OPPOSING EFFECTS OF DHEA REPLACEMENT IN ELDERLY SUBJECTS ON DECLARATIVE MEMORY AND ATTENTION AFTER EXPOSURE TO A LABORATORY STRESSOR

Aging is accompanied by a continuous decline of the adrenal steroid hormone DHEA and its ester DHEAS. Results from studies in rodents have demonstrated that DHEA(S) administration can enhance memory in several test paradigms. However studies from this laboratory did not find positive effects of DHEA treatment on cognitive performance in young and elderly humans. With respect to a possible mechanism of DHEA activity, effects on several neurotransmitter receptors as well as a possible antiglucocorticoid action are discussed. For high levels of glucocorticoids, a disruptive effect on hippocampal mediated memory is documented in rodents and humans. Therefore it was speculated that, if an antiglucocorticoid action of DHEA would underlie the observed beneficial effects of DHEA on memory, these effects might only be detectable if subjects are stressed (and therefore have high cortisol levels). To test this hypothesis 75 elderly women and men participated in a placebo controlled experiment. Subjects took DHEA (50 mg/day) or placebo for 2 weeks (double blind). Thereafter they participated in a standardized psychosocial laboratory stressor (Trier Social Stress Test; TSST). Before and after stress exposure subjects completed two declarative memory tests (visual-verbal and spatial) as well as one attention test. In addition recall of visual material learned before stress was assessed after stress. Baseline DHEAS levels were significantly lower compared with young adults. DHEA replacement increased DHEAS levels into ranges found in young subjects. DHEA-substituted subjects showed a trend towards a larger cortisol stress response. In the visual memory test subjects under DHEA recalled less items after stress which they had learned before stress. In the attention test however subjects under DHEA performed better than subjects from the placebo group after stress. No interaction between stress and DHEA was found for the spatial memory task. The effects of DHEA substitution on memory and attention after stress exposure seem to be heterogenous. While recall of previously learned material seems to be impaired, attention is enhanced. These results do not support the idea of a direct antiglucocorticoid or anti-stress effect of DHEA on hippocampal mediated memory functions.