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 = 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.