Explaining the Sex Difference in Coronary Heart Disease Mortality Among Patients With Type 2 Diabetes Mellitus

Background: Most studies suggest that diabetes is a stronger coronary heart disease (CHD) risk factor for women than men, but few have adjusted their results for classic CHD risk factors: age, hypertension, total cholesterol level, and smoking. Objective: To establish an accurate estimate of the odds ratio for fatal and nonfatal CHD due to diabetes in both men and women. Methods: We compared the summary odds ratio for CHD mortality and the absolute rates of CHD mortality in men and women with diabetes. We searched the MEDLINE and Cochrane Collaboration databases and bibliographies of relevant articles and consulted experts. Studies that included a nondiabetic control group and provided sexspecific adjusted results for CHD mortality, nonfatal myocardial infarction, and cardiovascular or all-cause mortality were included. Of 4578 articles identified, 232 contained primary data, and 182 were excluded. Two reviewers recorded data on study characteristics, quality, and outcomes from 50 studies. Results: Sixteen studies met all inclusion criteria. In unadjusted and age-adjusted analyses, odds of CHD death were higher in women than men with diabetes. From 8 prospective studies, the multivariate-adjusted summary odds ratio for CHD mortality due to diabetes was 2.3 (95% confidence interval, 1.9-2.8) for men and 2.9 (95% confidence interval, 2.2-3.8) for women. There were no significant sex differences in the adjusted risk associated with diabetes for CHD mortality, nonfatal myocardial infarction, and cardiovascular or all-cause mortality. Absolute CHD death rates were higher for diabetic men than women in every age strata except the very oldest. Conclusions: The excess relative risk of CHD mortality in women vs men with diabetes was absent after adjusting for classic CHD risk factors, but men had more CHD deaths attributable to diabetes than women.