Anemia in Association with Cognitive Impairment: A Systematic Review and Meta-Analysis.

ABSTRACT

BACKGROUND: Prevalence of both anemia and cognitive impairment tends to increase with age. Individual studies have recently shown that anemia could be associated with cognitive impairment. OBJECTIVE: To investigate the association between anemia and cognitive impairment including dementia. METHODS: Two of the authors systematically searched PubMed, EMBASE, and the Cochrane library to retrieve observational studies reporting a relationship between anemia and cognitive impairment from 1964 to July 10, 2019. Case-control and cohort studies were included, and odds ratios (ORs) or relative risks (RRs) with 95% confidence intervals (CIs) for the risk of cognitive impairment were calculated using a random-effects model. RESULTS: In total, 16 observational studies including eight case-control studies and eight cohort studies were included in the final analysis. Anemia was significantly linked to cognitive impairment (OR or RR 1.51; 95% CI 1.32-1.73) in a random-effects meta-analysis, albeit with medium heterogeneity (I2 = 47.8%). Meta-estimates of dementia from prospective population-based cohort studies were similar (RR 1.46; 95% CI 1.22-1.76) without substantial heterogeneity (I2 = 23.2%). CONCLUSION: Our meta-analysis indicates that anemia is associated with cognitive impairment. Further prospective research is warranted to determine the cause-effect relationship of anemia with cognitive impairment and whether treatment of anemia might reduce the risk of dementia.