We all know sleep is important, but it is often under-appreciated. Sleep is a low hanging fruit to make progress in almost any goal, no matter what it may be. By tending to our sleep-related needs, we can maximize our productivity throughout the day, enhance immune system function, balance hormones, improve recovery, and overall cultivate a deeper connection with the world around us with the extra boost of energy.
The National Sleep Foundation recommends that adults ages 18-64 years old should sleep 7-9 hours a night. However, every person has a different load of stress and activity in their life. Therefore, an individual’s workload, amount of exercise, underlying sickness, or other stressors influence the amount of sleep required for adequate rest each night.
Regardless of the individual amount of sleep needed per night, if your body learns to function on low levels of energy over the course of a period of insufficient sleep, there will be less energy to facilitate recovery from daily stressors. While caffeine and other stimulants cannot substitute for sleep, but they do help to counteract some of the effects of sleep deprivation. Additionally, the body excels in managing acute damage or stress by utilizing our fight or flight system to allow us to meet challenges while performing at a high level. While it is beneficial that our bodies can adapt and function at low energy levels, chronic stress without recovery is temporary and will lead to burnout and decreased function of all bodily systems.
Not getting enough sleep, while still allowing us to function in a seemingly normal manner, impairs motor and cognitive functions. A person who is sleep deprived will typically experience reduced ability to concentrate, memory lapses, loss of energy, fatigue, lethargy, difficulty with complex thought, delayed response to stimuli, and emotional instability.
Furthermore, chronic lack of sleep has been associated with many adverse health conditions, including chronic fatigue, diabetes, high blood pressure, heart disease and even musculoskeletal injury. Studies in which subjects underwent short-term sleep deprivation to examine the immediate effects of a lack of sleep were found to have heightened blood pressure, lowered blood glucose levels and increased inflammation. It follows that long-term persistence of these symptoms could lead to more deep-rooted dysfunction. Sleep disturbances are also highly prevalent in chronic pain patients and have been shown to deteriorate the pain condition. It has been hypothesized that descending pain control may be compromised by disturbed sleep.
Sleep is the number one recovery mechanism from stress and it affects the way we look, feel and perform on a regular basis. We tend to think of sleep as a time when the mind and body shut down, but this isn’t the case. During sleep, the body is in an elevated anabolic state, meaning that repair mechanisms are used throughout the body when we are resting. Sleep is an active process during which important processing, restoration and strengthening occur.
One of the essential roles of sleep is to consolidate memories. Our brain takes in unlimited amounts of information throughout the day. While we sleep, experiences, memories and skills are processed and stored from short-term memory to long-term memory in more efficient and permanent brain regions. This results in higher proficiency and better recollection the next day.
In addition to improved memory of past information, sleep also helps us synthesize new ideas. While you are sleeping, pieces of knowledge can be pulled together from different experiences and parts of the brain to create novel concepts.
A recent study found that when subjects slept abundantly throughout the night, cellular waste byproducts that were accumulated in the interstitial space were removed. This clearance of toxins also allows the brain to function optimally the next day.
An internal biological clock, known as the circadian clock, regulates the timing for sleep in humans. The activity of this clock is coordinated by light input during the day, which promotes wakefulness, and melatonin secretion during the night, which makes us sleepy. Most hormone secretion is controlled by the circadian clock or in response to physical events.
Sleep is one the events that modify the timing of secretion of certain hormones. Hormone imbalances that occur as a result of sleep deficiency increase the prevalence of mood swings and anxiety and predispose the body to weight gain.
While we are resting, our body stimulates the parasympathetic nervous system. Lack of sleep stimulates our fight or flight system instead of the parasympathetic system, which has been associated with greater secretion of cortisol, a stress hormone. Elevations of evening cortisol levels in chronic sleep loss are likely to promote the development of insulin resistance, a risk factor for obesity and diabetes. Additionally, the regulation of leptin, a hormone released by the fat cells that signals satiety to the brain and thus suppresses appetite, is markedly dependent on sleep duration. Decreased leptin levels in individuals who lose sleep may lead to feelings of hunger, despite adequate food intake. One study that examined shorter sleep duration found decreased leptin levels to be significantly correlated with increased BMI.
Another hormone that is influenced by sleep is growth hormone. Growth hormone plays a key role in growth, body composition, cell repair and metabolism, with the highest secretion levels occuring at night. It has been hypothesized that nocturnal growth hormone increases are involved in various tissue repair mechanisms throughout the body.
Studies have shown that sleep deprivation also decreases levels of glycogen, which is the body’s principal store of energy used for mental and physical activity. Because the brain does not typically utilize fat for energy, glycogen is the only source of spare energy for brain cells. During the metabolically active wakeful period, glycogen is exhausted. Glycogen supply takes time and reduced activity to restore. Both muscle and liver glycogen levels have been shown to replenish with recovered sleep, providing our brain with the energy to function optimally.
If you are not sure how to get a good night of rest, look no further. To optimize sleep and wake up feeling refreshed, start by tackling some of the following tips in the blog post next week!
Article written by Dr. Jessica Khani, PT, DPT, CSCS
The information provided is not medical advice and is not intended to be used in place of seeking advice from a professional.
“Sleep Duration as Risk Factor for Diabetes Incidence in a Large US Sample.” Sleep Research Society. Sleep. Dec 2017. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2276127/.
“Association Between Sleep Disorders, Obesity, and Exercise: A Review.” Nature and Science of Sleep. Dovepress. March 2013. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3630986/
“How Much Sleep Do We Really Need?” National Sleep Foundation. 2018