Tobacco and Nicotine Use Among US Adult “Never Smokers” in Wave 4 (2016–2018) of the Population Assessment of Tobacco and Health Study

Abstract

Introduction

A common criterion for being labeled a “never smoker” is having smoked <100 lifetime cigarettes. This category is often used as an unexposed reference group to estimate the relative harm from cigarettes. We examined the amount of current and past cigarette and non-cigarette tobacco/nicotine use among adults who met this “never smoker” criterion.

Methods

We analyzed cross-sectional data from 17 179 adult “never smokers” (ie, reported <100 lifetime cigarettes) in Wave 4 (2016–2018) of the Population Assessment of Tobacco and Health (PATH) Study, a United States nationally representative sample. We used PATH-derived variables to describe “never smokers’” demographics as well as cigarette and non-cigarette tobacco/nicotine use.

Results

Approximately half of “never smokers” were young adults (49.3%). Most were white (68.6%) with some college or more (64.4%). Most “never smokers” had tried any cigarette or non-cigarette tobacco/nicotine in their lifetime (66.7%), 8.5% smoked cigarettes in the past 30 days, and 5.3% were current experimental (ie, some days or every day) cigarette smokers. By definition, “never smokers” reported smoking <100 lifetime cigarettes. One fifth (22.8%) had a lifetime history of established regular non-cigarette tobacco/nicotine use and 8.6% were current established regular non-cigarette tobacco/nicotine users. In total, 9.4% of “never smokers” were current experimental or established regular users of combustible tobacco.

Conclusions

The 100-cigarette lifetime threshold includes substantial amounts of current and past tobacco use and thus does not represent lack of exposure to cigarette or non-cigarette tobacco. “Never smoker” reference groups may produce underestimates of the relative harms from cigarettes.

Implications

The <100 lifetime cigarettes criterion may not capture what many would consider true “never smokers.” Relying on the current definition of “never smokers” as a reference group will include a substantial number of those currently and recently using combustible tobacco and thus produce data that may underestimate the relative harm from cigarettes. Prospective longitudinal research is needed to compare how the 100-cigarette lifetime threshold versus other definitions of regular cigarette smoking differ in predictive validity of clinically meaningful outcomes and health harms to determine the optimal criteria to define established cigarette smoking.

Introduction

With over 480 000 smoking related deaths per year, cigarette smoking remains the leading preventable cause of death in the United States.^1,2 A common criterion for status as an ever versus never cigarette smoker is self-reported lifetime consumption of more versus less than 100 cigarettes.³ While this cutoff is not empirically-based,³ the 100-cigarette threshold definition has been used in multiple national surveys,^4–9 is recommended by the World Health Organization,¹⁰ reported in the Surgeon General’s report¹ and often is the sole criterion for “never” (<100) versus “ever” (≥100) cigarette smokers. Importantly, the <100 lifetime cigarettes criterion is commonly used to define a reference category of “never smokers” in studies estimating the health effects of cigarettes.^1,11,12 However, little is known regarding the amount of cigarette or non-cigarette tobacco use among adults who report <100 lifetime cigarettes (ie, “never smokers.”)¹³

Prior research has identified some cigarette smoking among “never smokers.” For example, one analysis of 2008 US adults found use of the ≥100 lifetime cigarettes criterion decreased the national prevalence estimate of past 30-day cigarette smokers by 1.9%.⁹ Another analysis of PATH Wave 1 data (2013–2014) identified approximately 3% of adult respondents as “non-regular” current cigarette smokers who reported smoking fewer than 100 cigarettes in their lifetime.¹⁴ Similarly, use of the ≥100 lifetime cigarettes criterion decreased prevalence estimates of “current smokers” in a Canadian national sample of youth and adults between 1999 and 2006 by approximately 1%–3% in comparison to “past 30-day” and “daily or occasional” definitions of current smoking.³ These studies identified current or recent cigarette smoking among adults with <100 lifetime cigarettes^3,9,14 but did not describe the characteristics of “never smokers,” nor address non-cigarette tobacco use among these adults who report <100 lifetime cigarettes.

