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Primary Psychiatry. 2010;17(2):19-21
Dr. Neubauer is associate director of the Johns Hopkins Sleep Disorders Center and assistant professor in the Department of Psychiatry at the Johns Hopkins University School of Medicine in Baltimore, Maryland. He is also medical director of the Psychiatry Mobile Treatment Program at the Johns Hopkins Bayview Medical Center.
Disclosure: Dr. Neubauer is consultant to sanofi-aventis and Takeda.
Please direct all correspondence to: David N. Neubauer, MD, Johns Hopkins Bayview Medical Center, 4940 Eastern Ave, Box 151, Baltimore, MD 21224.
I’ll sleep when I die,” is the attitude of millions of people who get to bed too late and get up too early, leaving insufficient time in between for adequate sleep. Getting sufficient sleep is important for the mental and physical health of all people—whether healthcare providers or patients. Unfortunately, cultural values tend to neglect the importance of sleep and society undermines opportunities to achieve an optimum amount of sleep. Both lifestyle choices and schedules for work and school challenge the natural biological drive to sleep ~8 hours most nights. The result is varying degrees of chronic sleep deprivation resulting in daytime sleepiness and cognitive impairment, dependence on caffeine, and an increased risk for assorted health problems.1
I am certainly glad that I live in this time in history with electricity, cable television, cell phones, and the Internet. Along with all the technological advances, conveniences, and luxuries they provide, we also pay a price with the lifestyle changes they promote. We would be sleeping a lot more if we did not have so many distractions and demands on our schedules. Many of us are sleeping 1–2 hours a night less than our ancestors f 100–200 years ago.2 A large percentage of our working population sleeps ~6–6.5 hours during the work week. While they may sleep somewhat longer on weekends, this pattern does not protect against the cumulative sleep debt as the work week progresses.3
The Centers for Disease Control (CDC) and Prevention recently released a report4 analyzing data from a large-scale 2008 survey of adults in the United States. The study included 403,981 respondents from all 50 states, the District of Columbia, and three US territories. The subjects answered question from the Behavioral Risk Factor Surveillance System (BRFSS), which is a state-based random-digit-dialed telephone survey of noninstitutionalized people at least 18 years of age. Previous smaller BRFSS assessments had suggested that many people believed that they were getting insufficient sleep, so the analysis of the 2008 data included all of the US.
The BRFSS survey for 2008 included the question, “During the past 30 days, for about how many days have you felt you did not get enough rest or sleep?” The analysis categories were 0 days, 1–13 days, 14–29 days, and 30 days. The findings were remarkable: Only 30.7% of the respondents reported having no days of insufficient rest or sleep and 11.1% stated that they did not get enough rest or sleep on any of the previous 30 days. Interestingly, the prevalence of insufficient rest or sleep for all 30 days generally declined with age, suggesting that work schedules and other lifestyle choices among the younger age groups may be major contributing factors. The rate was the highest in the 25–34-year old group and lowest in those ≥65 years of age. Retired individuals had the greatest percentage of people reporting no days of insufficient rest or sleep. However, the response rate for insufficient rest or sleep for all 30 days was elevated for people reporting that they were unemployed or unable to work, raising the question of whether conditions interfering with the ability to work might also be undermining the ability to achieve adequate rest or sleep. The CDC report suggested that healthcare providers should routinely assess patients for chronic sleep insufficiency so that appropriate interventions or referrals can be recommended.4
Who says we need 8 hours of sleep most nights? Although there is no absolute measurement of sleep need, considerable evidence supports an average of ~8 hours as the optimum amount. Healthy sleepers typically will sleep slightly >8 hours when they are given an ample opportunity to sleep without any time constraints. Since many people are mildly sleep deprived, it is common for them to sleep well >8 hours when an unlimited opportunity occurs, such as may happen with weekends and vacations. There is some degree of individual variation, however. Certain individuals appear to have greater or lesser sleep requirements, functioning very well with only 5 hours or needing as much as 9 hours nightly. However, most people who say that they get by fine on only 5–6 hours per night likely would demonstrate some impairment on cognitive testing and would sleep more if they spent more time in bed. The people who are sleep deprived during the work week tend to have cumulative impairment as the week progresses.1 Some people seem to be especially sensitive to the effects of sleep deprivation and are less tolerant of shift work schedules.5
How quickly people fall asleep in the daytime during brief experimental nap opportunities reflects the effects of the curtailment of nighttime sleep. The average time to fall asleep during daytime naps decreases with shorter nighttime sleep. Impairment on cognitive performance tests is very sensitive to sleep restriction and is readily apparent in studies of acute and chronic sleep deprivation. In one chronic sleep restriction study,6 commercial truck drivers remained in a sleep laboratory setting for 2 weeks. Groups of the subjects were assigned to 7 consecutive nights of 3, 5, 7, or 9 hours in bed. Throughout the daytime various cognitive and physiologic testing was performed. Among these was the multiple sleep latency test, which involves nap opportunities in the morning and afternoon. It is no surprise that the subjects with the shorter times in bed had significantly shorter daytime average sleep latencies. Psychomotor vigilance testing (PVT), which involves the reaction time to a visual stimulus, assessed the speed of responses and number of response lapses. PVT performance deterioration was evident for all of the groups, except for those subjects allowed 9 hours in bed. Even a subsequent period of 3 nights with 8 hours in bed did not completely reverse the cognitive impairment in the subjects limited to 3, 5, and 7 hours in bed. In a similarly designed study,1 healthy subjects remained in a laboratory setting for 20 days and were limited to 4, 6, or 8 hours in bed for 14 consecutive nights. Subjects in the groups restricted to 4 and 6 hours in bed developed behavioral alertness impairments characteristic of those found with up to 3 nights of total sleep deprivation.
