title: Prenatal stress and childhood asthma in the offspring: role of age at onset.
abstract: BACKGROUND
  Asthma is a heterogeneous disorder with different phenotypes, and age at onset may define part of them. Little is known about possible association between prenatal stress and asthma phenotypes according to age at onset. We aim to investigate whether there is an association between prenatal stress and asthma, and if so, whether such an association differs according to age at asthma onset.
  
  
  METHODS
  We carried out a cohort study based on several national registers in Denmark, including all live singletons born during 1996-2007 in Denmark (N = 750,058). We identified children born to mothers who lost a close relative (a child, partner/spouse, a parent or a sibling) 1 year prior to or during pregnancy as the bereaved group. Using Cox proportional hazards regression model, we evaluated the hazard ratios (HRs) for asthma in children of bereaved mothers, compared with children of non-bereaved mothers.
  
  
  RESULTS
  Prenatal stress following maternal bereavement was associated with a marginally increased risk of asthma events in children aged 0-3 years [HR = 1.04, 95% confidence interval (CI): 1.00-1.07], while unexpected bereavement was associated with a higher risk (HR = 1.13, 95% CI: 1.02-1.24). There was no association between prenatal bereavement and asthma in children aged 4-15 years (HR = 1.02, 95% CI: 0.96-1.09).
  
  
  CONCLUSIONS
  Prenatal stress is possibly associated with asthma events in children aged 0-3 years, but not with asthma in children aged 4-15 years irrespective of age at asthma onset.
authors.affiliation: 1 Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark 2 Department of Epidemiology and Social Science on Reproductive Health, Shanghai Institute of Planned Parenthood Research, WHO Collaborating Center for Research in Human Reproduction, National Population & Family Planning Key Laboratory of Contraceptive Drugs and Devices, Shanghai, China lxq@ph.au.dk.
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Liu
authors.affiliation: 1 Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark 3 Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles, California, USA.
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
authors.affiliation: 4 National Centre for Register-Based Research, Aarhus University, Aarhus, Denmark 5 CIRRAU-Centre for Integrated Register-based Research, Aarhus University, Aarhus, Denmark.
authors.forename: Esben
authors.initials: E
authors.lastname: Agerbo
authors.affiliation: 2 Department of Epidemiology and Social Science on Reproductive Health, Shanghai Institute of Planned Parenthood Research, WHO Collaborating Center for Research in Human Reproduction, National Population & Family Planning Key Laboratory of Contraceptive Drugs and Devices, Shanghai, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Yuan
authors.affiliation: 6 Section for Environment, Occupation and Health, Department of Public Health, Aarhus University, Denmark.
authors.forename: Torben
authors.initials: T
authors.lastname: Sigsgaard
authors.affiliation: 1 Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark.
authors.forename: Jiong
authors.initials: J
authors.lastname: Li
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D001249:Asthma / Q000453:epidemiology*; D001601:Bereavement; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009035:Mothers / Q000523:psychology*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D016016:Proportional Hazards Models; D012307:Risk Factors; D013315:Stress, Psychological / Q000453:epidemiology*