Anemia and mortality in acute coronary syndromes: A systematic review and meta-analysis

Background Anemia is a common comorbidity among patients with acute coronary syndromes (ACS) and may adversely affect cardiovascular outcomes in these patients. We conducted a systematic review and meta-analysis to examine the association between anemia and mortality among patients with ACS. Methods We systematically searched MEDLINE to identify cohort studies and secondary analyses of randomized controlled trials examining the association between anemia and all-cause mortality among patients with ACS. Data were aggregated at 4 follow-up times (inhospital, 30 days, 1 year, and maximal available follow-up) using random-effects meta-analysis models. Results Twenty-seven studies met the inclusion criteria, involving 233,144 patients. Anemia was present in 44,519 (19.1%) of these patients. Anemic patients were generally older and had a higher prevalence of comorbidities including diabetes mellitus, congestive heart failure, cerebrovascular disease, and history of major bleeding. Anemia was associated with an increased risk of crude all-cause mortality (relative risk 2.08, 95% CI 1.70-2.55) and reinfarction (relative risk 1.25, 95% CI 1.02-1.53) at maximal available follow-up. When adjusted risk ratios from individual studies' multivariable regression analyses were pooled, the magnitude of the associated mortality risk was attenuated but remained significant at maximal follow-up (hazard ratio 1.49, 95% CI 1.23-1.81). Clinically and statistically significant increases in mortality were observed as early as at 30 days post-ACS and persisted at 1 year. Conclusions Anemia in patients with ACS is independently associated with a significantly increased risk of early and late mortality.