The hypothalamic pituitary adrenal axis (HPA) in aging

Salivary cortisol in the elderly

Abstract

Introduction: salivary cortisol has been frequently used as a marker of stress. Cortisol has an important diurnal rhythm with peak elevations at the dawn hours, called cortisol awakening response (CAR) with a drop during the day. Aging changes in the hypothalamic pituitary adrenal (HPA) axis are contradictory.

Objective: this study examines the diurnal variation of salivary cortisol levels in elderly subjects living in the community.

Design: a descriptive cross-sectional study.

Medium: populational. Participants of IMIAS study (International Mobility in Aging Study).

Participants: four hundred and fifty people over 65, men and women with a subsample (100) for the sampling of salivary cortisol.

Measurements: participants collected ten saliva samples, five per day, for two days in this way: when getting up, 30 minutes (half an hour) after waking up, an hour after waking up, in the afternoon at 3 pm and at bedtime. Cortisol was assessed by enzyme radioimmunoassay. CAR, the area under the curve and the curve of diurnal pattern were evaluated.

Results: an amputee CAR with a flattened diurnal profile and lower levels at night was found. Curve pattern found is considered a "normal" pattern of circadian rhythm of cortisol aging, characterized by having a low CAR and a slow fall throughout the day.

Conclusions: The elderly have a lower cortisol response to awakening with a reduced diurnal rhythm probably involving an altered HPA axis regulation with aging