BACKGROUND: Allergic rhinitis and asthma as single entities affect more boys than girls in childhood but more females in adulthood. However, it is unclear if this prevalence sex-shift also occurs in allergic rhinitis and concurrent asthma. Thus, our aim was to compare sex-specific differences in the prevalence of coexisting allergic rhinitis and asthma in childhood, adolescence and adulthood. METHODS: Post-hoc analysis of systematic review with meta-analysis concerning sex-specific prevalence of allergic rhinitis. Using random-effects meta-analysis, we assessed male-female ratios for coexisting allergic rhinitis and asthma in children (0-10 years), adolescents (11-17) and adults (> 17). Electronic searches were performed using MEDLINE and EMBASE for the time period 2000-2014. We included population-based observational studies, reporting coexisting allergic rhinitis and asthma as outcome stratified by sex. We excluded non-original or non-population-based studies, studies with only male or female participants or selective patient collectives. RESULTS: From a total of 6539 citations, 10 studies with a total of 93,483 participants met the inclusion criteria. The male-female ratios (95% CI) for coexisting allergic rhinitis and asthma were 1.65 (1.52; 1.78) in children (N = 6 studies), 0.61 (0.51; 0.72) in adolescents (N = 2) and 1.03 (0.79; 1.35) in adults (N = 2). Male-female ratios for allergic rhinitis only were 1.25 (1.19; 1.32, N = 5) in children, 0.80 (0.71; 0.89, N = 2) in adolescents and 0.98 (0.74; 1.30, N = 2) in adults, respectively. CONCLUSIONS: The prevalence of coexisting allergic rhinitis and asthma shows a clear male predominance in childhood and seems to switch to a female predominance in adolescents. This switch was less pronounced for allergic rhinitis only.

Mariona Pinart is a recipient of a 'Sara Borrell' postdoctoral contract (CD11/00090) from the Fondo de Investigaciones Sanitarias (FIS), Ministry of Economy and Competitiveness, Spain. This work was initiated and supported by MeDALL, a collaborative project conducted within the European Union under the Health Cooperation Work Programme of the 7th Framework Programme (Grant Agreement No. 261357).