title: Socioeconomic conditions across life related to multiple measures of the endocrine system in older adults: Longitudinal findings from a British birth cohort study.
abstract: BACKGROUND
  Little is known about how socioeconomic position (SEP) across life impacts on different axes of the endocrine system which are thought to underlie the ageing process and its adverse consequences. We examined how indicators of SEP across life related to multiple markers of the endocrine system in late midlife, and hypothesized that lower SEP across life would be associated with an adverse hormone profile across multiple axes.
  
  
  METHODS
  Data were from a British cohort study of 875 men and 905 women followed since their birth in March 1946 with circulating free testosterone and insulin-like growth factor-I (IGF-I) measured at both 53 and 60-64 years, and evening cortisol at 60-64 years. Indicators of SEP were ascertained prospectively across life-paternal occupational class at 4, highest educational attainment at 26, household occupational class at 53, and household income at 60-64 years. Associations between SEP and hormones were investigated using multiple regression and logistic regression models.
  
  
  RESULTS
  Lower SEP was associated with lower free testosterone among men, higher free testosterone among women, and lower IGF-I and higher evening cortisol in both sexes. For example, the mean standardised difference in IGF-I comparing the lowest with the highest educational attainment at 26 years (slope index of inequality) was -0.4 in men (95% CI -0.7 to -0.2) and -0.4 in women (-0.6 to -0.2). Associations with each hormone differed by SEP indicator used and sex, and were particularly pronounced when using a composite adverse hormone score. For example, the odds of having 1 additional adverse hormone concentration in the lowest compared with highest education level were 3.7 (95% CI: 2.1, 6.3) among men, and 1.6 (1.0, 2.7) among women (P (sex interaction) = 0.02). We found no evidence that SEP was related to apparent age-related declines in free testosterone or IGF-I.
  
  
  CONCLUSIONS
  Lower SEP was associated with an adverse hormone profile across multiple endocrine axes. SEP differences in endocrine function may partly underlie inequalities in health and function in later life, and may reflect variations in biological rates of ageing. Further studies are required to assess the likely functional relevance of these associations.
authors.affiliation: MRC Unit for Lifelong Health and Ageing at UCL, London, UK; Centre for Longitudinal Studies, UCL Institute of Education, London, UK. Electronic address: david.bann@ucl.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Bann
authors.affiliation: MRC Unit for Lifelong Health and Ageing at UCL, London, UK.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Hardy
authors.affiliation: MRC Unit for Lifelong Health and Ageing at UCL, London, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Cooper
authors.affiliation: Department of Human Metabolism, The University of Sheffield, Sheffield, UK.
authors.forename: Hany
authors.initials: H
authors.lastname: Lashen
authors.affiliation: Andrology Research Unit, School of Biomedicine, University of Manchester, UK.
authors.forename: Brian
authors.initials: B
authors.lastname: Keevil
authors.affiliation: Andrology Research Unit, School of Biomedicine, University of Manchester, UK.
authors.forename: Frederick C W
authors.initials: FC
authors.lastname: Wu
authors.affiliation: School of Clinical Science, Bristol University, Bristol, UK.
authors.forename: Jeff M P
authors.initials: JM
authors.lastname: Holly
authors.affiliation: MRC Epidemiology Unit, University of Cambridge, Cambridge, UK.
authors.forename: Ken K
authors.initials: KK
authors.lastname: Ong
authors.affiliation: School of Social and Community Medicine, Bristol University, Bristol, UK.
authors.forename: Yoav
authors.initials: Y
authors.lastname: Ben-Shlomo
authors.affiliation: MRC Unit for Lifelong Health and Ageing at UCL, London, UK.
authors.forename: Diana
authors.initials: D
authors.lastname: Kuh
mesh_terms: D015331:Cohort Studies; D004703:Endocrine System / Q000503:physiopathology*; D005260:Female; D054625:Healthcare Disparities; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012923:Social Class; D006113:United Kingdom / Q000453:epidemiology
keywords: Cortisol; Insulin-like growth factors; Socioeconomic factors; Testosterone; Thyroid