By Brandon R. Peters, M.D.
A lack of adequate sleep has become an integral part of our modern world, but not without consequences. Sleep is the last thing we get to at the end of a busy day, and it is the first to be sacrificed when a lack of time demands it. What is the harm of not getting quite enough sleep? Consider some of the profound and significant effects of sleep deprivation, affecting everything from mood to thinking to pain tolerance to hormones. Most importantly, better understand whether inadequate sleep may actually kill you.
Research shows that the average amount of sleep needed to avoid the adverse effects of sleep deprivation is 8 hours and 10 minutes. This being said, there are a number of factors that contribute to your individual sleep needs. Some people need more or less sleep, and this is likely genetically based. The amount of sleep needed also changes as we age, with children needing more than elderly adults.
The key is to consider how much sleep you need to obtain on a regular basis to wake up feeling rested with no adverse daytime effects or need of naps. Though the average sleep need may be 7 to 8 hours, an individual may fall anywhere across a bell-shaped curve. Therefore, it is important to remember that if you need 10 hours to feel rested, you will be sleep deprived when you only get 8.
There are a number of common causes of sleep deprivation. The most obvious is sleep restriction, in which an inadequate amount of time is allowed for sleep. Other sleep disorders may also contribute by limiting or fragmenting sleep, including insomnia, sleep apnea, and restless legs syndrome. A sleep environment that is not conducive to rest may also play a role.
What are the consequences of sleep deprivation? The most obvious is sleepiness; not sleeping enough leads to feeling sleepy and a strong desire for sleep. This drowsiness may result in napping or a short time to sleep onset, called sleep latency. It may be subjectively reported by the Epworth sleepiness scale or objectively measured with the multiple sleep latency test (MSLT) or maintenance of wakefulness test (MWT).
A lack of sleep can also lead to mood changes and difficulties with thinking and behavior. Not only can someone become cranky or irritable, but difficulty sleeping often contributes to anxiety and depression. Impairment of the frontal lobe of the brain may also interfere with higher level cognitive processes called executive functions. This can undermine judgment, critical thinking, relationships, problem solving, planning, and organization.
Studies have shown that sleep deprivation can profoundly affect memory and performance. Attention, concentration, and vigilance become impaired. People who sleep less than 7 hours per night have reaction times that are similar to those who are completely sleep deprived for one or even two nights. This leads to errors, accidents, and impaired work performance. The scary thing is that when you are chronically sleep deprived, you may not even recognize the level of impairment.
Memory becomes compromised in sleep deprivation, with decreased attentiveness affecting our ability to process information. Immediate recall and short-term memory both become impaired. Research shows that memory processing and consolidation occur in sleep and it has a key role in learning and problem solving. When we don't sleep enough, this capacity becomes greatly diminished.
The mind may even begin to act out in strange ways. A lack of sleep may lead to disorientation, manifesting as confusion. About 80 percent of normal people will have visual hallucinations if sleep deprived long enough. Approximately 2 percent of 350 people who were sleep-deprived for 112 hours began experiencing symptoms similar to acute paranoid schizophrenia. Fortunately, all of these symptoms resolve with adequate rest without permanent sequelae.
There can also be important changes in the body as a result of sleep deprivation. People who do not sleep enough more likely complain of fatigue, malaise, aches, pains, stomach upset, and diarrhea. Inadequate sleep is associated with a poor conception of personal health, with more frequent complaints. In addition, studies show there is a decreased threshold for heat and pressure pain (increased pain sensitivity) that is related to a loss of slow-wave sleep.
Clear hormonal shifts occur with sleep deprivation. A loss of sleep in children may affect growth hormone release, leading to a shorter stature. Prolonged wakefulness may also affect the thyroid gland, with increased energy needs changing hormone levels. Sleep deprivation is strongly associated with weight gain due to changes in appetite hormones called leptin and ghrelin.
There are other impacts of not meeting our sleep needs. The brain and nervous system are influenced similar to the effects of drinking alcohol. There may be slurred speech, jumpy eye movements, reflex changes, tremor, droopy eyelids, and a risk for seizures. The overall body temperature may decrease. Inadequate sleep may also affect the immune system, compromising our ability to fight infection.
Though these numerous problems may be substantial, the bottom line is this: Can sleep deprivation kill you? Animal studies dating back to 1894 demonstrate that total, sustained sleep deprivation can be fatal. Chronic sleep deprivation seems to have a more subtle, yet nevertheless significant, risk. Those who sleep less than five hours per night have two to three times the risk of heart attack. This seems to be related to a pro-inflammatory state that occurs with sleep deprivation that increases the risk of chronic disease. For the same reason, shift workers have an increased risk of developing breast and colorectal cancer.
The greatest danger related to chronic sleep deprivation may be due to traffic accidents. Not only do drowsy drivers fall asleep behind the wheel, but they are also subject to inattentiveness with decreased response time, visual tracking, and hand-eye coordination. Since 1994, more than 20 studies with driving simulators demonstrate impairment equivalent to being legally drunk. In one study, sleep deprived subjects drove off the road every 5 minutes, which was correlated to a blood alcohol level of 0.08 percent. Sleeping less than 7 hours per night on average increases this risk.
People who work overnight may be particularly vulnerable to accidental harm. Major disasters such as the Exxon Valdez oil spill and the Chernobyl nuclear meltdown have been linked, in part, to errors made as the result of sleep deprivation. Resident physicians in hospitals now have restricted hours in an attempt to reduce medical errors and patient harm. Safety regulations have been implemented among long-haul truck drivers and airline pilots to reduce the frequency of accidents.
Sleep deprivation clearly has important effects on the quality of our life. There may be chronic, insidious problems as well as immediate risks. In order to avoid the serious consequences associated with inadequate sleep, it is imperative that we meet our individual sleep needs. This will help us to wake feeling more refreshed and preserve the quality and safety of the time we spend awake.
Brandon R. Peters, M.D., is the writer on sleep for About.com, a neurology-trained sleep medicine specialist in Novato, Calif., and adjunct clinical faculty at the Stanford Center for Sleep Sciences and Medicine. This Center is the birthplace of sleep medicine and includes research, clinical, and educational programs that have advanced the field and improved patient care for decades. To learn more, visit us at: http://sleep.stanford.edu/.
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