title: Oral contraception, body mass index, and asthma: a cross-sectional Nordic-Baltic population survey.
abstract: BACKGROUND
  Emerging evidence suggests that sex steroid hormones may influence airways obstruction, and that metabolic status may modify potential effects.
  
  
  OBJECTIVE
  This study investigated the association between use of oral contraceptive pills (OCPs) and asthma in a Nordic-Baltic population-based study, while taking into account possible interplay with body mass index (BMI).
  
  
  METHODS
  Postal questionnaires were sent to subjects in Denmark, Estonia, Iceland, Norway, and Sweden from 1999 to 2001 (response rate in women, 77%). Pregnant women, women using hormone replacement therapy, and women >45 years were excluded. Analyses included 5791 women 25 to 44 years old, of whom 961 (17%) used OCP. Logistic regression analyses included adjustment for smoking, irregular menstruation, BMI, age, type of dwelling, and center.
  
  
  RESULTS
  Oral contraceptive pills were associated with increased risk for asthma (odds ratio, 1.42; 95% CI, 1.09-1.86), asthma with hay fever (1.48; 1.08-2.03), wheeze with shortness of breath (1.27; 1.02-1.60), hay fever (1.25; 1.06-1.48), and >/=3 asthma symptoms (1.29; 1.05-1.58). The findings were consistent between centers. The associations were present only among normal weight women (BMI 20-25 kg/m(2), asthma: 1.45; 1.02-2.05) and overweight women (BMI >25kg/m(2): 1.91; 1.20-3.02), but not among lean women (BMI <20 kg/m(2): 0.41; 0.12-1.40). Interaction between BMI and OCP in association with asthma was significant (P(interaction) < .05).
  
  
  CONCLUSIONS
  Women using oral contraceptive pills had more asthma. This was found only in normal weight and overweight women, indicating interplay between sex hormones and metabolic status in effect on the airways. The findings originate from a cross-sectional postal survey and should be interpreted with caution; it is recommended that asthma symptoms are included in clinical trials of oral contraception.
authors.affiliation: Department of Gynecology and Obstetrics, Haukeland University Hospital, Bergen, Norway.
authors.forename: Ferenc
authors.initials: F
authors.lastname: Macsali
authors.forename: Francisco Gómez
authors.initials: FG
authors.lastname: Real
authors.forename: Ernst Reidar
authors.initials: ER
authors.lastname: Omenaas
authors.forename: Line
authors.initials: L
authors.lastname: Bjorge
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.forename: Karl
authors.initials: K
authors.lastname: Franklin
authors.forename: Cecilie
authors.initials: C
authors.lastname: Svanes
mesh_terms: D000328:Adult; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology; D015992:Body Mass Index; D003278:Contraceptives, Oral, Hormonal / Q000009:adverse effects*; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D004957:Estonia / Q000453:epidemiology; D004967:Estrogens / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D009664:Norway; D011372:Progestins / Q000009:adverse effects*; D006255:Rhinitis, Allergic, Seasonal / Q000453:epidemiology* / Q000209:etiology; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology
chemical_list: D003278:Contraceptives, Oral, Hormonal; D004967:Estrogens; D011372:Progestins