Tea, coffee, and caffeine intake and risk of dementia and Alzheimer's Disease: a systematic review and meta-analysis of cohort studies

Abstract

Background Limited and conflicting evidence exists on the associations between tea, coffee, and caffeine intake and risk of dementia and Alzheimer's Disease (AD). This meta-analysis aimed to elucidate these associations and quantify potential dose-response relationships. Methods PubMed, EMBASE, and Web of Science were searched up to 11 June 2024 for the cohort studies. Random effects models calculated pooled relative risks (RR) and 95% confidence intervals (CI), with dose-response relation assessed using restricted cubic splines. The Grading of Recommendations Assessment Development and Evaluation (GRADE) tool was used to assess the risk of bias. Results Our analysis encompassed 38 cohorts, totaling 751,824 participants and 13,017 dementia and 17,341s AD cases. For dementia, compared with the lowest category, the pooled RRs (95% CI) in the highest category of tea, coffee, and caffeine were 0.84 (0.74-0.96, n=6), 0.95 (0.87-1.02, n=9), and 0.94 (0.70-1.25, n=5), with all rated as low certainty in GRADE. For AD, the pooled RRs (95% CI) in the highest category of tea, coffee, and caffeine compared to the lowest category were 0.93 (0.87-1.00, n=6), 1.01 (0.90-1.12, n=10), and 1.34 (1.04-1.74, n=2), with certainty ratings of low, low, and very low, respectively. Dose-response analysis indicated a non-linear relationship coffee intake (Poverall=0.04 and Pnonlinear=0.01) and dementia risk, showing that the protective association for risk of dementia 1 to 3 cups/day of coffee intake. A linear association of tea intake and risk of dementia, with significantly decreased risk of dementia for each 1 cup/day increase in tea consumption (0.96, 95% CI 0.94-0.99, Poverall = 0.01 and Pnonlinear = 0.68). Conclusion Increased tea consumption was associated with decreased risk of dementia and AD, and a non-linear relation was found between coffee and dementia, supporting public health recommendations for dementia prevention.