Maternal bereavement and childhood asthma-analyses in two large samples of Swedish children.

Fang Fang,Petra Arck,Catarina Almqvist,Cecilia Lundholm,Paul Lichtenstein,Niklas Långström,Caroline Olgart Höglund,Mats Lekander,Christian Taube

doi:10.1371/journal.pone.0027202

Abstract

BackgroundPrenatal factors such as prenatal psychological stress might influence the development of childhood asthma.Methodology and Principal FindingsWe assessed the association between maternal bereavement shortly before and during pregnancy, as a proxy for prenatal stress, and the risk of childhood asthma in the offspring, based on two samples of children 1–4 (n = 426 334) and 7–12 (n = 493 813) years assembled from the Swedish Medical Birth Register. Exposure was maternal bereavement of a close relative from one year before pregnancy to child birth. Asthma event was defined by a hospital contact for asthma or at least two dispenses of inhaled corticosteroids or montelukast. In the younger sample we calculated hazards ratios (HRs) of a first-ever asthma event using Cox models and in the older sample odds ratio (ORs) of an asthma attack during 12 months using logistic regression. Compared to unexposed boys, exposed boys seemed to have a weakly higher risk of first-ever asthma event at 1–4 years (HR: 1.09; 95% confidence interval [CI]: 0.98, 1.22) as well as an asthma attack during 12 months at 7–12 years (OR: 1.10; 95% CI: 0.96, 1.24). No association was suggested for girls. Boys exposed during the second trimester had a significantly higher risk of asthma event at 1–4 years (HR: 1.55; 95% CI: 1.19, 2.02) and asthma attack at 7–12 years if the bereavement was an older child (OR: 1.58; 95% CI: 1.11, 2.25). The associations tended to be stronger if the bereavement was due to a traumatic death compared to natural death, but the difference was not statistically significant.Conclusions/SignificanceOur results showed some evidence for a positive association between prenatal stress and childhood asthma among boys but not girls.

Highlights

The prevalence of childhood asthma is high in many countries [1]
Statistical analyses were conducted using SAS software version 9.1 (SAS Institute, Cary, NC, USA). For both younger and older samples, maternal bereavement was not associated with birth weight, gestational age, gender, or Apgar score at 5 minutes; exposed children were more likely delivered via a caesarean section (P,0.0001) (Table 1)
The crude incidence rate of asthma event was slightly higher among the exposed children if the bereavement happened during the year before pregnancy or the second trimester, compared to unexposed children

Summary

Introduction

The observed marked variation in prevalence among genetically similar populations implies that a substantial proportion of childhood asthma is attributable to environmental factors [2,3]. Based on several national health registers in Denmark, earlier studies have examined associations between maternal bereavement and various health consequences of the children [9,10,11,12,13,14]. Prenatal factors such as prenatal psychological stress might influence the development of childhood asthma

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