Sleep is one of the most important aspects of health that we can focus on. With that in mind, it is unfortunate that 70% of adults report that they don’t get enough sleep at least once a month, 25% only get sufficient sleep half of the time, and 11% get insufficient sleep every night (1). Beyond acting as our main source of rest and rejuvenation, sleep has a great impact on our brain, immune system, hormones, and even our emotions and decisions! It is a huge aspect of everyone’s day-to-day functioning and a key area of focus for our team who centers on fostering longevity and wellness.
How the Brain “Cleans” Itself During Sleep
It has long been known that sleep gives us energy, helps heal sickness, aids us in maintaining normal functioning, and overall supports our general health (2). However, the actual mechanics behind how it accomplishes those things were a mystery until quite recently. A 2017 study proved that our brains contain an extensive network of blood and lymphatic vessels (3). In general, lymphatic vessels run alongside blood vessels through the rest of the body, take blood from the vessel, filter the immune cell- and waste-containing lymph, and then return the “cleaned” or “detoxified” blood back into the circulatory system (3).
Further discovery and study of this system have brought us to a new understanding of how these lymphatic vessels function within the brain. This system has taken on the moniker “the glymphatic system”, as a nod to the importance of glial cells (a type of neuro-functional cell) working in tandem with the lymphatic system (3). Throughout the day, our bodies produce byproducts such as beta-amyloids that, if left in the brain and its fluids for too long, can become toxic to the brain. To combat this, glial cells work with the lymphatic system during sleep to regulate certain markers in cell membranes to allow for a huge increase in cerebrospinal fluid (3). The space that holds this fluid increases about 60% in the brain, allowing for the extra fluid to flow uninhibited, cycle through the brain’s lymphatic vessels, and thoroughly sweep out toxins and debris (3).
If the brain doesn’t get sufficient sleep, it is unable to perform this important process and can be affected in a number of ways. Inadequate sleep can impair cognitive abilities, emotional reasoning, and even judgment and decision-making (3). Chronic sleep deprivation, even after just a few nights, is comparable to being intoxicated with alcohol when comparing decreased reaction times and cognitive dysfunction (3).
Sleep is also important for cognitive functioning in terms of forming new memories, consolidating learned skills, and general performance (3). This is why the link between memory and sleep is becoming a focused area of study. Difficulty falling asleep, staying asleep, or poor quality of sleep are all risk factors for long-term cognitive decline, including neurodegenerative diseases such as dementia and Alzheimer’s (4). Studies have shown that shorter sleep duration is linked to overall lowered cognitive function, and some studies even posit that it is specifically the beta-amyloids and other byproducts not being cleared out during sleep that leads to Alzheimer’s (3, 4). Given that sleep loss is usually credited to be a symptom of dementia, further study may show that a focus on healing sleep patterns may help alleviate some of the symptoms or progression of dementia and other neurodegenerative disorders (3).
One way to think about sleep and the brain is to consider it as though having a switch, similar to an on/off switch. Either it can be awake, taking in sensory information, responding to external stimuli, and engaging with the outside world, OR it can be asleep, activating the “glymphatic system” and clearing out debris and toxins (2). Because it needs to switch “off” in order to remain healthy, you can see why getting adequate sleep each night is an important part of our focus on overall function, healthy aging, and increasing lifespan and healthspan. And this is just taking into consideration one part of the body!
How Sleep Affects the Immune System
While our immune systems are always working, certain immune system functions increase during sleep and can only function fully during this time. Just as the brain is able to synthesize and form new memories during sleep, the immune system is able to form immunological memories and function better because it is able to peak during sleep (5). Additionally, the two stress systems (the HPA axis and the sympathetic nervous system) down-regulate during the early stages of sleep (5). This means that certain hormones (like cortisol and epinephrine) decrease, allowing others that promote cell growth and restoration to increase sharply (5). This acts as a short-term green light to the immune system to send beneficial pro-inflammatory signals, which support immune cells to function better, live longer, and produce their byproducts at a higher rate (5). Immune cells are also able to migrate at a much faster rate throughout the body during sleep, functioning to a greater degree than during the time the body is awake (5). All of these factors come together to greatly boost immune activation during sleep.
