Abstract
Sex discordance in asthma prevalence has been previously reported, with higher prevalence in males before puberty, and in females after puberty; the adolescent “switch”. However, cross-sectional studies have suggested a narrowing of this discordance in recent decades. We used a combination of cross-sectional and longitudinal modelling to examine sex differences in asthma, wheeze and longitudinal wheezing phenotypes in two UK birth cohorts, the Avon Longitudinal Study of Parents and Children (ALSPAC; born 1991–92 with data from age 0–18 years) and the Millennium Cohort Study (MCS; born 2000–02 with data from age 3–10 years). We derived measures of asthma and wheeze from questionnaires completed by mothers and cohort children. Previously-derived ALSPAC wheezing phenotype models were applied to MCS. Males had a higher prevalence of asthma at 10.7 years in ALSPAC (OR 1.45 95%CI: 1.26, 1.66 n = 7778 for current asthma) and MCS (OR 1.42 95%CI: 1.29, 1.56 n = 6726 for asthma ever) compared to females, decreasing in ALSPAC after puberty (OR 0.94 95%CI: 0.79, 1.11 n = 5023 for current asthma at 16.5 years). In longitudinal models using restricted cubic splines, males had a clear excess for asthma in the last 12 months and wheeze in the last 12 months up until 16.5 years of age in ALSPAC. Males had an increased risk of all derived longitudinal wheezing phenotypes in MCS when compared to never wheeze and no evidence of being at lower risk of late wheeze when compared to early wheeze. By comparing data in two large, contemporary cohorts we have shown the persistence of sex discordance in childhood asthma, with no evidence that the sex discordance is narrowing in recent cohorts.
Highlights
Higher incidence and prevalence of asthma have been previously reported in males in childhood and in females in adolescence and adulthood [1,2,3]
We investigated whether the increased male prevalence is attenuating in recent years as some previous studies have indicated[8, 9].We analysed the sex discordance in prevalence of asthma and wheeze in The Avon Longitudinal Study of Parents and Children (ALSPAC, recruited 1991–1992), a birth cohort where study children have reached puberty and the Millennium Cohort Study (MCS, recruited 2000–2002) a more recent cohort where the study children have not yet transitioned through puberty but we may still expect to find a higher prevalence of males with asthma in early childhood
There is a higher prevalence of both asthma and wheeze in ALSPAC males up to 13.8 years where the Odds Ratio (OR) is 1.26 for asthma in the last 12 months and 1.30 for wheeze in the last 12 months(Fig 2 and Table E in S1 Appendix)
Summary
Higher incidence and prevalence of asthma have been previously reported in males in childhood and in females in adolescence and adulthood [1,2,3]. The age of this gender switch has not been precisely determined, with conflicting research on whether pubertal stages or puberty are associated with the switch in prevalence [1, 4, 5]. These differences appear to stem from biological differences between sexes as well as sociocultural and environmental differences. Longitudinal Studies in collaboration with the UK Data Service and is available online by application https://discover.ukdataservice.ac.uk/series/?sn= 2000031#access
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