Key Points

• Sleep studies allow doctors to measure how much and how well you sleep. They also help show whether you have sleep problems and how severe they are.
• Sleep studies are important because untreated sleep disorders can increase your risk for high blood pressure, heart attack, stroke, and other medical conditions. People usually aren't aware of their breathing and movements while sleeping. They may never think to talk to their doctors about sleep- and health-related issues that may be linked to sleep problems.
• Sleep studies can help doctors diagnose sleep-related breathing disorders (such as sleep apnea), sleep-related seizure disorders, parasomnias (such as sleepwalking), narcolepsy, insomnia, and circadian rhythm disorders.
• Four common sleep studies are used to help diagnose sleep-related problems: polysomnogram (PSG), multiple sleep latency test (MSLT), maintenance of wakefulness test (MWT), and an actigraph test.
  • A PSG is an overnight sleep study that records brain activity, eye movements, heart rate, and blood pressure. It also records the amount of oxygen in your blood, how much air is moving through your nose while you breathe, and chest movements that show whether you're making an effort to breathe. In some cases, breathing sounds, including snoring, also are recorded. Your doctor also may use a PSG to find the right setting for you on a continuous positive airway pressure (CPAP) machine.
  • An MSLT is a daytime sleep study that measures how sleepy you are. It records brain activity to show various stages of sleep. It also shows how long it takes you to fall asleep.
  • An MWT is a daytime sleep study that measures your ability to stay awake. Results may be used to show whether your inability to stay awake is a public or personal safety concern or to assess your response to treatment.
  • The actigraph sleep study measures sleep–wake behavior while you go about your normal routine. Results give your doctor a better idea about your sleep habits, such as when you sleep or nap and whether the lights are on while you sleep. The actigraph is a small device that's usually worn like a wristwatch.
• If you often feel very tired during the day, talk to your doctor. This is a common sign of a sleep disorder. Other common signs of sleep disorders are listed in "Who Needs a Sleep Study."
• Certain medical conditions have been linked to sleep disorders. These include heart failure, coronary artery disease, obesity, diabetes, high blood pressure, and stroke or transient ischemic attack (TIA, or "mini-stroke"). If you have one of these conditions, talk with your doctor about whether it would be helpful to have a sleep study.
• Sleep studies are painless. The PSG, MSLT, and MWT studies are usually done in a sleep center. The room the study is done in may look like a hotel room. You don't have to go to a sleep center for an actigraph test. You wear the device while you go about your normal daily routine.
• After the sleep study, your doctor will get the results. The results will include information about sleep and wake times, sleep stages, abnormal breathing, the amount of oxygen in the blood, and any movement during sleep.
• Your doctor will study the results and use them and your medical and sleep histories to make a diagnosis and help develop a treatment plan. You may not get the diagnosis until a few weeks after the sleep study.
• The risks of sleep studies are minimal. There is a small risk of skin irritation from the sensors. The irritation will go away once the sensors are removed.