A large prospective cohort study conducted by researchers at Massachusetts General Brigham, the Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard University examined data from 131,821 participants in the Nurses’ Health Study (NHS) and the Health Professionals Follow-up Study (HPFS). The results showed that moderate consumption of caffeinated coffee (2-3 cups per day) or black tea (1-2 cups per day) was associated with lower risk of dementia, slower cognitive decline, and better preservation of cognitive abilities. This research Japan Automobile Manufacturers Association.
“As we were exploring the potential for dementia prevention tools, we thought something as common as coffee might be a promising dietary intervention, and having unique access to high-quality data through more than 40 years of research allowed us to put that idea into action,” said lead author Daniel Wang, MD, PhD, associate scientist in the Channing Division of Network Medicine at Massachusetts General Brigham Medical School and assistant professor at Harvard Medical School. Mr. Wang is also an assistant professor in the Department of Nutrition at the Harvard Chan School and an associate member of the Broad Institute. “Although our results are encouraging, it is important to remember that the effect sizes are small and there are many important ways to protect cognitive function as we age. Our study suggests that consuming caffeinated coffee and tea may be one piece of that puzzle.”
Why prevention is important for dementia
Early prevention of dementia is especially important because current treatments have limitations and are generally only marginally effective after symptoms begin. As a result, scientists have increasingly focused on lifestyle factors such as diet that can influence the progression of cognitive decline.
Coffee and tea contain compounds such as polyphenols and caffeine that are thought to support brain health. These substances may help reduce inflammation and limit cell damage, both of which are associated with cognitive decline. However, previous studies on coffee and dementia have yielded mixed results, often with short study periods and limited data on long-term consumption patterns and different types of beverages.
Long-term data provides clearer insights
The NHS and HPFS datasets helped address these gaps. Participants were followed for up to 43 years, with repeated assessments of diet, dementia diagnosis, subjective cognitive concerns, and objective cognitive performance. Researchers analyzed how consumption of caffeinated coffee, tea, and decaf coffee was associated with long-term brain health.
Of the more than 130,000 participants, 11,033 developed dementia during the study period. People who consumed large amounts of caffeinated coffee had an 18% lower risk of developing dementia than those who drank little or no caffeine. They also reported lower rates of subjective cognitive decline (7.8% vs. 9.5%) and better performance on certain objective cognitive tests.
Caffeine may play an important role
A similar pattern was observed among tea drinkers, but the same association was not found for decaffeinated coffee. This suggests that caffeine may be an important factor behind the observed brain-related benefits, but further research is needed to confirm the underlying mechanisms.
The strongest effects were seen in participants who drank two to three cups of caffeinated coffee or one to two cups of tea per day. High levels of caffeine intake did not appear to cause harm. Instead, it showed benefits comparable to the moderate intake range highlighted in the study.
“We also compared people with different genetic predispositions to developing dementia and found the same results: coffee and caffeine are likely to be equally beneficial for people at high and low genetic risk for developing dementia,” said lead author Yu Zhang, MBBS, a doctoral student at the Harvard Chan School and a research trainee at the Massachusetts General Brigham.
Study authors and funding
In addition to Wang and Zhang, Contributors to Mass General Brigham included Yuxi Liu, Yanping Li, Yuhan Li, Jae H. Kang, A. Heather Eliassen, Molin Wang, Eric B. Rimm, Frank B. Hu, and Meir J. Stampfer. Additional authors are Walter C. Willett and Xiao Gu.
This research was supported by National Institutes of Health grants UM1 CA186107, U01 HL145386, U01 CA167552, R01 HL60712, P30 DK46200, R00 DK119412, R01 AG077489, RF1 AG083764, and R01 NR019992. The funding bodies had no role in study design, data collection, analysis, manuscript preparation, or decision to publish.
