A large-scale, long-term observational study suggests an association between the daily consumption of caffeinated coffee and tea and a reduced risk of dementia, alongside slower cognitive decline. The research, which tracked over 130,000 participants for up to 43 years, indicates that individuals consuming specific amounts of these beverages showed an approximately 18% lower risk of developing dementia compared to those with low or no consumption.
Researchers and experts emphasize that the findings demonstrate an association, not a direct cause-and-effect relationship, and further studies are needed to confirm any causal link.
Study Overview
The research, published in JAMA, analyzed data from 131,821 participants collected between 1986 and 2023. These participants were drawn from two major US public health initiatives: the Nurses’ Health Study and the Health Professionals Follow-up Study. The study was conducted by investigators from Mass General Brigham, Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard.
Key Findings
During the study period, 11,033 participants developed dementia. The analysis revealed several patterns related to caffeinated beverage consumption:
- Dementia Risk: Participants with the highest intake of caffeinated coffee demonstrated an approximately 18% lower risk of dementia compared to those with low or no consumption. Similar patterns were observed with higher tea intake.
- Optimal Intake: The strongest associations were reported in individuals consuming two to three cups of caffeinated coffee or one to two cups of caffeinated tea daily.
- Cognitive Decline: Caffeinated coffee drinkers showed lower rates of subjective cognitive decline (7.8% versus 9.5% in those with low or no consumption) and performed better on objective tests of overall brain function.
- Decaffeinated Beverages: Decaffeinated coffee intake did not show a significant association with dementia risk or cognitive function.
- Genetic Predisposition: The observed associations were consistent across participants, irrespective of their genetic predisposition to developing dementia.
Research Methodology
Researchers utilized repeated assessments of diet, dementia diagnoses, subjective cognitive decline, and objective cognitive test scores over the extensive follow-up period. This methodology involved comparing outcomes among individuals who consumed caffeinated coffee, caffeinated tea, or decaffeinated coffee. The study attempted to account for confounding factors by excluding participants with major chronic diseases at the outset.
Potential Mechanisms and Limitations
The study authors propose that caffeine and polyphenols, present in coffee and tea, may contribute to brain protection through mechanisms such as enhancing vascular health, reducing inflammation, mitigating oxidative stress, and improving metabolic health. Caffeine has also been linked to lower rates of type 2 diabetes, a known risk factor for dementia.
However, the researchers and external experts cautioned that the observational nature of the study prevents definitive proof of causality.
Other lifestyle factors or underlying health conditions among caffeine consumers could contribute to the observed lower risk. For example, individuals with poor sleep patterns, which may increase cognitive decline risk, might avoid caffeine to improve sleep quality. Additionally, experts noted that while caffeine can enhance motivation, it can also elevate blood pressure, which is a known risk factor for dementia.
Expert and Researcher Perspectives
Dr. Daniel Wang, a senior author from Mass General Brigham, commented that while the results are encouraging, the observed effect size is small, and multiple factors contribute to cognitive function protection. Lead author Yu Zhang highlighted the consistency of findings, suggesting potential benefits of coffee or caffeine regardless of genetic risk for dementia.
Dr. Céline Gounder, a CBS News medical contributor, advised caution, reiterating that the study identifies an association rather than causation. She recommended against altering diets based solely on these findings.
Researchers emphasized that dementia prevention remains a critical focus due to the limited effectiveness of existing treatments once symptoms manifest.
General Dementia Prevention Strategies
Experts and organizations like the Alzheimer's Association advise individuals not to rely on a single dietary change for dementia prevention. Instead, they recommend a holistic approach encompassing proven strategies, including:
- Engaging in regular physical exercise.
- Maintaining a balanced diet.
- Managing weight effectively.
- Addressing hearing loss, which has been identified as a potential warning sign of dementia risk.
- Ensuring adequate sleep.
- Addressing other risk factors such as obesity, smoking, excessive alcohol consumption, and high blood pressure.
It is estimated that approximately half of dementia cases globally could be prevented or delayed by addressing such modifiable lifestyle factors.