Welcome to Focus on Fatigue.
We’re all familiar with that tired feeling we get when we know we haven’t gotten enough sleep the night before. But if we get less sleep than we need each day, day after day, then our level of tiredness starts to level out. This is about the time we declare that we have ‘gotten used to it.’ But is this really the case? Can we ‘get used to’ less sleep than we usually need?
This is the question we’ll be asking in this month’s Focus on Fatigue.
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Can I train my body to need less sleep?
There are many areas of life in which each of us is able to demand increasingly greater capacity from our body and it will adapt accordingly. For example, if I want to have stronger muscles, I can use weights to train them to be stronger. If I want to learn a new skill I can spend time practicing that skill and be sure of seeing improvement in my performance.
The great majority of adults require between seven and nine hours of sleep in every 24-hour period to function at their full potential. Many of us wonder, however, if this is really a fixed amount. If we reduce the amount of sleep we are getting for long enough, won’t our bodies adapt to the new schedule? Can we train our bodies to need less sleep?
Sleep restriction, the act of not sleeping for as long as your body needs, will result in a feeling of sleepiness the next day. It seems logical, then, that continuing to restrict sleep will make you sleepier and sleepier as the days progress. But this isn’t the case. After a few days of sleep restriction we generally find that our level of sleepiness hits a plateau. We still feel sleepy, but we stop getting worse. This is where the feeling that we’ve gotten used to the lack of sleep comes from.
Unfortunately, it turns out that our subjective feeling of sleepiness tells us very little about how well we are performing tasks in our everyday lives.
I am awake, I am a-zzzzzzzzzzzzzzz
People who are sleep deprived have less choice about when they sleep.
Many studies have investigated the likelihood of people falling asleep when they are well-rested as opposed to when they are sleep deprived. These studies have found that, if sleep is restricted, people are more likely to fall sleep in a quiet environment and they will do so faster than normal. This is true even if they resist the urge to sleep. Once they are sleeping, the brain will generally descend rapidly through the stages of sleep much faster than usual, in an attempt to recover from the deprivation. This means a lower quality of sleep.
Also, there is an increase in the likelihood of microsleeps. These are brief moments of sleep, lasting from less than a second up to thirty seconds, during which a person is unable to respond to stimuli. Microsleeps can result in behaviours such as head nodding, blank staring, and drifting across lanes while driving. A person may or may not be aware that they are experiencing microsleeps.
The important thing to remember here is that while your motivation to train your body to need less sleep might be high, your tired brain may just take the choice away from you without you even realising it.
What if I reduce my sleep slowly?
If you take a person that normally sleeps eight hours a night and make them stay awake all night then they will have a sleep debt of eight hours. This person’s performance on cognitive tests will decrease dramatically from what it was when they were well-rested. This much is obvious.
What we want to know is: What happens if we spread that eight hour sleep debt out over a number of nights? For example, if we reduce our sleep from eight hours to six hours for four nights in a row (still a sleep debt of eight hours) will we perform as badly as the person who accumulated their sleep debt all at once.
The evidence suggests that the answer is no. The six hours of sleep that is achieved each night does help reduce the decrease in performance.
That does not mean, however, that our performance isn’t suffering. It’s still getting worse, just at a slower rate. By the time two weeks is up our sleep debt will be great enough that we are, indeed, likely to perform as poorly as a person who has suffered one, or even two, nights of total sleep deprivation.
Over time our performance may plateau (stop getting worse) but it will never be as good as it was when we were well-rested.
What about the long-term?
The studies talked about so far have generally lasted from one to two weeks. What if we restricted our sleep for much longer? It takes a long time to develop a strong body or become an expert in a new skill. Can’t we take a similar long-term view of sleep restriction?
Long-term controlled studies of sleep restriction would not generally be possible due to the ethical implications such studies would entail. However, we can look at studies of the general population that have included details of sleep times to see what health consequences are associated with sleep deprivation. Indeed, long-term sleep deprivation has been associated with the following illnesses: high blood pressure, heart disease, stroke, obesity, depression and other mood disorders, attention deficit disorder, poor quality of life and increased mortality.
Is it worth it?
Sleep restriction, for the purpose of training the body to need less sleep, sounds like a great idea in theory. Who wouldn’t love to have a few more hours of awake time in their day. However, the research evidence does not support the feasibility of such an endeavour. Before making such a momentous decision about your life, I suggest you sleep on it.
- Dinges, D. F., Rogers, N. L. and Baynard, M. D. (2005) Chronic Sleep Deprivation. In: Kryger M. H., Roth T., Dement W. C. (Eds.) Principles and Practice of Sleep Medicine (4th ed). Philadelphia, PA: WB Saunders Company, p. 67–76.
- Durmer, J. S. and Dinges, D. F. (2005) Neurocognitive consequences of sleep deprivation. Seminars in Neurology, 25(1), 117-129.
- Van Dongen HPA, Maislin G, Mullington JM, Dinges DF. The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. SLEEP 2003;2:117-126.
- Belenky, G., Wesensten, N. J., Thorne, D. R., Thomas, M. L., Sing, H. C., Redmond, D. P., Russo, M. B. and Balkin, T. J. (2003) Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: A sleep dose-response study. Journal of Sleep Research, 12, 1-12.
- Orzel-Gryglewska, J. (2010) Consequences of sleep deprivation. International Journal of Occupational Medicine and Environmental Health, 23(1), 95-114.
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Article: Consequences of Sleep Deprivation
This paper presents the history of research and the results of recent studies on the effects of sleep deprivation in animals and humans. Humans can bear several days of continuous sleeplessness, experiencing deterioration in wellbeing and effectiveness; however, also a shorter reduction in the sleep time may lead to deteriorated functioning. Sleeplessness accounts for impaired perception, difficulties in keeping concentration, vision disturbances, slower reactions, as well as the appearance of microepisodes of sleep during wakefulness which lead to lower capabilities and efficiency of task performance and to increased number of errors. Sleep deprivation results in poor memorizing, schematic thinking, which yields wrong decisions, and emotional disturbances such as deteriorated interpersonal responses and increased aggressiveness. The symptoms are accompanied by brain tissue hypometabolism, particularly in the thalamus, prefrontal, frontal and occipital cortex and motor speech centres. Sleep deficiency intensifies muscle tonus and coexisting tremor, speech performance becomes monotonous and unclear, and sensitivity to pain is higher. Sleeplessness also relates to the changes in the immune response and the pattern of hormonal secretion, of the growth hormone in particular. The risk of obesity, diabetes and cardiovascular disease increases. The impairment of performance which is caused by 20–25 hours of sleeplessness is comparable to that after ethanol intoxication at the level of 0.10% blood alcohol concentration. The consequences of chronic sleep reduction or a shallow sleep repeated for several days tend to accumulate and resemble the effects of acute sleep deprivation lasting several dozen hours. At work, such effects hinder proper performance of many essential tasks and in extreme situations (machine operation or vehicle driving), sleep loss may be hazardous to the worker and his/her environment.