The prevalence of asthma as a single entity seems to have a male predominance before puberty and a female in adulthood. However, it remains unclear if such a prevalence sex-switch at around puberty also exists for subjects with allergic multimorbidity. The aim of the present study was to examine sex-specific differences in the prevalence of coexisting allergic rhinitis and asthma before, during and after puberty. Systematic review and meta-analysis based on electronic searches (MEDLINE/EMBASE) in July 2014. Inclusion criteria: population-based observational studies, all age groups, sex-stratified reports of coexisting rhinitis and asthma in the last 12 months, all languages. Using random-effects meta-analyses, we examined male-female ratios (MFR) for allergic rhinitis and coexisting asthma for the age groups 0-10, 11-17, and above 17 years. From a total of 9952 citations, 10 studies (with N=93483) met the inclusion criteria and were grouped into the 3 age categories as closely as possible. The MFR for rhinitis with co-existing asthma in children (0–10y; 6 studies N=6) was 1.65 (1.52; 1.78), 0.61 (0.51; 0.72) in youths (11–17y; N=3) and 1.03 (0.79; 1.35) in adults (18+y; N=2). While no heterogeneity was seen among the lower age groups, moderate heterogeneity was found among the studies in the adult group (I 2 = 41%). Our worldwide systematic review with meta-analysis found a clear sex-switch in allergic respiratory multimorbidity prevalence from a male predominance in childhood to a female in adolescence, whereas in adulthood both sexes seemed to be equally affected. Particularly the few sex-specific analyses in older populations require further research.
