Association of smoking cessation after new-onset type 2 diabetes with overall and cause-specific mortality among Korean men: a nationwide population-based cohort study

INTRODUCTION: This study aimed to examine the association between smoking cessation after new-onset type 2 diabetes and overall and cause-specific mortality risks among Korean men. RESEARCH DESIGN AND METHODS: The Korean National Health Insurance Service-National Health Screening Cohort database was searched, and 13 377 Korean men aged ≥40 years diagnosed with new-onset type 2 diabetes between 2004 and 2007 were included and followed up until 2013. We defined smoking status changes by comparing participants’ answers in the last survey before diagnosis to those in the first survey after diagnosis. We estimated the adjusted HR (AHR) and 95% CI for mortality risk using multivariable Cox proportional hazards regression models. RESULTS: We identified 1014 all-cause mortality events (cancer, n=406 and cardiovascular disease (CVD), n=184) during an average follow-up duration of 7.2 years. After adjustment for all confounding factors, the reduced risk of all-cause mortality was more significant among short-term quitters (AHR 0.78; 95% CI 0.64 to 0.95), long-term quitters (AHR 0.68; 95% CI 0.54 to 0.85), and never smokers (AHR 0.66; 95% CI 0.56 to 0.78) compared with current smokers (p for trend <0.001). The lower risk of mortality from cancer was significant among the short-term quitters (AHR 0.60; 95% CI 0.44 to 0.83), long-term quitters (AHR 0.67; 95% CI 0.46 to 0.90), and never smokers (AHR 0.50; 95% CI 0.39 to 0.65) compared with current smokers (p for trend <0.001). There was no significant association between changes in smoking status and death from CVD. Smoking cessation after diagnosis in non-obese individuals (AHR 0.73; 95% CI 0.58 to 0.92) and exercisers (AHR 0.54; 95% CI 0.38 to 0.76) was significantly associated with reduced mortality risk than current smoking. CONCLUSIONS: Smoking cessation after new-onset type 2 diabetes was associated with reduced mortality risk.