Large Study Finds No Evidence That Low-dose Aspirin Reduces Alzheimer’s Risk

Taking daily low-dose aspirin does not seem to reduce the risk of dementia, cognitive decline, or Alzheimer’s disease, new clinical trial data show.

The results were published in Neurology in a study, titled “Randomized placebo-controlled trial of the effects of aspirin on dementia and cognitive decline.”

Aspirin is a widely-used anti-inflammatory medication. Among its uses, low-dose daily aspirin is taken to decrease the likelihood of future heart attacks in people who have had a heart attack.

Increased inflammation, particularly in the brain, has been associated with the development of Alzheimer’s disease. Because of this, low-dose daily aspirin is thought to potentially help reduce the risk of Alzheimer’s, but this idea hasn’t been rigorously tested.

The Aspirin in Reducing Events in the Elderly (ASPREE) clinical trial (NCT01038583) enrolled 19,114 people, 70 or older, in Australia and the United States. For African-American and Hispanic participants in the U.S., the age limit was lowered to 65 years, because of their higher risk of disease. At enrollment, all participants had no signs of dementia or heart disease.

Participants were randomized to take 100 mg daily of aspirin (9,525 people), or a placebo (9,589). Participants were followed via regular phone calls and annual in-person meetings. A battery of cognitive assessments was administered after the first year, then every other year. If their cognitive assessments indicated possible dementia, the participants were referred for additional evaluations. Individuals who hit this referral “trigger,” but were not diagnosed with dementia, were deemed to have mild cognitive impairment (MCI).

Participants in both groups were followed for a median of 4.7 years (range 3.6–5.7 years). In this time, 283 people in the aspirin group were diagnosed with dementia, as were 292 people in the placebo group. The rate of dementia was not significantly different between the groups: slightly under seven events per 1,000 person-years for each group. Rates of MCI also did not differ between the two groups.

Of the dementia cases, 41% were classified as probable Alzheimer’s. The disease rate was not significantly different at just under three events per 1,000 person-years in each group.

The rate of cognitive decline (a significant decrease in cognition scores over time) — about 25 events per 1,000 person-years — was also not significantly different between the groups.

No differences were found between the groups in subgroup analyses, including age, sex, ethnicity, health factors, and prior use of aspirin or related anti-inflammatory medicines.

It is worth noting that the rates of dementia and MCI in the ASPREE study are somewhat lower than what has been reported in other published studies, which may have decreased the statistical power of this study to detect significant differences between the groups. The researchers who authored the study speculated that “this lower incidence is likely explained by the inclusion of participants who were relatively healthy at baseline.”

“This study provides no evidence that low-dose aspirin initiated in relatively healthy older adults is effective in preventing dementia, clinically probable [Alzheimer’s disease], or MCI, or in reducing cognitive decline during active treatment,” the researchers wrote. “This conclusion was consistent across a series of participant subgroups.”