Predictors of e-cigarette use among individuals with asthma: findings from a cross-sectional population-based study

The use of electronic cigarettes (e-cigarettes) among individuals with asthma is rising, yet limited evidence exists on predictors of use in this clinical population. Understanding factors associated with e-cigarette use may help inform public health interventions. In this study, we analysed data from 2671 individuals aged 16 years and older with doctor-diagnosed asthma, drawn from the 2017, 2018, 2019, and 2021 waves of the Scottish Health Survey. Current e-cigarette use was defined as self-reported use at the time of the survey. We used multivariable logistic regression to examine factors associated with current e-cigarette use among individuals with asthma, estimating adjusted odds ratios (aORs), 95% confidence intervals (CIs), and p values for age, sex, education, socio-economic deprivation, smoking status, alcohol consumption, and self-rated health. Overall, 193 participants (7.2%) reported current e-cigarette use. Current smokers had significantly higher odds of using e-cigarettes compared to never smokers (aOR: 38.9; 95% CI: 18.5-82.0; p < 0.001). Former smokers also had increased odds of e-cigarette use relative to never smokers (aOR: 32.0; 95% CI: 15.2-67.2; p < 0.001). Each one-category increase in age group (spanning approximately 10 years) was associated with a 23% reduction in the odds of current e-cigarette use (aOR: 0.77; 95% CI: 0.69-0.86; p < 0.001). Participants living in less deprived areas had 15% lower odds of current e-cigarette use for each one-quintile increase in the Scottish Index of Multiple Deprivation (aOR: 0.85; 95% CI: 0.74-0.97; p = 0.016). E-cigarette use was not significantly associated with sex, educational level, alcohol consumption, or self-rated health. These findings indicate that e-cigarette use among individuals with asthma is more prevalent among younger participants, those living in socioeconomically deprived areas, and those with a current or former smoking history. Further longitudinal research is needed to explore usage trajectories and respiratory health impacts in this clinical population.