Sleep Apnoea Test (Polysomnogram)

What are sleep studies?

A sleep study is a medical test used to determine the nature and severity of a patient's sleep disordered breathing (SDB) condition. Otherwise known as 'diagnostic sleep studies' or 'polysomnograms', sleep studies may be done in the home or by staying overnight in a specialised sleep clinic.

The recorded data – blood oxygen levels, brainwave activity, cardiac activity, sleeping position, limb movements, etc – is studied and analysed by a sleep scientist and independent sleep physician. The data provides enough information for the sleep specialists to diagnose the condition and prescribe an appropriate form of treatment.

The study results show patterns in brain activity, breathing signals and oxygen levels that may indicate interruptions to sleep. In many cases, the results would be surprising to patients, who are otherwise not aware of the nocturnal events that occur during their sleeping hours.

what are sleep studies?

Who needs a sleep study?

It is not possible for the sleep physician or medical doctor to investigate whether or not you have a sleep problem while you are awake, hence a routine office visit is not sufficient for a proper sleep diagnosis. That is why you would need to undertake an overnight sleep study, which is a powerful diagnostic tool to help doctors assess the factors that may be keeping you from getting the restful sleep you need.

If you are experiencing symptoms like persistent and loud snoring or belong to the high-risk group – for example, males over the age of 65 – you are more likely to develop a sleeping disorder.

You may wish to talk to your sleep physician or medical doctor if you have the following symptoms: Loud and persistent snoring; choking and gasping for air during sleep (usually observed by a bed partner); frequent morning headaches; lethargy and lack of concentration during the day; loss of memory; and daytime sleepiness.

The issue is even more urgent if you belong to the high-risk group: Males over the age of 65; obese, smokers; drinkers, type 2 diabetes patients.

If you know someone who frequently snores and has two or more of these conditions in either category, there is a good chance the person may be suffering from a type of sleep-disordered breathing and would require a proper diagnosis.

sleep studies

Sleep apnoea test - Why is sleep study done?

The sleep study test or polysomnogram measures your body's response to sleep problems and gauges how well you sleep. For example, it detects pauses in breathing that is commonly associated with obstructive sleep apnoea (OSA). In severe cases, the pauses can occur 30 times or more per hour. These studies are important because people are usually not aware of their nocturnal breathing patterns and behaviours or the risks involved with untreated sleep problems.

The most common type of sleep disorder is obstructive sleep apnoea (OSA), which accounts for 52% of all apnoeas in Australia.1 The condition is defined as complete or partial blockage of the airways for about 10 seconds or more. OSA occurs when the tissues in the back of the upper throat collapse – in the relaxed state of sleep – and obstructs the air passage. In most cases, the person is not aware of these nocturnal episodes and may subconsciously wake up gasping or choking.

As sleep apnoea typically manifests in noisy snoring, most patients see a doctor about the condition when it has negatively affected the sleep quality of their bed partners.

The untreated condition can potentially result in mild to serious medical conditions such as:

  • High blood pressure
  • Stroke
  • Heart failure
  • Fatigue
  • Depression
  • Diabetes
  • Anxiety

Sleep apnoea patients are also more prone to drowsy driving which increases the risk factor for motoring accidents and death. Young children with untreated sleep apnoea are more likely to be hyperactive and inattentive, symptoms commonly misdiagnosed as attention-deficit hyperactivity disorder.

Preparing for a sleep study

As mentioned, the polysomnogram involves a non-invasive – and generally comfortable – procedure so there is nothing to be worried about. Nonetheless, it is always a good idea to be prepared for any type of medical procedure so that there won’t be any surprises along the way.

Before going for a sleep study, you will normally be given a form that helps you to keep a diary of your sleep habits. For about two weeks leading up to the sleep study, you will be asked to fill out daily questions such as the number of hours of sleep you clocked the night before, unusual stress factors, incidents that awoken you from sleep, etc.

You would be advised to keep to your normal sleep habits and routines, at least for about two to three days prior to the study. The reason for this is because the doctor is trying to assess your typical sleep patterns, and the results will not be as accurate if you are more or less rested than normal. You should refrain from taking any sedatives or consume caffeinated drinks the night before the test.

If you are taking the study at a sleep clinic, don’t forget to pack your sleepwear – or even a special pillow – that you would normally need for your bedtime comforts. All that is left to do during the study itself is simply to relax. The sleep technicians will place the necessary monitors and set up the recorder before leaving you to settle into bed, and of course, get some sleep.

sleep apnea test


Sleep study procedure: What to expect from a polysomnogram

The sleep study usually takes place in what resembles a hotel room. The key is to make you feel comfortable as if you are sleeping at home, hence apart from the relatively compact monitoring equipment, you would not feel like you’re in a typical clinical environment.

