0231 Effects of Sleep Restriction and Fragmentation on the Autonomous Nervous System

Abstract

Introduction: Many mentally and physically high demanding jobs (e.g., shift-workers, astronauts) cause sleep fragmentation and deprivation. Impaired sleep can lead to an impaired autonomic nervous system, associated with stress, and increased morbidity and mortality. We investigate the effects of short-term sleep fragmentation and sleep restriction on the autonomic tone. We hypothesized (1) that autonomic parameters mirror effects of sleep restriction and fragmentation and (2) that sleep fragmentation has stronger negative effects on the autonomic tone than sleep restriction. Methods: A randomized cross-over design with 20 healthy male participants (mean age: 39.9 ± 7.4 years, mean BMI: 25.5±2.2 kg/ m2) was used. Each participant underwent 2 x 4 nights, experiencing both interventions separated by a wash-out phase of one week. The protocol included one baseline night, one intervention night of either sleep deprivation (5 hours) or sleep fragmentation (light on every hour) and two recovery nights of undisturbed sleep. Full laboratory-based polysomnography was conducted. Additionally, electrocardiography and continuous blood pressure were recorded under paced breathing at 12/min before falling asleep (evenings) and after waking up (mornings). Parameters of the autonomic tone-parameter of the heart rate variability (standard deviation of normal to normal R-R intervals-SDNN). Results: SDNN increased each night and was higher in the mornings compared to the evenings before. During sleep restriction, the change in SDNN (morning-evening) significantly increased from baseline to intervention (2.2±17.8ms to 22.0±26.7ms; p<0.05). During sleep fragmentation, the change in SDNN did not differ significantly and showed a small decrease from baseline to intervention (16.2±33.1ms to 10.8±24.3ms; n.s.). Comparing both interventions, the overall SDNN difference became significant (intervention night-baseline night: restriction 19.8ms vs. fragmentation-5.8ms; p<0.05). Conclusion: Sleep restriction had a stronger but more positive effect on the autonomic nervous system than sleep fragmentation. However all effects remained to be small due to limited sample size and just one night intervention.