Sleep: The Body’s Natural Repair and Recharge Cycle

By: Jovenia Salazar Lindsay, RN, MSN, MBA, PhD Candidate 

Introduction

I had often wondered why my late father, who was extremely insistent that we, his children, go to bed early and rise early each morning, while other children in our community played late into the night. However, this was a habit he firmly impressed upon us. My father had many reasons. One was that bad elements generally were known to occur at night, and retiring early was a way to keep oneself safe. Two, our bodies would be renewed and energetic each day, and our minds active and alert when we achieve good sleep and rise early in the morning, allowing us to accomplish more during the day. More than advice, he showed us by example, retiring early each night and greeting each new day with strength, energy, and focus.

Today, science confirms what my father lived and taught: sleep is not a luxury—it is a necessity. Adequate sleep is essential for repairing the body, refreshing the mind, and supporting long-term health at every stage of life. Regardless of age, our physical bodies require sufficient rest to replenish internal reserves, enabling us to manage the daily demands and stresses we face both mentally, emotionally, and physically. Unfortunately, sleep is increasingly taken for granted in today’s digital and media-driven world. The Centers for Disease Control and Prevention reports that more than one in three adults in the United States do not get the recommended seven hours of sleep per night (Liu et al., 2016). Adding to the concern, nearly 80% of adults report losing sleep due to social media, which has been identified as a leading cause of sleep disruption, with the prevalence rising to 93% among young adults aged 18 to 25 (Ladd, 2023).

These statistics serve as a wake-up call, reminding us that sleep is not merely downtime but a biological necessity. Meanwhile, while good sleep offers numerous benefits, this article highlights three key areas of impact: the effects of sleep on our immune system and tissue repair or healing, on our brain (including memory, creative thinking, and problem solving), and on our digestive system, appetite, and metabolism.  

Sleep: Immune System, Tissue Repair or Healing

Our body is constantly under surveillance through its patrol system, which I refer to as our body’s army or immune cells.  We have what I call front-line armies (innate immune cells) and the second line of defense (adaptive immune cells). Both are important for our health and daily protection from health invaders, threats, injuries, pathogens, or infections.

When our body is invaded by threats, pathogens, infections, or injuries, our body’s front-line armies (innate immune cells), such as monocytes, macrophages, neutrophils, and dendritic cells, are always ready to fight and to help us heal any damage that has been done (Irwin, 2015). Research shows that our immune cells detect health threats for immediate removal, with the immune cells, such as macrophages, shifting to a pro-repair state to promote tissue repair and healing (Bender et al., 2025).

Additionally, our body’s second line of defense, or the adaptive immune cells, such as the T cells and B cells, are the memory builders. I like to think that during the initial invasion of our body by health threats, these memory cells are recording and taking photographs for future use. Hence, in the subsequent invasion, these memory T and B cells enable our immune system to recognize the same family of threats or pathogens more quickly in the future, allowing for a faster and stronger defense against reinfection (Irwin, 2015).

During a good night's sleep, our physical body is outwardly at rest, but our internal systems are at work. When we sleep, our innate immune cells, as well as our T cells and B cells, are strengthened and fortified, providing effective and robust immunity and protection (Irwin, 2015). Research further shows that disruption of this internal immune process can lead to prolonged inflammation and impaired healing (Bender et al., 2025). Unfortunately, prolonged sleepless nights disrupt our body’s critical immunity-strengthening process. Irwin (2015) reports that when our sleep is chronically disrupted, T cells and B cells weaken, making our immune system less effective. Meanwhile, our innate immune cells (i.e., monocytes, macrophages) become overactive, leading to increased inflammation in the body (Irwin, 2015). This means that deprivation of sleep is not only detrimental to our overall well-being but also particularly harmful to our immune cells, making us more prone to health issues and illnesses.

Sleep: Brain (Memory, Creative Thinking, Problem Solving)

I define sleep as our natural bodily process characterized by heavy or closed eyes, reduced awareness of the external environment, and a reversible state of unconsciousness that naturally returns to wakefulness. This wake-sleep cycle is regulated by our internal body clock, known as the circadian rhythm. During sleep, we undergo two phases of natural unconsciousness, termed non-rapid eye movement (Non-REM) and Rapid eye movement (REM) sleep (Brinkman et al., 2023). Non-REM is the stage of sleep that transitions from light consciousness to a deeper level of sleep, characterized by muscle relaxation, accompanied by a decrease in heart rate and body temperature (Patel et al., 2024). Next is REM, where our muscles experience temporary paralysis (muscle atonia) to prevent us from acting out our dreams, while the brain remains highly active (Brinkman et al., 2023).  A typical night usually consists of 4 to 5 complete cycles of Non-REM and REM sleep (Brinkman et al., 2023).  

Research shows that not only does good sleep, with a complete cycle of Non-REM and REM replay, solidify memories from our previous experiences through engram cells, but also prepares our brain for future experiences and learning through engram-to-be cells (Ghandour et al., 2025). Additionally, by cycling between these two stages throughout the night, the brain builds and reshapes complex knowledge, strengthening our memory, our creative thinking, and problem-solving in distinct ways (Lewis et al., 2018). This process becomes critically important for each of us to function well, particularly in challenging days, such as those faced by healthcare personnel, where critical thinking and problem-solving are vital for patient care and clinical decision-making. Further reports show that sleep deprivation, both before and after learning or experiencing events, impairs memory, weakens retention, and results in poor performance (Newbury et al., 2021).

