Effect of smoking cessation and post-cessation weight change on suicide mortality in type 2 diabetes: A nationwide cohort study

Aims: This study investigated whether smoking cessation was associated with suicide mortality in people with type 2 diabetes (T2DM) and examined how post-cessation weight changes influence this association. Methods: We utilized data from the South Korean National Health Insurance Service database, including 456,936 adults with T2DM who underwent health examinations between 2015 and 2016. Subjects were categorized as recent smoking quitters (n = 96,797) or current smokers (n = 360,139) based on their responses from two consecutive health checkups. Results: During a mean follow-up of 5.7 years, a total of 1,397 suicide deaths were recorded. Individuals who had recently quit smoking exhibited a significantly lower risk of suicide death (hazard ratio [HR]: 0.82, 95 % confidence interval [CI]: 0.72–0.94) compared to those who continued smoking. Among quitters, those with a stable weight (HR: 0.83, 95 % CI: 0.70–0.99) or increased weight (HR: 0.75, 95 % CI: 0.59–0.95) had a reduced suicide mortality, while those with significant weight loss did not show a risk reduction (HR: 0.96, 95 % CI: 0.70–1.31). Conclusions: Smoking cessation was associated with a reduced risk of suicide mortality in people with T2DM. This effect persisted even among those who gained or maintained weight after quitting.