in preventing exposure to SHS and HTP aerosols in indoor places is unknown. The present study analysed national data from the ITC Japan Survey to evaluate the effectiveness of the enhanced regulations in reducing exposure to SHS and HTP aerosols in indoor places in Japan, including restaurants/cafés, bars/pubs and workplaces. We also estimated whether there were reductions in smoking and HTP use within the home, following studies that have found that SF laws in public places led to reductions in smoking in private places.¹⁷

Materials and methods

Study design

The present study focused on the ITC Japan Surveys conducted between 2018 and 2021 (waves 1–4) in adults aged ≥20 across eight geographical regions of Japan (table 1). The study population includes four groups defined by tobacco use status: those who smoke cigarette-only (‘cigarette-only’), use HTP-only (‘HTP-only’), both smoke and use HTP (‘dual’), and not using any tobacco products (‘no tobacco use’). Participants were sampled and recruited from the Rakuten Insight’s Japan web panel,¹⁸ with quotas according to smoking/HTP use status, sex (all four user groups), age (all groups except ‘HTP-only’) and geographical region (‘cigarette-only’).¹⁹ Those who responded that they had never heard about HTP were considered ineligible for the study. Each participant was invited to return to complete a follow-up survey, and additional participants were recruited to replace those lost to follow-up. At each wave, participants were asked questions about tobacco use (cigarettes, HTPs), tobacco use policies at home, sociodemographic factors, for example, sex, region of residence, education, income and marital status. Additionally, participants were asked questions about the effects of COVID-19 pandemic on their tobacco behaviours at waves 3 and 4.^{19 20}

Table 1. Characteristics of the ITC Japan Surveys participants included in the present analysis.

		Preimplementation				Postimplementation
		Wave 1		Wave 2		Wave 3		Wave 4
		N	%	N	%	N	%	N	%
Sex	Male	3235	70.1	3003	71.1	3000	68.4	2742	64.5
	Female	1380	29.9	1219	28.9	1387	31.6	1512	35.5
Mean age in years (SD, range)		48.4 (13.5, 20–80)		48.6 (12.9, 21–81)		48.3 (12.8, 20–91)		48.9 (12.9, 22–84)
Residential region	Hokkaido	336	7.3	287	6.8	260	5.9	242	5.7
	Tohoku	326	7.1	314	7.4	326	7.4	302	7.1
	Kanto	1661	36.0	1549	36.7	1644	37.5	1668	39.2
	Chubu	645	14.0	594	14.1	623	14.2	593	13.9
	Kansai	883	19.1	790	18.7	865	19.7	846	19.9
	Chugoku	264	5.7	247	5.9	237	5.4	215	5.1
	Shikoku	120	2.6	108	2.6	99	2.3	82	1.9
	Kyushu and Okinawa	380	8.2	333	7.9	333	7.6	306	7.2
Level of education	Up to high school	1646	36.0	1479	35.5	1450	33.5	1397	33.1
	Vocational school, junior college	840	18.4	790	18.9	875	20.2	886	21.0
	Undergraduate, postgraduate	2084	45.6	1901	45.6	2008	46.3	1934	45.9
Income (yen)	4 000 000 or less	1212	26.3	979	23.2	1002	22.8	1077	25.3
	>4 000 000 to 6 000 000	1042	22.6	947	22.4	885	20.2	880	20.7
	>6 000 000	1779	38.5	1813	42.9	1940	44.2	1790	42.1
	Not stated	582	12.6	483	11.4	560	12.8	507	11.9
Marital status	Not married	1879	41.0	1562	37.2	1659	38.1	1691	40.0
	Married	2708	59.0	2634	62.8	2697	61.9	2534	60.0
Tobacco use status	Cigarette-only	3263	70.7	1787	42.3	1836	41.9	1761	41.4
	HTP-only	166	3.6	971	23.0	936	21.3	880	20.7
	Dual cigarettes and HTPs	547	11.9	836	19.8	890	20.3	825	19.4
	No tobacco use	639	13.8	628	14.9	725	16.5	788	18.5

Data are numbers and unweighted %.

