Objective: Mounting evidence suggests that smoking is a cause of type 2 diabetes. We explored the association of cigarette smoking with diabetes incidence and mortality in a large cohort of Koreans.
Research design and methods: A 14-year prospective cohort study was performed on 1,236,443 Korean men and women, aged 30-95 years at baseline, who underwent standardized biennial medical examinations provided by the National Health Insurance Corporation (NHIC). Incident diabetes was identified on the basis of outpatient visits, hospitalization, or prescription medication treatment for diabetes, as captured in the NHIC database. Diabetes mortality was obtained through the national statistical office. Cox proportional hazards models were used to investigate associations of smoking with indicators of diabetes and diabetes mortality.
Results: Smoking was significantly associated with increased risk for diabetic outpatient treatment, hospitalization, and mortality among both men and women, and the risk among current smokers increased modestly with the number of cigarettes smoked daily (P(trend) < 0.0001 for all associations). Compared with never smokers, current male smokers who smoked ≥ 20 cigarettes/day had increased risk for incident diabetes defined by outpatient treatment (adjusted hazard ratio 1.55 [1.51-1.60]), incident diabetes defined by ≥ 3 prescription medications for diabetes (1.71 [1.63-1.80]), and death from diabetes (1.60 [1.25-2.06]). The risks for outpatient treatment among smokers were higher in men than in women with evidence for effect modification by sex and age (P(interaction) < 0.0001).
Conclusions: Our study provides longitudinal evidence that smoking increases the risk of incident diabetes and mortality.