Self-rated health differences between exclusive e-cigarette users and exclusive cigarette smokers: evidence from the 2017-2019 Scottish Health Survey.

The comparative health implications of e-cigarette use versus traditional cigarette smoking remain a critical focus in public health research. This cross-sectional study examined differences in self-rated general health between exclusive e-cigarette users and exclusive cigarette smokers, using data from the 2017-2019 Scottish Health Survey. A total of 2484 adults (aged 16 and above) were included and categorized as exclusive e-cigarette users (n = 565) or exclusive cigarette smokers (n = 1919). Self-rated health was assessed using a single-item measure with five response categories: "very bad," "bad," "fair," "good," and "very good". Generalized ordinal logistic regression models were used to estimate the association between nicotine product use and self-rated health, adjusting for age, sex, Scottish Index of Multiple Deprivation, marital status, ethnicity, alcohol consumption frequency, physical activity, presence of longstanding physical or mental health conditions, and age of smoking initiation. In the fully adjusted model, exclusive e-cigarette users had higher odds of reporting better self-rated health compared to exclusive cigarette smokers overall (OR = 1.26, 95% CI 1.05-1.51, p = 0.012). A graded relationship was also observed in the fully adjusted model, with progressively lower odds of reporting better self-rated health as smoking intensity increased, using exclusive e-cigarette users as the reference group. Heavy smokers (≥ 20 cigarettes/day) had the lowest odds of reporting better self-rated health (OR = 0.63, 95% CI 0.49-0.80, p < 0.001), followed by moderate smokers (10 to < 20 cigarettes/day) (OR = 0.81, 95% CI 0.66-0.99, p = 0.047). In contrast, light smokers (< 10 cigarettes/day) showed no significant difference in self-rated health compared to exclusive e-cigarette users (OR = 0.94, 95% CI 0.75-1.18, p = 0.614). These findings indicate that exclusive e-cigarette use is associated with better self-rated health compared to exclusive cigarette smoking, particularly among moderate and heavy smokers. Additional analyses revealed no significant differences in self-rated health among exclusive e-cigarette users based on prior smoking history (OR = 0.94, 95% CI 0.43-2.08, p = 0.882) or among exclusive cigarette smokers based on prior e-cigarette use (OR = 0.87, 95% CI 0.69-1.09, p = 0.219). These findings suggest that prior use is unlikely to explain the observed association between exclusive e-cigarette use and better self-rated health compared to exclusive cigarette smoking. Given the subjective nature of self-rated health, these findings should be interpreted with caution. Future longitudinal studies incorporating objective health measures are essential to assess the long-term impacts of e-cigarette use and inform evidence-based harm reduction policies.