The procedure involves attaching physiological monitors to your body and electrodes on your head to record your nocturnal breathing patterns as well as brain and physical activity during sleep. As such, you would want to keep yourself physically clean for the procedure. It is best that you avoid wearing any oily or sticky grooming products as they may make the experience less comfortable. A small sensor that measures blood oxygen will be placed on your finger.

The sleep study test may on occasion be combined with a CPAP test to check for sleep apnoea. If this is the case, you will take the polysonmogram first, followed by the CPAP monitoring in the second half of the night.

What is monitored during polysomnogram?

The polysomnogram (PSG) measures the quality of your sleep using a variety of devices:

  • Electroencephalogram (EEG) for brainwaves
  • Electroculogram (EOG) for eye and chin movements
  • Electrocardiogram (ECG/EKG) for heart rate and rhythm

In summary, the polysomnogram records and depicts a true picture of your sleep patterns by gathering the following types of data:

  • Brain waves
  • Heart rate
  • Eye/ chin/ limb movements
  • Snoring
  • Blood oxygen level
  • Breathing pattern
  • And others

sleep apnoea test, polysomnogram

Sleep study results & Sleep apnoea diagnosis

After a full night’s sleep is recorded, the sleep technician will tabulate the data and present them to a physician for analysis and interpretation. The turnaround time to get your results following the polysonmogram is usually around 1-2 weeks, but it depends on the clinic as well.

The physician will then offer his/her professional take on the results, offering therapy in the form of medication, continuous positive airway pressure (CPAP) or oral appliance. Surgery is usually only recommended in cases when conventional treatment does not work.

Diagnosis is generally based on the following indices:

Apnea Hypopnea Index (AHI)

The diagnosis for obstructive sleep apnoea is typically obtained from AHI readings that are derived from the polysomnogram. The AHI indicates the number of apnoeas (pauses in breathing) or hypopnoeas (shallow breathing) recorded during the study per hour of sleep. The extent and severity of OSA may be measured and classified according to the index as follows:

(AHI is expressed in number of apnoea events per hour)

  • Zero to minimal presence: AHI less than 5
  • Mild: AHI more than or equal to 5, but less than or equal to 15
  • Moderate: AHI more than or equal to 15, but less than 30
  • Severe: AHI more than or equal to 30

Respiratory Disturbance Index (RDI)

In addition to calculating the events of apnoeas and hypopnoeas, the RDI measures other more subtle breathing irregularities as well. That is why a patient’s RDI may be higher than his or her AHI.

What is the cost of sleep studies?

There are many clinics that offer overnight sleep studies that are bulk-billed for all Medicare patients, meaning no out-of-pocket expenses required. Private sleep studies are also available for self-funded patients or those with private health insurance cover.

Sleep Study FAQs

  • Q: Where can I undergo the procedure?

    The polysomnogram may be performed in a hospital based sleep unit, allowing trained sleep physicians to monitor and observe the patient throughout the night. It can also be done in the privacy of your own bedroom, using state of the art portable diagnostic recorder.

  • Q: What is the difference between the ‘in-clinic’ sleep study and the ‘in home’ version?

    The non-invasive and pain-free study involves attaching sensors and electrodes to the body and head of the patient. This part of the procedure is similar for both sleep study options, whether conducted in a sleep clinic or in the home. The only difference for the home-based study is that the recording unit is portable, thus allowing the patient the mobility to undergo the study in his/her own bed. This type of sleep study is much less expensive and daunting. Compared to the hospital-based sleep laboratory environment, the ‘in home’ monitoring method also provides a more accurate indication of what a normal night's sleep looks like for the particular patient.

  • Q: Are there any risks involved?

    The sleep study is a pain-free procedure that is comfortable for most. It may be mildly uncomfortable for those who are not used to the small leads being attached to their bodies using creams and tape. In rare cases, the cream may cause skin irritation.

Do not let Obstructive Sleep Apnoea (OSA) rob you of the adequate rest you need!

At Sound Sleeper, we can help with your sleeping disorder and provide a dental solution to your problems. Click here to locate a Sound Sleeper dentist near you today.


  1. "Re-awakening Australia." The Economic Cost of Sleep Disorders in Australia, 2010. October 1, 2011. Accessed December 16, 2015. Australia.pdf

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