Sleep gives your body and brain time to recover from the stresses of the day. After a good night's sleep, you perform better and are better at making decisions. Sleep can help you feel more alert, optimistic, and get along with people better. Sleep also helps your body ward off disease.

Different people need different amounts of sleep. Most adults need 7 to 8 hours of sleep a night for good health and mental functioning. Some adults need up to 9 hours a night.

There are many reasons why sleep is in such short supply.

• Busy schedules. Evening activities, whether it is work or social, are one of the top reasons people do not get enough sleep.
• Poor sleep environment. It is a lot harder to get a good night's sleep in a bedroom with too much noise or light, or that is either too cold or too warm.
• Electronics. Tablets and cell phones that ring and beep throughout the night disrupt sleep. They can also make it impossible to disconnect from the waking world.
• Medical conditions. Some health conditions can prevent deep sleep. These include arthritis, back pain, heart disease, and conditions such as asthma that make it hard to breathe. Depression, anxiety, and substance abuse also make sleep hard to come by. Some medicines disrupt sleep.
• Stress about sleeping. After several nights of tossing and turning, just being in bed can make you anxious and awake, even when you are very tired.

Sleep disorders

Sleep problems are a big reason why many people can't get enough sleep. Treatment can help in many cases.

• Insomnia, occurs when you have trouble falling asleep or sleeping through the night. It is the most common sleep disorder. Insomnia can last for a night, a couple of weeks, or for months on end.
• Sleep apnea is a condition in which your breathing pauses throughout the night. Even if you do not wake up all the way, sleep apnea repeatedly interrupts deep sleep.
• Restless legs syndrome can keep you awake with the desire to move your legs anytime you are resting. Often restless legs syndrome comes with uncomfortable feelings such as burning, tingling, itching, or creeping in your legs.

Lack of sleep affects more than just the person who is short on shut-eye. Fatigue has been linked to accidents both large and small. Overtiredness led to the human errors behind several large disasters including the Exxon-Valdez oil spill and the Chernobyl nuclear accident. Poor sleep has contributed to numerous airplane crashes.

Each year, up to 100,000 car accidents and 1,550 deaths are caused by exhausted drivers. Drowsy driving impairs alertness and reaction time as much as driving while drunk.

Lack of sleep can also make it harder to stay safe on the job. It can lead to medical errors and industrial accidents.

Without enough sleep, your brain may struggle to perform basic functions. You may find it hard to concentrate or remember things. You may become moody and lash out at co-workers or people you love.

Just as your brain needs sleep to restore itself, so does your body. When you do not have enough sleep, your risk goes up for several illnesses.

• Diabetes. Your body does not do as well controlling blood sugar when you do not get enough sleep.
• Heart disease. Lack of sleep can lead to high blood pressure and inflammation, two things that can damage your heart.
• Obesity. When you do not get enough rest from sleep, you are more prone to overeat. It is also harder to resist foods high in sugar and fat.
• Infection. Your immune system needs you to sleep so it can fight colds and keep you healthy.
• Mental health. Depression and anxiety often make it hard to sleep. They also can become worse after a string of sleepless nights.

Talk with your health care provider if you are often tired during the day, or lack of sleep makes it hard to do daily activities. There are treatments available to improve sleep.

Centers for Disease Control and Prevention website. Sleep and sleep disorders. www.cdc.gov/sleep/index.html. Updated September 7, 2022. Accessed November 24, 2022.

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Sullivan SS, Carskadon MA, Dement WC, Jackson CL. Normal human sleep: an overview. In: Kryger M, Roth T, Goldstein CA, Dement WC, eds. Principles and Practice of Sleep Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 2.

Van Dongen HPA, Balkin TJ, Hursh SR, Dorrian J. Performance deficits during sleep loss and their operational consequences. In: Kryger M, Roth T, Goldstein CA, Dement WC, eds. Principles and Practice of Sleep Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 79.

Updated by: Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.