The Journal of Allergy and Clinical Immunology
Volume 123, Issue 2 , Pages 391-397, February 2009

Oral contraception, body mass index, and asthma: A cross-sectional Nordic-Baltic population survey

Ferenc Macsali, MD
- Department of Gynecology and Obstetrics, Haukeland University Hospital, Bergen, Norway
- Bergen Respiratory Research Group, Institute of Medicine, University of Bergen, Bergen, Norway
- Reprint requests: Ferenc Macsali, MD, Department of Gynecology and Obstetrics, Haukeland University Hospital, 5021 Bergen, Norway.
Francisco Gómez Real, MD, PhD
- Department of Gynecology and Obstetrics, Haukeland University Hospital, Bergen, Norway
- Bergen Respiratory Research Group, Institute of Medicine, University of Bergen, Bergen, Norway
Ernst Reidar Omenaas, MD, PhD
- Center for Clinical Research, Haukeland University Hospital, Bergen, Norway
- Bergen Respiratory Research Group, Institute of Medicine, University of Bergen, Bergen, Norway
Line Bjorge, MD, PhD
- Department of Gynecology and Obstetrics, Haukeland University Hospital, Bergen, Norway
Christer Janson, MD, PhD
- Department of Medical Sciences, Respiratory Medicine and Allergology, Uppsala University, Uppsala, Sweden
Karl Franklin, MD, PhD
- Department of Respiratory Medicine, University Hospital, Umeå, Sweden
Cecilie Svanes, MD, PhD
- Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway
- Bergen Respiratory Research Group, Institute of Medicine, University of Bergen, Bergen, Norway

Received 23 May 2008; received in revised form 21 October 2008; accepted 27 October 2008. published online 05 January 2009.

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/m², asthma: 1.45; 1.02-2.05) and overweight women (BMI >25kg/m²: 1.91; 1.20-3.02), but not among lean women (BMI <20 kg/m²: 0.41; 0.12-1.40). Interaction between BMI and OCP in association with asthma was significant (Pinteraction < .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.

Key words: Asthma, oral contraceptives, body mass index, RHINE, ECRHS

Abbreviations used: BMI, Body mass index, ECRHS, European Community Respiratory Health Survey, HRT, Hormone replacement therapy, OCP, Oral contraceptive pill, OR, Odds ratio, RHINE, Respiratory Health in Northern Europe

Supported by the Icelandic Research Council, the Swedish Heart and Lung Foundation, the Vårdal Foundation for Health Care Science and Allergy Research, the Swedish Association Against Asthma and Allergy, the Norwegian Research Council project 135773/330, the Norwegian Asthma and Allergy Association, the Danish Lung Association, and the Estonian Science Foundation grant no. 4350. F.M. was supported by a grant from the Regional Health Authority of Western Norway and from the Norwegian Foundation for Health and Rehabilitation.

Disclosure of potential conflict of interest: K. Franklin receives grant support from the Swedish Heart and Lung Foundation. L. Bjorge is a member of the Norwegian Cancer Society, the Amathea Foundation in Hordaland, and the Norwegian Society for Obstetrics and Gynecology. The rest of the authors have declared that they have no conflict of interest.

PII: S0091-6749(08)01917-9

doi:10.1016/j.jaci.2008.10.041