”Sleep is that golden chain that ties health and our bodies together.” – Thomas Dekker
What is the purpose of sleep?
The one thing that most sleep experts agree on is that they don’t actually know the purpose, or even function, of sleep [1]. Pretty wild, huh?
There are good theories, but at this point, they are just theories. The most reasonable at present is that sleep is used to ‘cement’ the learning of both physical and mental skills. Neuroscientists believe that the first 0-5 years of life are when human beings learn the fastest and the most. It would make sense then, that the sleep requirements at these ages would be higher, which we know to be true.
Arguably, sleep is more important than food. In some circumstances, people can survive 20 or more days without food [2], however, you won’t survive for more than two weeks without sleep [3].
The physical effects of a lack of sleep.
A lack of sleep has been shown to negatively impact almost every organ system in the body, including but not limited to [4–10]:
Musculoskeletal - decrease in power, reaction time, accuracy, and endurance which are critical in athletic endeavors.
Endocrine – increase in inflammatory molecules, which are associated with a multitude of chronic disease states including obesity, high blood pressure, and high cholesterol.
Cardiovascular – increase in sympathetic nervous system activity (fight or flight response) that increases heart rate and blood pressure.
Lymphatic/immune – poor sleep is linked to an increased risk of infection and decreased ability to recover from infection.
Digestive – changes in hormones that regulate hunger lead to increased appetite and increased food intake, making weight management more difficult.
Reproductive – sleep deprivation has been shown to decrease fertility in both men and women.
Sleep affects pain as well. A decrease in quantity or quality of sleep makes us more susceptible to the experience of pain. Interestingly, it seems that a lack of sleep affects pain more so than pain affects our ability to sleep [11].
The cognitive effects of a lack of sleep.
Most of the research available concerning a lack of sleep is regarding its effects on cognition.
Sleep deprivation has shown to [12-15]:
· Decrease attention span, correlating directly with the amount of sleep deprivation.
· Increase impulsivity.
· Increase substance addiction behavior.
· Increase aggression, anxiety, and irritability.
· Decrease the ability to recognize emotions in others (which is pretty important for effective communication).
So how much do we need?
How much sleep is required will vary from individual to individual, with some needing more and some less. Most of the research indicates that 7-8 hours of sleep per night is ideal.
Again, different people have different needs, but if you’re trying to optimize your sleep schedule for better health, it’s best to consider yourself closer to the norm, and not an outlier.
If you are a “short-sleeper” or “long-sleeper,” you are at increased risk of all-cause mortality when you habitually sleep less than 6 hours, or more than 9 [16].
When to sleep.
Our bodies have a natural circadian rhythm (an internal clock located in the brain, set at 24 hours, which regulates the sleep-wake cycle). Our circadian rhythm is tethered to the environmental 24 day-night cycle. The presence or absence of light is the main signal that helps us set our circadian rhythm. Having our sleep cycle in sync with the environmental cycle (sleep at night, be awake during the day) is the best way to optimize our sleep.
Sleep banking and naps.
Sleep ‘banking’ is when you add a little extra sleep before an anticipated sleep deprivation event. Studies are preliminary, but generally, sleep banking is seen as having a positive effect [17]. Sleep banking would be useful as a temporary, as-needed technique, but shouldn’t replace consistent, healthy sleeping routines.
Naps are generally seen as positive as well.
Short naps (10-20 minutes), cause us to feel more alert and refreshed upon awakening. The cognitive benefits of short naps tend to wear off after 1-3 hours.
Long naps (90-120 minutes), can leave a person feeling groggy immediately upon waking. But, the positive effects of a long nap can be seen up to 24 hours later [18]. Therefore, the duration of your nap should be determined by the needs of your subsequent situation. Naps are best if they’re taken in the early afternoon.
How to get a good night's sleep.
You’ve probably come across articles before that stress the importance of sleep hygiene.
“Strong sleep hygiene means having both a bedroom environment and daily routines that promote consistent, uninterrupted sleep [19].”
The information is pretty standard and readily available on the web. (Vitale et al., 2019) [20] provides a summary of good sleep hygiene techniques.
Avoid blue light from TVs, computer screens, and phones at least 2 hours before bed. They reduce melatonin production which is an important hormone with regards to regulating sleep. Consider blue light dampening software or blue light reducing glasses.
Get in some natural light when you first wake up, around 10 minutes will do.
Don’t hit the snooze button. It doesn’t benefit your sleep to get those extra 5 minutes after the alarm has already gone off.
Meditation may be beneficial.
Lower fat, higher carbohydrate, and higher protein foods near bedtime may promote better sleep.
Topical or oral magnesium supplements may improve sleep if you’re deficient. (If you’re taking any kind of medications, first speak with your prescribing doctor before taking any supplements).
Use Melatonin. (Studies are conflicted on whether or not to use melatonin supplements. I find them effective. Consult with your prescribing doctor if you take any medications, and follow manufacturer directions as to the recommended amount of melatonin to take).
Reduce your fluid intake before bed, so you’re less likely to need to wake up and use the restroom.
Keep the ambient temperature between 60-70 degrees. This is largely an individual preference.
Replace your mattress (as a last resort, they’re expensive). First, try sleeping on a different bed in your house for at least a week. If your sleep experience improves, then consider a new mattress. If not, your sleep quality unlikely has anything to do with your sleeping surface and you can go another route.
Summary
We need sleep to optimize a variety of physical and mental functions. Follow good sleep hygiene rules and try to keep a regular sleep schedule that is 7-8 hours in duration in line with our natural circadian rhythm.
Glossary
Cognitive: of, relating to, or involving conscious mental activities (such as thinking, understanding, learning, and remembering).
Circadian: relating to the regular changes in a person or thing that happen in 24-hour periods.
Topical: made to be put on the skin.
Ambient: surrounding on all sides.
Works Cited
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2. Lieberson, A. D. (2004, November 08). How Long Can a Person Survive without Food? Retrieved from https://www.scientificamerican.com/article/how-long-can-a-person-survive-without-food/
3. How Long Can Humans Stay Awake? (2002, March 25). Retrieved from https://www.scientificamerican.com/article/how-long-can-humans-stay/
4. Brotherton, EJ, Moseley, SE, Langan-Evans, C, Pullinger, SA, Robertson, CM, Burniston, JG and Edwards, BJ (2019) Effects of two nights partial sleep deprivation on an evening submaximal weightlifting performance; are 1 h powernaps useful on the day of competition? CHRONOBIOLOGY
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8. Besedovsky, L., Lange, T., & Haack, M. (2019). The Sleep-Immune Crosstalk in Health and Disease. Physiological Reviews, 99(3), 1325-1380. doi:10.1152/physrev.00010.2018
9. Dáttilo, M., Antunes, H. K., Galbes, N. M., Mônico-Neto, M., Souza, H. D., Marcus Vinícius Lúcio Dos Santos Quaresma, . . . Mello, M. T. (2019). Effects of Sleep Deprivation on Acute Skeletal Muscle Recovery after Exercise. Medicine & Science in Sports & Exercise, 52(2), 507-514. doi:10.1249/mss.0000000000002137
10. Rae, D. E., Chin, T., Dikgomo, K., Hill, L., Mckune, A. J., Kohn, T. A., & Roden, L. C. (2017). One night of partial sleep deprivation impairs recovery from a single exercise training session. European Journal of Applied Physiology, 117(4), 699-712. doi:10.1007/s00421-017-3565-5
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