Sleep plays a vital role in good health and affects your well-being throughout life. The way you feel while you are awake depends in part on what happens while you are sleeping.
During sleep, your body is working to support healthy brain function and maintain your physical health. In children and teens, sleep also helps support growth and development. Getting inadequate sleep over time can raise your risk for chronic health problems. It can also affect how well you think, react, work, learn, and get along with others.
Learn how sleep affects your heart and circulatory system, metabolism, respiratory system, and immune system and how much sleep is enough.
1. Heart and circulatory system
When you fall asleep and enter non-REM sleep, your blood pressure and heart rate fall. During sleep, your parasympathetic system controls your body, and your heart does not work as hard as it does when you are awake. During REM sleep and when waking, your sympathetic system is activated, increasing your heart rate and blood pressure to the usual levels when you are awake and relaxed. A sharp increase in blood pressure and heart rate upon waking has been linked to angina and heart attacks.
People who do not sleep enough or wake up frequently may have a higher risk of:
- High blood pressure
- Ischemic heart disease
Your body makes different hormones at different times of day. This may be related to your sleep pattern or your circadian clocks. In the morning, your body releases hormones that promote alertness, such as cortisol, which helps you wake up. Other hormones have 24-hour patterns that vary throughout your life; for example, in children, the hormones that tell the glands to release testosterone, estrogen, and progesterone are made in pulses at night, and the pulses get bigger as puberty approaches.
The way your body handles fat varies according to various circadian clocks, including those in the liver, fat and, muscle. For example, the circadian clocks make sure that your liver is prepared to help digest fats at appropriate times. Your body may handle fat differently if you eat at unusual times.
Studies have shown that not getting enough quality sleep can lead to:
- Increased levels of hormones that control hunger, including leptin and ghrelin, inside your body
- Decreased ability to respond to insulin
- Increased consumption of food, especially fatty, sweet, and salty foods
- Decreased physical activity
- Metabolic syndrome
All of these contribute to overweight and obesity.
4. Respiratory and immune systems
During sleep, you breathe less often and less deeply and take in less oxygen. These changes can cause problems in people who have health problems such as asthma or chronic obstructive pulmonary disease (COPD). Asthma symptoms are usually worse during early morning sleep. Likewise, breathing problems in people who have lung diseases such as COPD can become worse during sleep.
Sleep also affects different parts of your immune system, which become more active at different times of day. For example, when you sleep, a particular type of immune cell works harder. That is why people who do not sleep enough may be more likely to get colds and other infections.
5. Problems with thinking and memory
Sleep helps with learning and the formation of long-term memories. Not getting enough sleep or enough high-quality sleep can lead to problems focusing on tasks and thinking clearly. Sleep deprivation and deficiency also affects performance of daily activities, including driving and schoolwork.
So how much sleep is enough?
Experts recommend that adults sleep between 7 and 9 hours a night. Adults who sleep less than 7 hours a night may have more health issues than those who sleep 7 or more hours a night. Sleeping more than 9 hours a night is not necessarily harmful and may be helpful for young adults, people who are recovering from sleep deprivation, and people who are sick.
How much sleep children should get depends on their age. Sleep experts consider naps to be appropriate for children under age 7.
The recommended hours of sleep, including naps, for different ages:
- For newborns younger than 4 months, sleep patterns vary widely.
- Babies 4 months to 1 year old should sleep 12 to 16 hours per day.
- Children 1 to 2 years old should sleep 11 to 14 hours per day.
- Children 3 to 5 years old should sleep 10 to 13 hours per day.
- Kids 6 to 12 years old should sleep 9 to 12 hours per day.
- Teens 13 to 18 years old should sleep 8 to 10 hours per day.
Talk to your doctor or your child’s doctor if you think you or your child is sleeping too much or too little.
This article and research originally appeared on the website of the National Heart, Lung and Blood Institute.