title: Health behaviours, socioeconomic status, and mortality: further analyses of the British Whitehall II and the French GAZEL prospective cohorts.
abstract: BACKGROUND
  Differences in morbidity and mortality between socioeconomic groups constitute one of the most consistent findings of epidemiologic research. However, research on social inequalities in health has yet to provide a comprehensive understanding of the mechanisms underlying this association. In recent analysis, we showed health behaviours, assessed longitudinally over the follow-up, to explain a major proportion of the association of socioeconomic status (SES) with mortality in the British Whitehall II study. However, whether health behaviours are equally important mediators of the SES-mortality association in different cultural settings remains unknown. In the present paper, we examine this issue in Whitehall II and another prospective European cohort, the French GAZEL study.
  
  
  RESULTS
  We included 9,771 participants from the Whitehall II study and 17,760 from the GAZEL study. Over the follow-up (mean 19.5 y in Whitehall II and 16.5 y in GAZEL), health behaviours (smoking, alcohol consumption, diet, and physical activity), were assessed longitudinally. Occupation (in the main analysis), education, and income (supplementary analysis) were the markers of SES. The socioeconomic gradient in smoking was greater (p<0.001) in Whitehall II (odds ratio [OR] = 3.68, 95% confidence interval [CI] 3.11-4.36) than in GAZEL (OR = 1.33, 95% CI 1.18-1.49); this was also true for unhealthy diet (OR = 7.42, 95% CI 5.19-10.60 in Whitehall II and OR = 1.31, 95% CI 1.15-1.49 in GAZEL, p<0.001). Socioeconomic differences in mortality were similar in the two cohorts, a hazard ratio of 1.62 (95% CI 1.28-2.05) in Whitehall II and 1.94 in GAZEL (95% CI 1.58-2.39) for lowest versus highest occupational position. Health behaviours attenuated the association of SES with mortality by 75% (95% CI 44%-149%) in Whitehall II but only by 19% (95% CI 13%-29%) in GAZEL. Analysis using education and income yielded similar results.
  
  
  CONCLUSIONS
  Health behaviours were strong predictors of mortality in both cohorts but their association with SES was remarkably different. Thus, health behaviours are likely to be major contributors of socioeconomic differences in health only in contexts with a marked social characterisation of health behaviours. Please see later in the article for the Editors' Summary.
authors.affiliation: INSERM U1018, Centre for Research in Epidemiology and Population Health, Hôpital Paul Brousse, Villejuif, France. silvia.stringhini@inserm.fr
authors.forename: Silvia
authors.initials: S
authors.lastname: Stringhini
authors.forename: Aline
authors.initials: A
authors.lastname: Dugravot
authors.forename: Martin
authors.initials: M
authors.lastname: Shipley
authors.forename: Marcel
authors.initials: M
authors.lastname: Goldberg
authors.forename: Marie
authors.initials: M
authors.lastname: Zins
authors.forename: Mika
authors.initials: M
authors.lastname: Kivimäki
authors.forename: Michael
authors.initials: M
authors.lastname: Marmot
authors.forename: Séverine
authors.initials: S
authors.lastname: Sabia
authors.forename: Archana
authors.initials: A
authors.lastname: Singh-Manoux
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000009:adverse effects / Q000208:ethnology; D003431:Cross-Cultural Comparison; D004032:Diet / Q000009:adverse effects / Q000208:ethnology*; D015444:Exercise; D005260:Female; D005602:France / Q000453:epidemiology; D015438:Health Behavior / Q000208:ethnology*; D054624:Health Status Disparities; D006801:Humans; D008019:Life Style; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009026:Mortality / Q000208:ethnology*; D016016:Proportional Hazards Models; D011446:Prospective Studies; D057185:Sedentary Behavior / Q000208:ethnology; D012907:Smoking / Q000009:adverse effects / Q000208:ethnology*; D012923:Social Class; D006113:United Kingdom / Q000453:epidemiology