A greater prevalence of insomnia also may contribute to the rise in sleep loss, but probably to a lesser extent than do occupational or lifestyle changes.
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Adults are sleeping less to get more work accomplished and are staying up later to watch television or use the Internet NSF, b. In the past 10 or more years, research has overturned the dogma that sleep loss has no health effects, apart from daytime sleepiness.
The studies discussed in this section suggest that sleep loss less than 7 hours per night may have wide-ranging effects on the cardiovascular, endocrine, immune, and nervous systems, including the following:. Many of the studies find graded associations, insofar as the greater the degree of sleep deprivation, the greater the apparent adverse effect although the difference may not reach statistical significance.
Another common finding is the relationship that adverse effects occur with either short or long sleep duration, as compared to a sleep time of 7 to 8 hours. This type of association is often described as a U-shaped relationship. It should be noted, however, that the majority of these studies are observational in nature, and thus definite causal inferences cannot be made. In the discussion that follows, and wherever possible, potential physiological mechanisms behind epidemiological associations and that support the plausibility of a true causal relationship are noted.
When a person sleeps less than 7 hours a night there is a dose-response relationship between sleep loss and obesity: the shorter the sleep, the greater the obesity, as typically measured by body mass index BMI —weight in kilograms divided by height in meters squared. Although most studies were cross-sectional, one prospective study was a year cohort study of nearly adults. By age 27, individuals with short sleep duration less than 6 hours were 7. Another study, a large population-based study of more than 1, adults, found a U-shaped relationship between sleep duration, measured by polysomnography, and BMI Figure Adults who slept 7.
The U-shaped association also applies to other health outcomes, such as heart attacks. The impact of sleep loss diminishes with age. The study also sought to investigate physiological mechanisms behind the relationship between sleep duration and BMI. Measuring two appetite-related hormones, the study found that sleep insufficiency increased appetite. Sleep insufficiency was associated with lower levels of leptin, a hormone produced by an adipose tissue hormone that suppresses appetite, and higher levels of ghrelin, a peptide that stimulates appetite Taheri et al.
Another study—a small randomized, cross-over clinical trial—also found that sleep restriction was associated with lower leptin and higher ghrelin levels Spiegel et al. The findings suggest that a hormonally mediated increase in appetite may help to explain why short sleep is related to obesity. Curvilinear relationship between BMI and average nightly sleep. Obesity also contributes to obstructive sleep apnea OSA. This most likely occurs through fat deposition in airways, causing them to narrow.
The relationship has been found in well-designed epidemiological studies of young children Locard et al.
Taken as a whole, the body of evidence suggests that the serious public health problem of obesity may continue to grow as sleep loss trends continue to worsen. It also suggests that addressing obesity will likely benefit sleep disorders, and treating sleep deprivation and sleep disorders may benefit individuals with obesity Taheri et al.
Two large epidemiological studies and one experimental study found an association between sleep loss and diabetes, or impaired glucose tolerance. Impaired glucose tolerance, which is a precursor to diabetes, is manifested by glucose levels rising higher than normal and for a longer period after an intravenous dose of glucose. In the Sleep Heart Health Study, which is a community-based cohort, adults middle-aged and older who reported 5 hours of sleep or less were 2. Those reporting 6 hours per night were about 1.
Both groups were also more likely to display impaired glucose tolerance. Adults with sleep times of 9 hours or more also showed these effects, a finding consistent with the Nurses Health Study. Adjustment for waist girth, a measure of obesity, did not alter the significance of the findings, suggesting that the diabetes effect was independent of obesity. Sleep duration impacts prevalence of diabetes.
NOTE: Data were adjusted for age, sex, race, waist girth, caffeine, alcohol, smoking, and apnea-hypopnea index. The relationship between shorter sleep times and impaired glucose tolerance is also supported by an experimental study in which 11 healthy male volunteers were restricted to 4 hours of sleep for a total of six nights Spiegel et al. Even after this relatively short period of time, the study found that sleep loss, compared with a fully rested state, led to impaired glucose tolerance.
The effect resolved after restoring sleep to normal. Glucose clearance was 40 percent slower with sleep loss than with sleep recovery.kinun-houju.com/wp-content/bumeharoq/521.php
Medical Causes of Sleep Problems
Further, mice that have a mutation in a gene that regulates circadian rhythms have metabolic disorders Turek et al. The association between sleep loss and diabetes or impaired glucose tolerance may mediate the relationship between sleep loss and cardiovascular morbidity and mortality, as discussed below. Sleep loss and sleep complaints are associated with heart attacks myocardial infarction and perhaps stroke, according to several large epidemiological studies Eaker et al.