Tobacco use in the U.S. is changing:^15,16 regular cigarette smoking continues to decrease,^1,17 intermittent smoking has increased,^18,19 the use of e-cigarettes has increased dramatically,²⁰ and the use of some other tobacco products have remained relatively stable.^1,17,21–24 Changes in tobacco use are further complicated by the fact that polytobacco use is common both among cigarette smokers (40%) and users of non-cigarette tobacco (52%–86%).²¹ Though use of non-cigarette tobacco products is common^17,22–24 and harmful,¹² the prevalence of non-cigarette tobacco use among adults who report <100 lifetime cigarettes is unknown.¹³ Cigarette or non-cigarette tobacco use among adults who report <100 lifetime cigarettes challenges the assumption that “never smokers” are unexposed to tobacco-related harm and, importantly, could falsely decrease estimates of relative harm from cigarette smoking. Thus, more information is needed on tobacco use among “never smokers.” We used recent data from Wave 4 of the Population Assessment of Tobacco and Health (PATH) Study to describe demographic characteristics, cigarette smoking, and non-cigarette tobacco use among US adults who reported smoking <100 cigarettes in their lifetime (ie, “never smokers”). We do not test the validity of the 100 lifetime cigarettes threshold in comparison to other definitions of regular cigarette smoking.

Methodology

Data are from the public use files from Wave 4 of the PATH survey of US non-institutionalized adults, collected between December 1, 2016 and January 3, 2018.^4,25 The PATH Study was approved by the Westat Institutional review board and collected US nationally representative data using audio-computer assisted self-interviews (ACASI) in English or Spanish.^4,25 We used cross-sectional data from the 33 822 adult (aged ≥18 years) Wave 4 respondents. Information on the PATH Study design, recruitment, and methodology are available elsewhere.^4,26 We used PATH Study-derived variables and terminology to maintain consistency with prior publications that report findings from the PATH Study. Table 1 includes the PATH Study-derived definitions of the tobacco use categories used in this analysis. Readers should refer to Table 1 to ensure correct interpretation of PATH Study definitions.

Table 1.

Definitions of Tobacco and Nicotine Use Categories Within the Population Assessment of Tobacco and Health (PATH) Study

Tobacco and nicotine use categories	PATH Study Definition
Ever tried	“Respondents who have ever used [the tobacco product]… even one or two times.”
Used in past 30 days	“Respondents who have used [the tobacco product] within the past 30 days.”
Current experimental use	Respondents who endorsed use in past 30-days and “have never used [the tobacco product] fairly regularly, and currently use every day or some days.”
Current experimental every day use	Respondents who endorsed current experimental use, denied established regular use and reported using every day in the past 30 days.b
Ever established regular use a	“Respondents who have ever used [the tobacco product] fairly regularly.”
Former established regular use a	“Respondents who have ever used [the tobacco product] fairly regularly, have not used them within the past 12 months or currently use not at all.”
Current established regular use a	“Respondents who have ever used [the tobacco product], have ever used [the product] fairly regularly, and currently use every day or some days.”
Current established every day use a	“Respondents who have ever used [the tobacco product], have ever used [the product] fairly regularly, and currently use every day.”

^aReported for non-cigarette tobacco or nicotine use only because we use a sample of “never regular smokers” (<100 lifetime cigarettes) for this analysis. ^bFor example, someone who smoked cigarettes every day for the past 30 days but reported <100 lifetime cigarettes was defined as a current experimental every day user by the PATH Study. PATH = Population Assessment of Tobacco and Health.

We identified 17 179 respondents who reported smoking <100 cigarettes in their lifetime (ie, “never smokers”). Our first goal was to report demographic characteristics (Table 2) among “never smokers.” Our second goal was to describe the prevalence of current and past use of several tobacco and nicotine products among “never smokers” (Table 3). The overarching aim of this paper was to describe “never smokers” and thus we do not make statistical comparisons between sub-groups of “never smokers.”

Table 2.

“Never” and “Ever” Cigarette Smoker Demographics Within the Population Assessment of Tobacco and Health (PATH) Study

