摘要：Objectives. We assessed the impact of trying electronic cigarettes (e-cigarettes) on future cigarette smoking in a sample of smokers enrolled in college. Methods. In this longitudinal study, first-semester college students at 7 colleges in North Carolina and 4 in Virginia completed a baseline survey and 5 follow-up surveys between fall 2010 and fall 2013. Current cigarette smoking at wave 6 was the primary outcome. Participants (n = 271) reported current cigarette smoking at baseline and no history of e-cigarette use. We measured trying e-cigarettes at each wave, defined as use in the past 6 months. Results. By wave 5, 43.5% had tried e-cigarettes. Even after controlling for other variables associated with cigarette smoking, trying e-cigarettes was a significant predictor of cigarette smoking at wave 6 (adjusted odds ratio [AOR] = 2.48; 95% confidence interval [CI] = 1.32, 4.66), as were friends’ cigarette smoking (AOR = 4.20; 95% CI = 2.22, 7.96) and lifetime use of other tobacco products (AOR = 1.63; 95% CI = 1.22, 2.17). Conclusions. Trying e-cigarettes during college did not deter cigarette smoking and may have contributed to continued smoking. There has been considerable growth in the availability, marketing, sales, and use of electronic nicotine delivery systems, often referred to as “e-cigarettes,” over the past several years. Product sales in the United States have doubled every year since 2008, and securities analysts estimate the e-cigarette market is now approximately a $2.5 billion industry. 1 E-cigarette use has rapidly increased among adolescents and adults. From 2011 to 2012, rates of ever using e-cigarettes among US middle and high school students doubled from 3.3% to 6.8%. 2 Similar increases have been seen among US adults. 3,4 Recent data suggest that e-cigarette use is highest among young adults. Data from the 2012–2013 National Adult Tobacco Survey show that young adults aged 18 to 24 years had a higher prevalence of e-cigarette use (8.3%) than did the adult population as a whole (4.2%). 5 Similarly, with data from dual frame surveys of national probability samples of adults, McMillen et al. found that current e-cigarette use in 2013 by young adults aged 18 to 24 years (14.2%) was higher than was that among adults aged 25 to 44 years (8.6%), 45 to 65 years (5.5%), and older than 65 years (1.2%). 4 Available data on e-cigarette use by college students are limited, with most coming from single-state or individual campus studies. 6–9 College students are an important group to study for several reasons. First, young adulthood is a period of many life transitions and accompanying stress. 10 The tobacco industry is well aware of this vulnerable period and recognizes it as a promising period for tobacco use initiation and transition to addiction. 11 Thus, college students are a target market for the tobacco industry. 11,12 College students are often early adopters of novel products and have historically been at the forefront of societal changes in substance use that later materialize in the general population. 13 In a cross-sectional study of college students in North Carolina in 2009, Sutfin et al. 6 found that college students’ lifetime prevalence of e-cigarette use was 4.9%, which was higher than were rates of use among other adults at the time, 14,15 suggesting that college students were early adopters of e-cigarettes. 6 Additionally, there was an association between e-cigarette use and sensation seeking in bivariate, but not multivariable, models. However, membership in Greek letter organizations was associated with e-cigarette use in multivariable models. These data suggest that college students may be drawn to e-cigarettes owing, at least in part, to their novelty. Finally, college students are an important group to study because they have a unique pattern of cigarette smoking that is often marked by social and occasional smoking. 16–18 Studying how e-cigarettes are used by this group and how use may affect cigarette smoking is important for understanding the ultimate public health impact of this product. Only a handful of longitudinal studies have assessed the relationship between e-cigarette use and subsequent cigarette smoking behavior. However, studying how people use this product is critical to our understanding of the overall public health effects. To date, 6 observational longitudinal studies have been published, with just 3 using population-based samples. Five studies found either no association between e-cigarette use and quitting cigarettes or an association with lower odds of quitting cigarettes, 19–23 with 1 study finding e-cigarette use associated with a reduction in the number of cigarettes smoked. 19 However, only 1 study assessed the intensity of e-cigarette use and associations with quitting cigarettes. 24 Results revealed that the most intensive e-cigarette users at follow-up (daily users for at least 1 month) were more likely to have quit smoking (1 month abstinence). However, intermittent e-cigarette use (using e-cigarettes regularly but not daily for more than 1 month) was not associated with increased quitting. Only 1 longitudinal study focused on young adults; to our knowledge, no longitudinal studies have focused on college students. 22 We measured the impact of e-cigarette use during the college years on current cigarette smoking. We included those who reported current cigarette smoking at baseline with no history of e-cigarette use. We measured trying e-cigarettes during the subsequent 4 waves and current cigarette smoking at wave 6, which corresponded to fall 2013. For most participants, wave 6 was during the fall of senior year.
