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Obstructive sleep apnoea (OSA)

Diagnosing OSA

On this page, we explain how and when OSA is diagnosed, sleep studies and what happens at a sleep clinic.

When is OSA diagnosed?

If you are displaying signs of OSA, you should talk to a health care professional about your symptoms and concerns.

Epworth Sleepiness Scale test

Before you talk to your GP, take a look at the Epworth Sleepiness Scale test. It helps to assess how likely you are to fall asleep in everyday situations. You could also take a look at the STOP-Bang questionnaire.  Bear in mind not everyone with OSA is sleepy.

Take your results along to your GP. Your GP will ask about your symptoms, your health, your medical history, and about how sleepy you are when awake. Your GP might give you lifestyle advice about the best ways to get a good night’s sleep, lose weight and stop smoking. 

The results of the Epworth Sleepiness Scale alone will not determine whether or not you should be referred to see if you have OSA.  If it’s suspected you might have OSA, you will usually be referred to a sleep clinic.

If your GP is not concerned, but you still are, keep trying to get a definite diagnosis. Keep asking to be referred to your local sleep service. For support and advice, call our helpline on 03000 030 555.

Going to a sleep clinic to diagnose OSA

What happens at a sleep clinic?

Sleep clinics are specialist clinics that assess, diagnose and treat people with a range of sleep problems, including OSA.

Once you’ve been referred, you’ll be assessed at the clinic – either in person or virtually through a remote session. Clinics assess people in different ways. Some arrange for you to have an overnight sleep study at home before you visit, while others will talk with you first before deciding if you need an overnight study.

Some people can qualify for a rapid assessment by a sleep service. For example, people who are pregnant, have a vocational driving job or have a job that requires high levels of attentiveness for safety. Also if you are due to have major surgery, or have heart rhythm problems, or difficult-to-control high blood pressure, the sleep study may be prioritised.  If you think you qualify for rapid assessment, talk to your doctor.

Assessment and diagnosis at the clinic

Clinics have at least one consultant and other staff, such as nurses and technicians. They will assess if you have OSA by asking questions and examining you, for example by taking measurements of your height and weight. They will also ask you to complete a form about how sleepy you are – usually the Epworth Sleepiness Scale. They may also arrange a sleep study.

Questions about your medical history

This involves talking about your symptoms and quality of life. If you have a partner bring them with you, so they can explain what happens when you’re asleep. A good clinical history helps the doctor to reach a diagnosis. It may include questions about:

  • how long you sleep and the quality of your sleep 
  • shift working (patterns and timings) 
  • your symptoms and how long you have had them
  • your smoking history
  • family history of sleep disorders, such as OSA or narcolepsy
  • your mental health
  • any medication you use or have used
  • how sleepy you are and when you might fall asleep
  • the effect on your work and ability to concentrate.

Examining you

This can include measuring:

  • your weight and height to find your body mass index (BMI)
  • your blood pressure
  • your neck circumference (size)
  • your jaw size and position

and assessing:

  • your face and jaw appearance and symmetry
  • the airflow in your nose
  • your upper airway to see if it’s obstructed
  • your teeth and having a look at the size of your tongue
  • the inside of your mouth.

What is a sleep study?

You’ll usually do a sleep study at home, using equipment lent to you for a night. A small number of people may need to go to hospital overnight for a more detailed study. 

If you’re worried about the study, ask the sleep clinic what will happen. You can do some simple things to prepare, such as:

  • avoiding alcohol or caffeine (like tea, coffee or fizzy drinks)
  • not taking a nap
  • avoiding strenuous exercise on the day.

Let the clinic know if you’ve got any special requirements. If you’re ill on the date of your study, it’s best to postpone it until you’re feeling better. 

For the study, you’ll be monitored as you sleep by equipment attached to you. This is completely painless, and you’ll be able to roll over and change positions. You may be asked to sleep on your back for a while to see if this affects your breathing. If you’re in hospital and experiencing obvious signs of OSA, you may be woken up to use a continuous positive airway pressure (CPAP) machine, so you can be assessed with and without it.

There are different kinds of sleep studies used to diagnose OSA. For example:

Oximetry

Oximetry measures the oxygen level in your blood. It’s usually done at home. You wear a small device with a sensor called a pulse oximeter. This measures your blood oxygen level and your pulse. You’ll have a clip on your finger or earlobe and a device on your wrist.

Respiratory limited sleep study 

Respiratory limited sleep study is an overnight test that can be done in hospital or at home. It measures your air flow, how your chest moves as you breathe, your heart rate and the oxygen level in your blood. Some devices register snoring sounds, body position and leg movements. Equipment will be attached to you with tape, wires and straps as you sleep. For more information and to see where the equipment will be attached to you, take a look at our breathing tests information.

Polysomnography or PSG

Polysomnography or PSG is an overnight study, done in a hospital room. It’s used when the results of other tests aren’t clear and in more complex cases. It assesses sleep and wakefulness by measuring your brain waves, eye movements and muscle movements. It also assesses your heart and lung function, by measuring your air flow, the movement of your chest, your oxygen levels and the activity of your heart activity. It films you while you sleep. For more information and to see where the equipment will be attached to you, take a look at our more detailed breathing tests information.

Reaching a diagnosis

You will be diagnosed with OSA if the results of your assessment are clear. If they aren’t, you may be asked to do more tests or to try a treatment called continuous positive airway pressure (CPAP). If CPAP helps, OSA is the most likely cause of your symptoms.

Your health care professional will want to check how severe your OSA is to find the best treatment for you. You may be told your OSA is mild, moderate or severe. This depends on how many times you stop breathing in the night and your symptoms during the day. People are often relieved to get a diagnosis of OSA because it helps explain how they’ve been feeling.

Next: Treating OSA

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Last medically reviewed: November 2021. Due for review: November 2024

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.