title: Caffeine intake from coffee or tea and cognitive disorders: a meta-analysis of observational studies.
abstract: BACKGROUND
  Observational epidemiological studies such as cross-sectional, case-control, and cohort studies have reported inconsistent findings regarding the association between caffeine intake from coffee or tea and the risk of cognitive disorders such as dementia, Alzheimer's disease, cognitive impairment, and cognitive decline.
  
  
  METHODS
  We searched PubMed and EMBASE in September 2014. Three evaluators independently extracted and reviewed articles, based on predetermined selection criteria.
  
  
  RESULTS
  Out of 293 articles identified through the search and bibliographies of relevant articles, 20 epidemiological studies from 19 articles, which involved 31,479 participants (8,398 in six cross-sectional studies, 4,601 in five case-control studies, and 19,918 in nine cohort studies), were included in the final analysis. The pooled odds ratio (OR) or relative risk (RR) of caffeine intake from coffee or tea for cognitive disorders (dementia, Alzheimer's disease, cognitive impairment, and cognitive decline) was 0.82 (95% confidence interval [CI], 0.67-1.01, I² = 63.2%) in a random-effects meta-analysis. In the subgroup meta-analysis by caffeine sources, the summary OR or RR of coffee intake was 0.83 (95% CI, 0.70-0.98; I² = 44.8%). However, in the subgroup meta-analysis by study design, the summary estimates (RR or OR) of coffee intake for cognitive disorders were 0.70 (95% CI, 0.50-0.98; I² = 42.0%) for cross-sectional studies, 0.82 (95% CI, 0.55-1.24; I² = 33.4%) for case-control studies, and 0.90 (95% CI, 0.59-1.36; I² = 60.0%) for cohort studies.
  
  
  CONCLUSIONS
  This meta-analysis found that caffeine intake from coffee or tea was not associated with the risk of cognitive disorders.
authors.forename: Young-Seok
authors.initials: YS
authors.lastname: Kim
authors.forename: Sang Mi
authors.initials: SM
authors.lastname: Kwak
authors.forename: Seung-Kwon
authors.initials: SK
authors.lastname: Myung
mesh_terms: D000544:Alzheimer Disease / Q000453:epidemiology* / Q000209:etiology; D002110:Caffeine / Q000009:adverse effects*; D016022:Case-Control Studies; D003069:Coffee / Q000009:adverse effects*; D003072:Cognition Disorders / Q000453:epidemiology* / Q000209:etiology; D015331:Cohort Studies; D003704:Dementia / Q000453:epidemiology* / Q000209:etiology; D006801:Humans; D012306:Risk; D013662:Tea / Q000009:adverse effects*
chemical_list: D003069:Coffee; D013662:Tea; D002110:Caffeine