Low-dose aspirin and risk of anaemia in older adults: insights from a Danish register-based cohort study

AIMS: To assess the risk of anaemia among low-dose aspirin (LDA) exposure in Danish older individuals in a real-world setting. METHODS AND RESULTS: Population based-cohort study conducted using Danish registers. The study population included older individuals (≥65 years) exposed to LDA between 2008 and 2013 for primary or secondary prevention of cardiovascular events. Over a 5-year follow-up, outcomes included anaemia incidence based on haemoglobin values and hematinic deficiency incidence based on antianaemic prescriptions. Among the 313 508 individuals included in the study population, those exposed to LDA (n = 59 869, 19.1%) had an incidence of hematinic deficiency determined by the use of antianaemic treatment of 9.6%, with an incidence rate ratio of 9.11 (95% confidence interval, CI: 8.81-9.41) when compared to non-users of LDA (n = 253 639, 80.9%), who had an incidence of 3.7%. Anaemia determined by haemoglobin value measurements was observed in 5.9% of those exposed to LDA, with an incidence rate ratio of 7.89 (95% CI: 7.58-8.21) when compared to non-users of LDA. Approximately, one in five individuals (n = 2 422, 21.5%) who experienced anaemia also experienced bleeding. Severe anaemia was observed in 1.3% of those exposed to LDA compared to 0.6% of those not exposed. Among the exposed, the reduction in haemoglobin and ferritin levels was associated with the severity of anaemia. CONCLUSION: These findings indicate that in a real-world setting, anaemia with LDA can occur in 6-10 older individuals out of every 100 LDA users during the first 5 years of treatment.