Key messages
– The diagnosis of obstructive sleep apnoea using limited channel sleep studies is less cumbersome than polysomnography and can be performed at the person's home rather than in a hospital laboratory.
– Using limited channel sleep studies results in little to no difference in sleepiness.
– However, much of the evidence is uncertain, in particular for Level IV studies.
What is obstructive sleep apnoea?
Obstructive sleep apnoea is a condition where the walls of the throat relax and narrow or close during sleep. This stops normal breathing and may lead to snoring, sleepiness and tiredness during the day, decreased quality of life, and increased risk of heart and blood vessel diseases such as stroke or a heart attack.
What did we want to find out?
The diagnosis of obstructive sleep apnoea can be made using an expensive and time-consuming test called polysomnography that is set in a sleep laboratory in a hospital. This takes many different measurements while the person is sleeping, such as brain activity, eye movements, muscle activity and heart rate. It is classed as a Level 1 sleep study. Alternative ways to diagnose obstructive sleep apnoea involve techniques that take fewer measurements. These are called limited channel sleep studies and are classified as Levels II, III and IV depending on the number of measurements taken (with Level IV having the least number). Such 'simplified' tests are less cumbersome and can be performed at the person's home rather than in a hospital laboratory. It is currently unknown whether diagnosing people with obstructive sleep apnoea with fewer measurements is better or worse than diagnosis in a laboratory.
What did we do?
We searched for clinical trials that compared polysomnography (Level I sleep study) to a limited channel (Levels III or IV) sleep study on measures that are relevant to people's lives, such as sleepiness, quality of life, deaths, and unwanted heart and blood vessel effects. We summarised the available results and rated our confidence in the evidence, based on factors such as trial methods and sizes.
What did we find?
We found three trials with 1143 people. One trial compared Level III sleep studies versus Level I sleep studies, one trial compared Level IV sleep studies versus Level I sleep studies, and one trial compared Level IV sleep studies versus Level III sleep studies versus Level I sleep studies. All three trials took place in hospitals. Treatment could have included using a continuous positive airway pressure machine (where a mask is placed over the person's mouth and nose to gently push air into the lungs to keep the airways open during sleep). People were then monitored for four to six months.
Level III sleep studies versus Level I sleep studies
Two trials including 701 people compared Level III versus Level I sleep studies. Level III sleep studies result in little to no difference in sleepiness or quality of life compared to Level I sleep studies. Level III sleep studies are probably slightly more cost-effective. Level III sleep studies may result in little to no difference in heart and blood vessel events, adherence to continuous positive airway pressure treatments or serious unwanted effects. Neither trial reported deaths.
Level IV sleep studies versus Level I sleep studies
Two trials including 573 people compared Level IV versus Level I sleep studies. There may be little to no difference between Level IV sleep studies and Level I sleep studies when looking at sleepiness and heart and blood vessel events such as heart attack and high blood pressure. The evidence is very uncertain for quality of life, adherence to continuous positive airway pressure treatments and serious unwanted effects. The Level IV sleep studies appeared to be half the cost of the Level I sleep studies. Neither trial reported deaths.
What are the limitations of the evidence?
All three trials included in our review were performed in academic (teaching) hospitals; it remains uncertain whether the results would be the same if conducted in people's homes. No trials reported deaths.
How up to date is the evidence?
The evidence is up to date to May 2023.
Level III sleep studies may result in little to no difference in clinical outcomes when compared to Level 1 sleep studies in people with suspected OSA. Level IV sleep studies may not increase sleepiness and may result in little to no difference in cardiovascular events and correlating risk factors compared to Level I sleep studies; the evidence was too uncertain to make statements for other outcomes. Overall, the body of evidence was limited, therefore more trials making this comparison are necessary, as are trials with a longer follow-up duration.
Obstructive sleep apnoea (OSA) is a common cause of sleep disturbance, characterised by the presence of repetitive upper airway obstruction during sleep. OSA is associated with sleepiness during the day, reduced quality of life and an increased risk of cardiovascular disease. OSA can be diagnosed using several different strategies. The current reference test is fully supervised polysomnography, which is expensive and time-consuming. Other diagnostic tests, referred to as limited channel sleep studies because they include fewer parameters than polysomnography, are less resource-intensive but may also have different diagnostic performances, resulting in a difference in clinical outcomes.
To assess the clinical impact (outcome on a participant level) of a strategy where treatment follows diagnostic testing (test-treatment combination) using limited channel sleep studies compared to polysomnography in people with suspected obstructive sleep apnoea (OSA).
We searched two databases (CENTRAL, MEDLINE) up to 11 May 2023 using search terms related to OSA and polysomnography developed by our information specialist.
We included randomised controlled trials that compared any limited channel sleep studies with Level I fully supervised polysomnography in adults (aged 18 years and older) with suspected OSA. Our primary outcome was sleepiness, and our secondary outcomes were quality of life, all-cause mortality, cardiovascular events and correlating risk factors, continuous positive airway pressure (CPAP) usage, serious adverse events, and cost-effectiveness.
Four review authors extracted data from the included trials and assessed the risk of bias. We summarised treatment effects using random-effects meta-analyses and expressed as mean difference (MD) or standardised mean difference (SMD) with corresponding 95% confidence intervals (CI) where possible. We used GRADE to assess the certainty of the evidence.
We included three trials with 1143 participants. One trial compared Level III sleep studies to a Level I fully supervised polysomnography, one trial compared Level IV sleep studies to Level I sleep studies, and one trial compared Level IV sleep studies versus Level III sleep studies versus Level I sleep studies. The follow-up of these trials ranged from four to six months.
Level III sleep studies versus Level I sleep studies
There is high-certainty evidence that Level III sleep studies result in little to no difference in sleepiness (MD 0.47, 95% CI −0.23 to 1.18; P = 0.19, I2 = 0%; 2 trials, 701 participants) or quality of life (SMD 0.01, 95% CI −0.14 to 0.16; P = 0.93, I2 = 0%; 2 trials, 701 participants) compared to Level I sleep studies. Level III sleep studies are also probably slightly more cost-effective (moderate-certainty evidence). There is low-certainty evidence that they may result in little to no difference in cardiovascular events and correlating risk factors, CPAP adherence (MD −0.18 hours per day, 95% CI −0.56 to 0.20; P = 0.36, I2 = 0%; 2 trials, 360 participants) or serious adverse events.
Level IV sleep studies versus Level I sleep studies
There is low-certainty evidence that Level IV sleep studies may not increase sleepiness compared to Level I sleep studies (MD 0.66, 95% CI −0.41 to 1.72; P = 0.23, I2 = 39%; 2 trials, 573 participants). Additionally, there is low-certainty evidence that they may result in little to no difference in cardiovascular events and correlating risk factors. For quality of life, CPAP adherence, serious adverse events and cost-effectiveness, the evidence is very uncertain. None of the included trials reported on all-cause mortality.