Sex Differences in Severe Asthma

Abstract

Background: Asthma is more prevalent in males during childhood but becomes predominantly female in adulthood. Cohort studies and registries of adult severe asthma demonstrate a higher prevalence and severity of disease in females.

Aim: To describe the differences in severe asthma patients in terms of biological characteristics across sex.

Methods: Clinical characterisation and sputum induction was perfomed as part of the WATCH cohort study in biologic naïve patients severe asthma patients. Sputum was analysed for differential cell count and supernatant proteins (PBS processed), measured by singleplex ELISA with between group differences assessed by Mann Whitney U tests. Analysis was replicated in a second severe asthma cohort (WSAC cohort), who had undergone a similar characterisation process.

Results: The analysis included 152 and 99 patients from WATCH and WSAC cohorts respectively. Both cohorts were predominantly female (57.9% and 60.6% respectively) with no difference between males and females in maintenance OCS use or exacerbation frequency in the last 12 months. Compared to females, male patients in the WATCH cohort had later onset disease and a higher frequency of nasal polyps whilst WSAC patients had higher serum total IgE and sputum eosinophil counts. In both cohorts, male patients had higher blood eosinophil counts, FeNO and sputum ECP. Additional differentiators were sputum EDN (measured in WATCH study) and sputum IL-5 (measured WSAC cohort).

Conclusion: Sex differences in asthma and severe asthma are well described with various putative mechanisms proposed. We demonstrate that signals of type 2 inflammation in blood and sputum are more frequently seen in males than females, despite a comparable level of corticosteroid therapy.