Gender differences in age-related changes in HPA axis reactivity

Possible differences between men acid women in age-related patterns of hypothalamic-pituitary-adrenal (HPA) axis response to challenge were examined to test the hypothesis that women show greater age-related increase in HPA axis reactivity to challenge. Twenty-six younger subjects, 9 men and 17 women, ages 22-26 and 14 older subjects, 7 men and 7 women, ages 67-88 participated in the study. Patterns of change in salivary "free" cortisol were measured in response to a standardized, 30-minute cognitive challenge, administered individually to each subject beginning at 1600 h, Consistent with previous research, there was a significant main effect for age with respect to baseline cortisol: older age was associated with higher baseline cortisol (P = <0 .001). Results also provide support for the hypothesized age-by-gender interaction with respect to patterns of response to challenge. There was a significant interaction with respect to maximum percentage increase over baseline (P<0.002): among younger adults, the men exhibited greater increases whereas among the older adults, the women exhibited greater increases. A similar, though only marginally significant pattern was seen for total area under the response curve (P=0.07). Repeated measures ANOVA confirmed the gender-by-age differences in the patterns of response (P=0.01 for time*age*gender interaction). (C) 2001 Elsevier Science Ltd, All rights reserved.