By comparing morning salivary cortisol and health-related quality of life (QoL) in two-year-old toddlers, this study is a contribution to the understanding of the association between stress and early asthma development. We also detected negative effects from moderate to severe acute bronchiolitis requiring hospitalisation in the first year of life and asthma risk factors, mostly atopic dermatitis, on QoL nine months later. Ventilatory support indicated lower QoL.
Cortisol was higher in infants during the stress of acute bronchiolitis than in controls. Although seeming contradictory, lower levels of cortisol coincided with lower QoL in the 203 two-year-old children with acute bronchiolitis in infancy, not in 155 controls. Adjustment for a possible causal link in the pathway, recurrent bronchial obstruction (rBO) as a proxy for asthma, indicates that early stage asthma partly explains this phenomenon. The two-year-old ones with rBO had lower cortisol, a sign of a weaker HPA axis, i.e. reduced interaction between the hypothalamus and the pituitary and adrenal glands. This is in accordance with studies showing lower cortisol in asthma and allergic disease, independent of medication.