HTP, heated tobacco product; ITC, International Tobacco Control; N, sample; SD, standard deviation.

Study participants

An online survey was completed by a total of 4913 participants at wave 1 (W1; February–March 2018), 4500 participants at wave 2 (W2; December 2018–January 2019), 4633 participants at wave 3 (W3; May–June 2020) and 4403 at wave 4 (W4; July–August 2021) (figure 1). At each wave, 3%–6% of the participants were then excluded due to data quality issues. The final sample included 4615 participants at W1, 4222 participants (2738 retained (59%), 1484 newly recruited) at W2, 4387 participants (2714 retained (64%), 1673 newly recruited) at W3 and 4254 participants (2679 retained (61%), 1575 newly recruited) at W4.

Figure 1. Timeline of the ITC Japan Surveys and flow of participant inclusions and exclusions. This figure shows the timeline of surveys and the numbers of participants who were recruited and who returned, those who were excluded due to unreliable responses, and those who were included at each survey wave in the present analysis. The amendment to the Japan Health Promotion Act was adopted in July 2018 and was implemented in April 2020. ITC, International Tobacco Control.

Definition of adults who use or do not use tobacco

In the present study, tobacco use and non-use were defined as follows: (1) ‘smoking,’ adults who currently smoke cigarettes at least weekly and smoked at least 100 cigarettes in their lifetime; (2) ‘HTP use,’ those who currently use HTP at least weekly and (3) ‘no tobacco use,’ those who smoke cigarettes less than weekly or not at all and use HTP less than weekly or not at all, and either never smoked or smoked less than 100 cigarettes in their lifetime or had quit smoking more than 2 years ago.

Outcome indicators

The following measures were used to evaluate the effectiveness of the revised HPA:

1. Observed indoor smoking: Participants who visited a restaurant/café or bar/pub in the last 6 months were asked if they observed people smoking indoors, and indoor workers were asked if they observed people smoking at work in the last 30 days. For the latter, the information was available at W2–W4. The responses were coded as ‘no’ (0) or ‘yes’ (1).

2. Self-reported indoor smoking: Participants who smoke who reported visiting a restaurant/café or bar/pub during the 6 months preceding the survey were asked if they smoked inside and those who worked inside a building were asked if they smoked cigarettes at work in the past 6 months. The responses were coded as ‘no’ (0) or ‘yes’ (1). Information on smoking at home was not available.

3. Observed indoor HTP use: Participants who visited restaurants/cafés or bars/pubs in the past 6 months were asked if they observed anybody using HTPs inside and those who worked indoors were asked if they observed anyone using HTPs in indoor areas at work in the last 30 days. These questions were asked only at W3 and W4. In addition, at each wave, participants were asked if they observed anyone using an HTP in indoor places where smoking is banned in the last 30 days. The responses were coded as ‘no’ (0) or ‘yes’ (1).

4. Self-reported indoor HTP use: Participants who use HTPs were asked if they used HTP in indoor public places including restaurants/cafés, bars/pubs, and workplaces, and homes in the past 30 days. The responses were coded as ‘no’ (0) or ‘yes’ (1). Responses from those who did not report visiting restaurants/cafés or bars/pubs in the past 6 months or those who did not work inside a building were coded as missing.

5. Absence of cigarette smoke-/HTP aerosol-free policies at home: Participants were asked which statement best describes their rules about smoking and HTP use at home: (1) ‘never allowed anywhere indoors’, (2) ‘allowed only in designated indoor areas’, (3) ‘allowed indoors without rules or restrictions’, and (4) ‘not allowed inside your home except under special circumstances’. 2 and 3 were coded as ‘absence of cigarette SF/HTP aerosol-free policy at home’ (1), and 1 and 4 were coded as ‘cigarette SF/HTP aerosol-free home’ (0). This indicator was assessed by tobacco use status ('smoking', 'HTP use' and 'no tobacco use').

Explanatory variables

Policy indicator (0, 1) was generated with 0 indicating preimplementation (W1 and W2) and 1 indicating postimplementation (W3 and W4). A survey wave was also used as an explanatory variable.

