Material hardship alters the diurnal rhythm of salivary cortisol

Background In the quest for biological mechanisms underlying socioeconomic differences in health outcomes, attention has turned to the role of the hypothalamic-pituitary-adrenocortical axis. As there is some evidence that both acute and chronic stress raise cortisol levels, and material hardship is a stressor, we examined the relationship of chronic material hardship with salivary cortisol levels over the day. Methods The data are from a survey of a sample of poor women aged 18-54. Up to four repeated measures of salivary cortisol levels were obtained from 188 women in this sample and modelled as a diurnal profile. Self-reports of a variety of sources of material hardship over the preceding year were combined into a single scale. Specific dimensions of the subjects' cortisol profiles were compared across levels of material hardship. Results Salivary cortisol varied over the day, and by level of reported material hardship. Upon awakening, salivary cortisol levels were comparable across hardship levels. But soon after waking, women at low levels of hardship experienced both a significantly sharper morning surge and subsequently a sharper decline in salivary cortisol (16.0 and 29.5 nmol/l/h) than women with high hardship levels (5.9 and 24.3 nmol/l/h). These differences in cortisol diurnal pattern tended to be related in a dose-response way to levels of material hardship. Conclusions Material hardship among poor women is associated with changes in the diurnal rhythms of cortisol, particularly in the waking response, which is blunted in women with high levels of hardship.