Low-Dose Aspirin and the Risk of Stroke and Intracerebral Bleeding in Healthy Older People – Secondary Analysis of a Randomized Clinical Trial is a study just published in the JAMA. It demonstrates another reason why low dose aspirin for the primary prevention of cardiovascular disease is harmful rather than therapeutic. The study found a significant increase in intracranial bleeding with daily low-dose aspirin but no significant reduction of ischemic stroke. Its abstract is below. Primary prevention is designed to prevent an event which has yet to occur – eg, a first stroke or heart attack. Secondary prevention is an attempt to prevent a recurrence of something that has already happened at least once.

The reason that aspirin may be useful in secondary prevention is that the risk of a stroke or heart attack in someone who has already had one is so much greater compared to an individual that has never had one of these that the risk:benefit ratio may be favorable for aspirin as a secondary preventative despite its propensity to cause bleeding.


Importance  Low-dose aspirin has been widely used for primary and secondary prevention of stroke. The balance between potential reduction of ischemic stroke events and increased intracranial bleeding has not been established in older individuals.

Objective  To establish the risks of ischemic stroke and intracranial bleeding among healthy older people receiving daily low-dose aspirin.

Design, Setting, and Participants  This secondary analysis of the Aspirin in Reducing Events in the Elderly (ASPREE) randomized, double-blind, placebo-controlled trial of daily low-dose aspirin was conducted among community-dwelling people living in Australia or the US. Participants were older adults free of symptomatic cardiovascular disease. Recruitment took place between 2010 and 2014, and participants were followed up for a median (IQR) of 4.7 (3.6-5.7) years. This analysis was completed from August 2021 to March 2023.

Interventions  Daily 100-mg enteric-coated aspirin or matching placebo.

Main Outcomes and Measures  Stroke and stroke etiology were predetermined secondary outcomes and are presented with a focus on prevention of initial stroke or intracranial bleeding event. Outcomes were assessed by review of medical records.

Results  Among 19 114 older adults (10 782 females [56.4%]; median [IQR] age, 74 [71.6-77.7] years), 9525 individuals received aspirin and 9589 individuals received placebo. Aspirin did not produce a statistically significant reduction in the incidence of ischemic stroke (hazard ratio [HR], 0.89; 95% CI, 0.71-1.11). However, a statistically significant increase in intracranial bleeding was observed among individuals assigned to aspirin (108 individuals [1.1%]) compared with those receiving placebo (79 individuals [0.8%]; HR, 1.38; 95% CI, 1.03-1.84). This occurred by an increase in a combination of subdural, extradural, and subarachnoid bleeding with aspirin compared with placebo (59 individuals [0.6%] vs 41 individuals [0.4%]; HR, 1.45; 95% CI, 0.98-2.16). Hemorrhagic stroke was recorded in 49 individuals (0.5%) assigned to aspirin compared with 37 individuals (0.4%) in the placebo group (HR, 1.33; 95% CI, 0.87-2.04).

Conclusions and Relevance  This study found a significant increase in intracranial bleeding with daily low-dose aspirin but no significant reduction of ischemic stroke. These findings may have particular relevance to older individuals prone to developing intracranial bleeding after head trauma.