Statistical analysis

We obtained frequencies and unweighted percentages to describe the characteristics of the analytical sample at each wave. For each key outcome (eg, observed smoking in restaurants at last visit), we estimated population-averaged prevalence at each of the four waves using generalised estimating equation (GEE) logistic regression models with a wave as a categorical explanatory variable because the time between waves varied. To assess the impact of the revised HPA on each key outcome, we estimated the prevalence of each outcome before (preimplementation) and after the implementation (postimplementation) and estimated ORs and 95% CIs associated with the policy indicator using GEE logistic regression models.

In all GEE logistic regression models, we applied an unstructured correlation matrix to account for potential within-individual correlations and survey weights.²⁰ Sampling weights for each survey wave were computed using a raking procedure and calibrated to target marginal joint population distributions of tobacco use status, sex, age groups, education and geographical regions based on the Japan Society and New Tobacco Internet Survey of the corresponding year,²¹ thus allowing generalisation to the Japanese population. The weights for the total sample were used for estimation of the prevalence of observed smoking/HTP use whereas the weights specific to each stratum of smoking/HTP use were applied in stratified analyses. Data from all four survey waves were pooled, and potential confounders were controlled to ensure comparability between waves. Control variables included age at survey (years), sex (female, male), education (up to high school, high school/vocational school/junior college, undergraduate/postgraduate), income (JPY6 000 000 or less, more than JPY6 000 000), marital status (married, not married), frequency/history of smoking/HTP use (daily, weekly, former and never), geographical region of residence (table 1), and the number of surveys completed (1–4) to account for time-in-sample effect^{20 22 23} (model 1). For the analysis of policy impacts, we ran model 1 and additionally adjusted for wave as a numeric variable to account for any linear secular trend (model 2).

Since the enforcement of the revised HPA coincided with the announcement of emergency state in Japan during the global COVID-19 pandemic, we assessed whether some changes in tobacco use due to the pandemic might have biased our results, by repeating the analysis in only those who use tobacco and reported experiencing no change (no increase or decrease) in their smoking/HTP use due to the pandemic.

All statistical analyses were conducted in STATA V.17. Statistical tests were two sided with an alpha level of 0.05.

Results

Characteristics of the study sample

A total of 9347 Japanese adults aged on average 46.3 years (standard deviaiton, SD=12.8, range: 20–91) at recruitment were included in the analysis. Nearly half (n=4615) of the participants were recruited at W1 and the rest (n=4769) were recruited to replenish the study sample at W2, W3 or W4. The participants completed on average 1.9 (SD=1.1) surveys. A breakdown of the participants by other sociodemographic characteristics and tobacco use status at each wave is presented in table 1.

Smoking in indoor public places

The weighted proportions of adults who observed someone smoking indoors (all groups combined) and those who smoked indoors (‘smoking’) at each wave are shown in figure 2 and online supplemental table 1. The results from model 1 showed that observed smoking decreased significantly after the implementation of the revised HPA in restaurants/cafés (53.0% (pre) to 24.9% (post), p<0.001) and bars/pubs (82.2%–55.5%, p<0.001), but not in workplaces (35.3%–30.1%, p=0.15) (table 2). The proportion of adults who smoke who reported indoor smoking decreased significantly in all three public venues after the implementation (restaurants/cafés, 51.1%–24.0%, p<0.001; bars/pubs, 81.3%–52.3%, p<0.001; workplaces, 71.0%–61.4%, p<0.001). Controlling for a linear secular trend (model 2), all ORs for observed indoor smoking and self-reported indoor smoking were less than 1.0 and the CIs excluded 1.0, except for observed smoking in workplaces (OR 1.15, 95% CI 0.66 to 2.02) and restaurants/cafés (OR 0.68, 95% CI 0.40 to 1.15).