	Never regular cigarette smokers N = 17 179 (51.5%, 95% CI = 50.7 to 52.3)		Ever regular cigarette smokers N = 16 062 (48.5%, 95% CI = 47.7 to 49.3)
	Raw n	Weighted % (95% CI)	Raw n	Weighted % (95% CI)
Sex: Female	9116	53.1 (51.9 to 54.4)	7737	47.7 (46.4 to 48.9)
Age:
18–24 years old	8545	49.3 (48.2 to 50.4)	2410	15.1 (14.1 to 16.1)
25–34 years old	3119	18.2 (17.4 to 19.0)	3692	22.7 (21.6 to 23.8)
35–44 years old	1627	9.5 (8.8 to 10.2)	2812	18.0 (17.0 to 19.1)
45–54 years old	1488	9.1 (8.5 to 9.7)	2627	16.2 (15.3 to 17.1)
55–64 years old	1237	6.9 (6.4 to 7.5)	2590	16.2 (15.3 to 17.2)
≥65 years old	1160	7.0 (6.3 to 7.7)	1930	11.8 (11.1 to 12.6)
Marital Status:
Married	5446	31.8 (30.7 to 32.8)	6339	40.4 (39.1 to 41.7)
Widowed, divorced, separated	1615	9.6 (8.9 to 10.5)	4112	25.0 (23.9 to 26.2)
Never married	10 047	58.1 (57.0 to 59.2)	5539	34.0 (32.6 to 35.5)
Education:
<High school	1825	9.9 (9.3 to 10.6)	2334	15.0 (14.2 to 15.8)
GED	541	2.9 (2.6 to 3.4)	1550	9.0 (8.3 to 9.6)
High school graduate	4287	24.6 (23.6 to 25.7)	3675	22.4 (21.4 to 23.5)
Some college or Associates degree	6107	36.4 (35.3 to 37.6)	5684	35.8 (34.7 to 36.9)
Bachelor's or advanced degree	4357	25.8 (24.6 to 27.0)	2743	17.3 (16.4 to 18.3)
Sexual Orientation: LGBTQ	1462	8.4 (7.7 to 9.1)	1434	8.9 (8.2 to 9.7)
Ethnicity:
Hispanic	4271	25.1 (24.0 to 26.1)	2259	14.2 (13.3 to 15.2)
Not Hispanic	12 908	75.0 (73.9 to 76.0)	13 803	85.8 (84.8 to 86.7)
Race:
White alone	11 687	68.6 (67.5 to 69.7)	12 295	77.1 (76.2 to 78.1)
Black alone	3251	18.5 (17.6 to 19.4)	2208	13.1 (12.4 to 13.8)
Other	2241	12.9 (12.3 to 13.6)	1559	9.8 (9.0 to 10.6)
Employment:
Full-time ≥35 hours per week	7593	44.1 (43.1 to 45.2)	7747	47.7 (46.5 to 49.0)
Part-time 15 to 34 hours per week	3007	17.7 (16.7 to 18.6)	1673	10.3 (9.6 to 11.0)
Part-time <15 hours per week	1221	7.1 (6.5 to 7.8)	696	4.6 (4.1 to 5.3)
Don’t currently work for pay	5261	30.6 (29.7 to 31.6)	5846	36.7 (35.6 to 37.8)

Never cigarette smoker = Smoked <100 cigarettes in lifetime; Ever cigarette smoker = Smoked ≥100 cigarettes in lifetime; CI = Confidence interval; GED = General education diploma; LGBTQ = Lesbian, gay, bisexual, transgender, or queer.

Table 3.

Tobacco and Nicotine Use Among “Never Smokers” (N = 17 179) Within the Population Assessment of Tobacco and Health (PATH) Study

	aAny tobacco/nicotine	bAny combustible tobacco	Cigarettes	e-Cigarettes	Cigars	Hookah	Pipes	Smokeless	Snus
Ever tried
Raw n	11 233	10 500	7996	5324	6151	5378	1464	1844	837
Weighted %	66.7	62.4	46.3	31.1	36.1	31.7	8.7	10.7	5.0
(95% CI)	(65.7, 67.8)	(61.3 to 63.5)	(45.1 to 47.5)	(30.0 to 32.1)	(34.8 to 37.4)	(30.7 to 32.8)	(8.0 to 9.5)	(10.0 to 11.5)	(4.4 to 5.6)
Used in past 30 days
Raw n	3861	2921	1545	1296	1578	648	153	601	207
Weighted %	22.0	16.6	8.5	7.4	8.9	3.8	0.9	3.3	1.2
(95% CI)	(20.1 to 23.1)	(15.6 to 17.6)	(7.7 to 9.3)	(6.8 to 8.1)	(8.3 to 9.7)	(3.5 to 4.3)	(0.6 to 1.2)	(2.9 to 3.8)	(1.0 to 1.4)
c Current experimental use (ie, every day use or some day use but never regular use)
Raw n	1067	923	971	312	463	225	58	62	53
Weighted %	5.7	4.9	5.3	1.9	2.4	1.3	0.4	0.4	0.3
(95% CI)	(5.2 to 6.3)	(4.4 to 5.4)	(4.7 to 5.9)	(1.6 to 2.3)	(2.1 to 2.9)	(1.0 to 1.6)	(0.2 to 0.6)	(0.3 to 0.6)	(0.2 to 0.5)
Ever established regular use
Raw n	3053	1997	e	940	1211	883	265	747	235
Weighted %	22.8	15.0	e	5.3	7.1	5.3	1.6	4.4	1.6
(95% CI)	(21.7 to 23.9)	(14.1 to 15.9)		(4.8 to 5.8)	(6.6 to 7.8)	(4.9 to 5.8)	(1.3 to 1.9)	(3.9 to 4.9)	(1.33 to 2.0)
d Former established regular use
Raw n	1467	1140	e	518	590	607	194	268	127
Weighted %	11.0	8.5	e	3.0	3.4	3.7	1.2	1.6	0.9
(95% CI)	(10.2 to 11.9)	(7.8 to 9.2)		(2.6 to 3.4)	(3.0 to 3.8)	(3.3 to 4.1)	(1.0 to 1.5)	(1.3 to 2.0)	(0.7 to 1.3)
Current established regular use
Raw n	1478	737	e	391	499	252	60	471	100
Weighted %	8.6	4.5	e	2.1	3.1	1.6	0.3	2.7	0.6
(95% CI)	(7.9 to 9.4)	(4.0 to 5.1)		(1.8 to 2.5)	(2.7 to 3.5)	(1.3 to 1.9)	(0.2 to 0.5)	(2.3 to 3.1)	(0.4 to 0.8)
Current established every day use
Raw n	586	104	e	146	89	15	13	336	49
Weighted %	3.3	0.6	e	0.8	0.5	f	f	1.9	0.3
(95% CI)	(2.9 to 3.8)	(0.5 to 0.8)		(0.7 to 1.0)	(0.4 to 0.7)			(1.6 to 2.2)	(0.2 to 0.4)

