Coffee and Tea May Lower Dementia Risk, Study Finds

Coffee and tea lovers, rejoice; decaf fans, rethink. Those cups of caffeine could lower your dementia risk, new research suggests.

In a long-term, observational study of nearly 132,000 healthy adults, daily consumption of two to three cups of caffeinated coffee or one to two cups of tea was associated with lowering dementia risk, slowing cognitive decline and preserving cognitive function. The findings were published Monday in the Journal of the American Medical Association.

“We are not recommending that people who don’t drink coffee start drinking,” said lead study author Dr. Yu Zhang, a research trainee at Mass General Brigham in Boston. “We are just seeing that for people who already drink coffee, the results are really reassuring.”

Decaffeinated coffee didn’t yield the same neuroprotective benefits.

In addition to Mass General Brigham, scientists at the Harvard T.H. Chan School of Public Health and the Broad Institute of MIT and Harvard studied the health and caffeine habits of health professionals from two research datasets, which collectively spanned 1980 to 2023.

The first involved more than 86,000 women, whose average age was 46, from the Nurses’ Health Study. The second involved more than 45,000 men, whose average age was 54, from the Health Professionals Follow-Up Study, a complementary project focused on men’s health.

To measure intake of regular coffee, decaf coffee and tea, participants completed diet questionnaires every two to four years. After a median follow-up period of nearly 37 years, more than 11,000 people had been diagnosed with dementia.

People who consumed more caffeinated coffee or tea were less likely to develop dementia, with a stronger association among those 75 and younger. Specifically, people who drank the most caffeinated coffee had an 18% lower risk compared with those who drank the least. Among tea drinkers, people who consumed the most had a 14% lower risk than those who consumed the least.

Researchers also determined the optimal number of cups, or 8-ounce servings, of each beverage. Compared with people who didn’t drink coffee or tea, those who had two to three cups of caffeinated coffee or one to two cups of tea per day had the lowest dementia risk. That’s about 300 milligrams of caffeine daily.

What’s more, the association between caffeinated coffee and tea intake and dementia risk held true for people who were at high risk of developing dementia, including those with the APOE4 gene, a significant genetic risk factor for Alzheimer’s disease.

Even so, Zhang said, dementia is a complex condition that can’t be wholly prevented by dietary intervention.

“Drinking coffee alone does not provide the magical effect that can prevent people from getting dementia,” he said.

Caffeine’s cognitive benefits are hard to isolate

Globally, 57 million people were living with dementia in 2021, according to the World Health Organization. The condition disproportionately affects women, and Alzheimer’s disease is its most common form.

Dr. Kellyann Niotis, a preventive neurologist at Weill Cornell Medicine in New York City, said her patients often ask her what they can do to decrease their odds of developing dementia, including whether coffee may help or harm them.

Previous research on coffee, tea and dementia risk has been inconclusive, said Niotis, who wasn’t involved in the study.

“It is really a big challenge to disentangle the effects of coffee as a whole from all of the other compounds that are also in coffee — and tea,” she said. “It’s definitely possible that these other compounds are interacting with each other, or synergistically with the caffeine itself, to exert some benefit.”

Beyond trace amounts of vitamins and minerals, such bioactive substances include polyphenols, which have antioxidant and anti-inflammatory properties, she said.

“The method of taking out the caffeine from coffee is not just extracting the caffeine; it’s also extracting other polyphenols that are in the coffee,” Niotis said. “It’s easy to say, ‘Well, it’s the caffeine that’s beneficial.’”

The new research has several limitations. It didn’t differentiate between regular or decaf tea, or tea type, such as black, green or white. Coffee preparation methods weren’t specified either. Factors such as roast level, bean origin and brewing technique may influence concentrations of caffeine and other compounds, the authors wrote.

Participants also self-reported caffeine consumption via soda and chocolate, which aren’t typically considered healthy.

In terms of total caffeine intake, researchers found that people who consumed more caffeine had a lower risk of dementia.

Coffee, tea may help safeguard cognitive health

Another part of the study measured participants’ subjective cognitive decline and objective cognitive function.

At several points throughout the follow-up period, all participants completed questionnaires that tested memory, attention, executive function and visuospatial skills.

Additionally, women older than 70 were tested using telephone-based cognitive assessments, including the East Boston Memory Test. Older men weren’t tested.

Higher intake of caffeinated coffee and tea was associated with lower prevalence of subjective cognitive decline and slightly better objective cognitive performance.

Benjamin Katz, an associate professor in the department of human development and family science at Virginia Tech, researches how lifestyle factors can influence cognitive function throughout a person’s life. He noted that the study didn’t cover energy drinks, which in shot form may contain more caffeine than a cup of coffee.

More research is needed on caffeine’s possible neuroprotective effects, said Katz, who wasn’t part of the study.

Additionally, the study didn’t mention whether people added milk, cream, sugar or other sweeteners to their drinks. Katz’s research has discovered a link between sugar-sweetened beverages and increased risk of cognitive impairment.

“If you’re drinking a couple cups of coffee but you’re putting sugar and milk into it, that may be counteracting the effects,” he said. “But [diet]’s really only a small component of a much larger set of lifestyle decisions that you would want to be focusing on to maintain brain health during aging.”

Aerobic exercise, for example, has been shown to support cognitive function, Katz said.

“In addition to things like getting enough sleep and not smoking, another big one is cognitive engagement, like doing a lifelong learning program,” Katz said. “If you’re an older adult, those are things that are really valuable.”