Why do we need sleep?
People who can get by on four hours of sleep sometimes brag about their strength and endurance. But recent scientific studies show that a lack of sleep causes many significant changes in the body and increases your risk for serious health concerns such as obesity, disease, and even early death.
Sleep is an important function for many reasons. When you sleep, your brain signals your body to release hormones and compounds that help:
decrease risk for health conditions
manage your hunger levels
maintain your immune system
But you can’t catch up or make up loss of sleep. In fact, consistently sleeping more than six to eight hours a night can negatively impact your health. Read on to learn why seven to eight hours of sleep a night is ideal.
Seven to eight hours for longevity
The healthy amount of sleep for the average adult is around seven to eight hours each night.
Researchers in the United Kingdom and Italy analyzed data from 16 separate studies conducted over 25 years, covering more than 1.3 million people and more than 100,000 deaths. They published their findings in the journal Sleep. Those who generally slept for less than six hours a night were 12 percent more likely to experience a premature death. People who slept more than eight to nine hours per night had an even higher risk, at 30 percent.
Researchers also found that people who reduced their sleep time from seven hours to five hours or less had 1.7 times the risk of death from all causes.
Sleep helps manage your appetite
Poor sleep habits can increase the body’s energy needs. At night, movement and need for calories is reduced. But when you are sleep-deprived, your brain will release chemicals to signal hunger. This can lead to eating more, exercising less, and gaining weight.
Researchers conducting a study of almost 5,000 Japanese adults with type 2 diabetes found that those who slept fewer than 4.5 hours or more than 8.5 hours had a higher body mass index (BMI) and higher A1C values. An A1C is a measurement of a person’s average blood sugar levels over the course of three months. Those who slept between 6.5 and 7.4 hours a night had the lowest A1C levels of all the participants.
Sleep deprivation also affects children. A 2014 study showed that children who slept less had an increased risk for obesity and high BMI. These risks can affect children as they mature.Sleep helps your immune system function
When you sleep, your immune system releases compounds called cytokines. Some cytokines have a protective effect on your immune system by helping to fight inflammation and infection. Without enough sleep, you may not have enough cytokines to keep from getting sick.
A 2013 research study found that sleep restrictions increase the amount of inflammatory compounds in a person’s body. These are the same compounds associated with conditions like asthma and allergies. The researchers studied people who had long-term sleep deprivation as well as limited sleep deprivation of four to five hours a night for a week. In both cases, the researchers found that the participants’ immune systems were affected by lack of sleep.
Sleep helps your memory
In addition to helping you focus, sleep helps protect and strengthen your memory. Research shows that sleeping after learning can help with memory retention. It also reduces interference from external events.
People who are sleep-deprived:
have a harder time receiving information due to the brain’s overworked neurons
may interpret events differently
tend to have impaired judgement
lose their ability to access previous information
It’s important to get seven to eight hours of sleep so that you can experience all the sleep stages. No one stage is responsible for memory and learning. Two stages (rapid eye movement and slow wave sleep) contribute to:
Read more about the benefits of sleep »
Lack of sleep increases disease risk
Lack of sleep is a public health problem, according to the Centers for Disease Control and Prevention (CDC). It’s known to be a contributing factor for many chronic health conditions, including:
obstructive sleep apnea
Sleep is a habit, just like eating healthy and exercise. While everyone misses a few hours of sleep sometimes, chronic lack of sleep is part of an unhealthy lifestyle and can increase your risk for serious health concerns.
Having a poor work-life balance, stress, and worry can all affect how much and how well a person sleeps. These kinds of stressors can lead to further inflammation and health problems in addition to lack of sleep.
How to get more sleep
The recommended seven to eight hours of sleep is mainly for adults, including older adults. Younger people may need more sleep. See the table below for the recommended amount of sleep by age.
Age Recommended hours of sleep per day
Infants 16-18 hours
Preschoolers 11-12 hours
Elementary at least 10 hours
Teens 9-10 hours
Adults (including seniors) 7-8 hours