People who drink a small amount of tea or coffee each day may face a lower risk of dementia, researchers say. A large US study found that those who regularly drank two to three cups of caffeinated coffee or one to two cups of caffeinated tea had a 15–20% lower dementia risk over four decades. They also showed slightly better cognitive performance than people who avoided caffeine.
The study, published in the Journal of the American Medical Association, analysed health data from more than 130,000 participants in long-running US studies. Caffeinated coffee drinkers showed less cognitive decline than those who chose decaf, while no protective link appeared for decaffeinated coffee.
The lead author, Yu Zhang of Harvard University, said the findings suggest a possible brain benefit but cannot prove cause and effect. Coffee and tea contain caffeine and polyphenols that may reduce inflammation, improve blood vessel health, and lower diabetes risk, all factors linked to dementia.
Experts caution against overinterpreting the results. Naveed Sattar of the University of Glasgow noted that caffeine can also raise blood pressure in some people, which may increase dementia risk. Researchers stress that tea and coffee are no substitute for proven measures such as exercise, healthy diet, good sleep, and controlling blood pressure.
