People who drink a few cups of tea or coffee each day may face a lower risk of dementia.
A US study followed more than 130,000 adults for up to 40 years.
Those drinking two to three coffees or one to two teas daily had 15–20% lower dementia risk.
Caffeinated coffee drinkers also showed slightly less cognitive decline.
Decaffeinated coffee showed no such link.
Researchers published the findings in Journal of the American Medical Association.
The study cannot prove caffeine protects the brain.
Lifestyle factors may explain some of the difference.
Lead author Yu Zhang from Harvard University said the results fit known biology.
Tea and coffee contain caffeine and antioxidants that may reduce inflammation and support blood vessels.
Caffeine also links to lower diabetes risk, which affects dementia rates.
Experts urge caution.
University of Glasgow professor Naveed Sattar said caffeine has mixed brain effects.
Researchers stress that exercise, sleep, and healthy diets matter most for brain health.