Regular use = endorsed smoking/using “fairly regularly.” Categories are not mutually exclusive (see Figure 1 and Supplementary Figure 1). See Supplementary Table 2 for tobacco use among adults who reported ≥100 cigarettes in their lifetime (ie, “ever” cigarette smokers). The terms used in this table represent PATH Study-derived variables and are defined in Table 1.

^aAny tobacco/nicotine includes use of cigarette and non-cigarette tobacco products and e-cigarettes for the Ever tried, Used in past 30 days, and Current experimental use categories but only includes use of non-cigarette tobacco products and e-cigarettes for the Ever established regular use, Former established regular use, Current established regular use, and Current established every day use categories.

^bAny combustible tobacco includes use of cigarettes, cigars, pipes, and hookah for the Ever tried, Used in past 30 days, and Current experimental use categories but only includes use of cigars, pipes, and hookah for the Ever established regular use, Former established regular use, Current established regular use, and Current established every day use categories.

^c Current experimental use refers to every day or some day use the past 30 days and excludes tobacco or nicotine users who were Ever established regular users. In the Any tobacco/nicotine and Any combustible tobacco categories, respondents who were an Ever established regular user of one tobacco product and a Current experimental user of another product were included as Established regular users and excluded from the Current experimental Any tobacco/nicotine and Any combustible tobacco use categories. Thus, there are fewer current Experimental Any combustible tobacco smokers than Cigarette smokers because some Cigarette smokers were also Established regular users of another combustible tobacco product and so were classified as Ever established regular users within the Any combustible tobacco column.

^dNote that Former established regular use in the Any tobacco/nicotine category excludes respondents who are former regular users of one product and current users of a different tobacco product. Respondents who are former regular users of one product and current users of a different tobacco product are categorized as Current established regular users of any tobacco/nicotine.

^eExcluded because this analysis is limited to never established regular cigarette smokers (<100 lifetime cigarettes).

^fOmitted due to small sample size. Estimates were considered statistically unreliable and thus findings were omitted when the denominator was less than 50 or the relative standard error (RSE) was greater than 30%.²⁷

“Never smoker” = Reported smoking <100 cigarettes in lifetime.

Respondents who reported <100 lifetime cigarettes were asked about their current and past cigarette and non-cigarette tobacco or nicotine product use. Tobacco or nicotine product use was not mutually exclusive and included cigarettes, e-cigarettes, cigars, hookah, pipes, smokeless tobacco, and snus. Of note, the PATH Study labels electronic products as electronic cigarettes or electronic nicotine products. We refer to this category of products collectively as e-cigarettes in this paper for brevity.

The categories of tobacco or nicotine use (Table 1) are nested such that all respondents who endorsed any tobacco or nicotine use category are included in the Ever tried category. There is then a distinction between former and current users. The Used in past 30 days category includes two mutually exclusive categories: Current experimental use (ie, some day or every day use, but not meeting a threshold of established use) and Current established regular use (ie, some day or every day use, and having met a threshold of established use). The Current established regular use category includes respondents with Current established every day use. The Ever established regular use category is also comprised of two mutually-exclusive groups: those with Former and Current established regular use.

