Daily Coffee or Tea Linked to Lower Dementia Risk in Major Study
Scientists have uncovered a potential link between daily consumption of coffee or tea and a reduced risk of dementia, according to a comprehensive new analysis of health records spanning decades. The findings suggest that individuals who regularly enjoy these caffeinated beverages may experience a significant protective effect against cognitive decline.
Substantial Reduction in Dementia Risk Observed
Health records for more than 130,000 participants revealed that over a period of up to 43 years, those who routinely drank two to three cups of caffeinated coffee or one to two cups of caffeinated tea daily exhibited a 15-20% lower risk of developing dementia compared to individuals who abstained from these drinks. The research, published in the Journal of the American Medical Association, indicates that men and women who consumed the most caffeinated coffee had an 18% lower risk of dementia relative to those with little or no intake, with similar results noted for tea consumption.
Enhanced Cognitive Performance Among Drinkers
Beyond the reduced dementia risk, the study also found that caffeinated coffee drinkers reported slightly less cognitive decline than those who opted for decaffeinated versions. Furthermore, these individuals performed better on certain objective tests of brain function, highlighting a potential association between habitual consumption and improved cognitive metrics. However, the effect appeared to plateau at the specified consumption levels, and no link was established between decaffeinated coffee and dementia risk.
Plausible Biological Mechanisms Under Scrutiny
Lead author Yu Zhang, a nutritional epidemiology researcher at Harvard University, explained that coffee and tea contain caffeine and polyphenols, which may protect against brain ageing by enhancing vascular health, reducing inflammation, and mitigating oxidative stress—a process where harmful free radicals damage cells and tissues. Additionally, substances in these beverages could improve metabolic health; for instance, caffeine is associated with lower rates of type 2 diabetes, a known risk factor for dementia.
Causality Remains Unproven Amidst Complex Factors
Despite the compelling findings, the research cannot definitively prove that daily caffeine intake directly causes reduced dementia risk. As Zhang noted, the study alone cannot establish causality, as caffeine drinkers might be less prone to dementia for other reasons. For example, if poor sleepers—who face a greater risk of cognitive decline—avoid caffeine to improve sleep quality, a similar correlation could arise. Naveed Sattar, a professor of cardiometabolic medicine at the University of Glasgow, emphasised that caffeine has both beneficial and harmful effects on the brain, such as raising blood pressure in some individuals, which is a significant driver of dementia.
Challenges in Future Research and Practical Implications
Confirming whether coffee and tea actively protect the brain presents substantial challenges. Gold-standard randomised trials, which would assign people to drink caffeinated or decaffeinated beverages for decades before assessing dementia diagnoses, are largely impractical. Instead, future studies might explore whether these drinks induce biological changes linked to brain function, detectable through scans or other tests. Zhang advised against viewing coffee or tea as a "magic shield," stressing that maintaining a healthy lifestyle—including regular exercise, a balanced diet, and good sleep—is crucial for optimal brain health. Researchers estimate that about half of global dementia cases could be prevented or delayed by addressing factors like obesity, smoking, and high blood pressure.