One of these studies, of incident cases of heart attacks in the Nurses Health Study, was discussed earlier because it also found increased incidence of diabetes Ayas et al. The cohort had no coronary heart disease at baseline. Ten years later, in , the likelihood of nonfatal and fatal heart attack was modestly increased for both short and long sleep duration. Similarly elevated risks were also found for sleeping 9 hours or more. The effects were independent of a history of hypertension or diabetes because additional adjustment for these conditions yielded slightly lower, but still significantly elevated, relative risks.
Several potential mechanisms could explain the link between sleep loss and cardiovascular events, including blood pressure increases, sympathetic hyperactivity, or impaired glucose tolerance. Experimental data, showing that acute sleep loss 3. Sleep loss is associated with adverse effects on mood and behavior.
Adults with chronic sleep loss report excess mental distress, depressive symptoms, anxiety, and alcohol use Baldwin and Daugherty, ; Strine and Chapman, ; Hasler et al. A meta-analysis of 19 original articles found that partial sleep deprivation alters mood to an even greater extent that it does cognitive or motor functions Pilcher and Huffcutt, Several studies of adolescents, including one with more than 3, high school students, found that inadequate sleep is associated with higher levels of depressed mood, anxiety, behavior problems, alcohol use Carskadon, ; Morrison et al.
Nevertheless, it is not clear from cross-sectional studies whether sleep influences mood or anxiety level, or vice versa.
What Causes Insomnia? | National Sleep Foundation
On the other hand, a large, 3-year longitudinal study of more than 2, middle school students ages 11 to 14 found that self-reported sleep loss was associated with more depressive symptoms and lower self-esteem over time Fredriksen et al. Therefore, although this study suggests an association, the evidence is still limited. Sleep loss is also associated with increased age-specific mortality, according to three large, population-based, prospective studies Kripke et al. The studies were of large cohorts, ranging from 83, to 1.
In three studies, respondents were surveyed about their sleep duration, and then they were followed for periods ranging from 6 to 14 years. Deaths in short or long sleepers were compared with those who slept 7 hours the reference group , after adjusting for numer ous health and demographic factors. Sleeping 5 hours or less increased mortality risk, from all causes, by roughly 15 percent. The largest American study, depicted in Figure , graphically illustrates what has been found in all three studies: a U-shaped curve, showing that progressively shorter or longer sleep duration is associated with greater mortality.
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Other epidemiological studies suggest that sleep-loss-related mortality is largely from acute heart attacks et al. Potential pathophysiological mechanisms accounting for the relationship, while poorly understood, have become the focus of growing interest and are discussed later in this chapter. Shorter or longer sleep duration is associated with greater mortality. Management and treatment of sleep loss are rarely addressed by clinicians, despite the large toll on society Chapters 4 , 5 , and 7.
There are no formal treatment guidelines in primary or specialty care for dealing with sleep loss Dinges et al. The most effective treatment for sleep loss is to sleep longer or take a short nap lasting no more than 2 hours Veasey et al. Catching up on sleep on the weekends—a popular remedy for sleep loss—does not return individuals to baseline functioning Szymczak et al. In a randomized clinical trial caffeine and modafinil showed similar benefits for performance and alertness Wesensten et al.
Modafinil is the only FDA-approved drug for shift work sleep disorder, although it is not approved for sleep loss. Behavioral approaches developed for insomnia also may be useful for sleep loss, but no formal studies have been undertaken expressly for sleep loss.
Furthermore, there have been no large-scale clinical trials examining the safety and efficacy of modafinil, or other drugs, in children and adolescents. Sleep-disordered breathing refers to a spectrum of disorders that feature breathing pauses during sleep. The most common disorder is characterized by obstructive apneas and hypopneas White, , where repeated episodes of collapse apneas or partial collapse of the pharyngeal airway occur, usually a result of obstruction by soft tissue in the rear of the throat.
Snoring, which is produced by vibrations of the soft tissues, is a good marker for OSA Netzer, et al. Apneas or hypopneas a reduction without cessation in airflow or effort typically result in abrupt and intermittent reduction in blood oxygen saturation, which leads to sleep arousal, often accompanied by loud snorts or gasps as breathing resumes.
Episodic interruptions of breathing also frequently cause cortical and brainstem arousals, interrupting sleep continuity, reducing sleep time, and causing increased sympathetic nervous system activation.