In addition to reporting tobacco use status separately by tobacco product, we created aggregate variables for any tobacco/nicotine and any combustible tobacco. The any tobacco/nicotine variable includes reported use of one or more of the tobacco or nicotine products (including e-cigarettes) assessed in PATH. The any combustible tobacco variable includes reported use of one or more of the following products: cigarettes, cigars, pipes, or hookah. In deriving the any tobacco/nicotine and any combustible tobacco variables, there were some circumstances in which respondents met criteria for multiple conflicting tobacco use categories. We categorized such respondents based on the most established or currently established tobacco product. For example, respondents who were both Current experimental users of one product and Ever established regular users of another product were categorized as Ever established regular users of any tobacco/nicotine product. Similarly, we categorized respondents who were both Current established regular users of one product and Former established regular users of another product as Current established regular users of any tobacco/nicotine.

We report the weighted proportion of “never smokers” separately by tobacco use status and tobacco product used with the total number of “never smokers” (N = 17 179) as the denominator (Table 3). For comparison, we also report the weighted proportion of “ever smokers” separately by tobacco use status and tobacco product used with the total number of “ever smokers” (N = 16 062) as the denominator (Supplementary Table 2). Respondents who reported past 30-day or experimental cigarette smoking were asked “On average, on those [days you smoked], how many cigarettes did you usually smoke each day?” We used responses to this question to calculate mean cigarettes per day on the days smoked for the “never smokers” who reported past 30-day or experimental cigarette smoking. In the Figure 1 and Supplementary Figure 1 we illustrate the nested structure of the tobacco use categories by reporting the proportion of each category using the superseding category as the denominator (eg, a cascade approach). Importantly, data for this analysis are cross-sectional and thus do not represent within-participant changes in tobacco use. In line with suppression guidelines for other national datasets, estimates were considered statistically unreliable and thus findings were omitted when the denominator was less than 50 or the relative standard error (RSE) was greater than 30%.²⁷ We conducted all analyses using Stata/Special Edition version 16.0 (StatCorp LP, College Station, TX) using SVY procedures to account for PATH sampling weights. We estimated variance using balanced repeated replication (BRR) with Fay's adjustment set to 0.3. Missing data were handled with listwise deletion per Stata's procedures.

Figure 1.

Any tobacco/nicotine product, any combustible tobacco product, and cigarette use categories among “never cigarette smokers” (ie, adults who report <100 lifetime cigarettes; N = 17 179) within the Population Assessment of Tobacco and Health (PATH) Study. ^aAny tobacco/nicotine includes use of cigarette and non-cigarette tobacco products and e-cigarettes for the Ever tried, Used in past 30 days, and Current experimental use categories but only includes use of non-cigarette tobacco products and e-cigarettes for the, Current established use categories. ^bAny combustible tobacco includes use of cigarettes, cigars, pipes, and hookah for the Ever tried, Used in past 30 days, and Current experimental use categories but only includes use of cigars, pipes, and hookah for the, Current established use categories. All denominators for weighted percentages (95% confidence intervals) are from the preceding category. Weighted percentages using the overall sample of “never smokers” (N = 17 179) as the denominator are displayed in Table 3. The terms used in this figure represent PATH Study-derived variables and are defined in Table 1. Data were collected cross-sectionally and do not represent within-participant change.

Results

Demographic Characteristics

Approximately half (51.5%, 95% CI = 50.7% to 52.3%) of PATH Wave 4 respondents reported smoking <100 cigarettes in their lifetime (raw N = 17 179; “never smokers”). Approximately half of “never smokers” were young adults (aged 18–24 years) and female. Most were white, non-Hispanic, never married (Table 2), and had some college education or more (64.4%, 95% CI = 61.3% to 63.5%). “Never smokers” differed from “ever smokers” on a number of sociodemographic variables. Most notably, there were substantially more young adult “never smokers” than young adult “ever smokers.”

Ever Tried, Past 30-Day Use, and Experimental Use

Most “never smokers” had tried any tobacco or nicotine product (cigarettes, non-cigarette tobacco, or e-cigarettes) in their lifetime (66.7%, 95% CI = 65.7% to 67.8%), the majority of which included one or more combustible tobacco products (cigarettes, cigars, pipe, or hookah; Table 3). Over 20% of “never smokers” had used any tobacco/nicotine product in the past 30 days and 16.6% (95% CI = 15.6% to 17.6%) had smoked a combustible tobacco product in the past 30 days. The most common products used in the past 30 days were cigars, cigarettes, and e-cigarettes. Those with past 30-day cigarette smoking reported a mean of 3.4 (95% CI = 2.9 to 3.8) cigarettes per day on the days they smoked. When stratified by age, more young adults (18–24 years of age; 5.1% [95% CI = 4.5% to 5.7%]) than older adults (25 years or older; 3.4% [95% CI = 3.0% to 3.9%]) reported past 30-day cigarette smoking (Supplementary Table 3).

