People who drink two to three cups of caffeinated coffee or one to two cups of caffeinated tea daily may have a lower risk of dementia and better cognitive performance, according to a US study of over 130,000 participants. The research, published in the Journal of the American Medical Association, found that habitual consumers had a 15-20% lower risk of dementia over 40 years compared to non-drinkers.
The study analysed health records from the Nurses' Health Study and the Health Professionals Follow-up Study, tracking diet, dementia diagnoses, and cognitive decline for up to 43 years. Caffeinated coffee drinkers showed an 18% lower dementia risk and slightly less cognitive decline than those who drank decaf, with similar results for tea. No link was found for decaffeinated coffee.
Lead author Yu Zhang, a nutritional epidemiologist at Harvard University, said the findings are consistent with plausible biology but cannot prove causality. Coffee and tea contain caffeine and polyphenols that may protect the brain by improving vascular health and reducing inflammation, oxidative stress, and type 2 diabetes risk.
Professor Naveed Sattar of the University of Glasgow cautioned that caffeine can have both beneficial and harmful effects, such as raising blood pressure, a dementia risk factor. He noted that a randomised trial would be needed to confirm net benefits, but such long-term studies are impractical.
Zhang advised against viewing tea or coffee as a 'magic shield', emphasising that a healthy lifestyle, regular exercise, balanced diet, and good sleep are crucial for brain health. About half of dementia cases worldwide are considered preventable by addressing factors like obesity, smoking, and high blood pressure.