Figure 2. Prevalences of observed and self-reported indoor cigarette smoking and HTP use. (A) Weighted proportion (%) of respondents who observed indoor smoking and of those who smoked indoors in a) restaurants/cafés, b) bars/pubs and c) workplaces. (B) Weighted proportion (%) of respondents who observed indoor heated tobacco products (HTP) use and/or of those who used HTPs in a) restaurants/cafés, b) bars/pubs, c) workplaces, d) cigarette smoke-free indoor places (places where cigarette smoking is banned) and e) homes. Weighted proportions were estimated using GEE logistic regression models adjusted for age, sex, education, residential region, income, marital status, frequency of smoking/HTP use and time-in-sample factor (model 1). The proportions and corresponding 95% CIs are presented in online supplemental table 1. The amendment to the Japan Health Promotion Act was adopted in July 2018 and was implemented in April 2020. HTP, heated tobacco product.

Table 2. The impacts of policy implementation on indoor cigarette smoking and HTP use and tobacco-free home policies.

Indoor tobacco use by facility type
			Model 1	Model 1	Model 2
Outcome indicator	Facility type	Pre/Post	Prevalence, % (95% CI)	OR (95% CI)	OR (95% CI)
Observed indoor cigarette smoking	Restaurants/cafes (n=6550)	Pre	53.0 (49.0 to 57.0)	Ref	Ref
		Post	24.9 (21.3 to 28.6)	0.28 (0.21 to 0.38)**	0.68 (0.40 to 1.15)
	Bars/pubs (n=5382)	Pre	82.2 (78.9 to 85.5)	Ref	Ref
		Post	55.5 (49.4 to 61.6)	0.25 (0.17 to 0.37)**	0.46 (0.22 to 0.96)*
	Workplaces (n=4363)	Pre	35.3 (29.3 to 41.3)	Ref	Ref
		Post	30.1 (26.1 to 34.1)	0.78 (0.56 to 1.09)	1.15 (0.66 to 2.02)
Self-reported indoor cigarette smoking (% among those who smoke)	Restaurants/cafes (n=4229)	Pre	51.1 (49.0 to 53.2)	Ref	Ref
		Post	24.0 (22.1 to 26.0)	0.29 (0.25 to 0.33)**	0.50 (0.35 to 0.71)**
	Bars/pubs (n=3640)	Pre	81.3 (79.6 to 82.9)	Ref	Ref
		Post	52.3 (49.3 to 55.3)	0.24 (0.20 to 0.28)**	0.38 (0.25 to 0.57)**
	Workplaces (n=3546)	Pre	71.0 (68.9 to 73.2)	Ref	Ref
		Post	61.4 (59.0 to 63.9)	0.64 (0.55 to 0.75)**	0.69 (0.50 to 0.95)*
Observed indoor HTP use	Restaurants/cafes (n=3646)	Post	19.6 (16.9 to 22.4)	–	–
	Bars/pubs (n=2604)	Post	53.9 (49.5 to 58.4)	–	–
	Workplaces (n=3319)	Post	36.4 (32.6 to 40.2)	–	–
	Smoke-free places (n=7849)	Pre	26.3 (22.2 to 30.3)	Ref	Ref
		Post	33.3 (29.0 to 37.6)	1.43 (1.00 to 2.03)*	2.50 (1.45 to 4.31)*
Self-reported indoor HTP use (% among those who use HTPs)	Restaurants/cafes (n=2367)	Pre	62.2 (58.4 to 66.0)	Ref	Ref
		Post	29.1 (26.0 to 32.3)	0.23 (0.18 to 0.29)**	0.19 (0.12 to 0.31)**
	Bars/pubs (n=2017)	Pre	84.8 (82.0 to 87.5)	Ref	Ref
		Post	49.9 (45.9 to 53.9)	0.16 (0.12 to 0.21)**	0.12 (0.07 to 0.20)**
	Workplaces (n=2877)	Pre	40.2 (36.5 to 43.9)	Ref	Ref
		Post	35.1 (32.1 to 38.2)	0.80 (0.65 to 0.98)*	0.74 (0.52 to 1.05)
	At home (n=2895)	Pre	75.4 (72.1 to 78.6)	Ref	Ref
		Post	73.0 (70.1 to 75.9)	0.88 (0.69 to 1.12)	0.77 (0.52 to 1.16)
Tobacco-free home policy by tobacco use status
			Model 1	Model 1	Model 2
Outcome indicator	Tobacco use status	Pre/Post	Prevalence (%)	OR (95% CI)	OR (95% CI)
Absence of smoke-free home policy	Cigarette smoking (n=5149)	Pre	66.9 (65.1 to 68.8)	Ref	Ref
		Post	65.9 (64.1 to 67.8)	0.95 (0.83 to 1.09)	1.05 (0.78 to 1.41)
	HTP use (n=2823)	Pre	65.8 (62.2 to 69.3)	Ref	Ref
		Post	62.1 (59.0 to 65.2)	0.84 (0.68 to 1.04)	0.93 (0.66 to 1.31)
	No tobacco use (n=932)	Pre	32.8 (28.3 to 37.2)	Ref	Ref
		Post	21.3 (17.7 to 24.8)	0.54 (0.40 to 0.73)**	0.58 (0.35 to 0.95)*
Absence of HTP-free home policy	Cigarette smoking (n=4837)	Pre	64.0 (62.0 to 66.0)	Ref	Ref
		Post	77.0 (75.3 to 78.7)	1.95 (1.68 to 2.26)**	1.33 (0.96 to 1.84)
	HTP use (n=2812)	Pre	74.7 (71.5 to 77.9)	Ref	Ref
		Post	80.3 (77.8 to 82.7)	1.41 (1.10 to 1.81)*	1.11 (0.74 to 1.64)
	No tobacco use (n=831)	Pre	31.4 (26.9 to 35.8)	Ref	Ref
		Post	42.8 (38.5 to 47.1)	1.67 (1.26 to 2.22)**	1.07 (0.66 to 1.72)