Over 5% of “never smokers” were current experimental users of any tobacco/nicotine product. Most of the current experimental use was accounted for by cigarette smoking (5.3%, 95% CI = 5.7% to 5.9%), followed by cigars and e-cigarettes. Experimental cigarette smokers reported a mean of 4.2 (95% CI = 3.6 to 4.8) cigarettes per day on the days they smoked during the past 30 days. When stratified by age, the prevalence of experimental cigarette smoking was similar between young adults (2.7% [95% CI = 2.4% to 3.2%]) and older adults (2.6% [95% CI = 2.2% to 3.0%]; Supplementary Table 3). Almost all of the current experimental tobacco users were some day users. For example, when experimental use across all tobacco products was combined, only 0.4% (95% CI = 0.3% to 0.7%) were current experimental every day users of any cigarette or non-cigarette tobacco product. We do not report findings for experimental every day users of individual tobacco products due to large RSEs resulting from small sample sizes.

Ever, Former, and Current Established Regular Use

Findings are limited to non-cigarette tobacco and e-cigarettes when reporting established regular use among “never smokers” because the PATH Study uses the ≥100 lifetime cigarettes criterion to define established regular cigarette smoking. Over 20% of “never smokers” reported ever established regular use of any non-cigarette tobacco/nicotine product, and most established regular use included combustible tobacco (Table 3). Cigars followed by e-cigarettes, hookah, and smokeless tobacco were the most common ever regularly used non-cigarette tobacco/nicotine products. The same products were among the most common for former regular tobacco/nicotine use. Of note, 8.6% (95% CI = 7.9% to 9.4%) of “never smokers” were current established regular users of any non-cigarette tobacco/nicotine product, with the most common being e-cigarettes followed by cigars and smokeless tobacco. When limited to combustible tobacco (ie, cigars, pipe, or hookah), 4.5% (95% CI = 4.0% to 5.1%) were current established regular users. In order to further explore current combustible tobacco use, we combined current regular established use with current experimental use and identified 9.4% (95% CI = 8.7% to 10.2%) of “never smokers” were current users of combustible tobacco. Finally, 3.3% (95% CI = 2.9% to 3.8%) were current daily regular users of any non-cigarette tobacco/nicotine product, with smokeless tobacco accounting for most of the established every day tobacco use. Overall, there was substantially more tobacco/nicotine use among “ever smokers” (Supplementary Table 2) than “never smokers” (Table 3).

Cascade of Tobacco Use Among “Never Smokers”

The Figure 1 reports cross-sectional data and illustrates the proportion of tobacco use following from the superseding category of tobacco use (eg, a cascade approach). Among “never smokers” who tried any cigarette or non-cigarette tobacco/nicotine product in their lifetime (Figure 1A), over one third had used any tobacco/nicotine in the past 30 days. Of those with past 30-day use of any tobacco/nicotine, over a quarter used any tobacco/nicotine experimentally (every day or some days) and over 35% were established regular users. Among experimental users of any tobacco/nicotine, fewer than 10% used daily. Among current established regular users of any tobacco/nicotine, nearly 40% used daily.

Among “never smokers” who tried any combustible tobacco (cigarettes, cigars, pipe, or hookah) in their lifetime (Figure 1B), over one quarter had smoked combustible tobacco in the past 30 days. Of those with past 30-day combustible tobacco use, over a quarter smoked combustible tobacco experimentally (every day or some days) and over 20% were established regular combustible tobacco smokers. Among those who smoked combustible tobacco experimentally, fewer than 10% smoked combustible tobacco daily. Among current established regular combustible tobacco smokers, over 10% smoked combustible tobacco daily.

Among “never smokers” who tried cigarettes in their lifetime (Figure 1C), over 18% smoked cigarettes in the past 30 days. Of those who smoked cigarettes in the past 30-days, nearly two thirds were current experimental (ie, some day or every day) cigarette smokers. Though less prevalent, there were similar patterns within non-cigarette tobacco/nicotine products among “never smokers” (Supplementary Figure 1).

