Aspirin is largely used for primary and secondary prevention of cardiovascular disease. Although the adverse effect of acute bleeding has been thoroughly analyzed, the potential effect of aspirin on the prevalence of anemia is still unclear, especially in senior individuals. We aimed to investigate the effect of low-dose aspirin on anemia events, hemoglobin concentration, and other haematologic parameters in the elderly by conducting a meta-analysis of randomized and observational trials.

We systematically searched PubMed, Embase, and Cochrane Central databases for studies comparing the hematological parameters and the prevalence of anemia between low-dose aspirin (≤ 325 mg) and non-aspirin users in individuals aged 60 years or older. We pooled mean differences (MD) for continuous outcomes and odds ratio (OR) for binary outcomes, with 95% confidence intervals (CI), under a random-effects model for both.

We included seven studies, consisting of three randomized controlled trials (RCTs), two cross-sectional, and two retrospective cohorts. The pooled data provided a total of 19,792 participants, of whom 9,771 (49.3%) were treated with aspirin; 55.4% were women and 44% had a history of smoking. There was no significant difference in the prevalence of anemia between aspirin users and non-aspirin users (OR 0.85; 95% CI 0.52 to 1.38; p = 0.50). Additionally, there was no significant difference in Mean Corpuscular Haemoglobin (MD 0.06 pg; 95% CI -0.37 to 0.49; p = 0.79), Mean Corpuscular Volume (MD -0.31 fl; 95% CI -1.17 to 0.56; p = 0.49), and hemoglobin concentration (MD -0.02 g/dL; 95% CI -0.26 to 0.21; p = 0.85) between the two groups. However, the mean change in hemoglobin concentration between baseline and follow-up was higher in the aspirin group when compared to non-aspirin users (MD -0.11 g/dL; 95% CI -0.17 to -0.05; p = 0.0002; I2 = 0%).

Our study, the first quantitative meta-analysis on this topic in a decade, utilizes rigorous methodology and a substantial patient cohort. Findings suggest that while low-dose aspirin does not increase anemia prevalence, it is associated with declining hemoglobin levels over time, likely due to minor or occult bleeding. Previous studies support this by showing increased fecal blood loss in aspirin users. Limitations include diverse study designs, short follow-up durations, gender-specific anemia criteria, and insufficient data on ferritin and iron levels.

In summary, low-dose aspirin was not associated with an increased prevalence of anemia. However, there was a meaningful correlation between aspirin intake and declining hemoglobin levels over time.