Daily consumption of coffee or tea may lower the risk of dementia, according to researchers.

Daily consumption of two to three cups of caffeinated coffee or one to two cups of tea may be associated with a lower risk of developing dementia later in life, as well as the potential to slow the progression of cognitive decline, according to new research. While the findings have excited both tea and coffee lovers, scientists stress that the results show correlation rather than definitive proof of cause and effect — and that a healthy lifestyle overall remains vital for brain health.

Over the course of approximately four decades, more than 130,000 adults in the United States were the subject of a large, long-term observational study that was published in the Journal of the American Medical Association (JAMA). The Nurses' Health Study and the Health Professionals Follow-Up Study, two well-known cohort studies that collect data on diet, lifestyle, and health, had participants. Researchers compared people who consumed different amounts of caffeinated coffee and tea with those who drank little or none. They found that those with moderate caffeine intake — roughly two to three cups of coffee or one to two cups of tea per day — had a lower risk of developing dementia and experienced slower cognitive decline compared with low or non-caffeine drinkers.

More specifically, those who drank more tea had a risk reduction of approximately 16%, while those who drank more coffee had a risk reduction of up to 18%. Both groups also generally performed better on cognitive tests assessing memory and mental function than those who drank little or no caffeinated beverages.

Importantly, decaffeinated coffee did not show similar protective associations, suggesting that caffeine, alongside other bioactive compounds in coffee and tea, may play a role.

Researchers speculate that caffeine's potential advantages may be due to a number of biological mechanisms. Caffeine and other compounds in coffee and tea — such as polyphenols — may help reduce inflammation, improve vascular health, and protect neurons from oxidative stress, all of which are factors linked to cognitive decline and neurodegenerative diseases.

Bioactive compounds found in tea and coffee have been investigated for their ability to protect the brain from oxidative damage and inflammation, two known factors that contribute to aging. Beyond caffeine itself, these plant-derived molecules may support the brain’s resilience against age-related changes and contribute to healthier brain aging, although the exact pathways remain under investigation.

Yet experts caution that a direct causal relationship between caffeine intake and dementia prevention cannot be established from this type of study alone. While the associations are statistically robust, the observational design means other lifestyle factors — such as physical activity, diet quality, sleep habits, and genetics — could also influence outcomes.

Contributors from the medical field emphasize that the results are "encouraging but not conclusive.". A CBS News medical contributor named Céline Gounder advised the general public to take the findings "with a huge grain of salt," noting that observational associations do not prove cause and effect. In a similar vein, experts caution against considering coffee or tea as a stand-alone prevention against dementia, despite the fact that moderate caffeine consumption correlates with a lower risk of dementia and a slower rate of cognitive decline. Instead, they recommend that individuals maintain balanced diets, regular physical activity, adequate sleep, and stress management as the foundation of cognitive health.

Additionally, the researchers point out that the observed patterns varied depending on the level of consumption. The strongest link between a lower risk of dementia and moderate consumption was found, but eating more than this did not appear to have any additional benefits. Millions of people worldwide are affected by dementia, which remains a significant public health issue worldwide. Scientists place a high priority on identifying lifestyle factors that could "delay onset or slow progression" because there is currently no cure.

Research shows that quitting smoking, maintaining a healthy weight, controlling blood pressure, and participating in mentally stimulating activities can all lower the risk of dementia. Tea and coffee are among the most widely consumed beverages globally, so even modest associations with better cognitive outcomes could have meaningful implications at a population level.

However, experts agree that moderation is essential, and excessive caffeine consumption can disrupt sleep or cause anxiety, negating any potential benefits. This is especially true for those who are sensitive to its effects. The most recent study adds to the growing body of evidence that moderate consumption of caffeinated beverages like coffee and tea may be associated with a lower risk of dementia and a slower rate of cognitive decline.

While the results are promising and reinforce the potential brain-health value of these beverages, they do not establish causation. Taking a holistic approach to health, which includes eating right, exercising, and getting enough sleep, is still important for maintaining cognitive function as people get older.