Seasonal Timing of Infant Bronchiolitis, Apnea and Sudden Unexplained Infant Death.

Chantel D Sloan,Emma K Larkin,Christian Rosas-Salazar,Edward Mitchel,Pingsheng Wu,Tina V Hartert,Larry J Anderson,Tebeb Gebretsadik,Kecia N Carroll,Steven M Varga

doi:10.1371/journal.pone.0158521

Chantel D Sloan, Emma K Larkin + Show 8 more

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https://doi.org/10.1371/journal.pone.0158521

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Abstract

Rates of Sudden Unexplained Infant Death (SUID), bronchiolitis, and central apnea increase in winter in temperate climates. Though associations between these three conditions are suggested, more work is required to establish if there is a causal pathway linking bronchiolitis to SUID through inducing central apnea. Utilizing a large population-based cohort of infants studied over a 20-year period (n = 834,595, from birth years 1989–2009)), we analyzed ecological associations between timing of SUID cases, bronchiolitis, and apnea healthcare visits. Data were analyzed between 2013 and 2015. We used a Cox Proportional Hazards model to analyze possible interactions between maternal smoking and maternal asthma with infant bronchiolitis on time to SUID. SUID and bronchiolitis both occurred more frequently in winter. An increase in bronchiolitis clinical visits occurred within a few days prior to apnea visits. We found a temporal relationship between infant bronchiolitis and apnea. In contrast, no peak in SUID cases was seen during peaks of bronchiolitis. Among those without any bronchiolitis visits, maternal smoking was associated with an increased risk of SUID: Hazard Ratio (HR) of 2.38 (95% CI: 2.11, 2.67, p-value <0.001). Maternal asthma was associated with an increased risk of SUID among infants with at least one bronchiolitis visit: HR of 2.40 (95% CI: 1.04, 5.54, p-value = 0.04). Consistent trends between bronchiolitis, apnea, and SUID were not established due to small numbers of SUID cases. However, interaction analysis revealed potential differential associations of bronchiolitis and SUID by maternal smoking, maternal asthma status.

Highlights

Sudden Unexplained Infant Death (SUID) is the death of a child less than 1 year old due to a cause that cannot be otherwise defined or detected
Comparisons in outcome (SUID or no SUID) and exposure variables for premature and term infants are shown in Table 1 and S1 Table
In infants with at least one bronchiolitis visit, having a mother with asthma was associated with higher risk of SUID [hazard ratios for those with mothers who did not have asthma or did not smoke, asthma: Hazard ratios (HRs) = 2.40, 95% confidence intervals (95% CIs): 1.04, 5.54, p-value = 0.039) whereas maternal smoking was associated with higher risk of SUID, smoking: HR = 2.38 (2.11, 2.67, p-value

Summary

Introduction

Sudden Unexplained Infant Death (SUID) is the death of a child less than 1 year old due to a cause that cannot be otherwise defined or detected. Studying biologically plausible causative pathways and risk factors is of the utmost importance to develop further preventive interventions and further reduce risk of SUID [1,2]. Respiratory syncytial virus (RSV) infects nearly every child by two years of age, and is the most common cause of bronchiolitis among infants [4]. RSV has become an important target in the study of viral induction of central apnea and has been suggested to be a risk factor for SUID [4,5,6,7,8]

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