Earth Vertical Motions Disrupt Sleep and Next Day Performance

Kyle A Kainec,1 Allison Ludwig,2 Megan Boltz,3 John G Oas,3 J. Lynn Caldwell,2 Daniel M Merfeld1,4 1Department of Otolaryngology – Head and Neck Surgery, Ohio State University Wexner Medical Center, Columbus, OH, USA; 2Leidos, Health Solutions, Reston, VA, USA; 3Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA; 4Department of Acceleration and Sensory Sciences, Naval Medical Research Unit Dayton, Wright Patterson Air Force Base, Dayton, OH, USACorrespondence: Daniel M Merfeld, Department of Otolaryngology, Ohio State University Wexner Medical Center, Columbus, OH, USA, Email merfeld.6@osu.eduPurpose: Overcoming travel-related sleep disturbances due to motions sensed by our vestibular system could help improve cognitive performance and sleep quality in many contexts. However, there is a lack of research that administers controlled motions to understand how motion negatively impacts sleep and cognitive performance.Patients and Methods: In this experiment, nine participants (21– 39 years, M = 30.3, SD = 6.76; 3 females) completed a 7-day protocol. During nights 1– 3, participants wore an Actiwatch and completed sleep diaries at home. On nights 4– 7, participants slept in the lab with polysomnographic recording equipment on a bed attached to a movement platform and completed a psychomotor vigilance test at 07:00AM, 1:00PM, 3:00PM, and 5:00PM. On nights 4 and 5, the bed did not move overnight. On nights 6 and 7, the bed was moved upward and downward at 1Hz up to 120 times overnight at levels between 0– 100% and 0– 600% of each participant’s awake perceptual vertical motion threshold, respectively.Results: Vertical motions significantly increased arousals from sleep (p =0.014) and worsened morning and midday psychomotor vigilance (p < 0.001). Arousals caused by vertical motions occurred less than natural arousals (p < 0.001) and had different spectral power (p =0.002). Larger motions strongly and significantly predicted a higher chance of causing arousals (β =0.0016, p < 0.001).Conclusion: These results provide evidence that overnight vertical motions disrupt sleep, lead to arousals that are distinct from natural arousals, and result in decreased cognitive performance. Strategies to reduce motion could help mitigate travel-related sleep disturbances.Plain Language Summary: Travel related sleep disturbances are prevalent but poorly understood. The results of this study provide evidence that vertical motions disrupt sleep, lead to arousals that are distinct from natural arousals, and result in decreased cognitive performance. Strategies to reduce the number and size of vertical motions may help overcome travel-related sleep disturbances. However, whether and how motion size, frequency, and direction impact brain processes, sleep, and cognitive performance remain critical knowledge gaps. Future studies examining stronger motions administered more frequently to a larger number of participants are needed. Further, the topographic and time-frequency EEG profiles of natural and motion related arousals need to be further examined to better understand how the brain processes motion during sleep. Earth-vertical motions during sleep: 1) Decreased next day cognitive performance. Bar graph with legend: Acclimation, Baseline, 0-100 percent, 0-600 percent. X-axis: Condition (unit not shown) with 1, 2, 3, 4. Y-axis: Lapses (Average Count) (unit not shown), range 0 to 7.5 with ticks 0, 2.5, 5.0, 7.5. Bar heights: condition 1 about 2; condition 2 about 3; condition 3 about 4.2; condition 4 about 6.5. 2) Increased how many arousals occurred overnight. Bar graph with same legend. X-axis: Condition (unit not shown) with 1, 2, 3, 4. Y-axis: Arousals (Average Count) (unit not shown), range 0 to 100 with ticks 0, 25, 50, 75, 100. Bar heights: condition 1 about 85; condition 2 about 60; condition 3 about 90; condition 4 about 98. 3) Caused arousals that were different than natural arousals. Line graph with legend: Motion-Related and Natural. X-axis: Frequency (unit not shown), range 0 to 32 with ticks 0, 8, 16, 24, 32. Y-axis: Spectral Power (microvolt superscript 2 over hertz), range negative 10 to 40 with ticks negative 10, 0, 10, 20, 30, 40. Both curves decrease from about 25 to 30 at frequency 0 toward about negative 10 near frequency 32, with the Motion-Related and Natural curves closely tracking each other across the frequency range. 4) Caused a greater proportion of arousals as motion magnitude increased. Scatter plot with a fitted line and band. X-axis: Percent of Threshold (percent), range 0 to 600 with ticks 0, 200, 400, 600. Y-axis: Proportion of Arousals (unit not shown), range 0 to 1.0 with ticks 0, 0.25, 0.50, 0.75, 1.0. Points span x about 0 to 600 and y 0 to 1.0 and the fitted line increases from lower y values at low percent of threshold to higher y values at higher percent of threshold. Text: beta equals .0016; standard error equals 0.0001; p less than .001. Across the four graphs, Condition-based comparisons of lapses and arousals are paired with frequency-domain spectral power curves and a percent-of-threshold relationship for arousal proportion.Four graphs showing sleep motion effects on lapses, arousals, spectral power and arousal proportion.Keywords: sleep, polysomnography, vertical, motions, cognition, arousals