Older adults who take daily low-dose aspirin at higher risk for anemia

Key takeaways:

• Taking low-dose aspirin every day was linked to a 23.5% risk for developing anemia within 5 years among older adults.
• Physicians should consider periodic hemoglobin monitoring for older people on aspirin.

Taking daily low-dose aspirin was linked to an increased incidence of anemia and a decline in blood iron levels among otherwise healthy older adults, according to the results of research published in Annals of Internal Medicine.

It is known that daily lose-dose aspirin intake increases major bleeding, but not many studies have evaluated its impact on anemia and iron deficiency, Zoe K. McQuilten, MB, PhD, an associate professor at the Monash University School of Public Health and Preventive Medicine, and colleagues wrote.

Current estimates indicate that roughly 30% of people aged 75 years or older worldwide are anemic, they wrote. Anemia in older adults — which WHO defines as hemoglobin less than 120 g/L for men and less than 110 g/L for women — is most commonly attributed to inflammation, iron deficiency and medical comorbidities.

“Anemia has been found to be associated with functional deficits, morbidity, and mortality in the elderly,” they wrote. “However, these associations do not imply causation; it is also unclear whether these potential effects of anemia on a person’s health are amenable to interventions.”

So, McQuilten and colleagues conducted a post-hoc analysis of the ASPREE randomized controlled trial to investigate the impact that low-dose aspirin might have on incident anemia, hemoglobin and serum ferritin concentrations.

The researchers evaluated a trial in which 19,114 primary care patients in Australia and the United States aged 70 years or older were randomly assigned to placebo or 100 mg of aspirin daily. They measured hemoglobin concentration annually in each participant and measured ferritin at baseline and 3 years after randomization in a large subset.

McQuilten and colleagues found that low-dose aspirin reduced ferritin and increased incident anemia in otherwise healthy older adults, independent of major bleeding. For older people on aspirin, periodic hemoglobin monitoring should be considered, they wrote.

Hemoglobin concentrations declined in both groups, but the aspirin group experienced a steeper drop over time, by 0.6 g/L (95% CI, 0.3-1) per 5 years compared with placebo.

According to the researchers, anemia incidence in the placebo group was 42.9 events per 1,000 person-years, whereas its incidence in the aspirin group was 51.2 events per 1,000 person-years (HR = 1.2; 95% CI, 1.12-1.29).

For those assigned to low-dose aspirin, the risk for developing anemia within 5 years was 23.5% (95% CI, 22.4%-24.6%), and the incident anemia rate was about 20% higher.

“Daily low-dose aspirin increased the risk for incident anemia by approximately 20%, which, after taking into account risk for clinically significant bleeding, was most likely due to occult blood loss given the observed steeper decline in ferritin in participants allocated to aspirin,” the researchers wrote.

Among the 7,139 participants with ferritin measurements at baseline and year 3, the aspirin group had a greater prevalence of ferritin levels less than 45 µg/L at year 3 — 13% vs. 9.8%. The aspirin group also saw greater overall decline in ferritin by 11.5% (95% CI, 9.3%-13.7%) compared with placebo.

McQuilten and colleagues additionally noted that a sensitivity analysis quantifying the effect of aspirin in the absence of major bleeding produced similar results.