Coffee, tea, and caffeine and the risk of cognitive disorders Original paper

In this meta-analysis of observational studies, higher intakes of coffee, tea, or caffeine were associated with a reduced risk of cognitive disorders.

The association between coffee, tea, and caffeine consumption and the risk of cognitive disorders (e.g., dementia and mild cognitive impairment).

A total of 389,505 participants (median ages of 45–96), including 18,459 cases of cognitive disorders.

A meta-analysis of 33 observational studies (22 prospective cohort studies and 11 case-control studies) was performed. In cohort studies, the follow-up period ranged from 1.3 to 28 years. Data comparing the lowest and highest intake categories were obtained from each study. The coffee intake categories ranged from less than 1 cup to 8 cups per day, and the tea intake categories ranged from never or rare intake to 5 cups per day.

Higher (compared to lower) coffee intake was associated with a 27% lower risk of cognitive disorders. With respect to specific cognitive disorders, higher coffee intake was associated with a 30% lower risk of dementia, but there was no association for mild cognitive impairment. Dose-response analyses indicated that drinking 2.5 cups of coffee per day was associated with the greatest reduction in cognitive disorder risk.

Higher (compared to lower) tea intake was associated with a 32% lower risk of cognitive disorders. Dose-response analyses indicated an inverse linear relationship, with an 11% reduction in cognitive disorder risk per additional cup of tea consumed per day (up to about 6 cups).

Higher (compared to lower) caffeine intake was associated with a 31% and 29% lower risk of dementia and mild cognitive impairment, respectively.

A limitation of the studies included in this meta-analysis is the lack of detail on coffee and tea consumption. Almost none of the studies differentiated between different types of tea. Thus, it’s unclear whether some types of tea are better than others for reducing the risk of cognitive disorders.

Also, although most of the studies adjusted their results for age, sex, and educational levels, only some adjusted for apolipoprotein E status (a major risk factor for dementia), BMI, and disease status (i.e., cardiovascular disease). Therefore, the results may be influenced by unmeasured or residual confounders.