Drinking moderate amounts of coffee or tea can significantly reduce the risk of cognitive disorders, including dementia, according to a recent study published in Nutrition Reviews.
Cognitive disorders associated with aging, such as Alzheimer’s disease, pose significant challenges for individuals and the healthcare system. Current pharmaceutical treatments have limited efficacy, which highlights the importance of exploring modifiable risk factors, including dietary patterns.
Although coffee and tea have been consumed for centuries, the impact of caffeine on brain health, particularly its role in cognitive disorder development, has been a subject of debate due to inconsistent findings across studies.
To provide clarity on this matter, a team of researchers from China Medical University led by Ying Zhu and Chun-Xiang Hu conducted an updated review of existing research. They performed a meta-analysis, a comprehensive investigation that incorporates multiple studies, to offer a more conclusive answer. To meet rigorous inclusion criteria, the studies had to be of high quality.
The researchers primarily focused on case-control studies, which compare individuals with and without a condition to identify potential causes, and cohort studies that track a group of people over time to assess the development of the specific condition of interest. These studies exclusively examined tea, coffee, or caffeine consumption as potential risk factors for cognitive disorders, specifically dementia, Alzheimer’s disease, or cognitive impairment without dementia (CIND).
Two researchers independently searched numerous databases to identify suitable studies for the meta-analysis. Ultimately, 22 cohort studies and 11 case-control studies published between 1990 and 2019 were included, involving a total of 389,505 participants, of which 18,459 had cognitive disorders.
The researchers performed statistical analyses on the combined data from the 33 studies.
The findings revealed a strong correlation between coffee and tea consumption and a reduced risk of cognitive disorders, with an overall relative risk of 0.73 for coffee and 0.68 for tea. In other words, individuals who regularly consume coffee or tea are approximately 27% and 32%, respectively, less likely to develop cognitive disorders compared to those who do not.
Additionally, through dose-response analysis, the researchers explored whether the quantity of daily coffee or tea consumed influenced the risk of cognitive disorders.
They discovered a nonlinear relationship between coffee consumption and the risk of Alzheimer’s disease, with the highest level of protection occurring at approximately 2.5 cups per day. Interestingly, further increases in daily coffee intake did not result in a significant change in the level of protection against cognitive disorders. Coffee consumption did not display any influence on the risk of developing CIND.
Moreover, a linear relationship was observed between tea consumption and cognitive disorders, with a consistent decrease in the risk of cognitive disorder-related mortality of 11% for individuals consuming one cup of tea per day.
Furthermore, the researchers conducted in-depth analyses to assess the impact of ethnicity and sex on the relationship between coffee or tea consumption and cognitive disorders. They found that coffee consumption was associated with a decreased risk of cognitive disorders in individuals of White ethnicity, while tea consumption showed a similar association among individuals of Asian ethnicity. Notably, the protective effects of coffee and tea consumption were stronger in men compared to women.
Zhu and colleagues concluded that “numerous studies have demonstrated that caffeine enhances cognitive performance in the short term and mitigates cognitive impairment in the long term. The molecular mechanisms underlying caffeine’s effects involve blocking excessively activated adenosine receptors, which integrates neurotransmitter signaling and modulates synaptic plasticity in regions related to memory and learning.”
In simpler terms, caffeine temporarily boosts brain function and safeguards against long-term cognitive issues by blocking specific overactive receptors, known as adenosine receptors. This process improves signaling and communication within relevant brain regions, resulting in enhanced memory and learning.
It is important to note some limitations of the study. Despite efforts to control for potential confounding variables, there is a possibility that unmeasured factors, such as tobacco and alcohol consumption, as well as income and educational levels, may have influenced the results. Further investigations are needed to validate the role of tea, coffee, and caffeine in the prevention of cognitive disorders.
The study titled, “Moderate coffee or tea consumption decreased the risk of cognitive disorders: an updated dose–response meta-analysis,” was conducted by Ying Zhu, Chun-Xiang Hu, Xu Liu, Rui-Xia Zhu, and Ben-Qiao Wang.
