Smoking Habit Change and Atrial Fibrillation Risk in Patients With Diabetes Mellitus: A Nationwide Observational Cohort Study in Korea.

BACKGROUND: Smoking and diabetes mellitus (DM) are known risk factors for atrial fibrillation (AF), but the impact of smoking habit changes on AF risk in patients with DM remains unclear. We aimed to evaluate the association between smoking habit changes and incident AF in patients with DM. METHODS: Using the Korean nationwide claims database, we identified patients with DM, defined as fasting glucose ≥ 126 mg/dL or use of antidiabetic medications. Smoking habits were assessed by self-reported questionnaires from two health assessments within a two-year interval, and patients were categorized as never smokers, ex-smokers, quitters, or current smokers. The primary outcome was incident AF. RESULTS: Among 1,354,907 patients with DM (median follow-up 5.93 years, interquartile range 5.30-6.33; mean age 60.0 years [SD 11.8], 51.0% male), current smokers had a 20% higher risk of AF than never smokers (adjusted hazard ratio [95% confidence interval], 1.20 [1.16-1.24]). While ex-smokers and quitters had lower risks than current smokers, their risk remained elevated relative to never smokers, by 8.5% (1.09 [1.04-1.13]) and 10% (1.10 [1.06-1.15]), respectively. Among patients with new-onset DM or DM duration < 5 years, quitters showed comparable AF risk to that of never smokers (1.06 [0.97-1.15] and 1.04 [0.95-1.13], respectively). CONCLUSION: Smoking cessation in patients with DM was associated with a lower risk of AF than continued smoking. Especially in new-onset DM, AF risk in quitters approached that of never smokers. Encouraging smoking cessation may be beneficial for preventing new-onset AF in patients with DM.