Coffee and Tea Drinkers Show Reduced Dementia Risk in Latest Research

Drinking two to three cups of coffee or one to two cups of tea daily may lower the risk of dementia, according to a new study published in the Journal of the American Medical Association. The research analyzed 131,821 participants over up to 43 years.

Researchers from Mass General Brigham, Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard conducted the study.

Study Tracks Over 130,000 Participants for Four Decades

The participants came from two long-running studies. The Nurses' Health Study included 86,606 women with data from 1980 to 2023. The Health Professionals Follow-Up Study included 45,215 men with data from 1986 to 2023. At the start, participants did not have cancer, Parkinson disease, or dementia.

During the study period, 11,033 participants developed dementia. The researchers tracked each person's coffee and tea intake through diet questionnaires completed every two to four years.

People who drank the most caffeinated coffee had an 18 percent lower risk of dementia compared with those who drank little or no caffeinated coffee. Tea drinkers who consumed the most had a 14 percent lower risk than those who consumed the least.

The benefits were most pronounced at moderate intake levels. Participants who consumed two to three cups of caffeinated coffee per day had the lowest dementia risk. For tea drinkers, one to two cups per day showed the greatest benefit.

Higher consumption did not increase the benefits further. The study found that moderate and high consumption both lowered dementia risk by similar amounts.

Decaffeinated coffee showed no association with dementia risk. This suggests that caffeine may be the active factor producing protective effects. However, researchers said more work is needed to confirm this.

Lead study author Dr. Yu Zhang, a research trainee at Mass General Brigham, said the results are reassuring for coffee drinkers.

"We are not recommending that people who don't drink coffee start drinking," Zhang said. "We are just seeing that for people who already drink coffee, the results are really reassuring."

The study also measured cognitive decline through questionnaires and tests. Caffeinated coffee drinkers had a lower prevalence of subjective cognitive decline, with a rate of 7.8 percent compared with 9.5 percent for those who drank little or no coffee.

Higher intake of caffeinated coffee and tea was associated with slightly better performance on cognitive tests measuring memory, attention, and executive function.

The study found the benefits applied across different age groups, with stronger associations among those 75 and younger.

Senior author Daniel Wang, associate scientist at Mass General Brigham and assistant professor at Harvard Medical School, emphasized the effect size is small.

"While our results are encouraging, it's important to remember that the effect size is small and there are lots of important ways to protect cognitive function as we age," Wang said.

Coffee and tea contain bioactive ingredients including polyphenols and caffeine. These compounds may reduce inflammation and cellular damage, potentially protecting against cognitive decline.

Previous studies on coffee, tea, and dementia risk have produced inconsistent results. The new research addressed limitations through its extended timeframe and repeated assessments over a median of nearly 37 years.

Researchers calculated dementia cases per 100,000 people per year. Among those who did not drink caffeinated coffee, there were 330 new cases per 100,000 per year. Among moderate consumers, the rate dropped to 229 per 100,000 per year.

The study shows an association between caffeine consumption and lower dementia risk but does not prove causation. Other lifestyle factors may play a role.

Some experts cautioned about interpreting the results. Dr. Celine Gounder, CBS News medical contributor, said the results should be taken with caution. She noted that people may avoid caffeinated beverages for health reasons like high blood pressure, which is itself a dementia risk factor.

The researchers excluded people with major chronic diseases at the study's start and adjusted for factors such as age and smoking.

Gounder emphasized that proven methods for preventing dementia include exercise, improved diet, and weight management.

The research comes as dementia cases are expected to double in the United States over the next few decades. More than 7 million Americans currently live with Alzheimer's disease, the most common cause of dementia. Most current treatments do not begin until cognitive decline is already underway, making prevention critical.

The study adds to research examining coffee and tea consumption. Recent studies have linked moderate coffee drinking to lower risks of Alzheimer's and Parkinson's disease.

The findings may have public health implications given widespread coffee and tea consumption. The National Coffee Association reports that two thirds of Americans drink coffee daily, with the average consumer drinking three cups per day.

The researchers noted that more studies are needed to validate their findings and understand the mechanisms behind the associations. Future research should investigate whether a causal relationship exists and identify which specific compounds provide protective effects.