title: Psychological stress and hospitalization for childhood asthma-a nationwide cohort study in two Nordic countries.
abstract: OBJECTIVE
  Exposures to psychological stress in early life may contribute to the development or exacerbation of asthma. We undertook a cohort study based on data from several population-based registers in Denmark and Sweden to examine whether bereavement in childhood led to increased asthma hospitalization.
  
  
  METHODS
  All singleton children born in Denmark during 1977-2008 and in Sweden during 1973-2006 were included in the study (N=5,202,576). The children were followed from birth to the date of first asthma hospitalization, emigration, death, their 18(th) birthday, or the end of study (31 December 2007 in Sweden and 31 December 2008 in Denmark), whichever came first. All the children were assigned to the non-bereaved group until they lost a close relative (mother, father or a sibling), from when they were included in the bereaved group. We evaluated the hazard ratio (HR) of first hospitalization for asthma in bereaved children using Cox proportional hazards regression models, compared to those who were in the non-bereaved group. We also did a sub-analysis on the association between bereavement and first asthma medication.
  
  
  RESULTS
  A total of 147,829 children were hospitalized for asthma. The overall adjusted HR of asthma hospitalization in bereaved children was 1.10 (95% confidence interval (CI): 1.04-1.16), compared to non-bereaved children. The risk of asthma hospitalization was increased in those who lost a close relative at age of 14-17 years (HR=1.54, 95% CI: 1.23-1.92), but not in younger age groups. The association between bereavement and asthma hospitalization did not change over time since bereavement. In the sub-analysis in singleton live births during 1996-2008 recorded in the DMBR, bereavement was associated with a lower use of asthma medication (HR=0.87, 95% CI: 0.80-0.95).
  
  
  CONCLUSIONS
  Our data suggests that psychological stress following bereavement in late adolescence is associated with an increased risk of asthma hospitalization or lowers the threshold for asthma hospitalization.
authors.affiliation: Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark ; 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: Xiaoqin
authors.initials: X
authors.lastname: Liu
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
authors.forename: Esben
authors.initials: E
authors.lastname: Agerbo
authors.forename: Wei
authors.initials: W
authors.lastname: Yuan
authors.forename: Sven
authors.initials: S
authors.lastname: Cnattingius
authors.forename: Mika
authors.initials: M
authors.lastname: Gissler
authors.forename: Jiong
authors.initials: J
authors.lastname: Li
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000453:epidemiology / Q000523:psychology* / Q000628:therapy*; D001601:Bereavement; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D013315:Stress, Psychological / Q000453:epidemiology*; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult