It seems like there’s never enough time in the day to get everything done. Schedules quickly turn hectic, and sleep is often the activity that’s pushed to the back burner. However, it’s important to ensure you’re taking the time to rest, which means getting the right amount of sleep and the best quality sleep possible.
When you sleep well, you likely feel ready to take on the day. You may feel more productive, have an easier time focusing, or find your mood to be a little brighter. And these benefits aren’t just in your head. Research shows a strong connection between sleep duration, quality, and health.
Let’s dive into all the health benefits associated with sleeping well.
Sleep promotes muscle repair processes
During sleep, the body stimulates repair processes that help muscles recover from day-to-day damage. This anabolic—or building—phase typically occurs during deep sleep, which is the phase of sleep associated with the physical repair of cells and tissues. 
In deep sleep, the body releases amino acids (the building blocks of proteins) and free fatty acids that repair damaged muscles and build them back stronger. This process is especially important for those who exercise regularly and experience exercise-related muscle damage. Sleeping optimally is also associated with reduced fatigue and muscle soreness in athletes. 
Sleep is essential for cognitive functions
Sleep is critical for many cognitive functions, such as learning and memory consolidation—the process by which recent memories become long-term memories. This is because the neural connections that form long-term memories are strengthened during sleep. And studies show that getting consistent sleep is associated with improved memory. 
Conversely, a lack of sleep is associated with decreased mood and cognitive impairments.  In one study, sleep deprivation for even one full day was associated with mood disturbances and confusion. 
Sleep may promote metabolic health and blood sugar control
Sleep is linked to metabolic health in multiple ways. The first is that sleeping poorly may negatively impact blood sugar control and increase your risk for metabolic conditions. 
A suggested mechanism is that sleep deprivation alters the "hunger hormones." Leptin is a hormone that decreases your appetite, signaling that you’re full. Ghrelin is a hormone that increases your appetite, signaling that it's time to eat. Short sleep duration is associated with reduced leptin and increased ghrelin, meaning you may notice an increased appetite and decreased satiation if you don’t get enough sleep. [5,6] If this occurs during prolonged periods, you may even begin to see elevated levels of metabolic markers like fasting blood glucose and hemoglobin A1c.
The second is that having higher levels of blood sugar is also associated with poorer sleep. A 2019 study of caucasian and black Americans found that more people with prediabetes reported poor sleep than those with normal blood glucose levels. 
So improving your sleep may improve your blood sugar levels. And improving your metabolic health may improve your sleep.
Sleep can strengthen the immune system
Your immune system is charged with protecting your body from pathogens like damaged cells, bacteria, or viruses. When the body detects a pathogen, white blood cells are recruited first to expel the pathogen quickly. Then surrounding capillaries dilate, becoming barriers around the pathogen. This is known as the inflammatory response, and it works by keeping a pathogen in its place to prevent its spread to the rest of the body. The biomarker hsCRP rises in response to this inflammation. 
Studies show that getting quality sleep is associated with a strong immune system and vice versa. Researchers note that multiple pathways contribute to this relationship. While you’re asleep, many energy-consuming processes—like muscle activity and even breathing—slow down. That allows the body to divert its energy to maintain and strengthen the immune system. 
Sleep impacts body composition
Sleep quality and duration have also been linked to measures of body composition. Tissue regeneration and remodeling processes occur during sleep. So it’s not a surprising theory that adequate, quality sleep is likely beneficial for the maintenance of bodily tissues like bone, fat, and muscle.
And there’s scientific evidence to support this notion. One study conducted on middle-aged adults found that poor sleep may be a predicting factor of excess body weight.  Another study found that shorter sleep was associated with increased body fat and decreased lean body mass in women, though the finding was not found in men.  However, more research is required to determine whether there’s a cause-and-effect relationship between sleep and body composition.
Sleep may lower levels of stress
Cortisol is often referred to as the "stress hormone." During periods of stress, the body produces cortisol to initiate the fight or flight response. Cortisol levels also tend to be highest in the morning (to help wake you up) and decrease before bed. This shift in cortisol is paired with an increase in melatonin production—making you feel sleepy. However, chronic stress can interfere with this natural rise and fall of cortisol and make falling and staying asleep more challenging. 
Studies have looked at perceived stress and largely found associations indicating that higher perceived stress negatively impacts sleep duration and quality. [13,14]
Sleep may enhance longevity
Numerous studies agree that sufficient sleep helps support living a long life. One way to evaluate longevity in scientific studies is through the metric of all-cause mortality. All-cause mortality is the death rate from all causes of death for a population for a specific time period. Improving—so in this case lowering—the all-cause mortality rate is a somewhat roundabout way to measure longevity.
Large pooled analyses on sleep duration and all-cause mortality have shown that sleeping too little (less than six hours of sleep per day) and sleeping too much (more than nine hours) are associated with an increased risk of death compared to those who sleep between 6-9 hours per night.  However, the optimal sleep duration for most healthy adults is an even more narrow window at 7-9 hours per night. 
How can you track your sleep?
Fitness trackers are a convenient way to track your sleep. These watches or rings often provide information on sleep duration, REM sleep, and deep sleep and aggregate data in an app. But knowing how to interpret that data, especially in the context of other health metrics, isn’t always straightforward.
InsideTracker now syncs with Garmin, Fitbit, and Apple Watch trackers and pulls sleep (and heart rate data) to provide personalized insights on improving your sleep trends over time. In addition, InsideTracker also integrates sleep data with blood biomarker analysis and recommendations, since some blood biomarkers have a bidirectional relationship with sleep. This means that unoptimized sleep may negatively influence blood biomarkers and that some unoptimized biomarkers may negatively influence sleep.
- Optimal sleep duration for the average adult ranges from seven to nine hours a night
- Muscle building and recovery occur during deep sleep
- Sleep strengthens neural connections that improve cognitive function
- Sleep deprivation can negatively impact metabolism
- Quality sleep can help strengthen the immune system
- Low levels can help you sleep, and good sleep can help you feel less stressed
- Sleep can reduce your risk of all-cause mortality, which can mean a longer, healthier life