Daily low-dose usage of aspirin, a nonsteroidal anti-inflammatory drug commonly used to relieve headache, and reduce swelling or fever may lead to about 20 per cent increased risk of anaemia among healthy older adults, suggests a study.

The study, published in the journal Annals of Internal Medicine, showed that aspirin intake also led to a decline in ferritin, or blood iron levels, in otherwise healthy older adults.

These findings suggest that periodic monitoring of haemoglobin should be considered in older patients taking aspirin, said a joint team of researchers from the US and Australia.

Approximately half of older persons in the US have reported preventative aspirin use. One of the complications of aspirin use is an increased risk for major bleeding, particularly gastrointestinal bleeding.

Although the risk for overt bleeding due to aspirin has been well characterised, very few studies have measured the effect of aspirin on anaemia, particularly in older populations.

Researchers from Monash University, Melbourne conducted an analysis of the randomised controlled trial involving 19,114 persons aged 70 years or older who were randomly assigned to take 100 mg of aspirin daily or placebo.

Haemoglobin was measured annually, and ferritin was measured at baseline and three years after randomisation. The data showed that the risk for developing anaemia was 23.5 per cent among those assigned to receive low-dose aspirin.

These results were accompanied by a small but greater decrease in mean haemoglobin and a greater decline in ferritin concentrations among those receiving aspirin.

Differences in clinically significant bleeding events did not account for the overall difference in incident anaemia or the decline in ferritin observed in the trial.

It was most likely due to occult blood loss, given the observed steeper decline in ferritin in participants allocated to aspirin, the researchers said.