Daily cups of caffeinated coffee or mugs of tea may lower dementia risk

Downing a few cups of caffeinated coffee or mugs of tea each day may lower the risk of developing dementia, according to a long-term study.

The lowest risk was tied to drinking around two to three cups of caffeinated coffee or one to two cups of tea per day, compared with having none, the researchers report February 9 in the Journal of the American Medical Association. Consuming more of the beverages didn’t lower the risk further. There wasn’t a link between decaffeinated coffee and dementia risk.

The new U.S. analysis included data from the 1980s to early 2023 collected for the Nurses’ Health Study and the Health Professionals Follow-up Study. The researchers selected more than 130,000 participants who had not had cancer, Parkinson’s disease or dementia. Participants had answered dietary questionnaires every few years. Researchers tallied cases of dementia from death records or from participants’ self-reported medical diagnoses.

Moderate daily consumption of caffeinated coffee for women was around 2.5 cups and the highest consumption was around 4.5 cups, while men in those categories drank less. The top coffee drinkers overall tended to be younger and more likely to smoke.

There were 330 new cases of dementia per 100,000 per year among those who didn’t drink any caffeinated coffee. Among moderate consumers, it was 229 per 100,000 per year. That rate was lower for the group drinking the most. But with adjustments for factors such as age and smoking, moderate and high consumption both lowered the risk of dementia by a similar amount, 19 and 18 percent, respectively. Those who drank more tea also saw a lower risk. The study team didn’t have information on whether participants’ tea contained caffeine.

The researchers didn’t investigate why tea or caffeinated coffee might reduce dementia risk. Inflammation may play a role in the development of dementia. Past research has suggested that caffeine may reduce inflammation and that other compounds in coffee and tea may tamp down oxidative stress, which causes cellular damage. How much diet might contribute to the development of dementia, which is not fully understood, is complex to study, but the risk is unlikely to come down to just a cup or two of joe.