Health hazards associated with chronic sleep insufficiency are more difficult to establish, except for the fatalities and injuries obviously resulting from excessive sleepiness and inattention. However, emerging evidence does suggest that insufficient sleep can have negative consequences on endocrine, cardiovascular, metabolic, and immune functioning. Short-term sleep restriction studies have documented reduced glucose tolerance, sympathetic nervous system activation, increased blood pressure, increased inflammatory markers, and reduced leptin levels. Epidemiologic studies show that reduced sleep duration is associated with a greater body mass index and all-cause mortality.1
A decade ago it was shown that restricting the time in bed to just 4 hours for 6 nights was sufficient to impair glucose tolerance and increase both evening cortisol and sympathetic tone in healthy young adults.7 A 2009 study8 extended these short-term laboratory findings to long-term epidemiologic evidence associating short sleep duration with the development of type 2 diabetes or impaired glucose tolerance (IGT). The sample included 276 adults followed for a mean of 6 years. Compared with individuals reporting 7–8 hours of sleep, people with ≤6 hours of sleep had an adjusted relative risk of 2.78 for developing type 2 diabetes or IGT. Another recent study9 involved 495 adults assessed for coronary artery calcification by computed tomography on two occasions separated by 5 years. Sleep duration was estimated with wrist actigraphy and self reports. The investigators found a significant independent relationship between longer sleep duration and a lower incidence of calcification. One hour more of sleep was associated with a 33% decrease in the estimated odds of coronary calcification.
Curiously, epidemiologic studies of self-reported sleep duration often have revealed a U-shaped relationship between sleep length and all-cause mortality and with specific health risks. Compared with people reporting 7–8 hours of nightly sleep, those with shorter and longer durations have been found to have higher risks for worse health outcomes. However, there likely are important differences underlying the respective relationships. People frequently voluntarily restrict their sleep and pathological processes have been demonstrated in well-controlled sleep restriction experiments. In contrast, people may extend time in bed but cannot choose to sleep excessive periods of time. Reported long sleep durations probably represent surrogates for other factors predisposing people to greater pathology and higher mortality rates. Accordingly, long sleep duration should not be viewed as an independent risk factor as has been demonstrated for short sleep duration.10
Adequate sleep, like exercise and an appropriate diet, should enhance personal health. If more people slept an adequate amount there also would be major benefits for society. There is a huge economic burden associated with the widespread sleep debt. Fortunately, regulations regarding work schedules are in effect in some professions, including airline pilots, some commercial drivers, and medical trainees. However, the rules cannot regulate how much people sleep in their free time.11 It is a mistake to regard sleep as a waste of time. Rather, sleep should be seen as an investment in an improved waking life and better long-term health.12 PP
References
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2. Ferrara M, De Gennaro L. How much sleep do we need? Sleep Med Rev. 2001;5(2):155-179.
3. Van Dongen HP, 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;26(2):117-126.
4. Centers for Disease Control and Prevention (CDC). Perceived insufficient rest or sleep among adults - United States, 2008. MMWR Morb Mortal Wkly Rep. 2009;58(42):1175-1179.
5. King AC, Belenky G, Van Dongen HP. Performance impairment consequent to sleep loss: determinants of resistance and susceptibility. Curr Opin Pulm Med. 2009 Aug 26. [Epub ahead of print].
6. Belenky G, Wesensten NJ, Thorne DR, et al. Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study. J Sleep Res. 2003;12(1):1-12.
7. Spiegel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. Lancet. 1999;354(9188):1435-1439.
8. Chaput JP, Despres JP, Bouchard C, Astrup A, Tremblay A. Sleep duration as a risk factor for the development of type 2 diabetes or impaired glucose tolerance: analyses of the Quebec family study. Sleep Med. 2009;10(8):919-924.
9. King CR, Knutson KL, Rathouz PJ, Sidney S, Liu K, Lauderdale DS. Short sleep duration and incident coronary artery calcification. JAMA. 2008;300(24):2859-2866.
10. Stamatakis KA, Punjabi NM. Long sleep duration: a risk to health or a marker of risk? Sleep Med Rev. 2007;11(5):337-339.
11. Basner M, Dinges DF. Dubious bargain: Trading sleep for Leno and Letterman. Sleep. 2009;32(6):747-752.
12. Colten HR, Altevogt BM, eds. Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Washington, DC: The National Academic Press; 2006.
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