Why Does A Lack of Sleep Affect Performance?
By Michelle Zhang, Wellness Writer 
Dr. Jennifer Miller, PT, DPT
Dr. Jennifer Miller is an outpatient physical therapist. She earned her Doctor of Physical Therapy from Elon University, and a Bachelor of Science in Health Science from Minnesota State University-Mankato. She...Read more
The immediate effects of sleep deprivation are obvious—it’s hard to keep our eyes open, our thinking feels slower, and we pay less attention. The impact of chronic sleep deprivation is more subtle and severe and can lead to issues such as diabetes or weight gain.
We’ve all had a night of inadequate sleep or no sleep, and have suffered for it the next day. In this article, we discuss how our sleep cycle works, how many hours of sleep we need, the negative effects of missing sleep, and how we can work on getting a better night’s rest.
How Do We Sleep?
Our bodies’ circadian rhythm governs our sleep-wake cycle. Natural and environmental factors keep our internal clocks on track—the biggest cue for our bodies to wake up is daylight.
When we sleep, we cycle through four stages of sleep, consisting of rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. We sleep lightly in the first stage, then fall into a deeper sleep with the next two stages. REM sleep is the fourth stage, and when we dream—the longer we’re asleep, the more time we spend in the REM stage.
Much of our body recovery happens in the deep sleep stages, so getting less sleep can impact tissue, bone, and muscle repair.
How Much Sleep is Enough?
Most adults need seven to nine hours of sleep. However, several life factors can influence the amount of sleep you need.
- Young adults need the same amount (the standard seven to nine hours) of sleep as they age; seniors 65 or older, however, tend to sleep lighter and for shorter periods.
- Athletes need an extra hour or two—they should strive for 10 hours of sleep.
- Those who frequently wake in the night due to sleeping disorders or other problems will need a few extra hours to make up for lost sleep.
A sign you’re getting enough sleep is that you can wake up without an alarm clock at the same time every day.
General Effects of Sleep Deprivation
The consequences of sleep deprivation are more than just missing out on the benefits of a good night’s sleep. Extended wakefulness can have a deleterious effect on our bodies.
Decreased Cognition
Scientists are still learning how a lack of sleep impacts our cognition, but it’s widely agreed that sleep deprivation slows reaction time and negatively affects alertness and attention.
Driving when your thinking is impaired can have dangerous consequences. A 2017 review noted that many who are involved in sleep-related crashes are between the ages of 18 to 24 years old because of “decreased sleep opportunity, lower tolerance for sleep loss, and ongoing maturation of brain areas associated with driving-related decision making.”
Sleep deprivation also impacts worker productivity; a 2011 survey found workers with insomnia lost a little more than 11 days of work due to poor sleep patterns.
Impacts on Diet
Not getting enough sleep can change your responses to food. A 2014 study found that participants at a normal weight who slept only four hours each night found unhealthy food more appealing than those who slept nine hours.
There’s also evidence people eat more when they’re sleep-deprived. Many studies link weight gain with sleep deprivation.
Gaining weight increases the risk of obstructive sleep apnea and other health conditions such as type 1 and type 2 diabetes and cardiovascular disease.
Increased Stress
A 2017 study found poor sleep habits correlated with higher levels of blood pressure and increased amounts of cortisol, also known as the stress hormone. These raised levels may be why many people feel so irritable when they don’t get enough sleep.
A 2018 study measured the cortisol levels and subjective stress levels of adults between 18 and 72 years after sleep loss. Results showed higher stress levels due to sleep deprivation. The study also found that age did not affect sleep deprivation symptoms—we need to get a good amount of sleep no matter how old we are.
Decreased Body Immunity
As a 2017 review explained, the “human immune system and sleep both are associated and influenced by each other.” When we lose sleep, our bodies are more susceptible to disease.
Conversely, we try to sleep more when we’re sick to boost our bodies’ defenses.
Effects on Athletic Performance
In the midst of the COVID-19 pandemic, new research has emerged about the effect of sleep deprivation and sleep schedules on athletes. Dr. Elise Facer-Childs from the Turner Institute for Brain and Mental Health headed a study highlighting the importance of consistent sleep schedules. During the COVID-19 lockdowns, researchers found athletes had more consistent sleep schedules compared to before, when they would train one day, then rest the next (this is called “social jetlag”).
Higher social jetlag is associated with poorer sleep quality, so athletes and their coaches should take care to establish more consistent sleep schedules and good sleep hygiene habits, such as reducing screen time before bed. The study noted that, “Where possible, athletes should be given flexibility over timing of training for greater consistency between work and free days, and an effort should be made to increase the frequency of training and social interaction.”
