Get Some Z’s Please!

By Sarah Reitz

February 20th, 2018

 

“I’ll sleep when I’m dead” is a phrase we often hear (and may have even said ourselves) during particularly busy or exciting periods in our lives. At times, it can feel like sleep is just holding us back from doing what we want to do, whether that means accomplishing more at work, staying out later with friends, or watching just one more episode of Stranger Things. However, anyone who has pulled an all-nighter will tell you that you cannot escape sleep forever, no matter how hard you try. But is sleep actually that important? And is it really that bad to miss some sleep?

Everybody Sleeps

Sleep is defined as a period of behavioral inactivity during which an animal adopts a stereotyped posture (think humans laying on their side or back, or cats curling in a ball) and has reduced responsiveness to the external environment. One of the first clues about the importance of sleep is that sleeping is not something that is specific to any one species. Every animal, from microscopic worms and fruit flies to humans, displays some form of sleep. More than that, sleep is so critical that an animal that is completely sleep deprived over 2-4 weeks will actually die1. Since getting sleep is literally a matter of life or death, animals have adapted themselves to be able to sleep in some pretty extreme circumstances. For example, as underwater mammals, dolphins must be able to come to the surface for air throughout the day, which means that falling asleep underwater would put them at risk for drowning. To solve this problem, only one hemisphere, or half, of the dolphin’s brain will sleep at a time, leaving the other half awake so the dolphin can continue to get to the surface to breathe!

So what happens if I miss some sleep?

While complete sleep deprivation over long periods of time is ultimately deadly, the reality is that our brain will not let us go without sleep for this long. Instead, the most common form of sleep deprivation is short sleep, which for adults is defined as getting less than the recommended 7-9 hours of sleep each night2. By this definition, more than one third of Americans are not getting enough sleep! In fact, this sleep debt crisis has become so bad that the Center for Disease Control and Prevention (CDC) has named insufficient sleep a national health epidemic, affecting people across the country (Figure 1). The CDC refers to this as a national health epidemic because of the many known negative side effects of not getting enough sleep. So what are these effects?

figure 1
Figure 1. Age-adjusted prevalence of short sleep duration (<7 hours) among adults 18 years or older, 2014. Image by Center for Disease Control and Prevention.

Some of the effects of short sleep occur within neurons themselves. The brain contains distinct groups of neurons that are active when we are awake, and help to promote wakefulness. Scientists have examined the effects of insufficient sleep on one of these clusters of neurons, called the locus coeruleus (LC). When you don’t get enough sleep, neurons experience a build up of reactive oxygen species (ROS), which include molecules such as peroxide, superoxides, and hydroxyl radicals. Too many of these molecules in a single neuron can result in cell damage or death. After 1 night of short sleep, LC neurons respond to this increase in ROS by producing more antioxidant enzymes, which help remove the ROS and prevent damage to the cell. However, after only 3 nights of inadequate sleep this adaptive effect disappears and the LC neurons no longer produce antioxidant enzymes, resulting in the death of more than a quarter of the neurons in this region3. After 4 weeks of short sleep, neuronal death is even higher: almost a 40% loss of LC neurons. This isn’t limited to one brain region either. A similar level of cell death was also seen in another population of wake-active cells called orexinergic neurons4. Alarmingly, this cell loss appears to be permanent, even after periods of recovery sleep.

figure 2
Figure 2. Location of two populations of wake-active neurons in the brain. The orexinergic neurons (blue) are located in the hypothalamus while the locus coeruleus neurons (red) are found in an area of the brainstem called the pons. Cell death is found in both locations after only a few nights of short sleep. Other wake-active nuclei in the brain (not pictured) have yet to be examined after sleep deprivation.

Anyone who has ever been sleep-deprived can tell you that insufficient sleep also leads to a wide range of cognitive and physiological effects. The most noticeable of these is excessive daytime sleepiness, or feeling drowsy throughout the day. Along with this sleepiness comes decreases in mood, mental sharpness, memory formation, and judgement. This can have dangerous consequences, leading to increases in accidents and injuries. In fact, many large-scale accidents across the world – including the Exxon-Valdex oil spill, the Challenger space shuttle explosion, and the Chernobyl nuclear disaster – have been linked to human error likely due to sleep deprivation5. Furthermore, scientists have found that driving after going 24 hours without sleep is equivalent to driving with a BAC of 0.10%6. To put that in perspective, driving with a BAC of 0.05% is considered hazardous, and driving with a BAC over 0.08% is illegal!

