If you are experiencing symptoms of disrupted sleep and your doctor or respiratory consultant suspects you might have a sleep disorder, you may be referred for a sleep study, also called polysomnography.
This is an overnight diagnostic test that can be used to diagnose a range of sleep disorders including sleep apnoea (a condition that causes repeated interruptions to your normal breathing during sleep), as well as long-lasting insomnia, REM sleep disorder and restless legs syndrome.
Sometimes people feel a bit anxious about taking part in a sleep study, but it’s nothing to worry about and the results can help to determine what kind of treatment could help.
In this article, we will explain what happens during a sleep study and what information it is likely to reveal.
Why do I need to take part in a sleep study?
A sleep study is used to diagnose sleep disorders, as well as to create and manage the treatment plan for an existing condition. Polysomnography records your brain waves, breathing, heart rate and oxygen levels in your blood while you sleep, as well as your eye, leg and arm movements. The test is normally done at night at a specialist sleep disorders unit in a hospital or a sleep centre. While it is most often performed at night, it can sometimes be done during the daytime for shift workers.
When you fall asleep you enter a period of non-rapid eye movement (NREM) sleep. During this stage, your brain waves slow down. These are recorded with a test called an electroencephalogram or EEG. Following NREM sleep, brain activity increases and you enter rapid eye movement (REM) sleep. During REM sleep your eyes move quickly back and forth. This is when you are most likely to dream. Cycles of NREM and REM sleep typically last around 90 minutes and you go through multiple sleep cycles a night.
Preparing for a sleep study
You will receive detailed instructions on how to prepare for the sleep study. You should avoid alcohol or caffeine in the afternoon and evening before the test as these can interfere with your sleep patterns and may affect the results. Avoid taking a nap during the afternoon and do not apply lotions, gels or colognes to your skin as these can interfere with the electrodes.
If you are having the polysomnography at a sleep centre, you will arrive in the evening and stay overnight. You’ll be able to sleep in your own nightclothes and can bring items with you from home. You’ll have your own en-suite room, which will be dark and quiet. Rooms are equipped with a low-light video camera so the polysomnography technologist can see what is happening while you sleep. There is an audio system so they can hear you from outside the room.
What to expect
You will follow your normal bedtime schedule. Sensors will be placed on your scalp, temples, chest and legs. These will be connected by wires to a computer. They will monitor your brain waves, heart rate, eye movements, breathing patterns, snoring, limb movements and body position. A clip will be placed on your finger or ear. This will monitor levels of oxygen in your blood. The technologists will monitor you throughout the night and you can talk to them via the monitoring equipment if you need to.
During the sleep study, the team may invite you to try a positive airway pressure (PAP0 machine for sleep apnoea. This piece of equipment delivers a gentle steam of air via a face mask into your nose and mouth to help you breathe. There are two different types – continuous positive airway pressure (CPAP) which provides a constant stream of air and bilevel positive airway pressure (BPAP) which delivers more pressure when you breathe in and less when you breathe out.
After the study, the sensors are removed and you will be able to go home. You’ll be given a follow-up appointment to discuss your results.
What will the sleep study show?
The sleep study will reveal a wide range of information about your sleep patterns, including:
- Eye movements and brain waves which can help identify whether disruptions occur during particular stages of sleep
- Changes in heart and breathing rates or levels of oxygen in the blood, which could indicate sleep apnoea
- Movements or behaviours during sleep, which can be signs of REM sleep behaviour disorder
- Frequent leg movements which can be a sign of restless leg syndrome
For more information about diagnosing and treating sleep apnoea contact us.
Frequently Asked Questions
What if I don’t sleep well during the sleep study, will it affect the results?
No. You don’t need to have a full night’s sleep to obtain accurate results from the sleep study. Most people don’t sleep as well as they do at home.
What will happen after the sleep study?
The polysomnography technologist will evaluate the data. It is then reviewed by your clinician who will make a diagnosis. They will then discuss possible treatments with you.
Can I do a sleep study test at home?
There are home tests for sleep apnoea which monitor things like your heart rate, breathing patterns and blood oxygen levels. However, a sleep study carried out in hospital provides a broader range of measures, including assessing brain, heart and lung activity as well as leg and arm movements.