Drinking moderate amounts of caffeinated coffee or tea each day may be associated with a lower risk of dementia and slightly better cognitive performance, according to new long-term research. An analysis of health records from more than 130,000 participants followed for up to four decades found that those who regularly consumed two to three cups of caffeinated coffee or one to two cups of caffeinated tea daily had a 15 to 20 percent lower risk of developing dementia compared with non-drinkers.
While the findings suggest a potential protective link, researchers caution that the results do not prove that caffeine directly prevents cognitive decline.
Key Findings from Long-Term Studies
The study drew on data from two major US cohorts: the Nurses’ Health Study and the Health Professionals Follow-up Study. Together, they tracked 131,821 men and women for as long as 43 years, repeatedly assessing dietary habits, dementia diagnoses, cognitive decline and objective brain function test scores.
Participants who consumed the highest amounts of caffeinated coffee showed an 18 percent lower risk of dementia compared with those who drank little or none. Similar results were observed among tea drinkers. The apparent benefit plateaued at moderate levels, with no additional reduction in risk beyond two to three cups of coffee or one to two cups of tea daily. Notably, no significant association was found between decaffeinated coffee and dementia risk.
Possible Biological Explanations
Coffee and tea contain caffeine and polyphenols, compounds believed to support vascular health and reduce inflammation and oxidative stress. Oxidative stress occurs when unstable molecules known as free radicals damage cells and tissues, potentially contributing to brain ageing.
Caffeine has also been linked to improved metabolic health and lower rates of type 2 diabetes, itself a known risk factor for dementia. Researchers suggest these combined effects may contribute to the observed associations between moderate caffeine intake and cognitive outcomes.
Limits of Observational Evidence
Despite the encouraging data, the researchers stress that the study cannot establish causality. Individuals who consume caffeinated beverages may differ in other lifestyle factors that influence brain health. For example, people who avoid caffeine might do so because of sleep problems, which are independently linked to cognitive decline.
Randomized controlled trials lasting decades would provide stronger evidence but are largely impractical. Future research may instead focus on detecting biological changes associated with caffeine consumption through imaging or biomarkers.
Balancing Benefits and Risks
Experts note that caffeine has complex effects. While antioxidants and mild stimulation may enhance alertness and support learning or exercise, caffeine can also raise blood pressure in some individuals, and hypertension is a major contributor to dementia risk. The overall impact likely varies between individuals.
Researchers estimate that up to half of dementia cases worldwide could be prevented or delayed by addressing established risk factors such as obesity, smoking, excessive alcohol use, hearing loss and high blood pressure.
Conclusion
Moderate consumption of caffeinated coffee or tea appears to be associated with a reduced risk of dementia and modestly better cognitive performance over time. However, these findings should be viewed as part of a broader picture of brain health. A balanced diet, regular physical activity, adequate sleep and control of cardiovascular risk factors remain the most reliable strategies for supporting long-term cognitive function.