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Illustration of a trees losing its leaves to represent progression of dementia
  • Daily low-dose aspirin taken for an average of seven years did not affect the risk of dementia in adults with type 2 diabetes.
  • The aspirin regimen was neither protective nor harmful regarding dementia risk.
  • A heart attack or stroke was associated with at least double the risk of dementia. 

Taking daily low-dose aspirin for seven years did not affect the risk of dementia or mental decline among adults with type 2 diabetes, according to research presented today at the American Heart Association’s Scientific Sessions 2021

While daily low-dose aspirin has been used to reduce the risk of having a heart attack or clot-related stroke, it is also associated with internal bleeding including brain bleeds. ‘The overall effect of aspirin on dementia and cognitive impairment was uncertain,’ said study author, Jane Armitage, Professor of Clinical Trials and Epidemiology at Oxford Population Health. ‘Aspirin may be protective for dementia by preventing some strokes due to blockages, or it may increase the risk because of bleeding into the brain.’ 

Researchers aimed to assess the effects of low dose aspirin on the risk of dementia and cognitive impairment in participants enrolled in the ASCEND (A Study of Cardiovascular Events in Diabetes) trial. The ASCEND trial included 15,480 adults with type 2 diabetes living in the UK who had not experienced a stroke, heart attack or other circulatory issue, of whom 15,427 did not have any evidence of dementia at the beginning of the study. Half the participants took a single 100-milligram aspirin and half received an identical placebo pill daily. The study tracked participants for nearly nine years, with an average of about seven years of treatment and almost two additional years follow up. 

At the end of follow-up, the presence of dementia was determined by several methods: participant, doctor or carer reports during the trial; diagnoses listed in hospital admission data or death records; and other indicators of cognitive impairment listed in electronic health records. In addition, a cognitive function test (Telephone Interview for Cognitive Status and verbal fluency or the Healthy Minds test) was sought among survivors at the end of the scheduled treatment period. Researchers also noted the occurrence of serious illness, heart attacks, strokes or major internal bleeding. 

Researchers found 1,146 participants experienced “broad dementia,” meaning dementia, cognitive impairment, delirium or confusion; being prescribed dementia medications; or referral to a memory clinic or geriatric psychiatry. 

‘The results show no clear effect of daily low-dose aspirin on the risk of dementia with a non-significant 9% proportional reduction in risk. However, the uncertainty around this 9% benefit ranged from a 19% reduction in dementia risk to a 2% increase. This is reassuring given that millions of people worldwide regularly take aspirin to protect against the risk of heart attack and stroke and that an increase in the risk of dementia is unlikely. The results mean a modest benefit of aspirin on risk of dementia is possible, however, we would need studies with more people developing dementia to be sure.’ said Armitage. 

The researchers did find in observational analyses, however, that serious vascular events, such as a heart attack or major bleeding episodes like a stroke, were associated with an increased risk of dementia. There were 990 participants who survived a major vascular event, and 496 who survived a major bleed during the study. 


  • Having a major vascular event was associated with an almost two and a half fold excess risk of developing dementia during the study compared to those who did not have a major vascular event.
  • Having a major bleed was associated with twice the chance of having dementia compared to those who did not have a bleed. 

A limitation of the study is there may not be enough cases of reported dementia to make a clear assessment of the effect of low-dose aspirin on the risk of dementia. ‘A larger study with more cases of dementia may be able to detect any benefits or harms. We plan to continue to follow the trial participants for several more years to see if more cases of dementia emerge,’ Armitage said. 

The study was funded by Alzheimer’s Research UK, Bayer, the British Heart Foundation and the UK Medical Research Council.