Education and levels of salivary cortisol over the day in US adults

Background: Dysregulation of the hypothalamic-pituitary-adrenal axis is hypothesized to be an important pathway linking socioeconomic position and chronic disease. Purpose: This paper tests the association between education and the diurnal rhythm of salivary cortisol. Methods: Up to eight measures of cortisol (mean of 5.38 per respondent) over 2 days were obtained from 311 respondents, aged 18-70, drawn from the 2001-2002 Chicago Community Adult Health Study. Multi-level models with linear splines were used to estimate waking level, rates of cortisol decline, and area-under-the-curve over the day, by categories of education. Results: Lower education (0-11 years) was associated with lower waking levels of cortisol, but not the rate of decline of cortisol, resulting in a higher area-under-the-curve for more educated respondents throughout the day. Conclusions: This study found evidence of lower cortisol exposure among individuals with less education and thus does not support the hypothesis that less education is associated with chronic over-exposure to cortisol. © 2010 The Society of Behavioral Medicine.