For Doctors in a Hurry
- Researchers investigated how consuming caffeinated coffee, decaffeinated coffee, or tea relates to the long-term risk of developing dementia and cognitive decline.
- This prospective cohort study followed 131,821 male and female health professionals for up to 43 years to track incident dementia cases.
- High caffeinated coffee intake was associated with lower dementia risk compared to low intake (hazard ratio, 0.82; 95% confidence interval, 0.76 to 0.89).
- The authors concluded that consuming caffeinated coffee and tea is associated with a lower risk of dementia and modestly better cognitive function.
- Clinicians can note that consuming two to three cups of caffeinated coffee daily is associated with the most pronounced reduction in dementia risk.
The Enduring Debate Over Caffeine and Cognitive Decline
Patients frequently ask whether their daily coffee or tea habits will protect their aging brains, but the epidemiological evidence has historically offered mixed answers. Several meta-analyses suggest that moderate coffee and tea consumption may reduce the risk of cognitive deficits, Alzheimer disease, and vascular dementia, with one review of 38 cohorts encompassing 751,824 participants showing that drinking one to three cups of coffee daily reduces overall dementia risk [1, 2, 3]. However, data regarding the optimal daily intake remain conflicting, as dose-response analyses indicate a J-shaped or U-shaped curve where consuming three or more cups of coffee per day might actually increase the risk of all-cause dementia [4, 5]. Furthermore, previous research has often failed to isolate the effects of caffeine from other phytochemicals (biologically active plant compounds) by comparing caffeinated and decaffeinated beverages directly. A newly published cohort study tracking 131,821 participants over a median of 36.8 years now clarifies this relationship, demonstrating that the highest quartile of caffeinated coffee intake significantly lowers incident dementia risk (hazard ratio 0.82, 95% confidence interval 0.76 to 0.89) compared to the lowest quartile, offering precise clinical parameters for counseling patients on long-term cognitive preservation [6].
Tracking Cognitive Health Across Four Decades
Although previous research has explored dietary impacts on neurodegeneration, evidence linking coffee and tea to cognitive health remains inconclusive. A major methodological limitation is that most studies fail to differentiate caffeinated from decaffeinated coffee, obscuring whether the active stimulant or other plant compounds drive potential benefits. To resolve this ambiguity, researchers designed a prospective cohort study (an observational design that follows individuals forward in time to determine how baseline factors affect future outcomes) investigating the associations of coffee and tea intake with dementia risk and cognitive function. The primary exposures were intakes of caffeinated coffee, decaffeinated coffee, and tea.
The analysis drew upon two massive, well-established United States databases, yielding a total of 131,821 participants, of which 65.7 percent were female. The study included female participants from the Nurses' Health Study (NHS; n = 86,606 with data from 1980 to 2023) and male participants from the Health Professionals Follow-up Study (HPFS; n = 45,215 with data from 1986 to 2023). The mean age at baseline was 46.2 (standard deviation [SD], 7.2) years in the NHS cohort and 53.8 (SD, 9.7) years in the HPFS cohort. To ensure that early-stage neurodegeneration or severe systemic illness did not confound the results, the researchers established strict exclusion criteria. Participants did not have cancer, Parkinson disease, or dementia at study entry.
Capturing accurate dietary habits over a lifespan requires persistent measurement. Dietary intake was collected every 2 to 4 years using validated food frequency questionnaires, allowing the researchers to account for changes in consumption habits as participants aged. This continuous tracking enabled an exceptionally long observation period. Follow-up lasted up to 43 years, with a median of 36.8 years (interquartile range [IQR], 28 to 42 years). For practicing physicians, this extended timeline is highly relevant, as it captures dietary exposures during midlife, the critical window when the underlying pathology of dementia often begins to develop.
Defining Dementia and Cognitive Endpoints
To evaluate the long-term neurological impact of beverage consumption, the researchers established clear clinical endpoints. The primary outcome was dementia, which was identified via death records and physician diagnoses. Over the course of the follow-up period, the investigators recorded a total of 11,033 cases of incident dementia. Relying on physician diagnoses and mortality data ensures that the primary endpoint reflects clinically significant cognitive impairment rather than transient memory lapses.
Beyond formal dementia diagnoses, the study also evaluated earlier stages of cognitive impairment. Secondary outcomes included subjective cognitive decline, which was assessed by a questionnaire-based score with a range of 0 to 7. On this scale, higher scores indicate greater perceived decline by the patient. For the purpose of the analysis, cases of subjective cognitive decline were defined as those with a score of 3 or greater. Tracking subjective decline provides clinicians with insight into the prodromal phases of neurodegeneration, which often precede objective clinical deficits.
To complement the subjective reports, the researchers measured objective cognitive function, though this was assessed only in the NHS cohort. This evaluation utilized telephone-based neuropsychological tests to quantify cognitive performance. Specifically, these objective tests included the Telephone Interview for Cognitive Status (TICS) score, which has a range of 0 to 41. Furthermore, the objective tests included a measure of global cognition, defined as a standardized mean z score (a statistical measurement describing how far a value deviates from the group average) for all 6 administered cognitive tests. By incorporating both subjective questionnaires and standardized objective testing, the study captures a comprehensive picture of how caffeine intake influences the entire spectrum of cognitive aging.
