Sleep deprivation influences nearly all measures of performance
I cringe every time I hear the phrase “I’ll sleep when I’m dead” and fortunately, that reaction is becoming more common. Over the past 5–10 years, sleep has been getting a lot more attention. While we may, for the most part, be past the days of “sleep is for weaklings,” proudly acknowledging how little we average on a nightly basis, sleep still falls far down the priority totem pole for many people.
Sleep can be divided into five stages — one with rapid-eye-movement (REM) and four without — which occur across roughly 90-minute sleep cycles. While REM sleep is associated with dreams, non-REM is the period for energy conservation and nervous system recuperation.[1] During non-REM sleep, our body releases hormones, increases the synthesis of protein, and mobilizes free fatty acids to provide energy. As you will see shortly, sleep has a massive impact on diet and exercise, recovery from injury, and cognitive performance.
The level at which sleep loss becomes a problem
There are two primary categories of sleep loss. Sleep restriction (SR) refers to a partial disturbance of their normal sleep-wake cycle. This is the milder category of sleep loss. (Tuesday after the Superbowl)
Sleep deprivation (SD), meanwhile, refers to extreme cases of sleep loss, where both quality and quantity are significantly affected. (First few weeks after a child is born)
It is important to understand the duration of SD as it will impact the time it takes to recover and normalize your sleep. Unfortunately, we cannot bank our sleep, and sleeping in late on a random Saturday will not erase chronic sleep debt. All of the impacts of sleep I am about to cover typically occur in a state of SD. SR may lead to some changes as well, but they are typically milder and can be quickly reversed or compensated for.[2]
SLEEP INFLUENCES OUR HORMONE REGULATION
Let’s start with some of the hard science and the reasons why sleep is so imperative. Sleep has a large impact on our control of anabolic hormones (testosterone, growth hormone (GH), IGF-1), catabolic hormones (cortisol), and ‘hunger’ hormones (leptin and ghrelin). Our glucose tolerance and insulin secretion are modulated by the sleep-wake cycle.
This mix of hormones will impact both diet and exercise effectiveness. Additionally, sleep has a substantial impact on cognitive functioning. The changes in hormonal levels and cognitive functioning are impacted not only by the total duration of our sleep but the quality of our sleep as well.
Shorter sleep duration is associated with greater disturbances in these hormonal and metabolic variables. For example, ;eptin levels — which directly affects feelings of satiety — are lowest when we are in a state of sleep debt, signaling the brain an unnecessary need for extra caloric intake. The desire for snacking intesifies when we are tired.
Evening cortisol levels are highest when we are in a state of sleep debt and elevated cortisol levels can be detrimental to our ability to recover after physical activity.
HOMA (insulin resistance measure) levels post-breakfast are the highest in a state of sleep debt indicating a decrease in glucose tolerance and insulin sensitivity. Bascially, we are more susceptible to blood sugar spikes (which is a bad thing) when we are sleed deprived.
As you can see, our sleep duration and quality can significantly impact the effectiveness of dietary interventions. I’m only getting started
SLEEP INFLUENCES DIETARY EFFECTIVENESS
Insufficient sleep will lead to greater fat retention while stunting muscle development or potentially lead to muscle wasting.
A study by Nedeltcheva et al. took two matched groups and controlled their diet (10% caloric restriction) and exercise to be the same. The only variable that differed was the amount of sleep they received: 8.5 versus 5.5 hours. At the end of the trial, each group lost the same amount of weight, however, the group that slept 8.5 hours lost a 50/50 fat to muscle ration while the 5.5 hour group lost a 20/80 fat to muscle ratio. [3]
During NREM sleep, anabolic hormones are stimulated which increases the synthesis of protein and mobilizes free fatty acids for energy production.[1] This method of preventing amino acid catabolism (which requires a breakdown of muscle) is inhibited in a state of sleep debt. So, instead of using fat stores for energy when we sleep and building muscle, we break muscle down.
The scale will say your diet is working, but the mirror will be less kind if you are lacking sleep.
SLEEP IS NOT OPTIONAL FOR RECOVERY OR HIGH PERFORMANCE
Achieving a full sleep cycle is vital as each stage is a trigger for different physiologic events.
As stated, specific functions occur at each stage of sleep. For example, learning and motor memory, resulting from plastic reorganization within the brain requiring increased activation of the primary motor cortex, are associated with slow-wave sleep.[4] More specifically, it has been suggested that motor skill improvements are significantly associated with stage-2 non-REM sleep.[5] Sleep is not only necessary for remembering information, but for improving movement skills such as improving golf swing or playing the piano.
As mentioned earlier, SR and SD having different impacts on performance and recovery. For example, SR does not appear to affect single bouts of aerobic or strength performance. However, some evidence suggests sport-specific skill execution, submaximal strength, and muscular and anaerobic power decline following SR.[1]
Furthermore, SR resulting from less than 7 hours of sleep can impair alertness, reaction time, memory, and decision making. Individuals report heightened levels of sleepiness, depression, confusion, and poorer overall mood states as well.[1] The negative mood states have been linked to over-training.
While SD has some conflicting evidence as well, there remains ample consistency and strength to signify SD can significantly impact athletic performance and recovery. SD increases metabolic demand, perceived effort, restoration of muscle glycogen, and increased sympathetic and decreased parasympathetic cardiovascular modulation.[1] Basically, we perform worse physically and it is more challenging to recover.
Greater total sleep loss results in poorer overall mood states, increased fatigue, sleepiness and confusion, decreased vigor and liveliness, heightened depression, and decreases in logical reasoning, coding, and decision making. Both the speed and accuracy of cognitive, auditory, and memory tasks are impact SD as well.[1] Suffice it to say, SD will dramatically impact our effectiveness at our jobs, school, and training.
So, in summary, when we in sleep debt, through poor quality and/or insufficient duration, we struggle to recover and heal, our cognition significantly declined, our regulation of glucose diminishes, and we are hungrier. Not good.
HOW MUCH SLEEP DO WE NEED?
There is no universal number of hours. The typical range for adults is 7–9, for adolescents 8–10, and for young children 10–12.[10–12] Sleep duration varies depending on genetics, age, and stressors (e.g. activity level, job demands, stress levels, etc.). The best way to know how much sleep you need is to allow your body to wake up on its own. Yes, I mean without an alarm clock. An alarm clock should serve as a backup. Ideally, your circadian rhythm and routine will lead you to wake around the same time every day.
For example, I have not slept through the night past 7:15 in two years. Why is that? Because my 2-year old son has not slept past 7:15 his entire life. Now, I could easily go back to sleep (i.e. when on vacation sans my son), but those are one-off occasions.
Our bodies are finely tuned, complex machines that know when they receive optimal sleep. Here comes the uncomfortable recommendation. If you wake up 20 minutes before your alarm goes off, that does not mean say a quick prayer of thanks and close your eyes for 20 more glorious minutes; it means get out of bed. Contrary to anecdotal experiences and common belief, the snooze button is not your friend. You are better off establishing a routine by going to bed and waking at the same time every day.
The true value of sleep comes from achieving deep slow-wave sleep and moving through the cycles sequentially as they trigger the hormonal releases. The extra 20 minutes are not truly helping and can impair your normal timing. Instead, set the alarm for when you absolutely must be out of bed by. If you wake sooner, then you are likely more well-rested (your body made the decision) and you have more time on your hands. Double Bonus. One final note on sleep duration, you cannot make up for sleep debt with one solid night of sleep. If you are in chronic sleep debt, it takes up to nine consecutive days of adequate quality and duration of sleep to recover.[12]
SUFFICIENT HOURS IS NOT ENOUGH
Note that I have been referring to both quantity and quality of sleep. Simply lying in bed for 8 hours does not mean you received 8 hours of sleep. If you are tossing and turning all night, wake multiple times, or lie in bed for longer than 30 minutes before falling asleep, the quality is not great. You feel this when you wake in the morning.
