Sleep deprivation dramatically affects both our physical and mental health. We know sleep is important; after all, we spend one-third of our lives in the land of nod. When we do not get enough sleep, we feel terrible, are irritable, and make mistakes. And this is only scratching the surface of the problem. A poll conducted by the National Sleep Foundation (NSF) indicates that only 42% of adults report getting enough sleep . For adolescents, the statistics are more sobering, with only 31% of students in grades 9-12 reporting getting at least 8 hours of sleep or more on an average school night .
While sleep itself is often in the limelight, its regulation is equally important. Evolutionarily, humans sleep at night and are awake during the day, so it makes sense that our bodies are influenced by exposure to light and darkness. The master circadian clock, a tiny structure in the brain called the suprachiasmatic nucleus or SCN, receives light cues from the environment and then signals regulated patterns of activities in the body . The circadian rhythm, or biological clock, is a key regulator of our bodily functions. It regulates hormone secretion throughout the day, and thus controls involuntary processes such as sleep-wake cycles, appetite, alertness, and body temperature . Changes in the amount of sleep we get and when we sleep can affect timely hormone release, which in turn can affect appetite modulation, sleepiness, and even proper cellular function. For example, shift workers, who make up about 15%-20% of the American work force, report chronic fatigue and on-the-job errors due to sleep loss and to circadian disruption .
In terms of public health, chronic sleep loss and circadian disruption have been tied to many problems including obesity, hormone regulation, mental health, and cognitive performance—yet these findings have not been very well publicized. It is likely that addressing the sleep epidemic will help curtail other key public health issues.
Adequate sleep and hormonal balance
A major focus of public health is curbing the obesity epidemic. Obesity is the leading cause of a myriad of chronic health conditions. Further, at the national level, obesity costs the US about $147 billion annually in health care alone . Why not address obesity by fixing sleep patterns?
There are two critical appetite-influencing hormones: leptin and ghrelin, which signal fullness and hunger, respectively. Interestingly, sleep deprivation disrupts the concentration of these hormones by a two-fold value. When sleep deprived, leptin levels plummet (so we do not feel as satisfied after eating) and ghrelin levels spike (causing us to still feel hungry). There is strong evidence that this combination leads to weight gain [6-7]. With so many people not getting enough sleep, it is no wonder we also suffer from obesity. Sleep loss is, of course, not the sole cause of obesity, but its reversal is an inexpensive treatment for the condition.
Another hormone involved in sleep and circadian rhythm is melatonin. Melatonin is released at night and plays a role in the onset of sleepiness. Research in the last 20 years has shown that chronic suppression of melatonin release by exposure to artificial light leads to development of cancer. This exposure affects women working night shifts in particular: for nurses and flight attendants, for example, the rates of breast and ovarian cancer are significantly higher [8-10]. Artificial light exposure in homes and from computer monitors also diminishes the amount and quality of sleep we get . It goes without saying that before the invention of commercial lighting, people tended to follow more of a natural sleep-wake cycle, settling down at sunset and often rising at dawn. After World War I, electricity became available widely, allowing people to fend off sleep with artificial lighting. While lamps lit with fire cast light, it is not nearly the lux level exposure of artificial light. These changes have moved us away from our natural circadian rhythm and sleep cycle, and the consequences are only now starting to be seen. So far I have only given examples of physical changes, but there are also mental changes associated with sleep and circadian disruption.
Cognitive consequences of sleep loss
We all recognize our inability to pay attention when we do not get a good night’s sleep. What we may not realize is just how much our attention and reaction time are affected by sleepiness. A person who has not slept all night can be as incapacitated as someone who is legally drunk —yet most of us will get in a car without a second thought after having slept less than five hours. The American Automobile Association (AAA) estimates that one out of every six deadly traffic accidents are due to drowsy driving . “Willing” yourself to stay awake is impossible. When extremely sleepy, the brain undergoes microsleeps, brief blips of loss of consciousness lasting anywhere between a fraction of a second to 30 seconds. These microsleeps are just long enough for a driver to veer a truck off the road or for a train operator to miss a stop signal. About 25% of train operators and pilots admit that sleepiness has affected their job performance. Notably, one in five of them report that he or she made a serious error due to sleepiness . Even in the health profession sector, many doctors and nurses work on few hours of sleep, creating an environment where medical errors are easy to make .