Caffeinated Coffee and Tea Lower Dementia Risk
After adjusting for potential confounders and pooling results across cohorts, the researchers found that higher caffeinated coffee intake was significantly associated with lower dementia risk. The data revealed a stark contrast in clinical outcomes based on consumption levels. Specifically, the dementia risk was 141 versus 330 cases per 100,000 person-years when comparing the fourth (highest) quartile of caffeinated coffee consumption with the first (lowest) quartile. This translates to a substantial protective effect, as the hazard ratio for dementia risk comparing the highest to lowest quartile of caffeinated coffee intake was 0.82 (95% confidence interval [CI], 0.76 to 0.89). For practicing physicians, this 18 percent relative risk reduction provides concrete epidemiological support for the neuroprotective benefits of regular caffeinated coffee consumption.
Beyond formal dementia diagnoses, the protective association extended to earlier, prodromal stages of cognitive impairment. The analysis demonstrated that higher caffeinated coffee intake was associated with a lower prevalence of subjective cognitive decline, with rates of 7.8 percent versus 9.5 percent for the highest versus lowest quartile. Quantifying this relationship, the prevalence ratio for subjective cognitive decline comparing the highest to lowest quartile of caffeinated coffee intake was 0.85 (95% CI, 0.78 to 0.93). This indicates that patients who consume higher amounts of caffeinated coffee are significantly less likely to report the early memory and thinking issues that often precede clinical neurodegeneration.
To determine whether these benefits were specific to coffee or related to caffeine more broadly, the investigators analyzed other common beverages. They found that higher intake of tea showed similar associations with lower dementia risk and better cognitive outcomes. In stark contrast, decaffeinated coffee intake was not associated with lower dementia risk or better cognitive performance. For clinicians counseling patients on dietary habits, this lack of benefit from decaffeinated coffee is a critical distinction. It suggests that the observed neuroprotective effects are likely driven by caffeine itself, or its specific interactions with other compounds in the beverages, rather than the baseline phytochemical profile of the coffee bean alone.
In the NHS cohort, the researchers evaluated standardized neuropsychological metrics and found that higher caffeinated coffee intake was associated with better objective cognitive performance. When comparing consumption extremes, those in the highest quartile of caffeinated coffee intake had a higher mean TICS score than participants in the lowest quartile, with a mean difference of 0.11 (95% CI, 0.01 to 0.21). The investigators also assessed a standardized global cognition score across six administered tests. Participants in the highest quartile had a higher mean global cognition score (mean difference, 0.02 [95% CI, -0.01 to 0.04]) compared to the lowest quartile. However, clinicians should note that the association between caffeinated coffee intake and global cognition was not statistically significant (P = .06). This suggests that while caffeine may offer measurable benefits on specific cognitive screening tools like the TICS, its impact on broader composite cognitive metrics remains subtle.
To guide clinical recommendations regarding optimal beverage consumption, the investigators conducted a dose-response analysis. This evaluation showed nonlinear inverse associations of caffeinated coffee and tea intake levels with dementia risk and subjective cognitive decline. Rather than a simple linear benefit where more consumption always yields greater protection, the data revealed a specific threshold for maximum neuroprotection. The most pronounced associated differences were observed with an intake of approximately 2 to 3 cups per day of caffeinated coffee. For patients who prefer tea, the most pronounced associated differences were observed with an intake of approximately 1 to 2 cups per day of tea. Ultimately, the study demonstrates that greater consumption of caffeinated coffee and tea was associated with lower risk of dementia and modestly better cognitive function, with the most pronounced association at moderate intake levels. For practicing physicians, these specific quantities provide an evidence-based target when counseling aging patients on dietary habits to preserve long-term neurological health.
References
1. Li F, Liu X, Jiang B, et al. Tea, coffee, and caffeine intake and risk of dementia and Alzheimer's disease: a systematic review and meta-analysis of cohort studies.. Food & function. 2024. doi:10.1039/d4fo01750a
2. Griffiths A, Matu J, Tang EYH, et al. Foods, dietary patterns, and risk of vascular dementia: a systematic review.. Nutrition & metabolism. 2024. doi:10.1186/s12986-024-00880-2
3. Liu Q, Wu Y, Cheng H, et al. Habitual coffee consumption and risk of cognitive decline/dementia: A systematic review and meta-analysis of prospective cohort studies.. Nutrition (Burbank, Los Angeles County, Calif.). 2016. doi:10.1016/j.nut.2015.11.015
4. Mazzoleni E, Malavolti M, Rossetti A, Mazzoli R, Vinceti M, Filippini T. Coffee and tea consumption and risk of dementia: a dose-response meta-analysis of cohort and cohort-nested case-control studies.. Journal of epidemiology and population health. 2026. doi:10.1016/j.jeph.2026.203168
5. Wu L, Sun D, He Y. Coffee intake and the incident risk of cognitive disorders: A dose-response meta-analysis of nine prospective cohort studies.. Clinical nutrition (Edinburgh, Scotland). 2017. doi:10.1016/j.clnu.2016.05.015
6. Zhang Y, Liu Y, Li Y, et al. Coffee and Tea Intake, Dementia Risk, and Cognitive Function.. JAMA. 2026. doi:10.1001/jama.2025.27259
