People who drink moderate amounts of tea or coffee show a lower risk of dementia, researchers say.
A US study followed more than 130,000 adults for up to 43 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 than non-drinkers.
Decaffeinated coffee showed no protective link.
Researchers published the findings in the Journal of the American Medical Association.
The study cannot prove caffeine protects the brain.
Lifestyle factors may partly explain the results.
Lead author Yu Zhang from Harvard University said the evidence fits known biology.
Tea and coffee contain caffeine and polyphenols that may reduce inflammation and oxidative stress.
Experts say randomised trials remain impractical.
They stress that healthy habits still matter most for brain health.
