E-Cigarette Uptake, Dual Use, and Exclusive Cigarette Smoking Among Adults with Functional Disabilities: A Longitudinal Cohort Study

INTRODUCTION: E-cigarette use and dual cigarette-e-cigarette use are increasingly prevalent in the United Kingdom, yet few longitudinal UK studies have examined whether people with functional disabilities are at elevated risk of subsequent use of these products. We examined whether baseline functional disability was associated with the subsequent risk of exclusive e-cigarette use, dual use, and, for comparison, exclusive cigarette smoking among UK adults. METHODS: We conducted a prospective cohort analysis of 19,609 adults from the UK Household Longitudinal Study who were non-current users of both cigarettes and e-cigarettes at Wave 10 (2018-2019) and were followed to Wave 14 (2022-2023). The outcome was a four-category nicotine-use pattern at follow-up: neither current cigarette smoking nor current e-cigarette use (reference), exclusive cigarette smoking, exclusive e-cigarette use, and dual use, with current use defined as any ongoing use including less-than-monthly use. Functional disability was measured at baseline using twelve self-reported functional limitation domains and operationalised as any reported domain versus none; disability extent was also categorised as 0, 1, or ≥2 affected domains. Survey-weighted multinomial logistic regression estimated adjusted relative risk ratios (RRRs) controlling for age, sex, education, ethnicity, urban/rural residence and country of residence. RESULTS: At baseline, 4,910 participants (25.0%) reported at least one functional disability. By follow-up, 338 participants reported exclusive current e-cigarette use, 61 reported current dual use, and 216 reported exclusive current cigarette smoking. In fully adjusted multinomial models, with neither current cigarette smoking nor current e-cigarette use as the reference outcome, participants with functional disability were compared with those without functional disability. Functional disability was not associated with exclusive e-cigarette use (RRR = 0.98, 95% CI: 0.72-1.33, p = 0.915) or dual use (RRR = 0.57, 95% CI: 0.25-1.32, p = 0.191). In contrast, functional disability was associated with exclusive cigarette smoking (RRR = 1.41, 95% CI: 1.02-1.95, p = 0.038). Compared with participants reporting no disability domains, those reporting two or more domains had a higher relative risk ratio for exclusive cigarette smoking versus neither current cigarette smoking nor current e-cigarette use (RRR = 1.67, 95% CI: 1.08-2.55, p = 0.020). CONCLUSIONS: Among UK adults who were non-users of both products at baseline, functional disability was not associated with subsequent exclusive e-cigarette use or dual use but was associated with exclusive cigarette smoking. This product-specific pattern suggests that disability-related differences in nicotine uptake may be concentrated in combustible tobacco smoking rather than e-cigarette uptake.