Environmental exposures and recurrent wheeze in early childhood: a time-to-event study

Abstract

Background: Environmental exposures are risk factors for adverse respiratory health in infancy, and may accelerate time to persistent wheezing in early childhood.

Aim: To determine whether the time to recurrent wheeze in a cohort followed antenatally to 48 months, was associated with environmental risk factors.

Method: Among 520 mother-child pairs, standardized maternal interviews and annual clinical assessments of children were conducted. Land use regression and dispersion modelling characterized home address exposure to criteria pollutants. The probability of time to recurrent wheeze (two or more episodes of reported wheezing during the follow-up period) and ambient pollution, biomass fuel use and environmental tobacco smoke (ETS) association was achieved with the Kaplan-Meier hazard function and the Cox-proportional hazard model.

Results: Overall, 73% reported no wheezing and 11% recurrent wheeze. Mean pollutant exposure across did not vary by wheeze status. Time to recurrent wheeze (42.9 months) among children from households with biomass energy sources was shorter than those using electricity (45.9 months) (p=0.03), and 45.4 months and 46.5 months (p=0.04) among those with and without ETS exposure. ETS exposure resulted in an increased risk for recurrent wheeze compared to the non-exposed (adjusted HR=3.76, 95%CI=1.33-10.66), while an increased risk for biomass exposure was also noted (HR=3.09 (0.91, 10.45)). A non-statistically significant increased risk was associated with pollutant exposure.

Conclusion: Exposure to ETS and biomass use were risk factors associated with time to recurrent wheezing in early childhood. There was weak evidence for ambient pollutant exposure.