What happens during a sleep study — and do I need one?
If you or your partner have raised concerns about your breathing during sleep — or if a doctor has suggested that your snoring or daytime tiredness may have an underlying cause — a sleep study is likely to be one of the first investigations recommended. Yet for many patients, the idea of a sleep study still prompts uncertainty. What does it actually involve? Is it uncomfortable? Do I have to go to a hospital? And what will it tell us?
A sleep study is not an ordeal — it is a straightforward overnight recording that can, in a single night, answer questions that have gone unresolved for years.
This article sets out to answer those questions clearly. A sleep study is often the point at which years of unexplained symptoms finally begin to make clinical sense.
The underdiagnosis problem
Over 80% of adults with moderate-to-severe obstructive sleep apnoea are estimated to remain undiagnosed — with some research placing the figure as high as 85–90%.
Sleep apnoea is estimated to affect around 4.8% of the UK population — roughly 1.5 million people with moderate or severe disease — yet multiple peer-reviewed studies consistently indicate that over 80% of those affected are unaware of their diagnosis. In some studies and selected populations, the figure approaches 85–90%.
Taken together, these figures suggest that the United Kingdom is home to well over a million people with clinically significant, untreated sleep apnoea — most of whom do not know it.
The sleep study is the investigation that finally gives a name to symptoms many patients have been dismissing — or having dismissed — for years.
Home sleep studies vs in-laboratory testing
Sleep studies can be performed either in a sleep laboratory — where you spend the night under observation in a clinical setting — or at home using a portable monitoring device. In the vast majority of cases, a home sleep study provides sufficient diagnostic information and is considerably more convenient and comfortable for the patient.
At Hillser Clinic, we use home-based sleep studies as our standard diagnostic tool for suspected obstructive sleep apnoea. The portable monitoring device is small and unobtrusive, and most patients find it has little impact on their sleep.
In-laboratory polysomnography — a more comprehensive test that monitors additional parameters including brain activity, eye movements and muscle tone — may be recommended where more complex sleep disorders are suspected, or where home testing has produced inconclusive results.
What does the device measure?
A home sleep study device typically records:
Respiratory effort — whether you are making breathing movements during sleep.
Airflow — whether air is actually passing through the nose and mouth, and whether this is interrupted.
Oxygen saturation — the level of oxygen in your blood, which drops when breathing is obstructed.
Heart rate — which provides additional information about the cardiovascular impact of any breathing disturbances.
Body position — since sleep apnoea is often worse when lying on your back.
Snoring sounds — recorded by a small sensor to characterise the pattern and severity.
How is it set up?
The device is provided during a clinic appointment or sent to you directly, with clear written and video instructions for self-application. Sensors are typically attached to the finger, chest and nose using simple adhesive or elastic fastenings. The setup takes around five to ten minutes and requires no clinical expertise.
You wear the device during a normal night's sleep in your own bed, then return it the following morning. The recorded data is downloaded and analysed by our clinical team, and the results are discussed with you at a follow-up appointment — usually within a few days.
Who should have a sleep study?
A sleep study is recommended if you experience any combination of the following:
Loud or irregular snoring, particularly if witnessed pauses in breathing have been noted.
Excessive daytime sleepiness that is not explained by insufficient time in bed.
Waking unrefreshed despite adequate sleep duration.
Morning headaches, dry mouth, or frequent night-time waking.
Poor concentration, irritability or low mood that may be linked to poor sleep quality.
A sleep study is painless, carries no risk, and provides the clinical team with objective information that cannot be gathered from a consultation alone.
What happens after the results?
Once the data has been analysed, your results will be expressed as an Apnoea-Hypopnoea Index (AHI) — a measure of the number of breathing events per hour of sleep. This figure, combined with your oxygen saturation data and clinical history, allows your clinician to determine the appropriate next steps. These may range from lifestyle advice for mild cases through to CPAP therapy or further investigation with drug-induced sleep endoscopy (DISE) for more significant findings.
For comprehensive guidance on the diagnosis and management of obstructive sleep apnoea, including the role of sleep studies, refer to the NICE clinical guideline on this topic.