Do biomarkers of stress mediate the relation between socioeconomic status and health?

OBJECTIVES: To test the relation between socioeconomic status (SES) and biomarkers of chronic stress, including basal cortisol, and to test whether these biomarkers account for the relation between SES and health outcomes. DESIGN: Cross sectional study using data from the 2000 social and environmental biomarkers of aging study (SEBAS). SETTING: Taiwan. PARTICIPANTS: Nationally representative sample of 972 men and women aged 54 and older. MAIN OUTCOME MEASURES: Highest risk quartiles for 13 biomarkers representing functioning of the neuroendocrine system, immune/inflammatory systems, and the cardiovascular system: cortisol, adrenaline (epinephrine), noradrenaline (norepinephrine), serum dihydroepiandrosterone sulphate (DHEA-S), insulin-like growth factor 1 (IGF1), interleukin 6 (IL6), albumin, systolic blood pressure, diastolic blood pressure, waist-hip ratio, total cholesterol-HDL ratio, HDL cholesterol, and glycosylated haemoglobin; self reported health status (1-5) and self reported mobility difficulties (0-6). RESULTS: Lower SES men have greater odds of falling into the highest risk quartile for only 2 of 13 biomarkers, and show a lower risk for 3 of the 13 biomarkers, with no association between SES and cortisol. Lower SES women have a higher risk for many of the cardiovascular risk factors, but a lower risk for increased basal readings of adrenaline, noradrenaline, and cortisol. Inclusion of all 13 biological markers does not explain the relation between SES and health outcomes in the sample. CONCLUSIONS: These data do not support the hypothesis that chronic stress, via sustained activation of stress related autonomic and neuroendocrine responses, is an important mediator in the relation between SES and health outcomes. Most notably, lower SES is not associated with higher basal levels of cortisol in either men or women. These results place an increased burden of proof on researchers who assert that psychosocial stress is an important pathway linking SES and health.