Incidence and pathways of gender differences in adult asthma

For asthma, an interesting pattern of gender differences across the life span has been documented with higher prevalence rates in boys compared to girls, a reversing of the gender ratio in puberty, and a female preponderance in early adulthood. The picture is less clear for later adulthood, and, in women, for the menopausal transition. This gender-differential life course of asthma has been related, amongst other, to reproductive pathologies and hormonal factors. However, there is a range of further pathways likely to be relevant for gender differences, such as genetic, immunologic mechanisms, systemic inflammation, obesity and metabolic factors, differential time-activity patterns leading to different exposures, different help seeking, or gender biases in diagnosis and treatment.
This PhD project makes use of the on-going Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA), covering 20 years of longitudinal observation in a population aged 18-60 years at baseline in 1991. It assesses gender differences in asthma incidence and investigates two gender-related pathways which have a hypothesized impact on gender differences in asthma incidence and can be tested in the SAPALDIA cohort: firstly, reproductive pathologies and early menarche, and secondly the role of overweight/obesity as measured by lifetime history of body silhouettes.
Asthma incidence was higher in women than in men but decreased with increasing age. The female predominance was considerably stronger in non-sensitised adults compared with those with allergic sensitisation. The association between reproductive pathologies as well as early menarche and asthma incidence remained inconclusive. The risk of new-onset 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 and was most pronounced at age 60.
The completion of this PhD project, embedded in on-going research activities of the SAPALDIA cohort and linked to the European Respiratory Health Survey, contributes to open questions regarding asthma incidence in later adulthood and regarding gender-related differences. This study is among the few to report the cumulative incidence of adult-onset asthma by sex/gender in a population-based study with a high proportion of people aged >50 years of age. Our study is also the first to assess the role of overweight/obesity as measured by body silhouettes for asthma incidence in men and women. Given the importance of asthma in terms of disease burden as well as the epidemic of obesity, knowledge on these sex/gender related pathways is crucial and adds a further argument for obesity prevention strategies.