INTRODUCTION:
Early smoking initiation predicts long-term tobacco use and may be linked to other unhealthy behaviors in later life. This study examined associations between age at smoking initiation, current smoking status, and clustering of other health risk factors among adult smokers in Taiwan.

METHODS:
Data from the 2017 and 2021 National Health Interview Surveys (NHIS), population-based cross-sectional face-to-face surveys, were analyzed. The study included 5487 adults aged 30–64 with a smoking history, of whom 7.3% were early initiators (before age 15), 23.8% middle initiators (aged 15–17), and 63.5% late initiators (aged 18 and above). At the time of the interview, participants’ smoking status was categorized as current or former smokers, and health risk factors were assessed, including heavy episodic drinking, betel nut chewing, insufficient physical activity, and overweight/obesity. Binary and ordinal logistic regression analyses were performed, adjusting for sociodemographic variables.

RESULTS:
The proportion of former smokers was lowest among early initiators (19.2%), followed by middle (25.9%) and late initiators (29.3%). Early smoking initiation and current smoking were associated with increased risks of heavy drinking and betel nut chewing. Current smokers also had higher risk of insufficient physical activity, whereas age at initiation was not significant. Overweight/obesity risk was elevated among early initiators and former smokers. Ordinal regression indicated that, early (OR = 1.68, 95% CI = 1.41–2.01) and middle (OR = 1.20, 95% CI = 1.09–1.32) initiators had higher odds of additional health risk factors compared with late initiators, and current smokers had greater odds (OR = 1.37, 95% CI = 1.18–1.59) than former smokers.

CONCLUSIONS:
Preventing smoking initiation among adolescents and promoting smoking cessation are important strategies to reduce the clustering of multiple health risk factors in adulthood.