Neuroendocrine and Immunological Correlates of Chronic Stress in ‘Strictly Healthy’ Populations

<i>Background:</i> Chronic stress has been associated with detrimental or maladaptive neuroendocrine and immunological changes. <i>Objectives:</i> 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. <i>Methods:</i> 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. <i>Results:</i> 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. <i>Conclusions:</i> Our results suggest that the maintenance of health in chronically stressed populations may be associated with both protective and detrimental neuroendocrine and immunological changes.