There is good evidence that a daily baby aspirin reduces the risk for heart disease and stroke, and some have thought its inflammation-lowering effect might also help in delaying cognitive decline. But taking a daily low-dose aspirin did not appear to be effective in lowering the risk of Alzheimer’s disease or other forms of dementia, a new study reports.

For the study, in Neurology, researchers set up a controlled trial with 19,114 men and women older than 70 who were free of cardiovascular disease and dementia at the start.

Half were randomly assigned to take a daily 100-milligram aspirin, while the other half took a placebo.

After an average follow-up of almost five years with annual examinations, the researchers found no difference between the groups in diagnoses of Alzheimer’s disease or mild cognitive impairment. They did find declining cognitive function over time, but the speed and degree of that decline was the same in both groups.

The researchers found no effect in various subgroups, either — people with hypertension or diabetes, smokers or people with high cholesterol, or those who were overweight or obese. A limitation of the study was that patients were followed for less than five years.

“If you’re 70 or older and healthy, without evidence of cardiovascular disease, it’s very difficult to improve on your success. The relatively low risk of dementia in this study was not further lowered with aspirin,” said a co-author, Dr. Anne B. Newman, a professor of epidemiology at the University of Pittsburgh.

Heart issues not affected by omega-3 fatty acids, studies find

Omega-3 fatty acids have almost no effect, good or bad, on the risk for cardiovascular disease or cancer.

Those are the findings of two large studies, one an update in the Cochrane Database of Systematic Reviews and the second in the British Journal of Cancer, that combined data from dozens of randomized controlled trials.

In 28 high-quality trials covered in the Cochrane analysis, with durations ranging from one to more than seven years, pooled results showed little or no effect of omega-3 supplements on dying from any cause, dying from cardiovascular disease, cardiovascular events like heart attack or stroke, or heart rhythm disorders. There was low-quality evidence of a small effect on coronary heart disease mortality. The investigation showed little evidence of any benefit in the few trials that tested eating oily fish.

The analysis in the British Journal of Cancer showed no beneficial effect on cancer diagnosis or cancer death. But the review found that high doses of omega-3 supplements might very slightly increase the risk for prostate cancer and cancer death. The authors conclude that this slight increase is probably offset by small protective effects on cardiovascular disease.

The American Heart Association and the American Cancer Society both recommend omega-3s for reducing the risk of heart disease and cancer, but Lee Hooper, a reader in nutrition at Norwich Medical School who worked on both studies, said that the evidence does not support those recommendations.

“We’ve tried to get it right,” she said. “We’ve tried to make sure all the details are there. We’ve tried to check every way to make sure we’re not missing something. And all we see is these tiny harms and benefits that appear to balance each other out.”