Quality of Life, Salivary Cortisol and Atopic Diseases in Young Children

ABSTRACT Background Children with atopic disease may have reduced health-related quality of life (QoL) and morning cortisol. The link between QoL, cortisol and atopic disease is unclear. We aimed to determine if QoL was associated with morning salivary cortisol at two years of age, and if asthma, atopic dermatitis and/or allergic sensitisation influenced this association. Secondarily, we aimed to determine if QoL at one year of age was associated with salivary cortisol one year later. Methods and findings From the Bronchiolitis All SE-Norway study, enrolling infants during hospitalisation for acute bronchiolitis in infancy (bronchiolitis group) and population based control infants (controls), we included all 358 subjects with available Infant Toddler Quality of Life Questionnaire™ (ITQOL) consisting of 13 domains, and morning salivary cortisol measurements at two years of age. Additionally, QoL nine months after enrolment was available for 289 of these children at one year of age. Recurrent bronchial obstruction was used as an asthma proxy. Atopic dermatitis was defined by Hanifin and Rajka criteria and allergic sensitisation by a positive skin prick test. Associations between QoL and cortisol were analysed by multivariate analyses, stratified by bronchiolitis and control groups due to interaction. At two years of age, QoL was significantly associated with 8/13 QoL domains in the bronchiolitis group, but only with General health in the controls. The associations in the bronchiolitis group showed 0.06-0.19 percentage points changes per nmol/L cortisol for each of the eight domains (p-values 0.0001-0.034). The associations for all domains remained significant, but were diminished by independently including recurrent bronchial obstruction and atopic dermatitis, but remained unchanged by allergic sensitisation. In the bronchiolitis group only, 8/13 age and gender adjusted QoL domains in one-year old children were significantly associated with cortisol levels at two years (p= 0.0005-0.04). Conclusions: At two years, most QoL domains were associated with salivary cortisol in children who had been hospitalised for acute bronchiolitis in infancy, but for one domain only in controls. The associations were weakened, but remained significant by taking into account asthma and atopic dermatitis. The QoL in one-year old children was associated with salivary cortisol 10 months later.