Coffee and tea linked to lower rate of dementia

Adults who drank the most caffeinated coffee or tea over almost 37 years had a lower rate of dementia than those who drank little or none. That is the finding of a review by Harvard Health Publishing of a study published online on 9 February 2026 in the medical journal JAMA.

Harvard researchers looked at the diets of more than 131,000 people and followed them for an average of nearly 37 years. During that time, 11,033 of them were diagnosed with dementia, Harvard Health Publishing said.

People who drank the most caffeinated coffee, about two-and-a-half cups a day, had an 18% lower risk of dementia than those who drank little or no coffee, the review found. They also showed less decline on tests of thinking skills.

People who drank the most caffeinated tea, one to two cups a day, had similar results. Decaffeinated coffee did not show the same association, according to Harvard Health Publishing.

The study was observational and cannot prove that the drinks themselves protected participants’ brains, Harvard Health Publishing said. Other research suggests the inflammation-fighting effects of caffeine and polyphenol compounds, found in both coffee and tea, may play a role, though this has not been confirmed.

Close to 10 million new cases of dementia are diagnosed every year, according to the World Health Organization (WHO), whose figures show most people living with the condition are in low- and middle-income countries.

The NHS’s own guidance on lowering the risk of dementia does not mention coffee, tea or caffeine. It says around 4 in 10 cases could be prevented by changing risk factors that can be modified, including diet, weight, exercise, alcohol, smoking and blood pressure.

Age is the biggest risk factor for dementia and cannot be changed, though the condition is not a normal part of getting older, it adds.

There is no certain way to prevent all types of dementia, the guidance says, because researchers are still investigating how the condition develops.