You know you are achieving adequate duration and quality of sleep when you wake without fatigue or the immediate desire for a gallon of coffee. So how do we achieve high-quality sleep?
There are many anecdotal answers to the question (type of mattress, number of pillows, etc.) but also many evidence-based recommendations. One of the primary needs is a dark room. Light triggers the timing of our sleep-wake cycle through melatonin release.[13, 14] We can go in-depth on the impact this has on night-shift workers, time zone, where you live, etc. but I will focus on the sleeping environment.
The next is having either no noise or a “white noise” (e.g. a fan, a sound machine with repeating noise such as waves, rain, or actual white noise). For those who have put two and two together, yes, TV in the background is a solid ‘no-go’ for achieving good sleep. As much as you may think you are drowning out the noise (same goes for music), you have differing levels of cognitive function and awareness that challenges your ability to fall asleep and stay asleep. [15, 16] Outside the bedroom environment, you must consider the hours leading up to bedtime.
Avoid blue light as this too affects your circadian rhythm and timing of melatonin release. This means no computer, phone, or TV screens at least an hour prior to bed. Avoid caffeine at least 6 hours before bed (the caffeine half-life).[17] Avoid sleep aids (unless specifically prescribed by a physician, this blog is not intended to provide medical advice) and alcohol prior to bed as these impair sleep quality. While they may assist with falling asleep, they can alter our sleep cycles and impede our ability to achieve deep slow-wave sleep, however, some new drugs are attempting to improve slow-wave sleep. [18, 19] If consuming alcohol at night, it is best to have a moderate amount (e.g. 1 glass of red wine) with a meal as alcohol prior to sleep is associated with poor quality. [20]
Speaking of meals, avoid food consumption at least an hour prior to bed and avoid midnight snacks.[2, 11] I know, there are plenty of anecdotal experiences that fly in the face of several of these recommendations and the food one is potentially the straw the broke the camel’s back. Yes, going to bed hungry can be miserable and at times seem impossible. There are several issues with a meal immediately before bed going to bed:[21]
Our insulin sensitivity plummets prior to sleep and during sleep (without getting into too much detail, this is a primary reason why midnight snacking is on the ‘do not do’ list) leading to increased fat storage and exacerbation of pain due to the spikes in blood glucose.
Our body will be focused on digestion which can disturb our sleep quality.
Meal timing can impact our circadian rhythm.
INTEGRATING SLEEP EDUCATION INTO A PLAN OF CARE
By no means is this an exhaustive list of the methods to positively influence sleep. Some readers may vehemently challenge a few of the listed strategies. A couple of notes on this.
Sleep research lacks the robustness of other medical fields. There is conflicting evidence and we do not have a perfect understanding of sleep. Also, sleep is impacted by many individual variables such as genetics, stress, and demands of daily life. Some of the recommendations are unrealistic (night shift worker, a parent with kids who think sleep is more of a suggestion than a rule, living next to people who love randomly shooting off fireworks throughout the year, etc.) and have led to individual adaptations. Lastly, anecdotal evidence can often reign supreme.
Bear in mind that “getting by” is not the same as optimal. Obtaining 8+ hours of sleep will come at a cost. It is up to you and your patients whether the added time dedicated to preparing for and obtaining optimal sleep is worth it.
Sleep is often overlooked and often the missing link to health, performance, and recovery. These recommendations will not yield immediate results. Like many aspects of health, it requires consistency to adapt. In the end, we can not will ourselves to overcoming poor sleep. Determination is not enough. Furthermore, the added hours obtained by skipping sleep do not make up for the decrease in performance.
Sleeping may feel like a waste of time, but obtaining adequate sleep will greatly improve your effectiveness and efficiency when awake.
References
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