Sex hormones and systemic inflammation are modulators of the obese-asthma phenotype

Background: Both systemic inflammation and sex hormones have been proposed as potential mediators of the obese-asthma phenotype. The aim of this study was to examine the associations between sex hormones, oral contraceptive pill (OCP) use, systemic inflammation and airway inflammation in adults with asthma. Methods: Obese (n = 39) and nonobese (n = 42) females and obese (n = 24) and nonobese (n = 25) males with asthma were recruited. Females were further categorized as reproductive-aged (<50 years old; n = 36) or older (>50 years old; n = 45). Thirteen (36.1%) reproductive-aged females were using the OCP. Participants had induced sputum cell counts measured and blood analysed for sex hormones and inflammatory markers. Results: Obese reproductive-aged females had higher sputum % neutrophils than nonobese reproductive-aged females (45.4 +/- 24.3% vs 27.5 +/- 17.5%, P = 0.016); however, there was no difference in sputum neutrophils in obese compared with nonobese males (P = 0.620) or older females (P = 0.087). Multiple linear regression analysis found testosterone and OCP use to be negative predictors of sputum % neutrophils, while C-reactive protein and IL-6 were positive predictors of sputum % neutrophils. BMI and age were not significant predictors in the multivariate model. Reproductive-aged females using the OCP had significantly lower sputum % neutrophils than those not using the OCP (23.2 +/- 12.6% vs 42.1 +/- 23.8%, P = 0.015). Conclusions: This study suggests that sex hormones and systemic inflammation may be mediating the obese-asthma phenotype. The observation that OCP use was associated with lower sputum % neutrophils in reproductive-aged females warrants further investigation.