Highlights
- Moderate caffeinated coffee consumption (2 to 3 cups/day) was associated with an 18% reduction in incident dementia risk compared to non-consumers.
- Similar neuroprotective benefits were observed for tea consumption (1 to 2 cups/day), while decaffeinated coffee showed no significant association with cognitive outcomes.
- The study, spanning over 40 years of follow-up, also linked higher caffeine intake to lower prevalence of subjective cognitive decline and improved objective cognitive scores.
- Dose-response analysis revealed a non-linear relationship, suggesting that moderate intake provides the most pronounced benefit for brain health.
Background
Dementia remains one of the most significant public health challenges of the 21st century, with the global prevalence expected to triple by 2050 as populations age. Given the absence of a definitive cure, identifying modifiable lifestyle factors that can delay or prevent cognitive decline is a priority for clinicians and researchers. Caffeine, the world’s most widely consumed psychoactive substance, has long been a subject of interest due to its known effects on the central nervous system. However, previous evidence linking coffee and tea to cognitive health has been inconsistent. Many studies have lacked the longitudinal depth required to capture the slow progression of neurodegenerative diseases, and few have adequately distinguished between caffeinated and decaffeinated beverages. This study, published in JAMA (2026), provides high-level evidence from two of the most robust prospective cohorts in the United States, offering a clearer picture of how coffee and tea influence the long-term risk of dementia and cognitive function.
Study Design and Methodology
This prospective cohort study utilized data from the Nurses’ Health Study (NHS; n = 86,606, data from 1980-2023) and the Health Professionals Follow-up Study (HPFS; n = 45,215, data from 1986-2023). At baseline, all participants were free of cancer, Parkinson’s disease, and dementia. The study’s primary exposures—intakes of caffeinated coffee, decaffeinated coffee, and tea—were assessed every two to four years using validated food frequency questionnaires (FFQs), allowing for a detailed analysis of long-term consumption patterns.
The primary endpoint was incident dementia, identified through death records and physician-confirmed diagnoses. Secondary endpoints included subjective cognitive decline (SCD), assessed via standardized questionnaires, and objective cognitive function. The latter was evaluated specifically in the NHS cohort using telephone-based neuropsychological assessments, including the Telephone Interview for Cognitive Status (TICS) and a global cognition z-score derived from six distinct cognitive tests. The long-term nature of this study, with a median follow-up of 36.8 years, provides a unique opportunity to evaluate the role of dietary habits in the context of late-life cognitive health.
Key Findings
Caffeinated Coffee and Dementia Risk
Among the 131,821 participants followed for up to 43 years, there were 11,033 incident cases of dementia. After adjusting for potential confounders, including age, smoking status, physical activity, and metabolic health, the researchers found a significant inverse association between caffeinated coffee and dementia. Comparing the highest quartile of consumption to the lowest, the hazard ratio (HR) for dementia was 0.82 (95% CI, 0.76 to 0.89). This translates to 141 cases per 100,000 person-years in the highest quartile versus 330 cases in the lowest. Interestingly, the association was non-linear, with the most pronounced benefits observed at a consumption level of approximately 2 to 3 cups per day.
The Role of Tea and Decaffeinated Coffee
Tea consumption showed similar protective associations. Participants consuming 1 to 2 cups of tea per day had a lower risk of dementia and better cognitive profiles compared to non-consumers. However, the data for decaffeinated coffee told a different story. Decaffeinated coffee intake was not significantly associated with a lower risk of dementia or improved cognitive performance, suggesting that caffeine itself, or compounds uniquely present in caffeinated beverages, may be the primary driver of neuroprotection.
Cognitive Function and Subjective Decline
The study also examined the impact of these beverages on the quality of cognitive aging. Higher caffeinated coffee intake was associated with a lower prevalence of subjective cognitive decline (prevalence ratio, 0.85; 95% CI, 0.78 to 0.93). Regarding objective testing in the NHS cohort, those in the highest quartile of caffeinated coffee consumption had higher mean TICS scores (mean difference, 0.11; 95% CI, 0.01 to 0.21) compared to the lowest quartile. While the global cognition score was also higher, it did not reach the threshold for statistical significance (P = .06), suggesting that the benefits might be more pronounced in specific cognitive domains or perceived cognitive stability.
Expert Commentary and Mechanistic Insights
The results of this study are both clinically significant and biologically plausible. The primary mechanism likely involves caffeine’s role as a non-selective antagonist of adenosine receptors (specifically A1 and A2A). By blocking these receptors, caffeine can reduce the accumulation of amyloid-beta, decrease neuroinflammation, and modulate the release of neurotransmitters such as dopamine and acetylcholine, which are critical for memory and attention. Furthermore, coffee and tea are rich in polyphenols and antioxidants, such as chlorogenic acid and epigallocatechin gallate (EGCG), which may protect against oxidative stress—a hallmark of Alzheimer’s disease and other forms of dementia.
However, clinicians should interpret these findings with a nuanced perspective. While the data supports the benefits of moderate consumption, the non-linear nature of the association suggests a ceiling effect. Excessive caffeine intake can lead to sleep disturbances and increased anxiety, which are themselves risk factors for cognitive impairment. Additionally, the lack of association with decaffeinated coffee highlights the need for further research into the synergistic effects between caffeine and other phytochemicals. Limitations of the study include its observational nature, which precludes definitive causal conclusions, and the potential for residual confounding, although the researchers adjusted for a wide array of variables.
Conclusion
This landmark study provides robust evidence that moderate consumption of caffeinated coffee and tea is associated with a significantly lower risk of dementia and more favorable cognitive outcomes over a 40-year period. For clinicians, these findings suggest that for most healthy adults, continuing to enjoy 2 to 3 cups of coffee or tea daily may serve as a simple, accessible component of a neuroprotective lifestyle. As we look toward future research, clinical trials focusing on the mechanistic pathways of caffeine in the brain will be essential to translate these epidemiological observations into targeted preventative strategies.
References
Zhang Y, Liu Y, Li Y, et al. Coffee and Tea Intake, Dementia Risk, and Cognitive Function. JAMA. 2026;335(6):e2527259. doi:10.1001/jama.2025.27259.