[Austin Both is the Associate Performance Director of Athletic Lab]

In last week’s installment, we discussed the effects of cognition and physical capacity as a result of sleep deprivation. Perhaps, even more important than these aforementioned factors, is sleep’s ability to keep us alive (quite literally).

While there is not a single unanimous explanation as to why sleep is required for life, after tireless research, we do have a greater understanding of the physiological functions that make it so important (Harvard.edu). One such mechanism that affects cognition, mood, as well as our physical state, is the tendency for sleep deprivation to cause an increase in cortisol levels (INSEP, Hausswirth, Mujika, p.102). While natural fluctuations of cortisol are a natural and healthy response to stress, physical or otherwise, chronically elevated levels of cortisol can cause a host of negative effects. Sleep deprivation’s effect on cortisol levels is likely less than clinical cases. However, it can still cause high blood pressure, weakness, as well as sub-optimal metabolism of carbohydrates leading to weight gain (Saladin, p. 673).

Coupling with increased cortisol levels, disruption of the Autonomic Nervous System (ANS) can create even more issues in terms of energy and mood. The ANS often goes under the radar because we have no volitional control over its constituents; however, its control reaches numerous systems, including the endocrine system and cardiac muscle (Saladin, p.572). Lack of sleep can cause chronic hyperactivity of the sympathetic division of the ANS (INSEP, Hausswirth, Mujika, p.102), which is a state associated with excitation. As a result, this state will trigger consistently elevated heart rate and respiration (Saladin, p. 443.) This results in a dangerous duo with the aforementioned increased cortisol levels. This elevated sympathetic activity causes higher energy expenditure and stress levels which also serve to further increase cortisol levels, and a sensation of stress in general.

What we do know about sleep and survival, is that it is absolutely vital to maintain health from the perspective of our immune system. There is an enormous amount of evidence to date that links inadequate sleep to negative responses in the immune system. Examples of this negative effect come in the form of “increased circulating levels of proinflammatory markers” as well as decreased antibody production in response to a vaccine (Gamaldo, Shaikh, McArthru, 2012). The direct cause of sleep’s negative effect on immune function could come from a litany of mechanisms such as altered hormone secretions or general stress response, to name a few (INSEP, Hausswirth, Mujika, p.102). Ironically, these factors themselves can also be caused by sleep deprivation. Therefore, there is a significant compounding negative effect.

One example that combines factors relating to each of the areas discussed above is the effect of daylight savings time on heart health. Following the daylight savings adjustment in springtime in which we lose an hour of sleep, instances in heart attacks are increased by 24% on that day (TED, 2019).

Now that we know all of the horrors associated with poor sleeping habits, how can we improve upon them? Fortunately, the answer is quite simple, and it can be found right in the name. The key is developing habits of consistency. Setting a consistent schedule in which you go to sleep and rise at roughly the same time each day is paramount. Ideally, you will be able to maintain this habit on the weekends as well to maintain consistency. Other factors include avoiding blue light within an hour of going to sleep, avoiding excessive alcohol consumption, and avoiding caffeine in the latter parts of the day. There is no magic involved in getting good sleep, only discipline. If you want to perform at your best, both mentally, and physically; and you want to live healthy, you’d better sleep like you mean it!


  • Gamaldo, C.E., Shaikh, A.K., McArthur, J.C. (2012). The Sleep-Immunity Relationship. Neurologic Clinics 30(4), 1313-1343.
  • Institut National du Sport, de l’Expertise et de la Performance (INSEP), Hausswirth, C., Mujika, I. (2013). Recovery for performance in sport. Champaign, IL: Human Kinetics.
  • Saladin, K. (2010). Anatomy & Physiology: The unity of form and function. McGraw-Hill: New York, NY.
  • TED. (2019, June 3). Sleep Is Your Superpower / Matt Walker. Retrieved from https://www.youtube.com/watch?v=5MuIMqhT8DM
  • Why do we sleep anyway? (2007, December). Division of Sleep Medicine at Harvard Medical School. Retrieved on May 16, 202 from http://healthysleep.med.harvard.edu/healthy/matters/benefits-of-sleep/why-do-we-sleep