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Hopes that Aspirin might Delay Dementia are Dashed

Tuesday, April 21st, 2020

Cardiovascular issues are a key risk factor for dementia. Because aspirin can be beneficial for those who have had heart attack, some studies have suggested that it may also be beneficial to the brain. Scientists have hypothesised that aspirin may reduce the risk of dementia by lowering inflammation, minimising blood clots forming, or by preventing the narrowing of blood vessels in the brain. However, a recent study to come out of Monash University in Melbourne, in collaboration with a team of American investigators, has indicated that it is unlikely this protection extends to dementia[1].

A huge sample and rigorous design 

The study recruited 19,114 individuals living in the community who did not have any cognitive or heart issues. The majority were aged 70 years or older. Some participants were enrolled through general practitioners in Australia, whilst others were recruited through mailing lists and media advertisements in the United States. Half of the participants were randomly assigned to take a daily low-dose of aspirin (100mg). The remaining half were randomly assigned to act as the control group and took a daily inactive placebo instead. All participants took thinking and memory tests at the study outset, at annual follow-up sessions, and at the five-year study end. The study was conducted “double-blind”, meaning that neither the participant nor the assessing research team knew which tablet the participant was taking. This was part of a rigorous protocol to avoid any unconscious bias.

No difference in cognition between Aspirin and Placebo

By the study end, the researchers recorded the development of 575 new cases of dementia among the participants. They found no difference in the risk of developing mild cognitive impairment or dementia between those who took aspirin and those who did not. The findings were consistent across men and women and different ethnic groups.

A Question of Time

The sample was large enough that the team should have found an effect. It is possible that the dose of aspirin was too low. It might also be that that the length of the study – just under five years – was not long enough to show the possible benefits from aspirin. The study team note their aspirations to follow up participants in later years. Another consideration is that the participants were mostly healthy at baseline, meaning that they were at low risk of experiencing cognitive decline. Certainly, the incidence of dementia in the sample was low relative to other population studies. Further, the authors note that the study did not address the question of aspirin potentially being beneficial for the preservation of cognitive function in middle-aged adults when neurodegenerative processes are likely to begin.

Nonetheless, the final study message was clear – that taking aspirin solely based on potential cognitive benefits is unsupported in healthy older people.