Drinking a small amount of tea or coffee each day may lower the risk of dementia and slow cognitive decline, scientists say. A large US study following more than 130,000 people for up to 40 years found that those who drank two to three cups of caffeinated coffee or one to two cups of caffeinated tea daily had a 15–20% lower risk of dementia than non-drinkers. The research, published in Journal of the American Medical Association, also showed slightly better cognitive performance among caffeinated coffee drinkers compared with those who chose decaf.
Researchers analysed data from two long-running US health studies and found the benefit plateaued at moderate intake levels. No protective link appeared for decaffeinated coffee. The authors stressed the findings do not prove causation, as lifestyle factors could explain the difference. Lead author Yu Zhang of Harvard University said the results were consistent with biological theories, as caffeine and polyphenols may reduce inflammation, improve blood vessel health, and lower diabetes risk.
Experts urged caution. Naveed Sattar of University of Glasgow noted caffeine can also raise blood pressure in some people, which increases dementia risk. Researchers agree tea and coffee are not a cure, and that exercise, diet, sleep, and managing health risks remain the most effective ways to protect brain health.
