The cortisol awakening response and autonomic nervous system activity during nocturnal and early morning periods.

The current study focuses on autonomic nervous system activity during sleep as a physiological aspect of sleep quality, and investigated the associations between the cortisol awakening response (CAR) and autonomic activity during sleep and after awakening. Ambulatory electrocardiograms were obtained from 20 participants, who also provided saliva samples (at the time of awakening, and 30, 45, and 60 min after awakening) and rated the subjective quality of their sleep at home. Autonomic activity was assessed with the Lorenz plot indices, cardiac sympathetic index (CSI) and cardiac vagal index. Total salivary cortisol secretion after awakening was calculated as area under the curve with respect to ground (AUC(G)) and increase (AUC(I)). After controlling for confounding factors, including sleep duration and awakening time, cortisol AUC(G) and AUC(I) were both found to be negatively correlated with CSI during the 30 min before and after awakening: before (r = -0.526 and -0.601 respectively) and after (r = -0.540 and -0.493 respectively). Self-reported sleep quality was not associated with the CAR. These results suggest that the CAR is negatively affected by basal sympathetic activity immediately before and after awakening, but not affected by subjective sleep quality. Physiological arousals around the time of awakening might inhibit the CAR.

Salivary 3-methoxy-4-hydroxyphenylglycol increases after awakening in healthy young adults.

Levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) may reflect central noradrenergic activity. In this study, we investigated salivary MHPG changes after awakening, and explored their relationships with cortisol and peripheral autonomic activity. The participants were 25 college students. Saliva samples were collected on awakening and 30 min after awakening to determine MHPG and cortisol. Ambulatory electrocardiograms were obtained to assess heart rate, cardiac sympathetic index (CSI), and cardiac vagal index (CVI) before and after awakening. MHPG levels increased significantly during the first 30 min after awakening. Similarly, cortisol, heart rate, and CSI increased during the 30 min after awakening, but changes in MHPG did not correlate with changes in cortisol, heart rate, CSI, and CVI during that period. This study demonstrated that salivary MHPG levels increase after awakening, in common with cortisol, heart rate, and cardiac sympathetic activity.

Disorders of arousal and sleep-related bruxism among Japanese adolescents: a nationwide representative survey.

OBJECTIVE: The main objective of our study was to clarify the prevalence of disorders of arousal (confusional arousals, sleepwalking, sleep terrors) and sleep-related bruxism (teeth grinding) and their associated factors among Japanese adolescents. METHODS: Our study was designed as a cross-sectional sampling survey. The targets were students attending junior and senior high schools throughout Japan. The questionnaire asked for personal data and information on lifestyle, depressive state, and sleep status including the frequency of experiencing disorders of arousal and sleep-related bruxism. RESULTS: A total of 99,416 adolescents responded. The overall response rate was 63.7%, and 98,411 questionnaires were subjected to analysis. The prevalence of disorders of arousal was 7.1% (95% confidence interval [CI], 6.9-7.3%) among boys and 7.7% (95% CI, 7.5-7.9%) among girls. The prevalence of sleep-related bruxism was 2.3% (95% CI, 2.2-2.4%) among boys and 3.0% (95% CI, 2.8-3.2%) among girls. The factors associated with disorders of arousal were the grade in school, smoking habit, alcohol consumption, naptime (min), breakfast habit, participation in club activities, sleep duration, difficulty initiating sleep, nocturnal awakening, early morning awakening, subjective sleep assessment, snoring, decrease in positive feelings, and depression (all p<.001). The factors associated with sleep-related bruxism were gender, smoking habit, nocturnal awakening, snoring, early morning awakening, decrease in positive feelings, and depressive feelings (all p<.001). CONCLUSIONS: If disorders of arousal or sleep-related bruxism are observed in an adolescent, his or her smoking habit, alcohol consumption, sleep status, and depressive state should be considered.