Awakening cortisol responses are influenced by health status and awakening time but not by menstrual cycle phase

Recent evidence dsuggested that the free cortisol response to awakening is influenced by awakening time in healthy younger adults (Edwards et al., 2001). In order to investigate this association further, 179 community-dwelling subjects of a large age range (4-75 yrs) participated in the present study. The sample consisted of 99 women, 67 men and 13 children. Subjects were instructed to obtain saliva samples directly after awakening as well as 15, 30, 45, and 60 minutes thereafter. A first analysis revealed that salivary cortisol profiles after awakening in healthy subjects differed from profiles in subjects who reported health problems or a chronic disease (p = 0.02) with healthy subjects showing a larger cortisol response. Therefore, only healthy subjects were included in the following analyses. Subjects woke up between 0455 and 1203 h. Time of awakening strongly influenced the course of morning cortisol levels. Cortisol profiles differed significantly between two wake-up groups (p<0.001). Similarly. group differences for cortisol increase (p = 0.03) and area under the curve (p = 0.05) were also significant, with more pronounced responses in early awakeners compared to late awakeners. The findings are discussed with respect to the circadian cortisol rhythm and the effects of light exposure. Age was correlated with the cortisol levels immediately after awakening (r = 0.2, p = 0.04), the area under the cortisol curve ( r = -0.20, p = 0.05), and with time of awakening (r = -0.21, p = 0.04), respectively. No differences were found between males and females, or between profiles obtained during the follicular or luteal menstrual cycle phase. Also, no differences were observed between habitual smokers vs. non-smokers. These data suggest that the morning cortisol response is influenced by the awakening time but not by menstrual cycle phase. Moreover, health status and age appear to have an impact on this marker of adrenocortical activity, Wake-up time, health status and age should therefore be controlled for in future studies measuring cortisol responses to awakening. (C) 2002 Elsevier Science Ltd. All rights reserved.