Sleep: Digestive System, Appetite, and Metabolism)

Sleep and our internal clock (circadian rhythm) also play a surprising role in our appetite, digestion, and metabolism. There are many essential hormones involved in our appetite and digestion, but I would like to focus on two in particular: ghrelin and leptin. Ghrelin is our hunger hormone, and leptin is our appetite-suppressing hormone. Research reports that sleep and digestion are closely interconnected through our internal clock that helps regulate our appetite, gastrointestinal activity, and metabolism (Szakács, 2020). When sleep is deprived or disrupted, this balance is altered, as our ghrelin (the hunger hormone) increases and leptin (the satiety hormone) decreases, leading to increased hunger and food cravings. On a metabolic level, sleep deprivation contributes to impaired glucose utilization, increased caloric intake, and even leptin resistance, all of which are linked to obesity and metabolic disorders. (Szakács, 2020).  Additionally, Reutrakul & Van Cauter (2018) report that poor or irregular sleep disrupts the body’s internal clock, increasing the risk of obesity, diabetes, and other metabolic disorders. In short, our lack of sufficient sleep not only drives us to eat more but also disrupts how our food is digested and metabolized, ultimately compromising both our digestive health and long-term metabolic balance (Szakács, 2020).  

Putting It All Together

Adequate sleep is our body’s most natural way to repair and recharge. It restores our energy, strengthens our health, and sharpens our minds. Long before science confirmed the importance of sleep, scripture gave this wise counsel: “Cease to be idle… retire to thy bed early, that ye may not be weary; arise early, that your bodies and your minds may be invigorated” (Doctrine and Covenants 88:124). My father lived by these words without even learning about the scripture and science of sleep, and I now see how powerfully they align with modern research. When we honor both our physical body’s need for good sleep and the mind’s need for renewal, we not only live healthier lives but also perform our daily grind with smiles along with clear decisions, and move forward with timeless wisdom that will last for generations to come.

References

Bender, E. C., Tareq, H. S., & Suggs, L. J. (2025). Inflammation: A matter of immune cell life and death. NPJ Biomedical Engineering, 2(7). https://doi.org/10.1038/s44385-025-00010-4

Brinkman, J. E., Reddy, V., & Sharma, S. (2023, April 3). Physiology of sleep. In StatPearls [Internet]. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK482512/

Ghandour, K., Haga, T., Ohkawa, N., Fung, C. C. A., Nomoto, M., Fayed, M. R., Asai, H., Sato, M., Fukai, T., & Inokuchi, K. (2025). Parallel processing of past and future memories through reactivation and synaptic plasticity mechanisms during sleep. Nature communications, 16(1), 3618. https://doi.org/10.1038/s41467-025-58860-w

Irwin M. R. (2015). Why sleep is important for health: a psychoneuroimmunology perspective. Annual review of psychology, 66, 143–172. https://doi.org/10.1146/annurev-psych-010213-115205  

Ladd, M. (2023, June 6). Social media dominates pre-bedtime routine for U.S. adults, survey finds. Sleep Foundation. https://www.sleepfoundation.org/sleep-news/how-does-social-media-affect-sleep#references-196656

Lewis, P. A., Knoblich, G., & Poe, G. (2018). How Memory Replay in Sleep Boosts Creative Problem-Solving. Trends in cognitive sciences, 22(6), 491–503. https://doi.org/10.1016/j.tics.2018.03.009

Liu, Y., Wheaton, A. G., Chapman, D. P., Cunningham, T. J., Lu, H., & Croft, J. B. (2016, February 19). Prevalence of healthy sleep duration among adults — United States, 2014. Morbidity and Mortality Weekly Report, 65(6), 137–141. https://www.cdc.gov/mmwr/volumes/65/wr/mm6506a1.htm

Newbury, C. R., Crowley, R., Rastle, K., & Tamminen, J. (2021). Sleep deprivation and memory: Meta-analytic reviews of studies on sleep deprivation before and after learning. Psychological bulletin, 147(11), 1215–1240. https://doi.org/10.1037/bul0000348  

Patel, A. K., Reddy, V., Shumway, K. R., & Araujo, J. F. (2024, January). Physiology, sleep stages. In StatPearls. StatPearls Publishing. Physiology, Sleep Stages - StatPearls - NCBI Bookshelf

Reutrakul, S., & Van Cauter, E. (2018). Sleep influences on obesity, insulin resistance, and risk of type 2 diabetes. Metabolism, 84, 56–66. https://doi.org/10.1016/j.metabol.2018.02.010 

Szakács, Z. (2020). The relationship between sleep and digestion (Vol. 6, Issue 3). Central European Journal of Gastroenterology and Hepatology. https://doi.org/10.33570/CEUJGH.6.3.106

The Church of Jesus Christ of Latter-day Saints. (1835). Doctrine and Covenants. https://www.churchofjesuschrist.org/study/scriptures/dc-testament/dc/88?lang=eng&id=124

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