To diagnose sleep-related problems, doctors may use one or more of the following sleep studies:
- Polysomnogram (pol-e-SOM-no-gram), or PSG
- Multiple sleep latency test, or MSLT
- Maintenance of wakefulness test, or MWT
- Home-based portable monitor
Your doctor may use actigraphy if he or she thinks you have a circadian (ser-KA-de-an) rhythm disorder. This is a disorder that disrupts your body's natural sleep–wake cycle.
For a PSG, you usually will stay overnight at a sleep center. This study records brain activity, eye movements, heart rate, and blood pressure.
A PSG also records the amount of oxygen in your blood, air movement through your nose while you breathe, snoring, and chest movements. The chest movements show whether you're making an effort to breathe.
PSG results are used to help diagnose:
- Sleep-related breathing disorders, such as sleep apnea
- Sleep-related seizure disorders
- Sleep-related movement disorders, such as periodic limb movement disorder
- Sleep disorders that cause extreme daytime tiredness, such as narcolepsy (PSG and MSLT results will be reviewed together)
Your doctor also may use a PSG to find the right setting for you on a CPAP (continuous positive airway pressure) machine. CPAP is a treatment for sleep apnea.
Sleep apnea is a common disorder in which you have one or more pauses in breathing or shallow breaths while you sleep. In obstructive sleep apnea, the airway collapses or becomes blocked during sleep. A CPAP machine uses mild air pressure to keep your airway open while you sleep.
If your doctor thinks that you have sleep apnea, he or she might schedule a split-night sleep study. During the first half of the night, your sleep is checked without a CPAP machine. This will show whether you have sleep apnea and how severe it is.
If the PSG shows that you have sleep apnea, you'll use a CPAP machine during the second half of the split-night study. A technician will help you select a CPAP mask that fits and is comfortable.
While you sleep, the technician will check the amount of oxygen in your blood and whether your airway stays open. He or she will adjust the flow of air through the mask to find the setting that's right for you. This process is called CPAP titration.
Sometimes the entire study isn't done during the same night. Some people need to go back to the sleep center for the CPAP titration study.
Also, some people might need more than one PSG. For example, your doctor may recommend a followup PSG to:
- Adjust your CPAP settings after weight loss or weight gain
- Recheck your sleep if symptoms return despite treatment with CPAP
- Find out how well surgery has worked to correct a sleep-related breathing disorder
Multiple Sleep Latency Test
This daytime sleep study measures how sleepy you are. It typically is done the day after a PSG. You relax in a dark, quiet room for about 30 minutes while a technician checks your brain activity.
The MSLT records whether you fall asleep during the test and what types and stages of sleep you're having. Sleep has two basic types: rapid eye movement (REM) and non-REM. Non-REM sleep has three distinct stages. REM sleep and the three stages of non-REM sleep occur in regular cycles throughout the night.
The types and stages of sleep you have can help your doctor diagnose sleep disorders such as narcolepsy, idiopathic hypersomnia (id-ee-o-PATH-ick HI-per-SOM-ne-ah), and other sleep disorders that cause daytime tiredness.
An MSLT takes place over the course of a full day. This is because your ability to fall asleep changes throughout the day.
Maintenance of Wakefulness Test
This daytime sleep study measures your ability to stay awake and alert. It's usually done the day after a PSG and takes most of the day.
Results can show whether your inability to stay awake is a public or personal safety concern. Results also can show how you're responding to treatment.
Home-Based Portable Monitor
Your doctor may recommend a home-based sleep test with a portable monitor. The portable monitor will record some of the same information as a PSG. For example, it may record:
- The amount of oxygen in your blood
- Air movement through your nose while you breathe
- Your heart rate
- Chest movements that show whether you're making an effort to breathe
A sleep specialist might use the results from a home-based sleep test to help diagnose sleep apnea. He or she also might use the results to see how well some treatments for sleep apnea are working.
Home-based testing is appropriate only for some people. Talk with your doctor to find out whether a portable monitor is an option for you. If your doctor recommends this test, you'll need to visit a sleep center or your doctor's office to pick up the equipment and learn how to use it.
If you're diagnosed with sleep apnea, your doctor may prescribe treatment with CPAP. If so, he or she will need to find the correct airflow setting for your CPAP machine. To do this, you may need to go to a sleep center to have a PSG. Or, you may be able to find the correct setting at home with an autotitrating CPAP machine.
An autotitrating CPAP machine automatically finds the right airflow setting for you. These machines work well for some people who have sleep apnea. A technician or a doctor will teach you how to use the machine.
Actigraphy is a test that's done while you do your normal daily routine. This test is useful for all age groups and doesn't require an overnight stay at a sleep center.
An actigraph is a simple device that's usually worn like a wristwatch. Your doctor may ask you to wear the device for several days and nights, except when bathing or swimming.
Actigraphy gives your doctor a better idea about your sleep schedule, such as when you sleep or nap and whether the lights are on while you sleep.
Doctors can use actigraphy to help diagnose many sleep disorders, including circadian rhythm disorders (such as jet lag and shift work disorder). Doctors also may use the test to check how well sleep treatments are working.
Actigraphy might be used with a PSG or alone.