Socioeconomic conditions across life related to multiple measures of the endocrine system in older adults: Longitudinal findings from a British birth cohort study

David Bann,Rebecca Hardy,Rachel Cooper,Hany Lashen,Brian Keevil,Frederick C.W Wu,Jeff M.P Holly,Ken K Ong,Yoav Ben-Shlomo,Diana Kuh

doi:10.1016/j.socscimed.2015.11.001

Abstract

BackgroundLittle 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. MethodsData 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. ResultsLower 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. ConclusionsLower 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.

Highlights

Socioeconomic inequalities in premature mortality, as well as physical and cognitive function are known to be substantial in the UK and many other developed nations
Lower AIC values indicate an improved model fit, yet there are no well-established cut-points for determining the extent to which an improved model fit is large, moderate, or small. As both low and high hormone concentrations could indicate impaired endocrine regulation, we examined whether socioeconomic position (SEP) was associated with both high and low hormone concentrations; SEP indicators were cross-tabulated with hormones categorized as the lowest 12.5%, middle 75%, and highest 12.5%, and separate logistic regression models were conducted to test associations between SEP with risk of both low and high hormone concentrations
Men had higher free testosterone and insulin-like growth factor-I (IGF-I) concentrations at 60e64 years than women, while there was no evidence for a sex difference in evening cortisol (P 1⁄4 0.7; Table 1)

Summary

Introduction

Differences in endocrine function, and in rates of age-related changes, could partly underlie socioeconomic inequalities in health and function. SEP may be related to an adverse hormone profile across multiple axes, which may have additive and/or synergistic effects on physical and cognitive function in old age (Cappola et al, 2009; Hertoghie, 2005). 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. 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

Methods

Results

Conclusion