Your daily coffee or tea habit may offer a degree of protection against cognitive decline and dementia, according to research published in JAMA. The study, led by researchers at Harvard University, suggests that moderate consumption of these beverages could be a simple, accessible way to support brain health as we age.
The research team analyzed data from over 130,000 participants in the Nurses’ Health Study and the Health Professionals Follow-Up Study, tracking their dietary habits, medical histories, and cognitive function over a period of up to 43 years. The findings indicate that individuals who regularly consumed two to three cups of caffeinated coffee per day, or one to two cups of tea, exhibited a reduced risk of developing dementia.
A Long-Term Look at Coffee, Tea, and Brain Health
“Dementia develops over decades, and coffee and tea are things people drink every day,” explained Yu Zhang, MBBS, MS, a PhD student at the Harvard T.H. Chan School of Public Health and a research trainee at Mass General Brigham. “But many past studies were short or measured diet only once, and most didn’t differentiate caffeinated or decaf coffee.” This study aimed to address those limitations by leveraging the extensive, long-term data available through these established health studies.
The strength of the study lies in its prospective design and the repeated collection of dietary information. Participants consistently reported their coffee and tea intake every two to four years, allowing researchers to examine long-term patterns with greater accuracy. This detailed data, combined with information on lifestyle factors and medical history, provided a robust framework for investigating the relationship between beverage consumption and cognitive outcomes.
Of the 131,821 participants included in the analysis, 11,033 individuals were diagnosed with dementia during the follow-up period. Researchers found that those in the highest quartile of caffeinated coffee consumption – meaning they drank the most – had an 18% lower risk of dementia compared to those in the lowest quartile.
The study also assessed cognitive function through multiple measures, including medical diagnoses of dementia, self-reported cognitive decline, and objective cognitive testing conducted via telephone interviews. Caffeinated coffee drinkers demonstrated a lower prevalence of subjective cognitive decline (7.8% versus 9.5%) compared to those who consumed little to no caffeinated coffee. While tea drinkers showed similar trends, the benefits were not observed among those who consumed high amounts of decaffeinated coffee.
Correlation, Not Causation
The researchers emphasize that this study demonstrates an association between coffee and tea consumption and reduced dementia risk, but it does not prove a causal relationship. “We did our best to adjust for many lifestyle and health factors, but no study can control for everything,” Zhang noted. Other factors, such as underlying health conditions or unmeasured lifestyle variables, could potentially influence both beverage consumption and cognitive outcomes.
The study authors acknowledge the possibility that individuals with certain medical conditions may be advised to modify their caffeine intake, and that this advice could independently affect their risk of cognitive decline. They also point out that the statistical model may not have captured all relevant lifestyle factors.
A Small Effect, But Potentially Significant
While the observed effect size is relatively small, researchers consider the findings to be encouraging. “The effect size is small and there are lots of important ways to protect cognitive function as we age,” Zhang said. “Our study suggests that caffeinated coffee or tea consumption can be one piece of that puzzle.”
Coffee and tea contain a variety of bioactive compounds, including polyphenols and caffeine, which have been shown in previous research to possess neuroprotective properties. These compounds may help reduce inflammation and protect against cellular damage in the brain. However, the precise mechanisms by which coffee and tea might influence cognitive function remain to be fully understood.
“We are not recommending people who don’t drink coffee to start drinking it, but for people who already drink coffee or tea, our results are reassuring,” Zhang emphasized. “It’s best to view it as one small piece of a bigger prevention picture, alongside regular exercise, good sleep, and good cardiovascular health.”
Sarah Berry, a professor of nutritional sciences at King’s College London, who was not involved in the study, described the research as a “valuable addition” to the existing body of evidence. “This large-scale study provides convincing data suggesting that caffeinated coffee and tea are associated with a reduced risk of developing dementia and slightly better cognitive performance,” she said. However, she also cautioned that further research is needed to confirm these findings and establish a definitive causal link.
Reference: Zhang Y, Liu Y, Li Y, et al. Coffee and tea intake, dementia risk, and cognitive function. JAMA. 2026. Doi: 10.1001/jama.2025.27259
About the interviewee: Yu Zhang is a PhD student at the Harvard T.H. Chan School of Public Health and a research trainee at Mass General Brigham.
Yu Zhang was speaking with Alexander Beadle, Science Writer and Editor at Technology Networks.
