Lead: A new long-term analysis published in JAMA suggests habitual consumption of caffeinated coffee or tea is associated with a lower risk of dementia. The pooled study followed 131,821 participants across two U.S. cohorts for up to 43 years (median ~37 years) and documented 11,033 dementia cases. The largest apparent benefits were seen with moderate intake—about 2–3 eight-ounce cups of caffeinated coffee or 1–2 eight-ounce cups of tea per day. Decaffeinated coffee showed no association, implicating caffeine as a possible protective factor.
Key Takeaways
- The analysis combined 131,821 participants (86,606 women; 45,215 men) from two prospective cohorts with up to 43 years of follow-up and 11,033 dementia cases recorded.
- Highest caffeinated coffee consumers had an 18% lower dementia risk versus lowest consumers; highest tea consumers had a 14% lower risk.
- Optimal associations followed a dose-response pattern centered on moderate intake: ~2–3 cups/day for caffeinated coffee and ~1–2 cups/day for tea (one cup = 8 ounces).
- Decaffeinated coffee was not linked to reduced dementia risk or improved cognitive test scores in the female subcohort.
- Associations persisted after adjustment for age, smoking, BMI, physical activity, diet quality, alcohol, and medical history and were consistent across genetic risk strata for Alzheimer’s disease.
- Subjective cognitive decline reports were lower among caffeinated coffee and tea drinkers; in the women’s cohort, higher caffeinated coffee intake correlated with modestly better objective cognitive test performance.
- Because this is observational data, the study demonstrates association—not causation—and cannot rule out all sources of bias or reverse causation.
Background
Alzheimer’s disease and related dementias affect millions: more than 6 million people in the United States today, with projections near 13 million by 2050 if current trends continue. With few disease-modifying therapies available, preventing or delaying cognitive decline through lifestyle strategies is a major public-health focus. Everyday exposures such as diet and beverages are attractive targets because they are common, modifiable, and measurable in large cohort studies.
Coffee and tea contain bioactive compounds—most notably caffeine and various polyphenols—that have been hypothesized to reduce oxidative stress and neuroinflammation. Prior epidemiological studies on coffee, tea and cognitive outcomes have produced mixed results, often limited by small samples, short follow-up, or a single dietary assessment. Large, repeated-measures cohorts are therefore valuable for assessing long-term habitual intake and dementia risk.
Main Event
Researchers pooled repeated dietary data from two long-running U.S. prospective studies: the Nurses’ Health Study (begun 1976) and the Health Professionals Follow-Up Study (begun 1986). After excluding participants with cancer, Parkinson’s disease, or baseline dementia, 131,821 people remained in the analytic sample. Dietary intake of caffeinated coffee, decaffeinated coffee and tea was assessed every 2–4 years using validated food-frequency questionnaires to better capture habitual consumption over decades.
Over up to 43 years of observation (median follow-up ~37 years), investigators identified 11,033 dementia cases through physician diagnoses and death records. Statistical models adjusted for numerous confounders including age, smoking, physical activity, BMI, overall diet quality, alcohol intake, and medical history. The strongest inverse associations were seen for moderate habitual intake: roughly 2–3 cups/day of caffeinated coffee and 1–2 cups/day of tea.
The study reported an 18% lower dementia risk for the highest caffeinated coffee consumers compared with the lowest, and a 14% lower risk for the highest tea consumers. The protective association tracked with caffeine exposure: decaffeinated coffee did not show similar associations with dementia risk or with objective cognitive measures in the female cognitive subcohort. The authors conducted sensitivity analyses to test robustness and examined whether genetic susceptibility to Alzheimer’s modified the associations; results were broadly consistent.
Analysis & Implications
Interpretation requires caution. This is a well-powered observational study that benefits from repeated dietary measures and extensive covariate adjustment, which reduce— but do not eliminate—residual confounding. The persistence of associations across genetic risk strata strengthens the observation that habitual caffeinated beverage intake may be linked to lower dementia risk, but it cannot prove that caffeine or other beverage constituents are causative.
Biologically, plausible mechanisms exist: caffeine modulates adenosine receptors and may reduce neuroinflammation, while polyphenols in coffee and tea exert antioxidant effects and influence vascular health. These mechanisms could plausibly contribute to slower cognitive decline, particularly when combined with other brain-healthy behaviors. However, the inability to specify tea type (e.g., green vs. black) or coffee brewing method means effects might vary by preparation and were not resolved here.
From a public-health perspective, findings suggest moderate caffeinated coffee or tea could be one component of dementia risk reduction strategies alongside physical activity, healthy diet, sleep, and social engagement. Clinically, recommendations must be individualized: some people are sensitive to caffeine or have conditions (e.g., certain arrhythmias, anxiety disorders) where limiting caffeine is advised. The study’s cohorts were predominantly U.S. health professionals of European descent, so generalizability to other populations is uncertain.
Comparison & Data
| Measure | Value |
|---|---|
| Participants (total) | 131,821 (86,606 women; 45,215 men) |
| Follow-up | Up to 43 years (median ~37 years) |
| Dementia cases | 11,033 |
| Risk reduction — caffeinated coffee | 18% (highest vs. lowest intake) |
| Risk reduction — tea | 14% (highest vs. lowest intake) |
| Sweet spot | ~2–3 cups/day coffee; ~1–2 cups/day tea (8-oz cups) |
These figures show the main quantitative outcomes reported. The dose-response pattern points to moderate, consistent consumption rather than very high intake as the association’s peak. The absence of benefit for decaffeinated coffee in the reported analyses highlights caffeine’s potential role, but does not exclude effects from non-caffeine compounds in beverages.
Reactions & Quotes
“This large, repeated-measures study adds important evidence that habitual caffeinated beverages may be linked to lower dementia risk,”
Study authors (published in JAMA)
The authors framed their findings as an association observed across decades of follow-up in two established cohorts, emphasizing adjustments for multiple lifestyle and medical covariates. They also stressed that observational designs cannot establish causation.
“The results are intriguing but should be interpreted in the context of other lifestyle factors that influence brain health,”
Independent neurologist (commenting on implications)
Independent experts highlighted that coffee or tea should be considered part of a multifactorial approach to healthy aging, not a standalone preventive therapy.
Unconfirmed
- Whether caffeine itself causes reduced dementia risk remains unproven; randomized trials would be needed to test causality.
- Effect differences by tea type (green versus black) or coffee preparation (espresso, filtered, boiled) were not captured and remain uncertain.
- Residual confounding or reverse causation cannot be fully excluded despite sensitivity analyses.
Bottom Line
This large, long-term observational study strengthens the evidence that moderate habitual intake of caffeinated coffee (about 2–3 eight-ounce cups/day) or tea (about 1–2 eight-ounce cups/day) is associated with a lower risk of dementia and modest cognitive benefits. The lack of association for decaffeinated coffee points toward caffeine as a likely contributor, though mechanisms are not definitively proven.
For most people without contraindications, moderate caffeinated coffee or tea can reasonably be included as part of a brain-healthy lifestyle that prioritizes physical activity, a balanced diet, sleep, and social engagement. Individuals with caffeine sensitivity or medical reasons to restrict caffeine should consult their clinicians before changing intake based solely on these observational findings.
Sources
- EatingWell: Coffee or Tea? One May Be Better at Preventing Dementia (news article) — original article summarizing the study.
- JAMA (Journal of the American Medical Association) — peer-reviewed journal where the study was published (journal).
- Nurses’ Health Study (official cohort website) — long-running prospective study (official/academic).
- Health Professionals Follow-Up Study (HPFS) — Harvard T.H. Chan School of Public Health (official/academic).