title: Duration of residence and disease occurrence among refugees and family reunited immigrants: test of the 'healthy migrant effect' hypothesis.
abstract: OBJECTIVE
  The 'healthy migrant effect' (HME) hypothesis postulates that health selection has a positive effect on migrants' health outcomes, especially in the first years after migration. We examined the potential role of the HME by assessing the association between residence duration and disease occurrence.
  
  
  METHODS
  We performed a historical prospective cohort study. We included migrants who obtained residence permits in Denmark between 1 January 1993 and 31 December 2010 (n = 114,331). Occurrence of severe conditions was identified through linkage to the Danish National Patient Register. Hazard Ratios (HRs) were modelled for disease incidence by residence duration since arrival (0-5 years; 0-10 years; 0-18 years) adjusting for age and sex.
  
  
  RESULTS
  Compared with Danish-born individuals, refugees and family reunited immigrants had lower HRs of stroke and breast cancer within 5 years after arrival; however, HRs increased at longer follow-up. For example, HRs of stroke among refugees increased from 0.77 (95% CI: 0.66; 0.91) to 0.96 (95% CI: 0.88; 1.05). For ischaemic heart disease (IHD) and diabetes, refugees and family reunited migrants had higher HRs within 5 years after arrival, and most HRs had increased by end of follow-up. For example, HRs of IHD among family reunited migrants increased from 1.29 (95% CI: 1.17; 1.42) to 1.43 (95% CI: 1.39; 1.52). In contrast, HRs for TB and HIV/AIDS showed a consistent decrease over time.
  
  
  CONCLUSIONS
  Our analyses of the effect of duration of residence on disease occurrence among migrants imply that, when explaining migrants' advantageous health outcomes, the ruling theory of the HME should be used with caution, and other explanatory models should be included.
authors.affiliation: Danish Research Centre for Migration, Ethnicity and Health, Section of Health Services Research, Department of Public Health, University of Copenhagen, Copenhagen, Denmark; Section of Immigrant Medicine, Department of Infectious Disease, University Hospital Copenhagen, Hvidovre, Denmark.
authors.forename: Marie
authors.initials: M
authors.lastname: Norredam
authors.forename: Charles
authors.initials: C
authors.lastname: Agyemang
authors.forename: Oluf K
authors.initials: OK
authors.lastname: Hoejbjerg Hansen
authors.forename: Jørgen H
authors.initials: JH
authors.lastname: Petersen
authors.forename: Stine
authors.initials: S
authors.lastname: Byberg
authors.forename: Allan
authors.initials: A
authors.lastname: Krasnik
authors.forename: Anton E
authors.initials: AE
authors.lastname: Kunst
mesh_terms: D000328:Adult; D003718:Denmark; D054242:Emigrants and Immigrants; D004641:Emigration and Immigration; D005260:Female; D005500:Follow-Up Studies; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012036:Refugees; D012042:Registries; D012111:Residence Characteristics; D014171:Transients and Migrants
keywords: communicable disease; duración de residencia; duration of residence; durée de résidence; emigrantes; enfermedades transmisibles; immigrants; inmigración; maladies non transmissibles; maladies transmissibles; migration; non-communicable disease; refugees; refugiados; réfugiés