The detrimental effects of inadequate sleep are not limited to the brain, either. Short sleep has been linked to an increased risk of developing chronic diseases, including cardiovascular disease, type 2 diabetes, and obesity7-9. This may be due to the fact that sleep deprivation results in elevated inflammation and sympathetic nervous system activity, leading to increases in processes such as heart rate and blood pressure, two known risk factors for cardiovascular disease. Other effects of sleep deprivation include an increase in caloric intake, decreased glucose tolerance and reduced insulin sensitivity.

How can I improve my sleep?

The good news is that almost all of these negative effects disappear once you consistently get 7+ hours of sleep each night. By improving your sleep hygiene, or good sleep habits, you can ensure you are getting the necessary amount of sleep and reduce your risk of developing the effects discussed above. Sleep scientists and clinicians commonly recommend a specific set of tips for improving sleep. For starters, you should only use your bed for sleeping. Keeping a routine sleep schedule is also crucial. This means going to bed and waking up at the same time every day, even on weekends and holidays. Following these tips allows your brain to anticipate when and where sleep will occur each night, priming you to fall asleep more quickly. Another key is to cut out caffeine, alcohol, and electronics prior to bedtime. Both caffeine and the blue light emitted by electronic screens cause your body to feel more alert, making it more difficult to fall asleep. Alcohol, on the other hand, may make you feel more drowsy, but actually disrupts your sleep cycles throughout the night leaving you even more tired the next day.

By focusing on sleep hygiene and avoiding the cycle of sleep deprivation during the week followed by “catch up” sleep on the weekends, you can wake up feeling more refreshed and alert while also decreasing your risk for chronic diseases and preventing irreversible neuronal damage. Investing in my health by sleeping more? Now that’s something I can get behind.

 

 

Sources:

  1. Everson CA, Bergmann BM, Rechtschaffen A. Sleep deprivation in the rat: III. Total sleep deprivation. Sleep. 1989:12(1):13-21.
  2. Watson NF, Badr MS, Belenky G, et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. 2015;38(6):843–844.
  3. Zhang J, Zhu Y, Zhan G, Fenik P, Panossian L, Wang MM, Reid S, Lai D, Davis JG, Baur JA, Veasey S. Extended wakefulness: Compromised metabolics in and degeneration of locus ceruleus neurons. Neurosci. 2014;34(12):4418-4431.
  4. Zhu Y, Fenik P, Zhan G, Somach R, Xin R, Veasey S. Intermittent short sleep results in lasting sleep wake disturbances and degeneration of locus coeruleus and orexinergic neurons. Sleep. 2016;39(8):1601-11.
  5. Mitler MM, Carskadon MA, Czeisler CA, Dement WC, Dinges DF, Graeber RC. Catastrophes, Sleep, and Public Policy: Consensus Report. Sleep. 1988;11(1):100-109.
  6. Williamson, A, & Feyer, A. Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication. Occupational and Environmental Medicine 2000;57(10):649–655.
  7. Knutson KL, Ryden AM, Mander VA, Van Cauter E. Role of sleep duration and quality in the risk and severity of type 2 diabetes mellitus. Arch Intern Med2006;166:1768–1764.
  8. Kasasbeh E, Chi DS, Krishnaswamy G. Inflammatory aspects of sleep apnea and their cardiovascular consequences. South Med J2006;99:58–67.
  9. Taheri S. The link between short sleep duration and obesity: We should recommend more sleep to prevent obesity. Arch Dis Child2006;91:881–884.

Images:

Figure 1: Image from Center for Disease Control and Prevention. Behavioral Risk Factor Surveillance System 2014. https://www.cdc.gov/sleep/pdf/surveillance/Short_Sleep_US-Map_2014_Factsheets_508tagged.pdf

 

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