Discussion

Our findings identify substantial current and past cigarette and non-cigarette tobacco use among US adults classified as “never smokers” using the standard definition in the field. Most notably, over 20% used any tobacco/nicotine product in the past 30 days. Our estimates suggest that over 6.5 million adult “never smokers” are current some days or every day cigarette smokers. Further, over 10.6 million “never smokers” are current regular users of non-cigarette tobacco or nicotine products, with approximately 3.7 million cigar smokers, 3.3 million smokeless tobacco users, and 2.6 million e-cigarette users (Supplementary Table 1). These findings are noteworthy for three reasons: first, tobacco use among “never smokers” could reduce estimates of the relative health harms from cigarettes among “ever smokers.” Second, the “never smokers” with recent or experimental tobacco use identified in this analysis may be at increased risk of harm given that exposure to tobacco increases the risk of future established regular use of combustible tobacco and nicotine dependence.^28,29 Third, our findings build on existing literature^3,9,14 that challenge the assumption that adults who report <100 lifetime cigarettes are “never smokers.”

Prior research has identified substantial health harms from even small amounts of chronic intermittent or regular use of combustible tobacco.^11,12,30 Our findings demonstrate that a substantial number of adult “never smokers” are regular combustible tobacco users, which suggests tobacco-related harm could be occurring among some “never smokers.” Importantly, studies on the health harms of cigarettes commonly rely on this category of “never smokers” as the “unexposed” reference group for all estimates of relative risk^1,11,12 and thus may have consistently underestimated the harm from cigarette smoking. This issue could also affect analysis of the PATH Study's biomarker data. For example, tobacco use among “never smokers” could result in lower relative estimates of biomarker concentrations when “never smokers” are used as an “unexposed” comparison group. We know of no empirical tests of these possibilities. Future research is needed to compare biomarkers and estimates of health harm from cigarettes with versus without the <100 lifetime cigarette criterion to define “never smokers” as a reference group.

Our study builds on prior analyses of Canadian³ and US^9,14 datasets which demonstrate that use of the 100 lifetime cigarette criterion reduces estimates of current cigarette smoking by approximately 1%–3%. Our finding that most experimental cigarette smokers who report <100 lifetime cigarettes smoke intermittently (ie, non-daily) is consistent with prior research.⁹ Importantly, intermittent cigarette smokers suffer substantial smoking-related mortality,^11,30 and for many, but not all,³¹ intermittent smoking is persistent³² or progresses to regular smoking³³ rather than return to non-smoking.

We found nearly half of US adult “never smokers” are young adults (ie, 18–24 years old). This could be because the average age of cigarette smoking initiation is increasing in the US³⁴ and older adults have had more years to cross the 100 cigarette threshold than young adults. For example, recent national data indicate most (56%) daily cigarette smokers in the US report smoking their first cigarette during young adulthood.³⁵ A period of experimental smoking during young adulthood could result in occasional cigarette smoking for multiple years before crossing the 100 cigarette threshold as an older adult. Given the large proportion of young adult “never smokers,” our findings are likely due, in part, to tobacco use characteristics common among this age demographic. For example, intermittent cigarette smoking,^36,37 e-cigarette use,³⁸ and non-cigarette combustible tobacco use¹⁴ are common among young adults. Finally, young adults are less likely to successfully quit than older adults,³⁹ which compounds the risk of long-term smoking among the “never smokers” with recent tobacco use identified in this study.

“Never smokers” with recent or experimental tobacco use may be at high risk for future long-term regular combustible tobacco use. A prior systematic review of 27 studies identified exposure to tobacco among young adults increased the risk of future established smoking.²⁹ A US longitudinal study of nearly 8000 adolescents identified that 35% of experimental cigarette smokers with low intention to smoke and over 50% with high intention to smoke progressed to regular established cigarette smoking four years later.⁴⁰ Similarly, longitudinal research indicates use of other tobacco or nicotine products including e-cigarettes,^28,41,42 hookah,^43,44 cigar,⁴⁵ and smokeless tobacco⁴⁶ increase the likelihood of future cigarette smoking. Thus, the 22% of “never smokers” with past 30-day or experimental tobacco/nicotine product use identified in this study may be at high risk for establishing long-term cigarette smoking.

