Sleep apnoea affects more than 13000 Kiwis

by Sally Blundell / 13 July, 2017

Sleep apnoea is caused when soft tissue blocks the airway. Photo/Getty Images

Daytime tiredness may be a sign that you’re suffering from sleep apnoea, a disorder that can wake you several hundred times a night.

In Snooze: The Lost Art of Sleep, Australian essayist and former Catholic priest Michael McGirr recounts falling asleep during his own sermon. Unbeknown to him, the night-time gurgling and gargling of his body fighting for breath was waking him up as many as 290 times a night. As he writes in his literary jaunt through the history of sleep, “I was more than just tired, I was sick.”

Obstructive sleep apnoea (OSA) is one of a list of sleep disorders other than insomnia that includes narcolepsy (an almost uncontrollable need to fall asleep during the day); restless leg syndrome; periodic limb movement disorder (the involuntary kicking and jerking of the legs and arms during sleep); and parasomnias – sleepwalking, night terrors and sleep-eating.

OSA, which affects more than 13,000 Kiwis over the age of 18, is caused when soft tissue – the tonsils, tongue, soft palate and uvula (the dangly bit of flesh at the back of your throat) – flop down and block the airway. The resulting increase in carbon dioxide and decrease of oxygen and the work of various receptors in the throat, lungs and chest send a message to the brain that it needs to wake up. The brain obliges, essentially scaring the snorer awake with a gasp of air so brief they, like McGirr, are barely aware their sleep has been interrupted (in contrast to the wide-awake partner lying beside them).

The causes can be behavioural – excess weight, smoking, alcohol – or physiological. Those most at risk tend to have large tonsils, small airways, a high palate and an overbite. Although frequency increases with age, up to 3% of children have sleep apnoea.

Sleep apnoea on its own is unlikely to kill you. The main repercussion is fatigue – which is potentially fatal, if you consider the prevalence of sleepiness in car crashes. Actress Carrie Fisher’s death late last year was attributed to sleep apnoea, but the real cause is likely to have been complicated by drugs – an autopsy found cocaine, morphine and ecstasy in her system – and a build-up of fatty tissue in her arteries.

Obstructive sleep apnoea can be addressed by changes in behaviour (losing weight, cutting back on alcohol); surgery (removing and repositioning excess tissue in the throat); mandibular advancements (using a mouthpiece to push your tongue and lower jaw forward); or, most commonly, positive airway pressure (PAP), in which a pump pushes air through a mask into the breathing passage.

Not all sleep is created equal

Our 24-hour internal body clock is regulated by two systems: circadian and homeostatic. The circadian system is facilitated by melatonin, which is produced in darkness and makes us sleepy. The homeostatic system is responsible for balancing things out, bringing rest to a system that is not at rest. The chemical adenosine mediates the homeostatic system, inducing sleepiness as the day progresses (caffeine blocks this chemical; exercise boosts it).

On the vigilance end of our constant seesaw between sleep and wakefulness, our body releases dopamine, which is crucial for arousal, memory and motor function; histamine (which explains why antihistamines make us sleepy); and orexin, a neuropeptide lacking in those suffering from narcolepsy.

Supported by this daily roster of hormones and neurotransmitters, our body at night is ready to sleep. In The Sleep Solution, Chris Winter describes four levels of sleep. There are two stages of light sleep: these are the necessary passageway between wakefulness and sleep, taking up about half of our night-time sleep.

From there we go into deep sleep or slow-wave sleep, the restorative state that enables the body to block out external noises and movement and helps us maintain sleep (it is also the time of greatest hormone production). Deep sleep makes up 10 -20% of a night’s sleep.

REM (rapid eye movement) sleep comes in four to five cycles of about 20-40 minutes, usually beginning an hour and a half after falling asleep. While new theories suggest we do dream during deep sleep, REM sleep, which makes up about a quarter of our sleep, is generally known as dream sleep.

This article is an extract from the cover story of the July 15, 2017 issue of the New Zealand Listener – on sale July 10-16.

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