Athletes who are “night owls” should pay special attention to their sleep patterns, as the study found their mental health was more negatively affected than athletes who were “morning people.”
In addition, some studies have found athletes who skip out on sleep are at increased risk of injury.
A 2014 study surveyed more than 100 student-athletes and compared the data with the athletic department’s injury records. Athletes who slept for less than 8 hours were more likely to be injured.
“Adequate sleep can easily become compromised as student-athletes try to balance the multiple demands on their time,” a 2017 review noted.
Insufficient sleep also impacts the recovery of muscle injuries, as a 2019 study found. Sleep deprivation reduces protein synthesis, which limits muscle restoration.
“While most of my patients are not athletes, sleep still has a major impact on their performance during physical therapy (PT),” says physical therapist Dr. Jennifer Miller. “If they are sleep deprived during a PT session, we typically have a less productive session. They require more rest breaks, more time to learn or recall exercises, and their coordination can be negatively impacted. That’s why I strongly encourage my patients to practice good sleep hygiene.”
Effects of Sleep Deprivation
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Getting a Better Night’s Sleep
If you struggle to fall asleep or frequently wake in the night, you can optimize your schedule and bedroom for better sleep.
Establish and Stick to a Schedule
Establish a bedtime and wake time routine and keep to it, even on weekends—sleeping in can make it more challenging to get your sleep schedule back on track.
Try to exercise early in the day, as vigorous workouts out late in the evening may prevent you from falling asleep due to an increased heart rate. If the evening is your best workout time, then avoid strenuous exercise at least an hour before bed.
Cut out caffeine up to six hours before bed, as it can have a significant impact on how much sleep you get.
Set a Bedtime Routine
Turn off your electronics an hour or two before bedtime. If possible, keep all electronics such as a phone, tablet, computer, and TV out of your bedroom.
If worries creep up on you as you try to fall asleep, then take 15 minutes before bed to write down any stressful situations you’re facing and possible solutions.
Take a warm bath or shower 90 minutes before your bedtime to relax and cool down. The warm water increases blood flow to your hands and feet, which disperses body heat and lowers your core temperature. A cooler body temperature can make it easier to fall asleep.
Make Your Bedroom Conducive to Sleep
If you can, reserve your bedroom for sleep only—using your bedroom for exercise or work can distract you from thoughts of sleep at bedtime.
Sleep on a quality mattress for a good night’s rest. If your mattress is sagging or lumpy, it’s time to replace it.
Darken your bedroom. Use blackout curtains and an eye mask, and turn your clock to the wall, so the LED display doesn’t keep you awake. Turning your clock away also prevents anxious clockwatching when you’re trying to sleep.
Keep your bedroom cool. The room temperature should be between 60 to 75 degrees Fahrenheit, according to Harvard Medical School. If the cold wakes you up, raise the thermostat a couple of degrees. A cooling mattress also promotes a low body temperature for better sleep.
Dealing with Sleeplessness
If sleep eludes you, don’t get frustrated. Stress and anxiety lead to more lost sleep.
Get out of bed and relax with a cup of herbal tea. Read a few pages in a favorite book. Keep the lights dim and return to bed when you feel sleepy.
Adjusting Your Sleep While Traveling
When traveling between time zones, try to give yourself an extra day to adjust and overcome the first-night effect. Many do not get enough sleep the first night in a new environment, as the brain tells them to keep their guard up in a strange place.
Get a good night’s sleep before you travel as well—many travelers sleep only five hours the night before a trip.
Did We Help?
Missing one night of sleep is survivable, but the effects of consistent sleep loss can add up over time. A bedtime routine and a restful environment can help you fall asleep more quickly and stay asleep. Getting good sleep is essential for athletic performance.
If sleep loss is a frequent issue, you may wish to talk to your doctor— you might have a sleep disorder or other health condition.
This article is for informational purposes and should not replace advice from your doctor or other medical professional.
Michelle Zhang, Wellness Writer
Michelle Zhang is a regular contributor to our Zoma blog and is our go-to sleep researcher. In her time with Zoma, Michelle has researched and published many articles on widespread sleeping habits and troubles. In her time outside of Zoma, Michelle is an occupational therapist and long-distance runner. She believes leading a healthy lifestyle is the key to getting better sleep at night. Michelle's work has been featured on Men's Journal, The Frisky, and The Mighty.
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