Coffee and Tea May Protect Against Dementia but Hold the Decaf

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How Coffee May Protect Brain Health: A New Study Suggests The Benefits Aren't Just From Caffeine December 2018 

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Coffee and Tea May Protect Against Dementia but Hold the Decaf

Regular consumption of coffee and tea was associated with a lower risk for dementia and modest improvements in cognitive performance, independent of a person’s genetic predisposition, a new study showed.

Results from two large cohorts showed that the benefits were strongest among those with a daily intake of about 2-3 cups of caffeinated coffee or 1-2 cups of tea. These associations remained consistent even when accounting for high-risk genetic factors, including APOE4 genotype and Alzheimer’s disease polygenic risk scores.

“The overall patterns were broadly similar across genetic risk groups, suggesting these behaviors may be relevant across genetic risk levels — not only among people at lower genetic risk,” lead study author Yu Zhang, MBBS, MS, Channing Division of Network Medicine, Brigham and Women’s Hospital and Harvard Medical School, Harvard University, Boston, told Medscape Medical News.

The study was published online on February 9 in JAMA.

Coffee, Tea, and Dementia: What’s the Link?

Coffee and tea contain caffeine as well as bioactive compounds such as polyphenols, catechins, and chlorogenic acid, which may reduce oxidative stress, protect vascular function, and mitigate cellular damage in the brain.

Previous research has suggested that caffeine and coffee consumption may protect against cognitive decline and dementia, but many studies dichotomized intake levels and did not examine dose-response relationships. Few have been able to distinguish between caffeinated and decaffeinated beverages, and evidence regarding tea consumption has been mixed.

In this new prospective cohort study, researchers sought to clarify these relationships using repeated, detailed dietary assessments across two independent cohorts.

Participants in the National Health Service (NHS) (n = 86,606 women; mean age at baseline, 46.2 years) and the Health Professionals Follow-up Study (n = 45,215 men; mean age at baseline, 53.8 years) completed repeated food frequency questionnaires every 2-4 years to assess caffeinated and decaffeinated coffee and tea intake.

Participants with major chronic diseases at baseline or significant changes in coffee intake were excluded to reduce confounding.

Objective cognitive function was measured in the NHS cohort using the Telephone Interview for Cognitive Status (TICS), verbal memory tests, and a composite global z score. Subjective cognitive decline was assessed in both cohorts through questionnaires covering memory, executive function, attention, and visuospatial skills.

Caffeinated coffee intake was analyzed in quartiles, and decaffeinated coffee and tea in tertiles due to right-skewed distributions.

Analyses accounted for age, education, lifestyle factors, medical history, medication use, and other dietary variables.

Links to Dementia Risk

Over a follow-up period of up to 43 years, 11,033 participants developed dementia.

Moderate caffeinated coffee intake of about 2-3 cups/d was associated with an 18% lower risk for incident dementia compared with no coffee (hazard ratio [HR], 0.82; 95% CI, 0.76-0.89).

Tea consumption showed a similar pattern, with participants who reported moderate tea intake (1-2 cups/d) showing a 16% lower risk for dementia than those who drank no tea (HR, 0.86; 95% CI, 0.83-0.90).

In contrast, decaffeinated coffee intake was not associated with a reduced risk for dementia.

“The decaf findings suggest that caffeine may be an important contributor because caffeinated coffee and tea showed more consistent associations than decaffeinated coffee,” Zhang said.

However, he cautioned against overinterpreting decaf as ineffective.

“Coffee and tea contain many compounds like polyphenols and other bioactives that relate to neuroinflammation and vascular or metabolic pathways,” Zhang said. “Decaf consumption patterns can also differ, for example, people may switch to decaf because of caffeine intolerance or underlying health issues, which can complicate interpretation. So we can’t conclude caffeine is the only factor.”

Links to Cognitive Decline

In the pooled analyses, the likelihood of subjective cognitive decline was lower among moderate coffee drinkers than those who did not drink coffee (7.8% vs 9.8%). The association remained after multivariable adjustment (prevalence ratio [PR], 0.86; P < .001).

The same held for tea drinkers, with subjective cognitive decline significantly lower among moderate drinkers than those with no tea intake (8.1% vs 9.5%), even after adjusting for confounders (PR, 1.16; P < .001)

Objective cognitive testing in the NHS cohort showed small but measurable improvements in TICS and global cognition scores, with the difference between the highest and lowest caffeinated coffee intake categories being 0.11 points, corresponding to approximately 0.6 years of cognitive aging.

The strongest benefits were seen in participants younger than age 75, and consuming more than moderate amounts didn’t provide additional protection.

“From a clinical standpoint, a small shift in mean performance doesn’t translate to an immediate, noticeable change for an individual patient. However, at the population level, even modest differences, if sustained, could be meaningful when dementia is common and develops over long periods,” Zhang said.

Caffeine Not a Prescription

The researchers acknowledged several limitations, including the study’s observational design and lack of detail on tea type or coffee preparation in dietary assessments.

Cognitive testing was limited to the NHS cohort, dementia classification relied on self-report and death records, and participants were predominantly White health professionals, which may limit generalizability.

“I’d frame it as reassurance rather than a prescription,” Zhang said about the study’s findings.

“For people who already drink coffee or tea and tolerate caffeine, our findings support that moderate intake…is associated with lower dementia risk,” Zhang said.

“Counseling should still be individualized, especially for patients with insomnia, anxiety, or caffeine intolerance. And it should be positioned as one part of the broader prevention approach — alongside regular exercise, vascular risk control, sleep, and diet quality,” he added.

Lifestyle Trumps Caffeine

Commenting for Medscape Medical News, Courtney Kloske, PhD, director, scientific engagement, Alzheimer’s Association, Chicago, emphasized that a balanced and healthful overall diet may be more beneficial for brain health than focusing on one beverage or ingredient.

“While the modest cognitive benefits for higher levels of caffeine consumption are intriguing findings, more research is needed to better understand the underlying mechanisms and connections between caffeine and cognition,” said Kloske, who was not part of the study.

The observed benefits could also relate to other lifestyle and cognitive factors of caffeine drinkers, such as sleep, exercise, and reading, she noted, advising that clinicians emphasize comprehensive healthy lifestyle practices instead of focusing on individual dietary factors like caffeine.