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Sleep apnoea occurs when a person’s throat and upper airway become partly or completely blocked during sleep, causing short periods where breathing stops. These periods can last up to 90 seconds, and then the individual briefly awakens.

This can happen repeatedly throughout the night, interrupting sleep and leaving the individual tired after waking. The condition is known as a ‘silent killer’, as people with obstructive sleep apnoea are often unaware they have the disorder.

How airways are blocked

The airways become blocked when the muscles in the back of the throat relax. These muscles support the soft palate and the uvula (triangular piece of tissue) hanging from it, as well as the tonsils, side walls of the throat and the tongue.

As the throat relaxes, the airways narrow (or even close) as the individual tries to breathe. As the individual cannot get enough air, the oxygen levels in the blood fall. This prompts the brain to briefly rouse the individual from sleep so they can reopen their airway.


A person with obstructive sleep apnoea may experience the following:

  • Pauses in breathing while sleeping
  • Loud snoring
  • Tossing and turning
  • Waking up gasping for air
  • Feeling tired or not refreshed after sleep.

The impact

When a person stops breathing and oxygen levels drop, the body responds by releasing epinephrine (also known as adrenaline), a stress hormone. This helps the brain wake the body momentarily to breathe. When this happens over and over, adrenaline levels remain high. This can lead to high blood pressure and puts strain on the cardiovascular system.

Obstructive sleep apnoea has been associated with increased risk of recurrent heart attacks, stroke, atrial fibrillation, coronary artery disease, cardiac arrhythmias, sudden cardiac death and heart failure.

Those with untreated moderate to severe sleep apnoea also have a higher risk of:

  • Diabetes
  • Poor memory and lack of concentration
  • Headaches
  • Mood disorders and depression
  • Impacted sex drive, and male impotence.

The risk

Sleep apnoea occurs in 5-15 per cent of the population.1 While it can affect anyone, it is more common in people who:

  • Are male – men are two to three times more likely to have sleep apnoea than women
  • Are middle aged or older – sleep apnoea is significantly more common in older adults
  • Snore
  • Smoke – people who smoke are three times more likely to have obstructive sleep apnoea than those who do not
  • Are an unhealthy weight
  • Have a family history of sleep apnoea.

What is HRI doing?

The Cardiovascular Neuroscience Group is running several projects to understand how the brain controls breathing and blood pressure. Their focus is what goes wrong in the brain to uncover the mechanisms driving the cardiovascular consequences of sleep apnoea. They aim to identify new treatment to treat sleep apnoea sufferers and reduce the cardiovascular diseases which arise as a result.


  1. Parish JM et al. Obstructive Sleep Apnea and Cardiovascular Disease.

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