Drinking two to three cups of caffeinated coffee daily may help protect brain health, as research suggests coffee reduces dementia risk. In contrast, decaf coffee shows no such benefit, according to a long-term study of nearly 132,000 adults tracked for up to 43 years.
Caffeinated Coffee And Tea Show Protective Association
A large study published Monday in JAMA finds that moderate consumption of caffeinated coffee or tea is associated with reduced chances of developing dementia. Researchers followed 131,821 men and women for decades, analyzing dietary patterns alongside health outcomes.
Participants who consumed between one and five cups of caffeinated coffee had about 20 percent less dementia risk compared with those who consumed little or no caffeine, reinforcing evidence that coffee reduces dementia risk. Meanwhile, those who drank at least one cup of caffeinated tea daily experienced roughly a 15 percent reduction.
“This is a very large, rigorous study conducted long term among men and women that shows that drinking two or three cups of coffee per day is associated with reduced risk of dementia,” said Aladdin Shadyab, an associate professor of public health and medicine at the University of California, San Diego, who was not involved in the research.
The findings do not prove caffeine directly causes the benefit. However, independent experts note the researchers adjusted for factors including diet, medication use, education, socioeconomic status, smoking, mental illness, and family history of dementia.
Researchers Track Medical Professionals for Decades
The study drew participants from two ongoing cohorts: the Nurses’ Health Study and the Health Professionals Follow-up Study. Most were in their mid-40s or early 50s when the research began and completed repeated surveys on diet, lifestyle, and medical history.
Over time, 11,033 participants developed dementia, confirmed through physician diagnoses or death certificates. The protective association held even among individuals with genetic risk factors for Alzheimer’s disease or related conditions.
Dr. Daniel Wang, the study’s senior author and an epidemiologist specializing in neurodegenerative diseases at Mass General Brigham, said the benefit appeared to level off beyond about two and a half cups of coffee daily.
“Humans cannot metabolize any more of the bioactive compounds in coffee and tea,” Wang said, explaining the plateau effect.
Among roughly 17,000 women older than 70 who completed cognitive testing, higher caffeine intake was linked to slightly better scores, supporting evidence that coffee reduces dementia risk. Researchers estimated that cognitive decline in these participants slowed by about seven months.
Scientists say caffeine may help protect brain health by reducing neuroinflammation, improving vascular function, and enhancing insulin sensitivity — all factors linked to dementia risk — which supports evidence that coffee reduces dementia risk.
Experts Urge Moderation, Not Overconsumption
While the study found no clear harms from higher caffeine levels, some research suggests excessive intake may disrupt sleep or worsen anxiety.
Dr. Fang Fang Zhang, an epidemiologist at Tufts University who was not involved in the study, said her own 2025 research linked caffeine to lower mortality but found no added benefits beyond three cups.
“You don’t get additional benefits when you go beyond three cups,” Zhang said, adding that large amounts of milk or sugar may cancel potential advantages. The dementia study did not track those additions.
Experts caution that the participants — all medical professionals — may not perfectly represent the broader population. Still, Zhang noted that heavier caffeine drinkers in the study were also more likely to smoke or drink alcohol, suggesting they were not unusually health-conscious, even as evidence shows coffee reduces dementia risk.
For people who already consume caffeine, the results are reassuring, Shadyab said. But the findings do not necessarily mean non-caffeine drinkers should start.
Zhang suggested those curious about caffeine could “give it a try,” beginning with small amounts to gauge tolerance.
The strongest association appeared among adults younger than 75, reinforcing the idea that cognitive decline develops over decades.
“If you can change your health habits early, before midlife, that will be more beneficial,” Wang said.
Researchers acknowledged unanswered questions, such as whether some participants opted for decaffeinated beverages due to underlying health issues that may have raised dementia risk, even though evidence indicates coffee reduces dementia risk.
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