There is growing evidence that electronic cigarettes (e-cigarettes) might be associated with youth initiation of combustible cigarette smoking, and yet for adults, e-cigarettes hold potential as a cessation aid for combustible cigarette smoking. There is also growing concern over the health risks of e-cigarettes for individuals of all ages. This dissertation examines the prospective association between e-cigarette use and youth cigarette smoking initiation, adult cigarette smoking abstinence, and cardiopulmonary disease using four waves of the Population Assessment of Tobacco and Health study (2014-2018). This work enhances prior literature by incorporating novel analytic methods to account for previously unaddressed challenges in e-cigarette research, including time-dependent confounders that simultaneously act as causal intermediates, misclassification of self-reported e-cigarette use, and measurement of cumulative e-cigarette exposure.
Study 1 examines the association between time-varying e-cigarette initiation and cigarette smoking initiation in a cohort of cigarette and e-cigarette naïve youth at baseline, and employs marginal structural models (MSMs) to account for time-dependent confounding. MSMs allowed for the modeling of e-cigarette use as a time-varying exposure while appropriately adjusting for time-dependent confounders that otherwise produce overestimates of the association between vaping and cigarette smoking. Youth who initiated e-cigarettes over follow-up were three-times more likely than youth who did not initiate e-cigarettes to subsequently initiate combustible cigarette smoking. The association with smoking initiation appeared stronger for more frequent e-cigarette use.
Study 2 uses MSMs to examine the independent and joint association between e-cigarette use frequency at two time-points and combustible cigarette smoking abstinence. MSMs allowed for estimation of the simultaneous effect of e-cigarette use at multiple time points, as well as the direct effect of short-term e-cigarette use on smoking abstinence 24-months later. Consistent daily e-cigarette use was associated with four-times the likelihood of sustained 12-month cigarette smoking abstinence compared to no e-cigarette use over follow-up. Participants who reported consistent non-daily e-cigarette use were 70% less likely to achieve cigarette smoking abstinence than non-users.
Study 3 develops a novel measure of cumulative e-cigarette exposure (“vape-years”) using a volume-based approach to measuring e-cigarette dose. The study assesses the association between vape-years and incident cardiovascular disease, lung disease, and disease precursors (hypertension, wheezing/whistling in the chest, dry cough). The highest levels of cumulative e-cigarette exposure were associated with increased risk of incident cardiovascular disease and lung disease among participants with lower combustible smoking pack-years of exposure, though residual confounding by combustible smoking is likely. There was little association between cumulative e-cigarette exposure and disease precursors.
This dissertation demonstrates analytic techniques that can be used to address methodological challenges when evaluating longitudinal e-cigarette exposures. Findings provide evidence that e-cigarette use predisposes youth to initiate combustible cigarettes, and e-cigarettes can both help and hinder combustible smoking cessation depending on frequency of use. The association between cumulative e-cigarette exposure and cardiopulmonary disease risk remains unclear. Findings can inform e-cigarette regulations aimed at preventing youth vaping, reducing harm for adult tobacco users, and communicating health effects of vaping. / 2022-08-04T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/42838 |
| Date | 04 August 2021 |
| Creators | Harlow, Alyssa Fitzpatrick |
| Contributors | Ross, Craig S. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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