Coronary heart disease among diabetic and nondiabetic people - socioeconomic differences in incidence, prognosis and mortality

OBJECTIVE: To investigate coronary heart disease (CHD) morbidity and mortality and their patterning by socioeconomic status among diabetic and nondiabetic individuals in Finland. METHODS: All diabetic persons aged 35-74 years entitled to free anti-diabetic medication were drawn from the 1991-1996 national health insurance files along with nondiabetic referents. Outcome events for up to 6 years of follow-up, corresponding to 418,987 and 867,813 person-years in diabetic and nondiabetic people, respectively, were identified from national health insurance, hospital discharge and causes of death registers using personal identification codes. RESULTS: The annual CHD incidence for diabetic women and men was 2.7% and 3.7%, respectively, corresponding to relative risks of 3.55 (95% CI: 3.43-3.67) and 2.64 (95% CI: 2.56-2.72) compared to nondiabetic persons. The impact of diabetes on CHD mortality was greater, with relative death rates of 6.04 and 3.42 for women and men, respectively. CHD mortality and incidence displayed systematic socioeconomic trends with higher rates among worse-off diabetic and nondiabetic people, although gradients were generally steeper for nondiabetics. In the diabetic population, socioeconomic differences were rather similar for sudden CHD deaths and nonfatal CHD incident cases. For both genders, socioeconomic differences in mortality after CHD diagnosis were small in both diabetic and nondiabetic persons, except for the lowest compared to the highest income quintile. CONCLUSIONS: Socioeconomic CHD mortality differences among diabetic people in Finland were mainly explained by higher CHD incidence and particularly sudden deaths without prior CHD diagnosis. No systematic socioeconomic differences were found in long-term prognosis after CHD diagnosis.