title: Obesity and adult asthma: potential effect modification by gender, but not by hay fever.
abstract: OBJECTIVE
  First, we sought to estimate the magnitude of the cross-sectional associations between overweight/obesity and asthma stratified by gender and by self-reported hay fever and second we sought to assess both directions of causality in longitudinal analyses.
  
  
  METHODS
  We used cross-sectional and longitudinal data from a population-based cohort study (n=5114, ages 40-65 at baseline). After 8.5 years, 4010 adults were followed-up by questionnaires. Self-reported height and weight were used to calculate body mass index categories. Multivariate adjusted prevalence ratios (PRs), relative risks (RRs), and 95% confidence intervals (95% CI) were calculated using Poisson regression.
  
  
  RESULTS
  In cross-sectional analyses, adjusted PRs were comparable for overweight women and men but differed between obese women and men (PR 1.93, 95% CI 1.19-3.14 and PR 0.98, 95% CI 0.56-1.72). PRs were similar when stratified by hay fever. Longitudinal analyses suggested that overweight/obesity did not increase asthma risk substantially (RR 1.02, 95% CI 0.50-2.06), but a relation between asthma and subsequent weight gain could not be excluded (RR 1.34, 95% CI 1.01-1.77).
  
  
  CONCLUSIONS
  The prevalence of asthma is almost twice as high in obese versus normal weight women, but not in obese men. The association between overweight/obesity and asthma does not vary by hay fever. A causal relationship between asthma and incident weight gain cannot be excluded.
authors: Institute of Psychology, University of Heidelberg, Germany. adrian.loerbroks@psychologie.uni-heidelberg.de
authors: Adrian
authors: A
authors: Loerbroks
authors: Christian J
authors: CJ
authors: Apfelbacher
authors: Manfred
authors: M
authors: Amelang
authors: Til
authors: T
authors: Stürmer
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000453:epidemiology*; D015992:Body Mass Index; D015984:Causality; D015897:Comorbidity; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D004032:Diet; D005260:Female; D005500:Follow-Up Studies; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology; D006255:Rhinitis, Allergic, Seasonal / Q000453:epidemiology