Use of the 100 lifetime cigarettes cutoff to define “never smokers” is a misnomer because the criterion does not assess non-cigarette combustible tobacco smoking. Our findings challenge the assumption that adults who report <100 lifetime cigarettes are “never smokers” of any tobacco. In contrast most “never smokers” had tried smoking combustible tobacco and over 15% smoked tobacco in the past month. We suggest future tobacco research refrain from using the term “never smoker” to describe people who report smoking <100 lifetime cigarettes. Instead people who never tried combustible tobacco should be described separately from those who tried but never smoked tobacco regularly. Our findings do not fully address the validity of the 100 lifetime cigarette cutoff as a criterion to assess established regular cigarette smoking. Future research is needed to compare the predictive validity of the 100 lifetime cigarette threshold vs other definitions of regular cigarette smoking. Our findings support prior recommendations that criteria to define regular cigarette smoking should be selected based on research objectives and setting.³ Specifically, the decision to use the 100 cigarette criterion should be made with the understanding that over 20% of US adults who report <100 lifetime cigarettes are current or past regular non-cigarette tobacco users and over 5% are current experimental cigarette smokers. For example, research that aims to assess the health effects of tobacco or examine transitions to regular cigarette smoking should account for the substantial tobacco use among adults who report <100 lifetime cigarettes when defining a comparison condition.

Limitations and Assets

Limitations of our study include the use of cross-sectional data that do not address change in tobacco product use or status over time. All data rely on retrospective recall and self-report. Data collection for this analysis excluded people who are institutionalized²⁵ which could decrease estimates of tobacco use.⁴⁷ Importantly, we included only adults and results are likely to differ in adolescents. Further, use of the 100-lifetime cigarette threshold to define “ever” versus “never” smokers is uncommon among surveys of youth tobacco use (eg, National Youth Tobacco Survey⁴⁸). Approximately half of “never smokers” were young adults and many of the young adult experimental cigarette smokers identified in this analysis may continue to smoke.⁴⁹ Those who continue to smoke cigarettes will likely cross the ≥100 cigarette threshold later in life and thus could be identified as “ever smokers” in some longitudinal analyses. Nonetheless, our cross-sectional analysis identified that there is substantial cigarette and non-cigarette tobacco use among “never smokers” at any given time. Comparing the prevalence of daily use across tobacco products in this analysis is limited given that nondaily use is more typical for some tobacco products (eg, hookah).⁵⁰ Additionally, the proportion of current experimental cigarette smokers among “never smokers” (<100 lifetime cigarettes) is relatively small (ie, 5.3%). Though cigarette and non-cigarette tobacco use among “never smokers” could reduce estimates of relative harm from cigarette smoking, we know of no direct tests of this hypothesis.

To our knowledge, this is the first examination of cigarette and non-cigarette tobacco or nicotine product use among “never smokers” using the most widely used definition (<100 reported lifetime cigarettes) in its over 65-year history of use. Our analysis has a number of strengths including the use of a large, recent, US nationally representative survey that provides detailed data on tobacco use. We identify tobacco use among an understudied group who is often excluded from smoking research: people who report fewer than 100 lifetime cigarettes. Finally, we report multiple tobacco/nicotine products and describe tobacco use history using a number of different definitions (eg, past 30-day, experimental use, regular use).

Conclusion

Our study identifies substantial current and past cigarette and non-cigarette tobacco use among people who report <100 lifetime cigarettes, which mitigates the assumption that “never smokers” reflect a group that is unexposed to tobacco use. In contrast, research that uses the <100 lifetime cigarettes threshold should be interpreted with the understanding that over one fifth of “never smokers” are current or past regular non-cigarette tobacco/nicotine users with a similar proportion having used any tobacco/nicotine product in the past month. Importantly, this tobacco/nicotine use among “never smokers” could result in the underestimation of health harms from cigarettes given that research commonly relies on “never smokers” as an unexposed reference group for comparison. These findings provide important context for interpreting research that relies on the 100 lifetime cigarette criterion. However, prospective longitudinal research is needed to compare how different definitions of regular cigarette smoking differ in predictive validity of clinically meaningful outcomes and estimates of harm from tobacco to determine the optimal criteria to define established cigarette smoking.

Supplementary Material

A Contributorship Form detailing each author’s specific involvement with this content, as well as any supplementary data, are available online at https://academic.oup.com/ntr.

Funding

The authors were supported by training grant T32 DA 7242 from the National Institute on Drug Abuse, award number P20GM103644 from National Institute of General Medical Sciences, and award number U54DA036114 from the National Institute on Drug Abuse. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Declaration of Interests

EMK, PWC, JCW, and ACV have nothing to disclose. JRH has received consulting and speaking fees from several companies that develop or market pharmacological and behavioral treatments for smoking cessation or harm reduction and from several non-profit organizations that promote tobacco control. He also consults for Swedish Match on their harm reduction products.