So, it follows that impaired or inadequate sleep can cause important immunological effects. Not only does less time spent sleeping allow for less of the processes outlined above to occur, but it also leads to an overall decrease in normal immune function. Natural Killer (NK) cells, which respond to pathogens, kill infected cells, and even control early signs of cancer, are affected by disturbed sleep (6). After just one night of sleep deprivation, 18 of 23 healthy patients had a drop in NK activity - a 72% drop on average, to be specific (7)! This means that even one poor night’s sleep could potentially tip the scales in favor of becoming ill if you are exposed to certain pathogens. In one 2009 study, clinical trials showed that patients who got less than 7 hours of sleep over a period of two weeks were almost three times more likely to develop a cold than those who got 8 or more hours of sleep (8). In another large-scale study with over 16,000 participants, those who suffered from insomnia were far more likely to develop pneumonia than those who reported normal levels of sleep (9).
Hormonal Benefits from Sleep
Another aspect of our everyday health and systems’ good functioning is our hormones. Hormonal balance can prevent a number of problems by supporting heart, brain, and reproductive health, and even help keep us energized and performing at our peak. For example, men need testosterone for healthy muscle mass, strength, adiposity, bone density, sexual behavior and reproduction, and overall vigor and well-being (10). Because the majority of daily testosterone release occurs during periods of sleep, poor sleep is associated with reduced testosterone levels in men (10). In otherwise healthy young men, just one week of restricted sleep led to a drop in testosterone of up to 15%, which directly correlated to decreased performance and vigor on top of the other cognitive and emotional effects typically associated with sleep deprivation (10).
Women’s hormones are affected by sleep differently. Interestingly, women are at a higher risk for insomnia and poor sleep quality than men are, and hormones seem to be at the root of this difference (11). The menstrual cycle is associated with changes in circadian rhythms, and when hormones either drop or spike, sleep can be disturbed (11). This can create an unfortunate cycle, because disturbed sleep can negatively affect hormones, compounding the effect over time (11). This makes proper sleep hygiene all the more important for women experiencing hormone-related insomnia or other sleep disturbances.
Good Sleep Hygiene
Just as our health as a whole is a number of factors that come together to create an overall picture, so are there quite a few aspects or areas of focus in order to have good sleep hygiene. The basics include getting at least seven hours of sleep every night, keeping a consistent schedule, keeping naps to under an hour and before 3 pm, and avoiding caffeine 8 hours before you plan on sleeping (2, 12, 13). There are many other ways to improve sleep quality and duration (12, 13):
Reduce bright lights, noises, and all electronics in your bedroom. Keep your room quiet, dark, and cool.
Move your body every day, no later than 2-3 hours before bedtime. This can range from a long slow walk to an intense exercise.
Go outside and take in sunlight for at least 30 minutes every day to encourage your natural circadian rhythms.
Quit smoking, or avoid nicotine at least 8 hours before sleeping.
Avoid alcohol, large meals, and beverages late at night. This will keep you in lighter stages of sleep or can cause you to wake up to use the bathroom.
If you’re having trouble sleeping, move into a different room until you are tired. Use your bed exclusively for sleeping and sex.
Begin to unwind at least a half of an hour before sleeping. Consider creating a bedtime routine of relaxing and peaceful activities that you can engage in each night.
Track your sleep duration and quality, whether in a journal or through an app. This can bring a lot of insight you may not notice otherwise, and even help you create consistent patterns.
