Over the study period, 11,033 participants (about 8%) developed dementia. The findings were reported by researchers from Loughborough University, Harvard T.H. Chan School of Public Health, and other institutions.
Study Design and Methods
Participants reported their coffee and tea consumption through validated food frequency questionnaires administered every four years. Caffeine intake was calculated based on standard caffeine content per cup, according to the study. The analysis adjusted for potential confounders, including age, smoking, alcohol intake, physical activity, and medical history. At baseline, women reported an average of about four and a half cups of coffee or tea daily; men averaged about two and a half cups, as detailed in the report.
Researchers noted that participants who consumed more caffeinated coffee were generally younger but also had higher alcohol consumption, smoking rates, and calorie intake -- factors linked to increased dementia risk.
Key Findings on Dementia Risk
Consuming about 250–300 mg of caffeine per day -- roughly two to three cups of coffee -- was associated with a 35% lower dementia risk among adults aged 75 and younger, the study found. Drinking more than that did not provide additional protection, according to the data. An unexpected trend emerged with decaffeinated coffee: higher decaf intake was linked to faster memory decline. Researchers suggested that some participants may have switched to decaf after developing sleep issues, high blood pressure, or heart rhythm problems -- conditions themselves tied to cognitive decline, as noted by Eef Hogervorst, professor of biological psychology at Loughborough University, in a ScienceDaily article [1]. Tea consumption also showed benefits: One to two cups per day offered the strongest protection against dementia, though tea consumption in the U.S. is generally lower than coffee consumption, according to the report.
Biological Mechanisms Proposed
Caffeine blocks adenosine, a chemical that slows activity of neurotransmitters like dopamine and acetylcholine, which naturally decline with age and in Alzheimer's disease, the authors wrote [1]. Reducing this inhibition may help maintain brain cell activity, they said. Caffeine may also reduce inflammation and help regulate blood sugar metabolism. Additionally, the study cited prior research showing that regular consumption of more than two cups of coffee daily was associated with lower levels of amyloid plaques -- toxic protein clumps linked to Alzheimer's.
The authors noted that coffee and tea contain antioxidants and compounds that support blood vessel health, which may also contribute to brain protection. In his book The Better Brain Solution, Dr. Steven Masley referenced a Japanese study of over 23,000 adults older than age 65 showing a 20 to 25% lower risk of dementia among regular coffee drinkers [2]. Similarly, Gary Small and Gigi Vorgan in 2 Weeks to a Younger Brain reported that drinking one to three cups of coffee a day has been linked to a 65% lower risk for developing Alzheimer's and Parkinson's disease [3].
Limitations and Expert Commentary
The protective effect appeared to level off at higher intakes, consistent with the Yerkes-Dodson law, which posits that mental performance improves with stimulation only up to a point before declining, according to researchers [1]. They cautioned that measuring caffeine intake by cups is imprecise, as caffeine content varies by coffee type and preparation method. They also advised individuals with very high blood pressure to limit coffee to about one cup per day. The study's observational design cannot establish causation, and the sample consisted mainly of healthcare professionals, potentially limiting generalizability. However, similar patterns were observed in 38 additional studies, with caffeine drinkers showing a 6–16% lower dementia risk compared to non-drinkers.
A separate large-scale study published in the Journal of Nutrition, Health and Aging, using UK Biobank data, also found that coffee and tea consumption showed protective associations against all-cause dementia, while sugar-sweetened and artificially sweetened drinks were linked to increased risk [4]. An article on Mercola.com noted that the 2015 Dietary Guidelines for Americans said Americans could safely consume up to five cups of coffee a day with no detrimental effects [5].
References
- Eef Hogervorst. "This daily habit could lower dementia risk by 35%, scientists say". ScienceDaily via The Conversation. May 13, 2026.
- Dr. Steven Masley. The Better Brain Solution: How to Start Now At Any Age.
- Gary Small and Gigi Vorgan. 2 Weeks to a Younger Brain.
- Study Links Beverage Consumption to Dementia Risk, Finds Protective Effect for Coffee and Tea. NaturalNews.com. March 29, 2026.
- Mercola.com. "More Consensus on the Health Benefits of Tea". May 25, 2015.
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