title: Educational differences in cardiovascular mortality: The role of shared family factors and cardiovascular risk factors.
abstract: OBJECTIVE
  To explore the confounding effects of early family factors shared by siblings and cardiovascular risk factors in midlife on the educational differences in mortality from cardiovascular disease (CVD).
  
  
  METHODS
  Data from national and regional health surveys in Norway (1974-2003) were linked with data from the Norwegian Family Based Life Course Study, the National Educational Registry and the Cause of Death Registry. The study population consisted of participants with at least one full sibling among the health survey participants ( n=271,310). Data were available on CVD risk factors, including weight, height, blood pressure, total cholesterol and smoking.
  
  
  RESULTS
  The hazards ratio (HR) of CVD mortality was 3.44 (95% confidence interval (CI) 2.98-3.96) in the lowest educational group relative to the highest. The HRs were little altered in the within-sibship analyses. Adjusted for risk factors, the HR for CVD mortality in the cohort analyses was 2.05 (CI 1.77-2.37) in the lowest educational group relative to the highest. The respective HR in the within-sibship analyses was 2.46 (CI 1.48-2.24).
  
  
  CONCLUSIONS
  Using a sibling design, we did not find that the association between education and CVD mortality was confounded by early life factors shared by siblings, but it was explained to a large extent by CVD risk factors. These results suggest that reducing levels of CVD risk factors could have the greatest effect on mortality in less well-educated people.
authors.affiliation: 1 Institute of Health and Society, University of Oslo, Norway.
authors.forename: M K R
authors.initials: MKR
authors.lastname: Kjøllesdal
authors.affiliation: 2 Norwegian Institute of Public Health, Norway.
authors.forename: I
authors.initials: I
authors.lastname: Ariansen
authors.affiliation: 3 University of Copenhagen, Denmark.
authors.forename: L H
authors.initials: LH
authors.lastname: Mortensen
authors.affiliation: 4 MRC Integrative Epidemiology Unit, University of Bristol, UK.
authors.forename: G
authors.initials: G
authors.lastname: Davey Smith
authors.affiliation: 1 Institute of Health and Society, University of Oslo, Norway.|2 Norwegian Institute of Public Health, Norway.
authors.forename: Ø
authors.initials: Ø
authors.lastname: Næss
mesh_terms: D000293:Adolescent; D000328:Adult; D002318:Cardiovascular Diseases / Q000401:mortality*; D015331:Cohort Studies; D004522:Educational Status; D005260:Female; D054624:Health Status Disparities; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D035781:Siblings; D055815:Young Adult
keywords: Early life; cardiovascular mortality; cardiovascular risk factors; siblings; social inequalities