Separating the influences of means and daily variations of sleep on the stress-induced salivary cortisol response

Previous research regarding the effects of sleep quality and quantity on the acute stress response has yielded inconsistent findings. This may be attributed to various factors, including composite sleep components (i.e., means and daily variations) and mixed cortisol stress response (i.e., reactivity and recovery). Thus, this study aimed to separate the effects of means and daily variations of sleep on the reactivity and recovery of cortisol responses to psychological challenges. In study 1, we recruited 41 healthy participants (24 women; age range, 18–23 years), monitored their sleep during seven consecutive days via wrist actigraphy and sleep diaries, and adopted the Trier Social Stress Test (TSST) paradigm to induce acute stress. Study 2 consisted of a validation experiment using the ScanSTRESS paradigm, which included 77 additional healthy individuals (35 women; age range, 18–26 years). Similarly to the TSST, the ScanSTRESS induces acute stress using uncontrollability and social evaluation. In both studies, saliva samples from the participants were collected before, during, and after the acute stress task. Using residual dynamic structural equation modeling, both study 1 and study 2 demonstrated that higher means of objective sleep efficiency, and longer means of objective sleep duration were related to greater cortisol recovery. In addition, fewer daily variations in objective sleep duration were associated with greater cortisol recovery. However, there was no correlation between sleep variables and cortisol reactivity, except for the daily variations in objective sleep duration in study 2. No correlation was observed between subjective sleep and cortisol response to stress. The present study separated two features of multi-day sleep patterns and two components of cortisol stress response, providing a more comprehensive picture of the effect of sleep on the stress-induced salivary cortisol response, and contributing to the future development of targeted interventions for stress-related disorders.