MODULE SUPPLEMENT: ENDOCRINE SYSTEM
Aging, the Stress Response, Cortisol, and Cognitive Function

Of additional clinical importance, however, is the potential role that cortisol may play in cognitive aging (de Bruin, Vieira, et al., 2002; Hibberd, Yau, et al., 2000). Some of these data come from work related to the stress response. In response to stress, cortisol goes up higher and returns to baseline more slowly in older adults than in younger adults. This may be related to a decrease in the feedback inhibition of CRH and ACTH, possibly through decreased hippocampal glucocortical receptors.

Researchers have hypothesized that, because of the blunted response to feedback, the hippocampus would be exposed to excessive cortisol. Over time this would damage the hippocampus, cause further decrease in the negative feedback, and lead to higher levels of cortisol. In addition, these changes would also cause the memory alterations that occur with age because of the damage caused to the hippocampus. Although much of the early data were from animal studies, studies with humans have documented a blunted response to increased levels of cortisol (Wilkinson, Petrie, et al., 2001;l Wolf, Convit, et al., 2002), and a relationship between cortisol levels and memory impairment (de Bruin, Vieira, et al., 2002; Hibberd, Yau, et al., 2000).

The schematic below highlights some of the hypothesized relationships.

More data are needed to support this, especially in humans, but it emphasizes the importance preventing any system from getting out of balance.