Pathways from socioeconomic deprivation to bronchiolitis and subsequent childhood asthma

Introduction: Bronchiolitis and childhood asthma are major causes of morbidity among children in the UK, yet there are no preventative or curative measures for most children that develop these conditions. A better understanding of the longitudinal pathways to these conditions is warranted to design effective prevention policies. Using a social determinants of health framework, I explored the pathways between socioeconomic position, bronchiolitis and childhood asthma. Methods: I used national birth cohorts created from linked administrative datasets in my thesis. I used harmonic Poisson regression models to examine associations between socioeconomic deprivation and the seasonality of bronchiolitis admissions in England. I modelled typical trajectories of asthma/wheeze among children in Scotland using latent class growth analysis. Using causal inference methods, I estimated: the socioeconomic disparities in the risk of bronchiolitis admissions that would remain if maternal smoking during pregnancy were eliminated; and the socioeconomic disparities in the risk of chronic trajectories of asthma that would remain if bronchiolitis admissions were eliminated. Results: The peak timing of bronchiolitis admissions varied marginally across England, with earlier peaks in areas with higher population densities. After accounting for seasonal patterns, the North of England had disproportionately higher rates of admissions and, nationwide, disparities followed a socioeconomic gradient. I estimated that eliminating maternal smoking would reduce 20% of socioeconomic disparities in the risk of bronchiolitis admission. I identified four asthma/wheeze trajectories in children: no/infrequent, early-transient, early-persistent and intermediate-onset. Eliminating bronchiolitis admissions could reduce up to 18% of the disparities in the risk of chronic asthma by age ten. Conclusions: Intervening early on the most socioeconomically deprived populations should be central to policies aiming to reduce the incidence of bronchiolitis admissions and asthma. The contribution of other socioeconomically patterned risk factors, including pollution and housing conditions, should be investigated in future work.