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Obstructive sleep apnoea - hypopnoea syndrome (OSAHS)

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Sleep apnoea is a disorder of breathing during sleep where there is a cessation of airflow lasting at least 10 seconds and is often associated with oxygen desaturation (1).

According to the revised International Classification of Sleep Disorders, apnoea can be divided into three types (2)

  • obstructive sleep apnea
    • occurs due to upper airway obstruction, but movement of the chest wall (rib cage and abdomen) persists
    • the most common disorder of breathing during sleep
    • the patient is woken - not necessarily to full awareness - by airway obstruction
    • it is prominent during REM sleep (when muscle tone is at its lowest).
    • patients with this condition may wake from 3 to 400 times a night.
  • central sleep apnoea
    • is less common than obstructive apnoea
    • there is loss of both inspiratory air flow and the drive to breathe
    • seen in
      • most commonly, accompanying Cheyne–Stokes breathing
      • infants with an immature respiratory control system
      • adult patients with cerebrovascular or neuromuscular disease (3)
  • mixed
    • contains components of both obstructive and central sleep apnoea (1)

Obstructive sleep apnoea syndrome (OSAS) or obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is a condition with repetitive apnoeas and symptoms of sleep fragmentation, most commonly excessive daytime sleepiness. Majority of the patients have a combination of complete obstruction (apnoea) and partial obstruction (hypopnoea) (1,3).

The American Academy of Sleep Medicine definition of obstructive sleep apnoea syndrome is as follows:

  • combination of at least five obstructive breathing episodes per hour during sleep (apnoea, hypopnoea and respiratory effort related arousals events) and at least one of the following criteria:
    • excessive daytime sleepiness that is not better explained by other factors
    • two or more of the following symptoms that are not better explained by other factors:
      • choking or gasping during sleep
      • recurrent awakenings from sleep
      • unrefreshing sleep
      • daytime fatigue
      • impaired concentration (4)

Obstructive sleep apnoea syndrome and excessive daytime sleepiness (5)

  • obstructive sleep apnoea syndrome is the most common sleep related breathing disorder causing excessive daytime sleepiness
  • prevalence of obstructive sleep apnoea syndrome (defined by excessive sleepiness plus evidence of obstructive sleep apnoea syndrome on sleep study) varies from 4% in men aged 30-60y to 43% in morbidly obese middle aged men

When to suspect OSAHS (6)

  • take a sleep history and assess people for OSAHS if they have 2 or more of the following features:
    • snoring
    • witnessed apnoeas
    • unrefreshing sleep
    • waking headaches
    • unexplained excessive sleepiness, tiredness or fatigue
    • nocturia (waking from sleep to urinate)
    • choking during sleep
    • sleep fragmentation or insomnia
    • cognitive dysfunction or memory impairment

Be aware that there is a higher prevalence of OSAHS in people with any of the following conditions:

  • obesity or overweight
  • obesity or overweight in pregnancy
  • treatment-resistant hypertension
  • type 2 diabetes
  • cardiac arrythmia, particularly atrial fibrillation
  • stroke or transient ischaemic attack
  • chronic heart failure
  • moderate or severe asthma
  • polycystic ovary syndrome
  • Down's syndrome
  • non-arteritic anterior ischaemic optic neuropathy (sudden loss of vision in 1 eye due to decreased blood flow to the optic nerve)
  • hypothyroidism
  • acromegaly

Assessment scales for suspected OSAHS

  • when assessing people with suspected OSAHS:
    • use the Epworth Sleepiness Scale in the preliminary assessment of sleepiness
    • consider using the STOP-Bang Questionnaire as well as the Epworth Sleepiness Scale
    • do not use the Epworth Sleepiness Scale alone to determine if referral is needed, because not all people with OSAHS have excessive sleepiness

It is estimated that 5% of adults in the UK have undiagnosed OSAHS (6)

Comparison of drugs for excessive daytime sleepiness (EDS) in OSA (7)

  • found solriamfetol, armodafinil-modafinil and pitolisant reduced daytime sleepiness for patients with OSA already on conventional therapy, with solriamfetol likely superior
  • adverse events probably increased discontinuation risk of armodafinil-modafinil & solriamfetol


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