If you are having trouble falling asleep, staying asleep, don’t feel rested during the day, or are having trouble integrating some of the lifestyle tips above, give us a call! At Prime Health Associates, we focus on combining the best of conventional and alternative medical care. Our goal is to support your whole health and determine the root behind any issues you may be experiencing. We would love to partner with you to determine the right ways to focus on this important aspect of health and support you in finding overall wellness.
Dr. White is a traditionally trained physician. After graduating from the University of Oklahoma College of Medicine, he went on to complete residency training in emergency medicine & trauma at Washington University in St. Louis, then completed board certification. After many years in Emergency Medicine, Dr. White saw an opportunity to further help his patients through functional medicine, so he obtained extensive fellowship training in integrative and functional medicine, nutrition, and age management.
1. The State of SleepHealth in America. SleepHealth. https://www.sleephealth.org/sleep-health/the-state-of-sleephealth-in-america/#:~:text=In%20America%2C%2070%25%20of%20adults,report%20insufficient%20sleep%20every%20night.&text=It%20is%20estimated%20that%20sleep,all%20ages%20and%20socioeconomic%20classes.
2. Eugene, A. R., & Masiak, J. (2015). The Neuroprotective Aspects of Sleep. MEDtube science, 3(1), 35–40. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4651462/
3. U.S. Department of Health and Human Services. (2017, October 24). Brain cleaning system uses lymphatic vessels. National Institutes of Health. https://www.nih.gov/news-events/nih-research-matters/brain-cleaning-system-uses-lymphatic-vessels.
4. Spira, A. P., Chen-Edinboro, L. P., Wu, M. N., & Yaffe, K. (2014). Impact of sleep on the risk of cognitive decline and dementia. Current opinion in psychiatry, 27(6), 478–483. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4323377/
5. Besedovsky, L., Lange, T. & Born, J. Sleep and immune function. Pflugers Arch - Eur J Physiol 463, 121–137 (2012). https://doi.org/10.1007/s00424-011-1044-0
6. Eissmann, P. Natural Killer Cells. British Society for Immunology. https://www.immunology.org/public-information/bitesized-immunology/cells/natural-killer-cells#:~:text=Natural%20Killer%20(NK)%20Cells%20are,coming%20from%20a%20common%20progenitor.&text=They%20are%20named%20for%20this,to%20enhance%20the%20immune%20response.
7. Irwin, M., Mascovich, A., Gillin, J. C., Willoughby, R., Pike, J., & Smith, T. L. (1994). Partial sleep deprivation reduces natural killer cell activity in humans. Psychosomatic medicine, 56(6), 493–498. https://doi.org/10.1097/00006842-199411000-00004
8. Cohen, S., Doyle, W. J., Alper, C. M., Janicki-Deverts, D., & Turner, R. B. (2009). Sleep habits and susceptibility to the common cold. Archives of internal medicine, 169(1), 62–67. https://doi.org/10.1001/archinternmed.2008.505
9. Lin, C. L., Liu, T. C., Chung, C. H., & Chien, W. C. (2018). Risk of pneumonia in patients with insomnia: A nationwide population-based retrospective cohort study. Journal of infection and public health, 11(2), 270–274. https://doi.org/10.1016/j.jiph.2017.08.002
10. Leproult, R., & Van Cauter, E. (2011). Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA, 305(21), 2173–2174. https://doi.org/10.1001/jama.2011.710
11. Nowakowski, S., Meers, J., & Heimbach, E. (2013). Sleep and Women's Health. Sleep medicine research, 4(1), 1–22. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4327930/
12. National Institute of Health, U. S. D. of H. and H. S. (Ed.). (2006, April). In Brief: Your Guide to Healthy Sleep. NHLBI. https://www.nhlbi.nih.gov/files/docs/public/sleep/healthysleepfs.pdf.
13. Centers for Disease Control and Prevention. (2016, July 15). CDC - Sleep Hygiene Tips - Sleep and Sleep Disorders. Centers for Disease Control and Prevention. https://www.cdc.gov/sleep/about_sleep/sleep_hygiene.html.