title: Socioeconomic position across life and body composition in early old age: findings from a British birth cohort study.
abstract: BACKGROUND
  Previous studies have reported associations between lower lifetime socioeconomic position (SEP) and higher body mass index in adulthood, but few have examined associations with direct measures of fat and lean mass which are likely to have independent roles in health and physical functioning.
  
  
  METHODS
  We examined associations of SEP across life with dual-energy X-ray absorptiometry measures of fat and lean mass at 60-64 years using data from a total of 1558 men and women participating in the Medical Research Council (MRC) National Survey of Health and Development. We also examined whether associations of childhood SEP with fat and lean mass were explained by preadulthood weight gain (birth weight, 0-7 and 7-20 years) and adult SEP.
  
  
  RESULTS
  Lower SEP across life was associated with higher fat mass and higher android to gynoid fat mass ratio. For example, the mean difference in fat mass index comparing the lowest with the highest paternal occupational class at 4 years (slope index of inequality) was 1.04 kg/m(1.2) in men (95% CI 0.09 to 1.99) and 2.61 in women (1.34 to 3.89), equivalent to a 8.6% and 16.1% difference, respectively. After adjustment for fat mass, lower SEP across life was associated with lower lean mass in women, while only contemporaneous household income was associated in men. Associations between childhood SEP and outcomes were partly explained by preadulthood weight gain and adult SEP.
  
  
  CONCLUSIONS
  This study identified lifetime socioeconomic patterning of fat and lean mass in early old age. This is likely to have important implications and may partly explain socioeconomic inequalities in health and physical functioning.
authors.affiliation: MRC Unit for Lifelong Health and Ageing at UCL, London, UK.
authors.forename: David
authors.initials: D
authors.lastname: Bann
authors.forename: Rachel
authors.initials: R
authors.lastname: Cooper
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Wills
authors.forename: Judith
authors.initials: J
authors.lastname: Adams
authors.forename: Diana
authors.initials: D
authors.lastname: Kuh
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology*; D001724:Birth Weight; D001823:Body Composition; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D004522:Educational Status; D004651:Employment / Q000145:classification; D005260:Female; D006306:Health Surveys; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010290:Parents; D012737:Sex Factors; D012923:Social Class; D015430:Weight Gain; D055815:Young Adult
keywords: body composition; body fat distribution; muscle mass; obesity; socioeconomic factors