Data are number of participants included in each model, prevalence in %, ORs and respective 95% CIs. Prevalence was estimated using GEE logistic regression models adjusted for age, sex, education, residential region, income, marital status, frequency of smoking or HTP use and time-in-sample factor (model 1). ORs were additionally adjusted for wave (1–4, numeric) (model 2).

For the prevalence of observed cigarette smoking in indoor workplaces at preimplementation, only wave 2 was included in the analysis.

*p< 0.05, **p<0.001.

GEE, generalised estimating equation; HTP, heated tobacco product; n, sample; Post, postimplementation; Pre, preimplementation; Ref, reference.

HTP use in indoor public places and homes

The weighted proportions of adults who observed someone using HTPs indoors (all groups combined) and those who used HTPs indoors (‘HTP use’) at each wave are shown in figure 2 and online supplemental table 1. Observed indoor use of HTPs in key public venues was high at postimplementation, notably in bars/pubs (53.9%) (table 2). Following implementation, the proportion of those who use HTP who reported using HTPs indoor decreased significantly although the proportions were still substantial (model 1: restaurants/cafés, 62.2%–29.1%, p<0.001; bars/pubs, 84.8%–49.9%, p<0.001; workplaces, 40.2%–35.1%, p=0.03). The revised HPA was significantly associated with reduced indoor HTP use in restaurants/cafés (model 2: OR 0.19, 95% CI 0.12 to 0.31) and bars/pubs (model 2: OR 0.12, 95% CI 0.07 to 0.20) whereas no significant association was found for workplaces (model 2: OR 0.74, 95% CI 0.52 to 1.05). Furthermore, observed use of HTP in indoor public places where smoking cigarettes is prohibited increased after the implementation (model 1: 26.3%–33.3%, model 2: OR 2.50, 95% CI 1.45 to 4.31) although some decrease was observed from W3 (36.0%) to W4 (23.8%) (figure 2, online supplemental table 1). In-home settings, the proportion of those who use HTPs who use them indoors was high and did not significantly change between preimplementation and postimplementation (model 1: 75.4%–73.0%, model 2: OR 0.77, 95% CI 0.52 to 1.16).

