title: Caffeine does not increase the risk of atrial fibrillation: a systematic review and meta-analysis of observational studies.
abstract: BACKGROUND
  Atrial fibrillation (AF) is the most prevalent sustained arrhythmia, and risk factors are well established. Caffeine exposure has been associated with increased risk of AF, but heterogeneous data exist in the literature.
  
  
  OBJECTIVE
  To evaluate the association between chronic exposure to caffeine and AF.
  
  
  METHODS
  Systematic review and meta-analysis of observational studies.
  
  
  METHODS
  PubMed, CENTRAL, ISI Web of Knowledge and LILACS to December 2012. Reviews and references of retrieved articles were comprehensively searched.
  
  
  METHODS
  Two reviewers independently searched for studies and retrieved their characteristics and data estimates.
  
  
  RESULTS
  Random-effects meta-analysis was performed, and pooled estimates were expressed as OR and 95% CI. Heterogeneity was assessed with the I(2) test. Subgroup analyses were conducted according to caffeine dose and source (coffee).
  
  
  RESULTS
  Seven observational studies evaluating 115 993 individuals were included: six cohorts and one case-control study. Caffeine exposure was not associated with an increased risk of AF (OR 0.92, 95% CI 0.82 to 1.04, I(2)=72%). Pooled results from high-quality studies showed a 13% odds reduction in AF risk with lower heterogeneity (OR 0.87; 95% CI 0.80 to 0.94; I(2)=39%). Low-dose caffeine exposure showed OR 0.85 (95% CI 0.78 to 92, I(2)=0%) without significant differences in other dosage strata. Caffeine exposure based solely on coffee consumption also did not influence AF risk.
  
  
  CONCLUSIONS
  Caffeine exposure is not associated with increased AF risk. Low-dose caffeine may have a protective effect.
authors.affiliation: Laboratory of Clinical Pharmacology and Therapeutics, Faculty of Medicine, University of Lisbon, Lisboa, Portugal. dgcaldeira@hotmail.com
authors.forename: Daniel
authors.initials: D
authors.lastname: Caldeira
authors.forename: Cristina
authors.initials: C
authors.lastname: Martins
authors.forename: Luís Brandão
authors.initials: LB
authors.lastname: Alves
authors.forename: Hélder
authors.initials: H
authors.lastname: Pereira
authors.forename: Joaquim J
authors.initials: JJ
authors.lastname: Ferreira
authors.forename: João
authors.initials: J
authors.lastname: Costa
mesh_terms: D001281:Atrial Fibrillation / Q000139:chemically induced / Q000209:etiology* / Q000517:prevention & control; D002110:Caffeine / Q000009:adverse effects*; D003069:Coffee / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D018570:Risk Assessment; D012307:Risk Factors
chemical_list: D003069:Coffee; D002110:Caffeine