People who drink two to three cups of caffeinated coffee or one to two cups of caffeinated tea daily have a 15-20% lower risk of dementia compared to those who avoid these drinks, according to a US study of over 130,000 participants. The research, published in the Journal of the American Medical Association, also found that caffeinated coffee drinkers experienced slightly less cognitive decline and performed better on objective brain function tests than decaf drinkers.
The study analysed health records from the Nurses' Health Study and the Health Professionals Follow-up Study, tracking participants for up to 43 years. Those who consumed the most caffeinated coffee had an 18% lower risk of dementia, with similar results for tea. The protective effect plateaued at two to three cups of coffee or one to two cups of tea daily. No link was found with decaffeinated coffee.
Lead author Yu Zhang, a nutritional epidemiology researcher at Harvard University, cautioned that the study cannot prove causality. 'Our study alone can't prove causality, but to our knowledge, it is the best evidence to date looking at coffee and tea intake and cognitive health,' he said. The findings are consistent with plausible biology, as caffeine and polyphenols in these drinks may improve vascular health, reduce inflammation, and lower type 2 diabetes risk, a known dementia risk factor.
However, experts note that caffeine can have both beneficial and harmful effects. Professor Naveed Sattar of the University of Glasgow pointed out that caffeine raises blood pressure in some people, a significant driver of dementia. 'Caffeine does a multitude of things, some which may be beneficial, some which may be harmful, and the net effect can never be estimated until you do a randomised trial,' he said.
Zhang emphasised that coffee or tea should not be seen as a 'magic shield'. 'Maintaining a healthy lifestyle, getting regular exercise, having a balanced diet and getting good sleep are all important to get better brain health,' he said. Researchers estimate that about half of dementia cases worldwide could be prevented or delayed by addressing factors like obesity, smoking, excessive alcohol, hearing loss, and high blood pressure.