Absence of SF and HTP aerosol-free policies at home by tobacco use status

The weighted proportions of adults without a cigarette SF or HTP aerosol-free policy at home by tobacco use status (‘smoking’, ‘HTP use’ and ‘no tobacco use’) at each wave are shown in figure 3 and online supplemental table 2. In the group of adults who smoke and those who use HTPs, the proportion of those who did not have a cigarette SF policy at home did not change significantly (model 1: smoking, 66.9%–65.9%, p=0.47; HTP use, 65.8%–62.1%, p=0.11). However, the proportion decreased significantly in those who did not use any tobacco products after the implementation, meaning that more homes were SF after the implementation (32.8%–21.3%, p<0.001) (table 2). The association remained statistically significant after adjusting for wave (model 2: OR 0.58, 95% CI 0.35 to 0.95). The proportion of adults who did not have an HTP aerosol-free policy at home increased for all groups (model 1: ‘smoking’, 64.0%–77.0%, p<0.001, ‘HTP use’: 74.7%–80.3%, p=0.007, ‘no tobacco use’: 31.4%–42.8%, p<0.001). The implementation of the policy was associated with a suggestive increase in homes without HTP aerosol-free policies in those who smoke although the CI included the null (model 2: OR 1.33, 95% CI 0.96 to 1.84).

Figure 3. Weighted proportion of participants without a cigarette smoke-free (left) or HTP aerosol-free (right) policy at home by tobacco use status. Weighted proportion (%) by tobacco use status (‘smoking’, ‘HTP use’, ‘no tobacco use’) was estimated using GEE logistic regression models adjusted for age, sex, education, residential region and time-in-sample factor (model 1). Those who reported both cigarette smoking and HTP use ('dual') were included in both ‘smoking’ and ‘HTP use’ groups. The proportions and corresponding 95% confidence intervals are presented in online supplemental table 2. The amendment to the Japan Health Promotion Act was adopted in July 2018 and was implemented in April 2020. HTP, heated tobacco product.

Sensitivity analysis

When the study sample was restricted to those who smoke or use HTPs with no change in their habits of smoking/HTP use due to the COVID-19 pandemic, the associations between the implementation of the revised HPA and indoor smoking or use of HTPs were largely consistent with those from the primary analysis (online supplemental table 3).

Discussion

To our knowledge, this is the first study assessing the longitudinal impact of the revised HPA implemented in Japan. According to the results of the ITC Japan Survey, enhanced, but non-comprehensive SF regulations only partially reduced indoor tobacco use in public places, and indoor tobacco use remained common in public places and homes. It also showed that the revised HPA may have been counterproductive for HTP use in SF places and HTP aerosol-free home policies.

While smoking and HTP use in indoor food and beverage establishments decreased following the implementation of the revised HPA is encouraging, both remained quite high, particularly in bars/pubs. This is in contrast with the impacts of comprehensive SF regulations found in other countries. For example, the 2004 SF law in Ireland, the first country to have implemented a comprehensive law, with few exemptions and strong enforcement, led to more dramatic reductions in smoking in restaurants (85%–3%) and bars/pubs (97%–5%).¹⁷ The weaker impacts of Japan’s partial regulations are likely attributable to the substantial exemptions given to smaller food and beverage establishments and allowance of designated smoking/HTP use rooms in larger food and beverage establishments even though such a room has been shown to be ineffective in preventing exposure to SHS.²⁴ Another factor that may have contributed to the limited effectiveness is non-compliance, which warrants further investigation.

Our findings suggest that the revised HPA was not effective in reducing observed smoking in workplaces. The ineffectiveness in workplaces may be attributable to employers not being fully aware of or compliant with the revised HPA’s application to workplaces. The present study also indicates that the implementation of the revised HPA may have contributed to a rise in HTP use in indoor public places where smoking is banned. This increase could be attributed to the increased availability of HTP-designated areas in indoor public places and the risen popularity of HTPs. Such an increase in indoor HTP use might also reflect potential confusion about the revised regulations²⁵ which, in principle, ban both smoking and HTP use in indoor public places.

