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Dean Sherzai, M.D., MPH, MAS Ayesha Sherzai M.D.
Dean Sherzai, M.D., MPH, MAS Ayesha Sherzai M.D.

Why Sleep Is the Most Important Part of Your Day

Restorative sleep promotes accelerated brain growth.

“There will be sleeping enough in the grave,” or in other words, “There will be plenty of time to sleep once you’re dead.” It’s a famous quote, one that’s often attributed to Benjamin Franklin, among others. Whoever said it, though, is wrong. Science has shown undeniably that sleep is essential to our health and longevity.

Sleep is the body’s time to restore itself, allows for growth and development, and is necessary for our body’s immune system, amongst other important functions. Even without an in-depth understanding of the effects on the body at a biological level, most of us realize that sleep is a critical component that every living thing needs to survive (with the exception of some species like sharks, which do not sleep as humans do but instead have active and restful periods).

Whether we’re able to function on a few hours a night or commit to a solid nine hours of restful slumber, we need sleep for more than just survival—and today’s scientific proof overwhelmingly shows us that we all need to make sleep a priority.

Research from Harvard University has found that a lack of quality sleep affects our mood, motivation, judgment, and perception of events—which includes our memory. In fact, there is evidence that links poor sleep habits to increased rates of dementia. Losing sleep also has a direct impact on how we learn and retain information.

Sleep directly affects how we take in new information (acquisition), how we sort and amalgamate information (consolidation), and our ability to access this information consciously or unconsciously (recall). The Harvard study points out that these steps “are necessary for proper memory function,” and “many researchers think that specific characteristics of brain waves during different stages of sleep are associated with the formation of particular types of memory.”

Consider the last time you got a poor night’s sleep. How did you feel the next day? Were you more irritable? Did you feel sluggish or have difficulty concentrating? Perhaps you forgot certain details or even something someone said to you earlier that day. That’s due in part because your brain didn’t have the time it needed to cleanse and restore itself, reset your memory, and reboot all of the other critical functions of your body, including your immune system and metabolism.

It’s no coincidence that you feel a drop in energy or sometimes develop a cold after a poor night of sleep. Like a battery, your body hasn’t had the proper opportunity to recharge itself. In fact, John Hopkins Medicine notes that you’re three times as likely to catch a cold without sufficient rest.

They also state that you’re more likely to have cravings for sweet, salty, and starchy foods and that if you regularly get five hours of sleep a night or less, you have a 50 percent higher risk for obesity. With poor sleep, the risk for Type-2 diabetes triples, and the risks of developing heart disease, and high blood pressure increase.

In a 2017 study published through the U.S. National Institute of Health’s National Library of Medicine (NIH/NLM), those with sleep deprivation or sleep disruption also had an increased risk of developing:

  • Depression and anxiety
  • Hypertension
  • Cancer
  • Other metabolic disorders
  • An overall absence of habitual exercise

The study found that “sleep disruption is associated with increased activity of the sympathetic nervous system and hypothalamic—pituitary—adrenal axis, metabolic effects, changes in circadian rhythms, and proinflammatory responses. In otherwise healthy adults, the short-term consequences of sleep disruption include increased stress responsivity, somatic pain, reduced quality of life, emotional distress and mood disorders, and cognitive, memory, and performance deficits.”

There is more to sleep than what we perceive as just shutting off the brain. In actuality, the brain is still at work during sleep as it cycles through two main types of sleep: REM (Rapid Eye Movement) sleep and non-REM sleep. You’ve probably heard of REM sleep before and may know that it functions as the more beneficial cycle. However, new research from John Hopkins Medicine suggests that non-REM is more important for learning and memory restoration and may be the most restorative of the two cycles overall. As we sleep, we rotate through these two cycles about four to five times.

Researchers also point to the efficiency of the brain to purge waste products from brain cells during sleep. In a Wired article about the science of prioritizing sleep, Aric Prather, a sleep scientist at UCSF, says, “sleep is so critical for so many parts of our body and mind. It strengthens the immune system and helps regulate metabolism. It can clear out toxins that build up in the brain and prevent neurodegenerative diseases. Sleep is like the dishwasher of the brain.”

Unfortunately, there are many external factors that literally keep us up at night, and getting quality, stable sleep can be a challenge for many. Whether you’re dealing with a new baby, an existing health condition, work stress, family matters, or other problems that make it difficult to shut off at bedtime, the short and long-term effects of not getting enough sleep are prevalent enough that scientists like Prather are devoting their entire careers to studying sleep to understand it and help more people sleep better.

“When we look across all of the data that is available on sleep and health and sleep and psychiatric illness, the largest risk is when people get five hours of sleep or less,” says Prather in a video segment called Five Hours. “We’re still uncovering new things every day about how sleep works, but despite that, all of us know that sleep is fundamental to our health. I’m excited for sleep to raise its profile among other health behaviors and get the investment and care that it needs.”

If you’re experiencing prolonged sleep difficulties, reach out to and work with your primary care physician on a strategy to address any underlying health concerns to help optimize your sleep. Your total health depends on it.


Krause, A. J., Simon, E. B., Mander, B. A., Greer, S. M., Saletin, J. M., Goldstein-Piekarski, A. N., & Walker, M. P. (2017). The sleep-deprived human brain. Nature Reviews Neuroscience, 18(7), 404.‏

Peter-Derex, L. (2019). Sleep and memory consolidation. Neurophysiologie Clinique, 49(3), 197-198.‏

Nedergaard, M., & Goldman, S. A. (2016). Brain drain. Scientific American, 314(3), 44-49.‏

About the Author
Dean Sherzai, M.D., MPH, MAS Ayesha Sherzai M.D.

Dean Sherzai, M.D., Ph.D., is a co-director of the Alzheimer’s Prevention Program at Loma Linda University.
Ayesha Sherzai, M.D., a co-director of the Alzheimer’s Prevention Program at Loma Linda University.

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