Sex differences in baseline risk factors for the incidence of asthma between early adolescence and young adulthood

Abstract

Background: Several studies have shown sex differences in the prevalence of asthma and a relationship to age. The aim of the present study was to prospectively investigate the development of asthma, wheeze, rhinitis and allergic symptoms, between adolescence and adulthood. Furthermore, to determine if sex modifies the associations between baseline risk factors and incidence of asthma in early adulthood. Methods: In the study Screening Project Asthma in Schools(SPAIS), adolescents aged 12–15 years answered a standardised respiratory questionnaire (ISAAC) and underwent measurements of fractional exhaled nitric oxide (FeNO) and lung function (FEV1) at baseline. Two follow-ups with similar questionnaires were performed after four and 16 years, with 491 subjects participating in all three examinations. Results: The prevalence of asthma and wheeze were unchanged after four years, but had increased after 16 years. However, the increase was significant only for females. A more continuous increasein rhinitis and allergic symptoms showed no difference between the sexes. Sex interaction analysis showed that higher FeNO (p = 0.01) and family asthma (p = 0.02) increased the risk of incident asthma for males but not for females. Conclusions: An increased prevalence of respiratory symptoms was seen primarily between late adolescence and young adulthood, and was significant for females but not males. Allergic risk factors in early adolescence for incident asthma in early adulthood were confirmed in males but not in females. Awareness of these sex differences in the development of symptoms, and the associated risk factors, are important in clinical practice.