Gender differences in the association between life history of body silhouettes and asthma incidence : results from the SAPALDIA cohort study

Background: The association of obesity and asthma has been described in children and adults. However, whether a different life course of weight in men and women may explain gender differences in asthma incidence, has not been addressed. Objectives: Using data from the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults, we investigated the role of overweight/obesity as measured by body silhouettes at different life stages in men and women for asthma incidence. Methods: Our analysis included 5417 subjects who were asthma free at age 8, followed up to 2011, and had complete covariate information. The main predictor of interest was self-reported body silhouettes at age 8, menarche, 30, 45, menopause, and 60, and additionally changes in body silhouette number across these different time points. Asthma incidence was defined as newly reported doctor-diagnosed asthma after the body silhouette time point. Asthma incidence and its association with body silhouettes was analysed using sex stratified logistic regression, adjusting for age, atopy, urbanity, smoking, parental asthma, education and study area. Results: Men at age 60 had an increased risk of asthma incidence per unit increase in body silhouette number (OR 1.93, 95% CI 1.13–3.30). This association was stronger in women at age 60 (OR 2.78, 95% CI 1.49–5.18) and observed also at menopause (OR 1.35, 95% CI 1.03–1.78), as well as per unit change in body silhouette number between age 45 – menopause (OR 1.74, 95% CI 1.15–2.63). Conclusion: In this longitudinal study, the risk of incident asthma increased in men and women with a larger body silhouette in late adulthood. In women, this risk appeared present between age 45 and menopause. At age 60, both men and women were at higher risk of asthma incidence per unit increase in body silhouette, the risk being more pronounced in women. The age-related increase of obesity may underlie gender differences in asthma incidence at higher ages.