title: Meta-analysis of the association of beta2-adrenergic receptor polymorphisms with asthma phenotypes.
abstract: BACKGROUND
  Two common polymorphisms of the beta2-adrenergic receptor gene (Arg16Gly and Gln27Glu ) have been extensively studied for their possible association with asthma-related phenotypes, but the results of individual studies have been inconclusive.
  
  
  OBJECTIVE
  We aimed to integrate quantitatively the available evidence on the association of the Arg16Gly and the Gln27Glu polymorphisms with asthma, nocturnal asthma, asthma severity, and bronchial hyperresponsiveness.
  
  
  METHODS
  Meta-analysis of case-control and cohort studies using random effects models.
  
  
  RESULTS
  A total of 28 studies were included in the meta-analysis. The summary estimates suggested that neither the Gly16 nor the Glu27 allele contributes to asthma susceptibility overall (odds ratio [OR], 1.01; 95% CI, 0.90-1.13; and OR, 0.95; 95% CI, 0.83-1.09, respectively) or to bronchial hyperresponsiveness (OR, 0.90; 95% CI, 0.77-1.05; and OR, 1.07; 95% CI, 0.94-1.22, respectively). There was a strong association of Gly16 with nocturnal asthma (OR, 2.20; 95% CI, 1.56-3.11) and a less strong association with severe or moderate rather than milder asthma (OR, 1.42; 95% CI, 1.04-1.94). No such effects were seen for the Glu27 allele (OR, 1.02; 95% CI, 0.74-1.40; and OR, 0.82; 95% CI, 0.59-1.14, respectively). Moreover, there was evidence that Gly16 homozygotes had a much higher risk for nocturnal asthma (OR, 5.15; 95% CI, 2.44-10.84) and asthma severity (OR, 2.84; 95% CI, 1.62-4.96) than the Arg16 homozygotes.
  
  
  CONCLUSIONS
  The Gly16 allele of the beta2-adrenergic receptor gene predisposes to nocturnal asthma, and this may also explain the association with asthma severity. Neither polymorphism modulates the risk for bronchial hyperresponsiveness or mild asthma.
authors.affiliation: Department of Pediatrics, Universit of Ioannina School of Medicine, Greece.
authors.forename: Despina G
authors.initials: DG
authors.lastname: Contopoulos-Ioannidis
authors.forename: Eleni N
authors.initials: EN
authors.lastname: Manoli
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
mesh_terms: D000483:Alleles; D001249:Asthma / Q000235:genetics*; D016022:Case-Control Studies; D015331:Cohort Studies; D020022:Genetic Predisposition to Disease; D006720:Homozygote; D006801:Humans; D016017:Odds Ratio; D011110:Polymorphism, Genetic; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics*; D012307:Risk Factors
chemical_list: D018343:Receptors, Adrenergic, beta-2