Does Low-Dose Aspirin Result in Anemia in Older Patients?

Daily intake of low-dose aspirin increases the risk of major bleeding, but its effect on iron deficiency and anemia is less studied. This study, a post hoc analysis of the ASPREE trial (ASPirin in Reducing Events in the Elderly; ClinicalTrials.gov: NCT01038583), aimed to investigate the effect of low-dose aspirin on anemia, hemoglobin, and serum ferritin concentrations.

The study, conducted at primary care facilities in Australia and the U.S., included 19,114 patients aged 70 years or older (aged 65 or older for Black or Hispanic patients in the U.S.) randomized to receive 100 mg of aspirin or placebo. Hemoglobin concentration was measured annually in all participants, and ferritin levels were measured at baseline and 3 years after randomization in 7139 patients. 

The incidence of anemia was higher in the aspirin versus placebo group, with 51.2 events and 42.9 events per 1000 person-years, respectively (hazard ratio, 1.20; 95% confidence interval [CI], 1.12-1.29). Patients in the aspirin group experienced a more significant decrease in hemoglobin concentration than those in the placebo group (0.6 g/L per 5 years vs 3.6 g/L per 5 years, respectively [95% CI, 0.3-1.0 g/L]). 

Of the patients whose ferritin levels were measured, ferritin levels less than 45 µg/L at year 3 were more prevalent in the aspirin group than the placebo group (465 [13%] vs 350 [9.8%], respectively). Additionally, ferritin declined more significantly overall with aspirin (by 11.15%) than placebo (95% CI, 9.3%-13.7%). A sensitivity analysis quantifying the effect of aspirin in the absence of significant bleeding produced comparable results.