No effects of repeated forced wakings during three consecutive nights on morning cortisol awakening responses (CAR): A preliminary study

Objective: The cortisol. awakening response (CAR) is considered a reliable measure for the acute reagibility of the hypothalamus-pituitary-adrenal (HPA) axis. Whether repeated nightly awakenings at different times during the night also stimulate the HPA-axis and whether, consequently, the CAR is altered has not been tested, so far. We aimed to investigate whether three experimentally induced awakenings during three consecutive nights would be associated with HPA-axis stimulation and an altered morning CAR. Methods: The study sample consisted of 13 healthy adult women who were woken up three times in each of three consecutive nights. Cortisol. levels were measured immediately and 15min after each awakening in the night and in the morning, respectively. Also, the morning CARs after three nights of undisturbed steep were assessed. Results: A significant difference between night time cortisol responses to awakening and the morning CAR was found. White cortisol. Levels during the first half of the night did not rise significantly after awakening in the night, some reactivity was seen during awakenings in the very early morning hours, and pronounced awakening responses were observed in the morning before getting out of bed. Interestingly, the morning CAR after disturbed steep did not differ from the morning CAR following undisturbed steep. Conclusion: In healthy female individuals, the morning CAR appears to be unchanged even if steep was repeatedly interrupted by forced wakings. (C) 2007 Elsevier Ltd. All rights reserved.