A sleep study is a diagnostic test, performed at home or in a sleep lab, to determine whether a person has a sleep disorder. The most informative sleep studies test for:
- Brain waves (Electroencephalography)
- Heart rhythm and activity (Electrocardiography)
- Breathing Effort (Respiration)
- Muscle Activity (Electromyography)
- Blood Oxygen Saturation (SpO2)
These factors combine to provide a detailed snapshot of a person's sleep on a given night, and enable a trained sleep clinician to diagnose, or in limited cases identify the need for further testing.
But, not all sleep studies are created equal!
There are 2 types of sleep studies - overnight and daytime. Each of these in turn have variants that are appropriate for different situations and people
Level 1 sleep studies are performed in a sleep lab and are monitored overnight by a sleep technician. This type of sleep study is the most comprehensive and has a high rate of success as any technical issues that pop up through the night are resolved by the sleep technician in attendance.
This type of study is specifically used to diagnose sleep disorders where people have unusual muscle or brain activity in their sleep, such as people who experience periodic limb movement disorder or epilepsy.
Level 1 sleep studies are relevant to the sleep disorders of only approximately 10% of the population.
A Level 2 sleep study provides a similar level of detail to a Level 1 study, but is usually used to diagnose sleep disordered breathing, such as sleep apnea and snoring. This type of study is performed in the person’s home and is either set up on the person in a clinic, typically late in the day, or the person is instructed on how to set it up on themselves at home and given simple instructions to follow to make that process easy. The person is sleeping in their own bed rather than in a lab or hospital, thus recording sleep patterns in the natural environment.
A level 3 sleep study is a vastly stripped-down version of a level 2 sleep study. It only measures breathing effort, pulse, and oxygen levels. Level 3 studies are often offered by non – sleep specialist sales outlets, eg pharmacies, or are used to check on the progress of a patient once they are on on a treatment therapy.
In cases where a level 1 or 2 sleep study cannot be performed, a level 3 sleep study has been used to diagnose sleep disordered breathing and snoring, which can lead to the trial of a CPAP machine, but without the certainty of a correct diagnosis that Level 2 sleep study data provides.
Sometimes a Level 1 diagnostic test is performed during the day. In most cases it is for patients who are overnight shift workers, as the testing conditions need to be similar to their normal routine. A Level 2 sleep study can be performed during the day for some of these workers however if the study relates to a commercial driver’s licence.
Maintenance of Wakefulness Test (MWT)
This test is used to determine if a patient who is on treatment, either medication or a CPAP machine, has resolved the daytime tiredness associated with their condition.
This test is used regularly on commercial drivers to make sure that they are fit to work and have little to no risk of falling asleep while operating a vehicle or heavy machinery.
During the test, a patient is required to stay awake in a darkened room with no stimulation from bodily movements, humming, talking, listening to music or audio, or watching TV. The test is repeated multiple times, with breaks in-between.
A Level 1 overnight sleep study is required on the night before the MWT to make sure that the patient had an acceptable number of hours of sleep.
Multiple Sleep Latency Test (MSLT)
A Multiple Sleep Latency Test (MSLT) is used to determine if a patient suffers from narcolepsy, which is when someone has excessive daytime tiredness to the point that they have brief involuntary sleep episodes.
A MSLT is advisable if, during a normal diagnostic sleep study, the patient showed that they fell asleep much quicker than normal and have some accompanying symptoms such as:
Sudden loss of muscle control Muscle weakness Muscle paralysis Fatigue Hallucinations
A Level 1 overnight sleep study is required on the night before the MSLT to make sure that that patient had an acceptable number of hours of sleep.
During testing, the patient is put to bed in a darkened room with no stimulus and is monitored to see how quickly they fall asleep and how quickly they progress to deep (REM) Sleep. The test is repeated multiple times with breaks in-between.
CPAP Specialists are readily available to assist with determining which sleep study is appropriate, and in most cases can advise next steps to arranging a sleep study. For diagnosis of a suspected sleep disordered breathing and/or snoring, a Level 2 sleep study is usually adequate.
A Level 1 sleep Study is required if you are a commercial driver with a suspected sleep disorder, as it is a statutory requirement for the OSA sufferer to be monitored from time to time.
A Level 1 is also appropriate if the patient has confirmed or suspected neurological disorders like epilepsy, Parkinson’s disease (or as a study on the night before a MWT or MSLT sleep study.)
Level 3 sleep studies are best for remote individuals who cannot get access to a clinic or as a follow up test to see if treatment is working.