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Risk of anaemia increased among elderly patients taking low-dose aspirin

The risk of anaemia is higher among patients aged 70 years and older taking a daily dose of 100 mg of enteric-coated aspirin, according to a post hoc analysis of the ASPREE randomised controlled trial.

The Aspirin in Reducing Events in the Elderly (ASPREE) trial was designed to examine whether a daily dose of 100 mg of aspirin would prolong the healthy life span of older adults. While it is recognised that aspirin use in patients without cardiovascular disease lowers the risk of cardiac events but increases the risk of a major bleed, whether aspirin use also associated with anaemia is less certain.

Details of the ASPREE trial have been already published and revealed a higher all-cause mortality, largely due to cancer-related deaths, in those assigned to daily aspirin compared to placebo.

In the post hoc analysis of the ASPREE trial, published in the Annals of Internal Medicine, researchers investigated the effect of low-dose aspirin on incident anaemia, haemoglobin and serum ferritin concentrations.

Researchers assessed haemoglobin levels annually and ferritin levels at both baseline and after three years. The primary outcome was defined as incident anaemia but researchers also considered changes in haemoglobin and ferritin levels over time.

Aspirin use and anaemia

A total of 18,153 participants with a mean age of 74 years (44% male) were included, of whom 9,047 were randomised to a daily dose of 100 mg of enteric coated aspirin. Participants were followed for a median of 4.7 years after randomisation.

The incidence of anaemia was significantly higher in the aspirin group (hazard ratio, HR = 1.20, 95% CI 1.12 – 1.29). In addition, haemoglobin concentrations declined more steeply in those assigned to aspirin.

By year three, serum ferritin levels had reduced by an average of 11.5% in the aspirin group compared to those assigned to placebo. A higher proportion of patients assigned to aspirin experienced a major bleeding event compared to placebo (3% vs 2.1%). However, in sensitivity analysis, this difference did not account for the levels of anaemia seen between the two groups.

Overall the results suggested that the risk of developing anaemia within five years was 23.5% among those taking low dose aspirin.