HTP use inside homes was also common among tobacco users. While SF legislation has facilitated SF environments in the homes of those who smoke in some countries,^{17 26 27} in Japan, the majority of people who use tobacco did not have bans on smoking or HTP use in homes even after the implementation of the revised HPA. The marginally significant increase in the proportion of people who smoke without HTP-free home policy may be the result of fewer places for smoking/HTP use or more people working from home during the COVID-19 pandemic. It is possible that some people have switched from smoking to using HTPs in their homes since HTP aerosols contain lower levels of potential carcinogens and toxic chemicals than cigarette smoke although some toxicants, which are found in minuscule quantities, are exceeding the levels for cigarette smoke.13,16 This may have reduced exposure to harmful or potentially harmful chemicals in homes, but emerging evidence indicates respiratory^{28 29} and cardiovascular health³⁰ risks associated with HTP use.³¹ Therefore, it would be prudent to exercise caution when allowing HTP usage in homes especially when vulnerable people are present, such as pregnant women and children.^{32 33}

SF policies in Japan have been historically challenging due to persistent tobacco industry interference³⁴ and the instilled concept of ‘smoking manners,’ which has maintained the social acceptability of smoking.³⁵ Considering these challenges, the revised HPA represents a significant advance; however, the revised HPA includes several substantial exemptions and the long-standing problem of exposure to SHS continues. Furthermore, the revised HPA treats HTPs differently, stating that food and drinks can be served in an HTP-designated room but not in a smoking-designated room (where HTP use is also allowed).¹² Such a distinction might have enhanced the social acceptability of HTP use and led to voluntary SF rules banning only smoking. To the extent that secondhand HTP aerosol is less toxic than secondhand cigarette smoke, this may potentially represent a reduction in hazard. Nevertheless, since HTP aerosols contain carcinogens and other toxic chemicals, though at lower levels than cigarettes,13,16 governments should consider regulating HTP use in accordance with the scientific evidence regarding the harmfulness of HTP aerosols. Currently, the WHO FCTC does not distinguish between HTPs and cigarettes since both are tobacco products, thus, Parties are called on to regulate HTPs as they do cigarettes.

The following limitations should be considered when interpreting our results. The secondhand exposure was assessed using observation of smoking or HTP use. This information does not allow us to determine whether the participants observed someone smoking or using HTPs in the same room or in a separate smoking area/room inside the same establishment. Due to the fact that a separate smoking area/room does not always prevent SHS from leaking into adjacent areas,²⁴ our study’s results should not be construed as an overestimation of secondhand exposure. Furthermore, misclassification of observed indoor smoking or HTP use may be possible if participants mistook one for the other, despite being informed throughout the survey of the distinction between cigarettes and HTPs. Since the proportions were estimated among those who visited restaurants/bars within the 6 months preceding the survey, participants at W3 might have reported indoor smoking/HTP use before the implementation of the revised HPA. It is also true that some restaurants became SF before the revised HPA was fully enforced in 2020. Thus, by comparing before and after April 2020, we could have underestimated the impacts of the revised HPA. Along the same lines, adjusting for a survey wave to control for a potential secular time trend might have led to an underestimation of the effects. Finally, taking into account the timing of the revised HPA, which coincided with the declaration of an emergency state due to the COVID-19 pandemic in Japan, it is prudent to consider the possibility of confounding. While Japan did not have a strict lockdown, people may have reduced their drinking and dining on site. In addition, the changes we observed might also be partly attributed to certain psychosocial or behavioural changes following the COVID-19 pandemic, for example, more teleworking, fewer social gatherings.

Consequently, the enhanced indoor SF regulations stipulated in Japan’s revised HPA have shown some effectiveness, but only in a limited manner, and may even have had counterproductive effects regarding HTP use in SF places and HTP-free homes. These results are likely due to the presence of substantial exemptions and the special treatment of HTP within the revised HPA. Comprehensive SF laws without exemptions and strong enforcement like in Ireland and other countries could lead to substantial public health gains by protecting people from exposure to cigarette smoke and HTP aerosols in Japan.

Where authors are identified as personnel of the International Agency for Research on Cancer/ WHO, the authors alone are responsible for the views expressed in this article and they do not necessarily represent the decisions, policy or views of the International Agency for Research on Cancer/ WHO. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Data availability statement

Data are available on reasonable request.