Greater REM sleep instability is associated with increased nocturnal cortisol secretion and shortened REM sleep latency

Abstract

Introduction: Recently, REM sleep instability (RSI) has been associated with poor sleep quality [1]. Moreover, research on neuroendocrinological sleep regulation has linked poor sleep to increased nocturnal cortisol secretion. However, up to now, there are no findings concerning the association between RSI and cortisol secretion. Therefore, we investigated in the association between RSI and nocturnal cortisol secretion in a sample of healthy female participants. Methods: A total of 20 adult women took part in the study. Sleep was objectively assessed by sleep-EEG-recordings (mean sleep efficiency index (SEI): 78.8 ± 17.6%). Salivary samples for cortisol measurement were collected at 11.30 pm and at 6.00 am after awakening. Results: Greater RSI in the second half and the last third of the night were associated with increased cortisol secretion at midnight. Moreover, greater RSI in the second third of the night was associated to shorter REM sleep latency. No statistical association was found between salivary morning cortisol and RSI. Conclusion: The pattern of results supports the assumption that RSI as an unfavourable marker of sleep quality is associated with increased nocturnal cortisol secretion, which in turn reflects an increased activity of the stress response system. Further research focusing on the underlying mechanisms of RSI and sleep regulation is recommended. Reference: [1] Riemann D et al, Pharmacopsychiatry 2012; 45: 167 – 76