Coffee May Have Added Benefits for Dementia Risk

Alzheimer’s disease, the most common cause of dementia, affects more than 6 million people in the United States and is projected to nearly double to 13 million by 2050. With limited treatment options available, finding ways to prevent or delay cognitive decline is more important than ever. That’s why researchers are paying closer attention to everyday habits—including what you drink—that might help protect your brain.

Coffee is one of the most widely consumed beverages in the world, and it contains bioactive compounds like caffeine and polyphenols that may protect the brain by reducing oxidative stress and inflammation. Some earlier studies have explored the connection between coffee, tea and cognitive health, but findings have been inconsistent.

To fill these gaps, researchers from Harvard University designed a large-scale study that tracked more than 131,000 people for up to 43 years, using repeated dietary assessments to capture long-term habits. They looked specifically at caffeinated coffee, decaffeinated coffee and tea to determine which beverages—and which components—might be linked to better brain health. The results were recently published in JAMA. Let’s break down what they found.

How Was This Study Conducted?

Researchers used data from two well-known, long-running health studies: the Nurses’ Health Study, which began in 1976 and enrolled female registered nurses, and the Health Professionals Follow-Up Study, which started in 1986 and recruited male health professionals. Combined, the analysis included 131,821 participants—86,606 female and 45,215 male—who did not have cancer, Parkinson’s disease or dementia when the study began.

Participants reported their dietary habits every two to four years using validated food questionnaires that tracked how often they consumed specific foods and beverages, including caffeinated coffee, decaffeinated coffee and tea. These repeated assessments allowed researchers to capture long-term habits rather than relying on a single snapshot.

The primary outcome researchers looked for was dementia, which was identified through death records and physician diagnoses. They also assessed subjective cognitive decline—where participants reported noticing changes in their own memory and thinking—and objective cognitive function, which was measured through phone-based neuropsychological tests in the female cohort.

The researchers adjusted their analyses for a wide range of factors, including age, smoking status, physical activity, body mass index, diet quality, alcohol intake and medical history. This type of study—called a prospective cohort study—observes people over time to identify associations, though it cannot prove that one thing directly causes another.

What Did the Study Find?

Over the course of up to 43 years (a median follow-up of about 37 years), 11,033 cases of dementia were documented. The results showed that people who drank more caffeinated coffee had a significantly lower risk of developing dementia. Specifically, those with the highest intake had an 18% lower risk compared to those with the lowest intake. Tea drinkers saw similar benefits—the highest tea consumers had a 14% lower risk of dementia compared to the lowest consumers.

One of the most striking findings was the dose-response pattern. The greatest brain-health benefits were linked to moderate consumption—about 2 to 3 cups per day of caffeinated coffee or 1 to 2 cups per day of tea (with one cup defined as an 8-ounce serving). Drinking more than that didn’t appear to offer additional protection.

The study also found that caffeinated coffee and tea drinkers were less likely to report noticing changes in their memory and thinking—a measure known as subjective cognitive decline. In the female cohort, higher caffeinated coffee intake was also linked to modestly better performance on objective cognitive tests.

Interestingly, decaffeinated coffee was not associated with lower dementia risk or better cognitive performance, suggesting that caffeine itself may be a primary driver of the protective association. These associations held up regardless of genetic risk factors for Alzheimer’s disease and were consistent across both cohorts.

Study Limitations

There are several important limitations to keep in mind. First, this is an observational study, so it can show associations but can’t prove that caffeinated coffee or tea directly prevents dementia. Second, the food questionnaires did not capture details like the type of tea (i.e. green or black) or coffee preparation method, which could influence the concentration of beneficial compounds. Third, the study participants were predominantly health professionals of European descent, so the findings may not apply to everyone. Finally, reverse causation cannot be completely ruled out, since early cognitive changes could affect drinking habits—though the researchers took several steps to address this concern.

How Does This Apply to Real Life?

If you already enjoy a morning cup of coffee or afternoon tea, this research offers a reassuring reason to keep sipping. The evidence suggests that moderate, consistent intake of caffeinated beverages may be one piece of a larger puzzle when it comes to protecting your brain health as you age.

Here are some practical takeaways:

• Stick to moderate amounts. The sweet spot appears to be about 2 to 3 cups (8 ounces each) of caffeinated coffee or 1 to 2 cups of tea per day. More doesn’t appear to add extra brain-health benefits.
• Caffeine is key. Decaffeinated coffee didn’t show the same associations in this study, so if you’re choosing coffee with brain health in mind, opting for the caffeinated version may be worth considering.
• Tea counts, too. If you’re not a coffee drinker, tea consumption showed similar benefits. Whether you prefer black, green or another variety, regular tea consumption was also linked to lower dementia risk.
• Watch what you add. The study focused on the beverages themselves, not sugar-laden coffee drinks or heavily sweetened teas. To get the most potential benefit, try to keep added sugars and cream to a minimum.
• Think of it as part of a bigger picture. Coffee and tea alone will not prevent dementia. A brain-healthy lifestyle also includes regular physical activity, quality sleep, social connection and an overall balanced eating pattern rich in fruits, vegetables, whole grains and fish.

If you’re sensitive to caffeine or have a health condition that requires you to limit it, talk to your health care provider before making changes. This study shows an association—not a guarantee—so view your daily cup as one of many healthy habits that can support your brain over time.

Our Expert Take

A large, long-term study published in JAMA suggests that moderate intake of caffeinated coffee (about 2 to 3 cups per day) and tea (about 1 to 2 cups per day) is associated with a lower risk of dementia and modestly better cognitive function. The protective association appears to be linked to caffeine specifically, since decaffeinated coffee did not show the same benefits. While more research is needed, this study adds to growing evidence that your daily caffeinated beverage habit may be doing your brain a favor. Pair your coffee or tea with other healthy lifestyle habits for the best chance of keeping your mind sharp as you age.