Asthma prevalence in adults and children
Asthma prevalence seems to be still increasing as suggested by Borna et al., who investigated its change between 2008 and 2016 in Sweden. The authors observed a significant rise of reported frequencies of ever asthma, physician‐diagnosed asthma, use of asthma medication and current asthma, especially in young adults aged 16‐25 years.9At the same time, an increase in the prevalence of respiratory symptoms during the same period was reported, suggesting the possibility that actually, asthma is underdiagnosed. The potential risk factors for asthma remained the same during the study period.9
Recent studies assessed the prevalence of asthma in preschoolers (4.4 %) and elementary school children (6.4%) according to Global Initiative for Asthma (GINA) definition.8 While no significant difference between rural and urban children was observed, Branco et al. found an association with previously identified risk factors for asthma development, including parental asthma and antibiotics treatment in the first year of life.10 Liu et al. investigated the link between maternal hypothyroidism in the perinatal period and childhood asthma risk, in a population‐based cohort study using Danish national registers. A higher incidence of asthma was found compared to children born to mothers with no thyroid dysfunction. The risk was even higher if the mothers did not receive thyroid hormone treatment during pregnancy.11