Chronic sleep loss may do lasting damage

Having too little sleep may fuel disruptions in behavioural, motor, and neurophysiological responses, but what’s more worrying is that the deficits incurred over consecutive days of sleep deprivation may not be easily reversed and can linger even after being able to catch up on sleep for days, according to a study.

“The [findings suggest] that 7-day recovery following 10-day sleep restriction is sufficient only for the reaction speed to reverse to baseline, while the other behavioural, locomotor, and neurophysiological measures do not show such improvement,” the investigators said.

In the study, 19 healthy adults underwent 21 days of experiment, which comprised 4 days of normal day-to-day routine (baseline), 10 days of purposeful sleep restriction (a reduction of 30 percent relative to individual sleep requirement), then 7 recovery days of unrestricted sleep.

Throughout the study, the participants wore wrist sensors to monitor daily patterns of sleep and activity. They also underwent daily electroencephalography (EEG) to monitor brain activity, as well as completed Stroop tasks to assess reaction times and accuracy.

Performance (accuracy and reaction times from Stroop task), spontaneous locomotor activity (distributions of rest and activity durations from actigraphy), and EEG parameters (amplitudes, latencies, and scalp maps of event-related potentials from Stroop task and power spectra from resting states) deteriorated during the sleep-restriction phase. [PLoS ONE 2021;16:e0255771]

Furthermore, catching up on sleep for an entire week was not enough to reverse the deficits incurred over 10 consecutive days of sleep deprivation. Only one measure reverted to baseline values, and this was mean reaction time in Stroop task.

“A great diversity of research procedures and proportions of sleep restriction and recovery times makes it hardly possible to compare our results with those reported in the literature. However, we note a few similar findings pointing to the incomplete restoration of some behavioural indices,” the investigators said.

One study observed improvement in mean reaction time but not in the number of lapses, while another study reported no improvement in reaction time parameters (median, lapses, fastest, and slowest responses) even when objective sleepiness returned to baseline. [Chronobiol Int 2008;25:297-308; Am J Physiol Endocrinol Metab 2013;305:E890-E896]

Sleep-deprived world

“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,” the investigators explained.

“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,” they added.

For the most part, we live in a sleep-deprived world, where sleeping at night and getting enough hours of it is not an option for many. The investigators pointed to people whose professions involve atypical work schedules (health services, entertainment, transportation, energetic, and chemistry industries, among others) and a growing number of ‘regular’ day workers whose sleep-wake patterns become irregular due to periods of intense work requiring extra time and effort.

“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—[on] 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,” the investigators said.

“The disruption of the rest-activity rhythm is one of the common side-effects of remote work,” they added.

As such, according to the investigators, the saying that sleep is for the weak is no longer exclusive to workaholics and ambitious individuals. “We all treat restricted sleep as a norm.”

The present data, along with previous reports, serve as a reminder that cutting back on sleep may be a big mistake and that the “neurobehavioural consequences of chronic partial sleep deprivation cannot be overcome easily and last much longer than one expects,” they said.