Abstract
Prolonged periods of sleep restriction seem to be common in the contemporary world. Sleep loss causes perturbations of circadian rhythmicity and degradation of waking alertness as reflected in attention, cognitive efficiency and memory. Understanding whether and how the human brain recovers from chronic sleep loss is important not only from a scientific but also from a public health perspective. In this work we report on behavioral, motor, and neurophysiological correlates of sleep loss in healthy adults in an unprecedented study conducted in natural conditions and comprising 21 consecutive days divided into periods of 4 days of regular life (a baseline), 10 days of chronic partial sleep restriction (30% reduction relative to individual sleep need) and 7 days of recovery. Throughout the whole experiment we continuously measured the spontaneous locomotor activity by means of actigraphy with 1-minute resolution. On a daily basis the subjects were undergoing EEG measurements (64-electrodes with 500 Hz sampling frequency): resting state with eyes open and closed (8 minutes long each) followed by Stroop task lasting 22 minutes. Altogether we analyzed actigraphy (distributions of rest and activity durations), behavioral measures (reaction times and accuracy from Stroop task) and EEG (amplitudes, latencies and scalp maps of event-related potentials from Stroop task and power spectra from resting states). We observed unanimous deterioration in all the measures during sleep restriction. Further results indicate that a week of recovery subsequent to prolonged periods of sleep restriction is insufficient to recover fully. Only one measure (mean reaction time in Stroop task) reverted to baseline values, while the others did not.
Highlights
We evaluated the effects of 7 days sleep recovery following 10 days of sleep restriction on performance, spontaneous locomotor activity, and EEG parameters
Based on actigraphy recordings, 4 participants were removed from analysis due to failure to comply with the prescribed sleep restriction
The resulting distributions of activity as recorded in zero-crossing mode (ZCM) and proportional integrating measure (PIM) differ: ZCM has two clear peaks corresponding to daily activity and sleep, while PIM distribution monotonically falls down from low to high intensities
Summary
Apart from the professions ‘traditionally’ involved in so-called atypical work schedules (health services, entertainment, transportation, energetic and chemistry industries etc.) and suffering from sleep problems, there is a growing number of ‘regular’ day workers whose sleep-wake patterns become irregular due to periods of intense work requiring extra time and effort (infamous ‘deadlines’). Those working from home, on the one hand enjoy the flexibility of their work schedules, more autonomy and adaptation of working times to individual needs, but—from the other hand—they observe blurring of the boundaries between work and private life, resulting in “living at work” and problems with time-management and self-discipline. How it works with prolonged sleep restriction and in other aspects than mortality is not yet fully understood
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