Association of heated tobacco product use with risk of type 2 diabetes

INTRODUCTION: Heated tobacco products (HTPs) are marketed as safer alternatives to conventional cigarettes, but evidence on their metabolic health effects is limited. Cigarette smoking is a known risk factor for type 2 diabetes; understanding the association between HTP use and diabetes risk is important for tobacco control policy. METHODS: This cohort study included 29,584 workers (82.5% male; mean age 45.9 [SD 9.9] years) without diabetes at baseline (April 2018-March 2019) from the Japan Epidemiology Collaboration on Occupational Health study. Participants were categorized into five groups based on their self-reported tobacco use: those who have never smoked, those who formerly smoked, those who smoke cigarettes exclusively, those who use HTPs exclusively, and those who use both cigarettes and HTPs. Incident type 2 diabetes was identified from health checkups conducted from 2019 to 2025. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Analyses were conducted in 2025. RESULTS: During 140,797 person-years of follow-up, 2,141 participants developed type 2 diabetes (15.2 per 1,000 person-years). Incidence was higher among those who use tobacco products (18.5-21.7 per 1,000 person-years) than among those who have never smoked (11.3 per 1,000 person-years). Compared with those who have never smoked, those who use HTPs exclusively (HR 1.61; 95% CI 1.39-1.86), those who use both cigarettes and HTPs (HR 1.76; 95% CI 1.48-2.09), and those who smoke cigarettes exclusively (HR 1.53; 95% CI 1.34-1.74) had a higher risk of diabetes. Among those who have ever smoked, those who use HTPs exclusively had a comparable risk of diabetes to those who smoke cigarettes exclusively (HR 1.01; 95% CI 0.86-1.18), suggesting no observable reduction in risk within the follow-up period. Moreover, a dose-response association was observed between daily tobacco product use and the risk of diabetes across all tobacco use groups. CONCLUSIONS: Among those who use HTPs exclusively, most of whom had a prior history of cigarette smoking, HTP use was not associated with a lower risk of type 2 diabetes compared with smoking cigarettes exclusively during the follow-up period. As the findings cannot distinguish whether the elevated risk reflects an independent effect of HTP use or residual effects of prior cigarette exposure, longer follow-up is needed to evaluate whether diabetes risk differs over time between those who use HTPs and those who smoke cigarettes.