It can take more than a week to recover from memory and reaction speeds issues that develop after 10 days of poor quality sleep, according to a new study.
To discover whether it is possible to recover from sleep deprivation, and if so how long it takes, a team from Jagiellonian University of Krakow, Poland recruited volunteers to suffer through ten nights of broken, poor quality sleep.
During those ten nights, and a subsequent week of quality, uninterrupted slumber, the volunteers answered questions, wore wrist sensors and had daily EEG tests.
After the week of good sleep, the volunteers reaction speeds had returned to normal, but memory and other pre-sleep deprivation functions were still slower.
Jeremi Ochab, lead author, said previous studies had explored the impact of sleep deprivation, but this was the first to show it takes more than a week of solid sleep for reaction times and memory recall to return to normal levels.
It can take more than a week to recover from memory and reaction speeds issues that develop after 10 days of poor quality sleep, according to a new study. Stock image
WHAT IS MELATONIN?
Melatonin is a hormone which controls how asleep or awake people feel.
The hormone is produced in the pineal gland in the brain and its release into the body is controlled by light.
During the day, when the eye absorbs light, melatonin levels in the body are low and, as a result, we feel awake.
But when darkness settles and the amount of light being absorbed by the eye reduces (although this is disrupted in modern societies because of artificial light), more melatonin circulates round the body.
Melatonin prepares the body for sleep by slowing the heart rate, reducing blood pressure, and changing how heat is stored in the body – the body’s core temperature drops while the outside of the body and the limbs become warmer.
The hormone also makes people feel sleepy.
Melatonin supplements can be taken to aid sleep in people who have problems with it, as well as for certain medical conditions such as tinnitus or Alzheimer’s disease.
Sleep deprivation isn’t a new phenomenon, but the researchers say it appears to becoming more common in the modern world.
Sleep loss, especially over extended periods, can lead to changes in the circadian rhythm, lead to a loss in alertness, lower attention span and memory issues.
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,’ according to the Polish team.
As well as sleep monitors and EEG tests, volunteers in the study performed a range of reaction and memory tests, as well as answered questions.
Volunteers in the study slept in their own homes, not in a sleep room, during the 21 day experiment, and all were healthy.
For the 21 days the volunteers spent the first four days normally, sleeping as they usually would, followed by 10 days of ‘chronic partial sleep’ which is 30% of what someone would normally need. Finally they had a week of solid sleep.
‘Throughout the whole experiment the researchers continuously measured the spontaneous locomotor activity and put them through EEG measurements.
They measured how long the volunteers rested and performed different tasks, reaction times and accuracy and brain waves through the EEG.
‘We observed unanimous deterioration in all the measures during sleep restriction,’ the team explained, confirming the volunteers performed poorly with less sleep.
‘Further results indicate that a week of recovery subsequent to prolonged periods of sleep restriction is insufficient to recover fully. ‘
‘After seven days of recovery, the participants had not yet returned to pre-sleep deprivation performance on most measures of functioning. Only their reaction times had recovered to baseline levels,’ the team added.
They hope to continue their experiments with a wider group of volunteers in the future, as well as investigate longer recovery periods.
This would allow them to disentangle the order in which different brain functions return to normal, as some hadn’t returned fully after the seven days of good sleep.
As they stopped the research after a week of good sleep, they can’t currently pinpoint when other functions, such as memory recall, fully returned to normal.
To discover whether it is possible to recover from sleep deprivation, and if so how long it takes, a team from Jagiellonian University of Krakow, Poland recruited volunteers to suffer through ten nights of broken, poor quality sleep. Stock image
The authors add: ‘The investigation of the recovery process following an extended period of sleep restriction reveal that the differences in behavioural, motor, and neurophysiological responses to both sleep loss and recovery.’
This adds to earlier studies that found it takes a lot of quality sleep to make up for extended periods of broken or poor quality slumber.
An earlier study, published in August found that a 30-minute power nap in the middle of the day can’t make up for not getting a good sleep the night before.
Michigan State University experts measured the extent to which sleep deprivation led to cognitive impairment and found short naps to be only associated with slight relief from sleep deprivation – and only if you go into a deep sleep.
The findings of the Polish study into sleep recovery were published in the journal PLOS One.
ABOUT CIRCIDIAN RHYTHMS
Our internal circadian rhythms, or circadian clock, is responsible for waking our bodies up in the morning and ensuring they get a good night’s rest.
In a healthy person, cortisol levels peak at around 8am, which wakes us up (in theory), and drop to their lowest at 3am the next day, before rising back to its peak five hours later.
Ideally, this 8am peak will be triggered by exposure to sunlight, if not an alarm. When it does, the adrenal glands and brain will start pumping adrenaline.
By mid-morning, the cortisol levels start dropping, while the adrenaline (for energy) and serotonin (a mood stabilizer) keep pumping.
At midday, metabolism and core body temperature ramp up, getting us hungry and ready to eat.
After noon, cortisol levels start their steady decline. Metabolism slows down and tiredness sets in.
Gradually the serotonin turns into melatonin, which induces sleepiness.
Our blood sugar levels decrease, and at 3am, when we are in the middle of our sleep, cortisol levels hit a 24-hour low.
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