Smoking behavior change and risk of cardiovascular disease incidence and mortality in patients with type 2 diabetes mellitus

BACKGROUND: We aimed to examine the association between smoking behavior change and risk of cardiovascular disease (CVD) incidence and mortality in patients with type 2 diabetes mellitus (T2DM). METHODS: This study used nationwide data from the Korean National Health Insurance System and included 349,137 T2DM patients who smoked. Smoking behavior changes were defined with five groups: quitters, reducers I (≥ 50% reduction), reducers II (20–50% reduction), sustainers (± 20%), and increasers (≥ 20% increase) from the number of cigarettes/day at the baseline. RESULTS: During a median follow-up of 5.1 years, 6,514 cases of myocardial infarction (MI) (1.9%), 7,837 cases of ischemic stroke (IS) (2.2%), and 14,932 deaths (4.3%) were identified. Quitters had a significantly decreased risk of MI (adjusted hazard ratio [aHR] 0.80, 95% CI 0.75–0.86) and IS (aHR 0.80, 95% CI 0.75–0.85) compared to sustainers, whereas reducers did not have a significant association with the risk of MI (aHR 1.03, 95% CI 0.94–1.13) and IS (aHR 1.00, 95% CI 0.92–1.08) in reducer I. Quitters also had a lower all-cause and CVD mortality than sustainers. CONCLUSIONS: Smoking cessation was associated with decreased CVD incidence, and all-cause and CVD mortality among T2DM patients. However, smoking reduction was not associated with decreased risks for these. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12933-023-01930-4.