Coronary heart disease incidence and mortality, and all-cause mortality among diabetic and non-diabetic people according to their smoking behavior in Finland

BACKGROUND: As type 2 diabetes (T2D) patients have a high risk for coronary heart disease (CHD) and all-cause mortality and smoking is a major single risk factor for total and CHD mortality, it is important to understand the impact of smoking to the outcome events in comparison to people without T2D. Studies of excess risk of CHD incidence and mortality, and all-cause mortality in T2D patients related to smoking are controversial. We aimed to assess the risk of CHD incidence and mortality, and all-cause mortality in a large Finnish population cohort consisting of people with and without T2Daccording to smoking status. METHODS: Prospective follow-up of 28 712 men and 30 700 women aged 25–64 years living in eastern and south-western Finland. The data on mortality were obtained from the nationwide death register using the unique national personal identification number. Follow-up information regarding CHD was based on the Finnish Hospital Discharge Register for non-fatal outcomes. The Cox proportional hazards models were used to estimate the association between diabetes and smoking subgroups and the risk for total and CHD mortality. RESULTS: T2D patients who were smoking had higher all-cause mortality in both men (HR 3.76; 95% CI 2.95-4.78) and women (HR 4.51; 95% CI 2.91-7.00) than non-smoking diabetic men (HR 2.03; 95% CI 1.51-2.74) and women (HR 2.11; 95% CI 1.71-2.59). The CHD mortality risk for smoking men with T2D was higher (HR 6.15; 95% CI 4.22-8.96) than in non-smoking diabetic men (HR 2.62; 95% CI 1.60-4.29). Similar results were found in women revealing corresponding HR for CHD mortality of 6.92 (95% CI 2.79-17.19) for smoking, T2D women and 4.06 (95% CI 2.83-5.82) for non-smoking T2D women, respectively. Even though the risk of CHD incidence in T2D patients who had stopped smoking was statistically significantly higher than in their non-smoking non-diabetic counterparts, their CHD incidence was lower than in smoking T2D patients (HR in men 3.00; HR in women 2.80). CONCLUSION: It is important to address tobacco consumption in T2D patients, especially during primary health care contacts in order to reduce their high risk of CHD and all-cause mortality.