Response variability of salivary cortisol among older adults under psychological stress.

In this study, a quasi-experimental design with repeated measures was used to compare anxious (n = 129) and nonanxious (n = 186) older adults on the cortisol secretion rate attributable to an experimental stressor. Our results support the hypothesis that a first-order longitudinal factor model appropriately describes the cortisol concentration in three saliva samples collected at two experimental times. The model tested explained between 82.6 and 98.0% of the variance in cortisol concentration of the respondent's saliva samples at T1, and between 55.4% and 78.4% at T2. In the nonanxious group ((State-Trait Anxiety Inventory) STAI < 42), the magnitude of the experiment-related cortisol reactivity was, respectively 51 and 33% higher than the respondent's baseline reactivity level at both T1 and T2. By contrast, in the anxious group (STAI >or= 42), our results showed no significant gradient in the magnitude of the cortisol reactivity at either time. This result was interpreted to be in agreement with the helplessness reaction hypothesis. These results suggest that salivary cortisol is a valid measure that is sensitive to experimental stress, and may therefore, be useful in examining physiological response to stress.