Devastating transportation accidents aside, sleep deprivation leads to problems with decision-making, learning, and memory [15-16]. As we sleep, our brain moves through a series of cycles termed slow wave and non-slow wave sleep. Slow wave sleep has been shown to be a particularly important stage for memory consolidation ; sleep deprivation results in fewer completed sleep cycles in which to process information.
Sleep deprivation is also a severe problem for teenagers, and one we should be concerned about in the public health field. The circadian rhythm of teenagers shifts after puberty, making them feel sleepy 2-3 hours later than adults, and preventing them from being able to wake up as early in the morning [18-19]. Combined with early school start times, often before 7:30 am, this shift in sleep pattern has dire consequences.
A poll conducted by the NSF indicated that 80% of teenagers went to sleep well after 10:00 pm, yet 54% woke up between 5:00 am and 6:30 am on school days . In the past, youth did not always go to school so early. The modern start times for schools began in the early 19th century, when school became a place for day laborers to leave their children. After the 1950’s and 60’s, there was a slow push for earlier start times as school boards tried to minimize busing and operating costs . According to the U.S. Department of Education, 42% of schools now start before 8:00 am. Are we not setting up our youth for failure?
Students who do not get enough sleep often have trouble focusing, solving problems, and making decisions. Additionally, sleep-deprived teenagers are more likely to have behavioral and emotional problems that can lead to drug addiction and depression [21-22]. Students are also more likely to miss 1st and 2nd period classes due to difficulty waking up in the mornings . When in school, these students’ performance is compromised due to poor attention spans and less knowledge retention.
In the long run, poor academic achievement hurts both the individual and the community as a whole. Successfully educating future leaders, scientists, doctors, and teachers is an essential part of ensuring a positive public health outcome.
Sleep and depression
Teenagers are not the only group to suffer from emotional problems due to poor sleep. In the last few years, research into the relationship between sleep and depression has increased steadily. Depression affects about 1 in 10 adults in the United States  and can affect physical health, social life, work productivity, and community involvement. The costs of depression in terms of productivity loss is somewhere around 200 million missed workdays or between $17-44 million, not to mention health expenses .
The issue is complex, as depression can cause sleep problems and sleep problems can cause depression. However, there is evidence to suggest that correcting sleep onset or maintenance, also known as “sleep therapy,” improves the symptoms of depression . Sleep therapy is a form of cognitive behavioral therapy that is relatively inexpensive, and could be used to combat what should be considered a major public health issue.
Our current approach to sleep has left us at odds with nature. Perhaps we should view our need for sleeping pills to induce sleep, and for coffee to keep us awake, as signs that we are headed down the wrong path. Sleep plays an important role in a range of different health issues. From mental health to obesity, the effects of sleep deprivation are concerning. Current attempts to “fix” obesity and mental health are relatively costly and seem to have mixed outcomes; pharmacological approaches in particular are very expensive. If we treat sleep as a preventative measure, we may be able to reduce some of the personal and financial burden of devastating accidents, cancer, and chronic health problems. Additionally, improving work productivity and academic success through sleep has numerous benefits to society. I am not suggesting that sufficient sleep is a cure-all, but it is a step in the right direction. Sleep and circadian rhythms are often overlooked, and it is time for their debut as a public health issue.
1. Sleep in America: Bedroom Poll. 2011. National Sleep Foundation, 2011.
2. Eaton, D.K., et al., Youth risk behavior surveillance - United States, 2011. MMWR Surveill Summ, 2012. 61(4): p. 1-162.
