Neuroendocrine and immunological correlates of chronic stress in 'strictly healthy' populations

Chronic stress has been associated with detrimental or maladaptive neuroendocrine and immunological changes.

We assessed the neuroendocrine and immunological correlates of a realistic chronic stress experienced by strictly healthy caregivers of Alzheimer's disease patients and age-matched controls.

We screened 330 caregivers and 206 non-caregivers according to the 'strictly healthy' conditions established by the SENIEUR protocol. Forty-one strictly healthy caregivers (60.56 +/- 16.56 years) and 33 non-stressed controls (60.27 +/- 14.11 years) were selected for this study. Salivary cortisol and dehydroepiandrosterone sulfate (DHEAS) were assessed at multiple points by radioimmunoassay. Peripheral T cell proliferation and cellular sensitivity to glucocorticoids (corticosterone and dexamethasone, DEX) were evaluated by colorimetric assays. We also examined the hypothalamic-pituitary-adrenal (HPA) axis response to the administration of a low-dose DEX in vivo.

The caregivers were significantly more stressed, anxious and depressed than non-caregivers (all p < 0.0001), in contrast to similar cortisol levels. Caregivers had reduced DHEAS levels (-32%, p < 0.0001), an increased cortisol/DHEAS ratio (39.7%, p < 0.0001) and impaired HPA axis response to DEX intake. Caregivers had a higher T cell proliferation (p < 0.0001) and increased sensitivity to glucocorticoids in vitro (p < 0.01) as compared to non-stressed controls.

Our results suggest that the maintenance of health in chronically stressed populations may be associated with both protective and detrimental neuroendocrine and immunological changes.