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01.12.2015 | Research article | Ausgabe 1/2016 Open Access

BMC Public Health 1/2016

The importance of age, sex and place in understanding socioeconomic inequalities in allostatic load: Evidence from the Scottish Health Survey (2008–2011)

Zeitschrift:
BMC Public Health > Ausgabe 1/2016
Autoren:
Tony Robertson, Eleanor Watts
Wichtige Hinweise

Electronic supplementary material

The online version of this article (doi:10.​1186/​s12889-016-2796-4) contains supplementary material, which is available to authorized users.

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

EW: contributed to the design, conducted the initial analysis and drafted the initial manuscript, as well as commented on the final draft. TR: contributed to the design of the study, conducted further analyses and wrote the final manuscript. Both authors read and approved the final manuscript.

Abstract

Background

Given the broad spectrum of health and wellbeing outcomes that are patterned by socioeconomic position (SEP), it has been suggested that there may be common biological pathways linking SEP and health. Allostatic load is one such pathway, which aims to measure cumulative burden/dysregulation across multiple physiological systems. This study aimed to determine the contextual and demographic factors (age, sex and place) that may be important in better understanding the links between lower SEP and higher allostatic load.

Methods

Data were from a nationally representative sample of adults (18+): the Scottish Health Survey (2008–2011). Higher SEP (‘1’) was defined as having ‘Higher’-level, secondary school qualifications versus having lower level or no qualifications (‘0’). For allostatic load, a range of 10 biomarkers across the cardiovascular, metabolic and immune systems were used. Respondents were scored “1” for each biomarker that fell into the highest quartile of risk. Linear regressions were run in STATA, including SEP, age (continuous and as a 7-category variable), sex (male/female), urbanity (a 5-category variable ranging from primary cities to remote rural areas) and geographical location (based on 10 area-level healthboards). Interactions between SEP and each predictor, as well as stratified analyses, were tested.

Results

Lower SEP was associated with higher allostatic load even after adjusting for age, sex and place (b = −0.631, 95 % CI −0.795, −0.389, p < 0.001). There was no significant effect moderation between SEP and age, sex or place. Stratified analysis did show that the inequality identified in the baseline models widened with age, becoming significant at ages 35–44, before narrowing at older ages (75+). There was no difference by sex, but more mixed findings with regards place (urbanity or geographical location), with a mix of significant and non-significant results by SEP that did not appear to follow any pattern.

Conclusions

Inequalities in allostatic load by educational attainment, as a measure of SEP, are consistent with age, sex and place. However, these stratified analyses showed that these inequalities did widen with age, before narrowing in later life, matching the patterns seen with other objective and subjective health measures. However, effect moderation analysis did not support evidence of a statistically significant interaction between age and SEP. Context remains an important feature in understanding and potentially addressing inequalities, although may be less of an issue in terms of physiological burden.
Zusatzmaterial
Additional file 1: Allostatic Load clinical cut-offs. (DOCX 31 kb)
12889_2016_2796_MOESM1_ESM.docx
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