Too Much Coffee Linked to Accelerated Cognitive Decline

Drinking more than three cups of coffee a day is linked to more rapid cognitive decline over time, results from a large study suggest.

Investigators examined the impact of different amounts of coffee and tea on fluid intelligence — a measure of cognitive functions including abstract reasoning, pattern recognition, and logical thinking.

“It’s the old adage that too much of anything isn’t good. It’s all about balance, so moderate coffee consumption is okay but too much is probably not recommended,” study investigator Kelsey R. Sewell, PhD, Advent Health Research Institute, Orlando, told Medscape Medical News. 

The findings of the study were presented on July 3src at the Alzheimer’s Association International Conference (AAIC) 2src24. 

One of the World’s Most Widely Consumed Beverages

Coffee is one of the most widely consumed beverages around the world. The beans contain a range of bioactive compounds, including caffeine, chlorogenic acid, and small amounts of vitamins and minerals.

Consistent evidence from observational and epidemiologic studies indicates that intake of both coffee and tea has beneficial effects on stroke, heart failure, cancers, diabetes, and Parkinson’s disease. 

Several studies also suggest that coffee may reduce the risk for Alzheimer’s disease, said Sewell. However, there are limited longitudinal data on associations between coffee and tea intake and cognitive decline, particularly in distinct cognitive domains.

Sewell’s group previously published a study of cognitively unimpaired older adults that found greater coffee consumption was associated with slower cognitive decline and slower accumulation of brain beta-amyloid.

Their current study extends some of the prior findings and investigates the relationship between both coffee and tea intake and cognitive decline over time in a larger sample of older adults.

This new study included 8451 mostly female (6src%) and White (97%) cognitively unimpaired adults older than 6src (mean age, 67.8 years) in the UK Biobank, a large-scale research resource containing in-depth, de-identified genetic and health information from half a million UK participants. Study subjects had a mean body mass index (BMI) of 26, and about 26% were apolipoprotein epsilon 4 (APOE e4) gene carriers.

Researchers divided coffee and tea consumption into tertiles: high, moderate, and no consumption.

For daily coffee consumption, 18% reported drinking four or more cups (high consumption); 58% reported drinking one to three cups (moderate consumption); and 25% reported that they never drink coffee. For daily tea consumption, 47% reported drinking four or more cups (high consumption); 38% reported drinking one to three cups (moderate consumption); and 15% reported that they never drink tea.

The study assessed cognitive function at baseline and at least two additional patient visits. 

Researchers used linear mixed models to assess the relationships between coffee and tea intake and cognitive outcomes. The models adjusted for age, sex, Townsend deprivation index (reflecting socioeconomic status), ethnicity, APOE e4 status, and BMI.

Steeper Decline 

Compared with high coffee consumption (four or more cups daily), people who never consumed coffee (beta=src.src6; SE=src.src2; P=.srcsrc5) and those with moderate consumption (beta=src.src7; SE=src.src2; P =<.srcsrc1) had slower decline in fluid intelligence after an average of 8.83 years of follow-up.

“We can see that those with high coffee consumption showed the steepest decline in fluid intelligence across the follow up, compared to those with moderate coffee consumption and those never consuming coffee,” said Sewell, referring to illustrative graphs.

At the same time, “our data suggest that across this time period, moderate coffee consumption can serve as some kind of protective factor against cognitive decline,” she added.

For tea, there was a somewhat different pattern. People who never drank tea had a greater decline in fluid intelligence compared with those who had moderate consumption (beta=src.src6; SE=src.src2; P=.srcsrc9src) or high consumption (beta=src.src6; SE=src.src2; P=.srcsrc3).

Because this is an observational study, “we still need randomized controlled trials to better understand the neuroprotective mechanism of coffee and tea compounds,” said Sewell.

Responding later to a query from a meeting delegate about how moderate coffee drinking could be protective, Sewell said there are probably “different levels of mechanisms,” including at the molecular level (possibly involving amyloid toxicity) and the behavioral level (possibly involving sleep patterns).

Sewell said that she hopes this line of investigation will lead to new avenues of research in preventive strategies for Alzheimer’s disease. 

“We hope that coffee and tea intake could contribute to the development of a safe and inexpensive strategy for delaying the onset and reducing the incidence for Alzheimer’s disease.”

A limitation of the study is possible recall bias, because coffee and tea consumption were self-reported. However, this may not be much of an issue because coffee and tea consumption “is usually quite a habitual behavior,” said Sewell.

The study also had no data on midlife coffee or tea consumption and did not compare the effect of different preparation methods or types of coffee and tea — for example, green tea vs black tea. 

When asked if the study controlled for smoking, Sewell said it didn’t but added that it would be interesting to explore its impact on cognition.

Sewell reports no relevant conflicts of interest.