Objective: The purpose of our study was to confirm or refute the view that diabetes be regarded as a coronary heart disease (CHD) risk equivalent and to test for sex differences in mortality.
Research design and methods: This was a prospective cohort study of 7,052 men and 8,354 women aged 45-64 years from Renfrew and Paisley, Scotland, who were first screened in 1972-1976 and followed for 25 years. All-cause mortality was calculated as death per 1,000 person-years. A Cox proportional hazards model was used to adjust survival for age, smoking habit, blood pressure, serum cholesterol, BMI, and social class.
Results: There were 192 deaths in 228 subjects with diabetes and 2,016 deaths in 3,076 subjects with CHD. The highest mortality was in the group with both diabetes and CHD (100.2 deaths/1,000 person-years in men, 93.6 in women) and the lowest in the group with neither (29.2 deaths/1,000 person-years in men, 19.4 in women). Men and women with diabetes only and CHD only formed an intermediate risk group. The adjusted hazard ratio (HR) for CHD mortality in men with diabetes only compared with men with CHD only was 1.17 (95% CI 0.78-1.74; P = 0.56). Corresponding HR for women was 1.97 (1.27-3.08; P = 0.003).
Conclusions: Diabetes without previous CHD carries a lifetime risk of vascular death as high as that for CHD alone. Women may be at particular risk. Our data support the view that cardiovascular risk factors in diabetes should be treated as aggressively as in people with CHD.