3. Circadian Rhythms Fact Sheet. National Institutes of Health, 2014.
4. Sleep in America Poll: Planes, Trains, Automobiles, and Sleep. National Sleep Foundation, 2012.
5. Finkelstein, E.A., et al., Annual medical spending attributable to obesity: payer-and service-specific estimates. Health Aff (Millwood), 2009. 28(5): p. w822-31.
6. Van Cauter, E. and K.L. Knutson, Sleep and the epi- demic of obesity in children and adults. Eur J Endocrinol, 2008. 159 Suppl 1: p. S59-66.
7. Taheri, S., et al., Short sleep duration is associated with reduced leptin, elevated ghrelin, and increased body mass index. PLoS Med, 2004. 1(3): p. e62.
8. Kolstad, H.A., Nightshift work and risk of breast can cer and other cancers--a critical review of the epide- miologic evidence. Scand J Work Environ Health, 2008. 34(1): p. 5-22.
9. Davis, S. and D.K. Mirick, Circadian disruption, shift work and the risk of cancer: a summary of the evidence and studies in Seattle. Cancer Causes Control, 2006. 17(4): p. 539-45.
10. Stevens, R.G., et al., Breast cancer and circadian disruption from electric lighting in the modern world. CA Cancer J Clin, 2013.
11. Chellappa, S.L., et al., Human melatonin and alerting response to blue-enriched light depend on a poly-
morphism in the clock gene PER3. J Clin Endo- crinol Metab, 2012. 97(3): p. E433-7.
12. Dawson, D. and K. Reid, Fatigue, alcohol and perfor- mance impairment. Nature, 1997. 388(6639): p. 235.
13. AAA, Asleep at the Wheel : The Prevalence and Im- pact of Drowsy Driving, 2010: Washington, DC.
14. Duncan, B.W., A.K.Jha, and David W. Bates, Fatigue, Sleepiness, and Medical Errors. Agency for Health Research and Quality, 2012.
15. Stickgold, R. and M.P. Walker, Memory consolidation and reconsolidation: what is the role of sleep? Trends Neurosci, 2005. 28(8): p. 408-15.
16. Harrison, Y. and J.A. Horne, The impact of sleep deprivation on decision making: a review. J Exp Psychol Appl, 2000. 6(3): p. 236-49.
17. Born, J. and I. Wilhelm, System consolidation of memory during sleep. Psychol Res, 2012. 76(2): p. 192-203.
18. Carskadon, M.A., Patterns of sleep and sleepiness in adolescents. Pediatrician, 1990. 17(1): p. 5-12.
19. Carskadon, M.A., When Worlds Collide: Adolescent Need for Sleep Versus Societal Demands. Phi Delta Kappan, 1999. Vol. 80(No. 05): p. 348-353.
20. Wolf-Meyer, M.J., The Slumbering Masses: Sleep, Medicine, and Modern American Life2012: University of Minnesota Press.
21. Millman, R.P., Excessive sleepiness in adolescents and young adults: causes, consequences, and treat- ment strategies. Pediatrics, 2005. 115(6): p. 1774- 86.
22. Carrell, S.E., T.Maghakian, and James E. West., A’s from Zzzz’s? The Causal Effect of School Start Time on the Academic Achievement of Adolescents. American Economic Journal: Economic Policy 2014. 3.3: p. 62–81.
23. Center for Disease Control and Prevention, Morbid- ity and Mortality Weekly Report National Depression Screening Current Depression Among Adults. 2010. 59.
24. Carney, C.E., et al., A comparison of rates of residu- al insomnia symptoms following pharmacotherapy or cognitive-behavioral therapy for major depressive disorder. J Clin Psychiatry, 2007. 68(2): p. 254-60.
Nelly Papalambros is a second-year PhD/MPH student in the Northwestern University Interdepartmental Neuroscience (NUIN) program. She currently works in the laboratory of Dr. Phyllis Zee studying sleep and circadian rhythms. Nelly is interested in using science to advocate for evidence-based health policy.