Mortality in diabetes compared with previous cardiovascular disease: a gender-specific meta-analysis

Aims: Diabetes has been described as a cardiovascular disease (CVD) risk equivalent. There is evidence, however, that its impact may differ between women and men. For this reason, our study aimed to obtain gender-specific hazard ratios (HRs) comparing diabetes and CVD patients in terms of all-cause, CVD and coronary heart disease (CHD) mortality.

Methods: Individuals with diabetes (without CVD) and those with CVD (without diabetes) were examined through a systematic review of articles that provided gender-specific HRs for mortality. Searches included Medline, Embase and the Cochrane Library database (from January 1998 to December 2009) and exploded MeSH headings [cardiovascular diseases, risk, epidemiologic studies, case-control studies, cohort studies, mortality, outcome assessment (health care), sex factors, survival analysis and diabetes mellitus, type 2]. Two observers selected and reviewed the studies and hierarchical Bayesian random-effects models were used to combine HRs, thereby accommodating any between-study differences through inclusion of a between-study variance in HRs.

Results: Out of 5425 studies, nine were relevant (0.17%). CVD and CHD mortality in men was lower for diabetes alone (CVD mortality HR: 0.82, 95% CrI: 0.69-0.98; CHD mortality HR: 0.73, 95% CrI: 0.65-0.83). In contrast, rates appeared to be higher in women with diabetes alone (CVD mortality HR: 1.29, 95% CrI: 0.79-2.26; CHD mortality HR: 1.28, 95% CrI: 0.75-2.22), although wide credible intervals precluded any definitive conclusions. All-cause mortality in men was similar for diabetes and previous CVD (HR: 1.02, 95% CrI: 0.93-1.12) whereas, among women, it was at least as high and possibly higher for diabetes alone (HR: 1.25, 95% CrI: 0.89-1.76).

Conclusion: Compared with previous CVD, diabetes alone leads to lower CVD and CHD mortality risk in men, and similar all-cause mortality. In contrast, although further studies are needed, it is possible that diabetes leads to higher CVD, CHD and all-cause mortality in women.