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Take my breath away – obstructive sleep apnoea

23 Dec, 2009
An obstructive sleep apnoea sufferer fitting the apparatus that helps relieve the symptoms of the condition. Image credit: Wellcome Trust

Frank Govan fitting the apparatus that helps relieve the symptoms of his obstructive sleep apnoea

Waking hundreds of times a night, gasping for breath, but with no recollection in the morning sounds like the stuff of nightmares, yet for thousands of people with obstructive sleep apnoea, this is a nightly reality. Chrissie Giles talked to a man with the condition and a researcher who has dedicated her career to studying it, to find out what can be done to secure a good night’s sleep.

 

“I worked as a tax consultant in the City of London. One day I was in a one-to-one meeting with an important client and I just dropped off – bang! Fortunately, the client thought I’d died, which was less embarrassing that the truth: that I’d fallen asleep in the meeting.”

Frank Govan, now retired, recounts one of the troublesome experiences that come from living with obstructive sleep apnoea. This common condition causes people to stop breathing in their sleep, sometimes hundreds of times a night (see box, below). They don’t remember their wakings in the morning, but can suffer extreme fatigue and sleepiness throughout the day.

 

Sleep apnoea at a glance

Sleep apnoea occurs when a person’s airway becomes blocked as they sleep, causing them to stop breathing. These pauses can last from a few seconds to over a minute.

What causes this? When we sleep, our muscles relax. The upper airways (behind the tongue) are not reinforced with cartilage, so can go floppy. In extreme cases, the airway collapses entirely and blocks, preventing air from reaching the lungs. If this happens, the brain eventually detects the struggle for breath and the resulting drop in blood oxygen levels, triggering the person to wake up and breathe – often with a loud gasp or snort.

Sleep apnoea is more likely in people with narrowed airways, caused, for example, by large tonsils or a set-back lower jaw. Being overweight is also a risk factor, as the weight of fatty tissue around the neck can promote airway collapse. The bigger your collar size, the greater the risk of sleep apnoea.

Some 2-4 per cent of younger adults and over 15 per cent of elderly people have the condition. Overweight men make up the majority of cases, although it is not clear how many women are affected. Research into sleep apnoea has improved our understanding of the condition, and there is a cost-effective treatment that works for many people: continuous positive airway pressure (CPAP).

The years of intense tiredness – or feeling “zombified”, as Mr Govan describes it – takes its toll on patients and their families. Mr Govan’s sleepiness had become a standing joke among his friends. He was frequently so exhausted that he would fall asleep mid-meal at dinner parties: “I never saw dessert,” he says.

Research shows that obstructive sleep apnoea is a known risk factor for road accidents. Indeed, Mr Govan once fell asleep at the wheel while driving his family in the fast lane of the M6. Luckily, no one was hurt.

Spurred by this to seek help, Mr Govan saw his GP. Unfortunately, years of fruitless visits followed as a diagnosis remained elusive. In the end it was a chance comment made by his wife to an ear, nose and throat consultant at a dinner party that led to a referral to a sleep specialist and a diagnosis of obstructive sleep apnoea.

Mr Govan now uses a CPAP machine and a mask over his nose whenever he sleeps. A continuous stream of air is delivered, which keeps his airway open without interfering with breathing. The effects of just one night of CPAP were spectacular. “I felt refreshed and my energy had returned,” he says. “I had my life back.”

Sleep studies

Around the same time as Mr Govan was diagnosed, Mary Morrell was completing her PhD, studying the changes in breathing that occur during sleep. With a Wellcome Trust International Travelling Fellowship, she then worked at the University of Wisconsin-Madison in the USA with a group at the forefront of research into the control of breathing during sleep.

“The Fellowship introduced me to large scale sleep and breathing studies,” she says. “At that time there wasn’t an equivalent group in the UK researching the causes of sleep apnoea, so I went to the USA to get experience.”

Inspired by her Fellowship, Dr Morrell and colleagues in 1997 established the Clinical and Academic Unit of Sleep and Breathing at the Royal Brompton Hospital, National Heart and Lung Institute, Imperial College London. The Unit is dedicated to studying the control of breathing during sleep in patients, focusing particularly on sleep apnoea.

“The effects of sleep apnoea are particularly devastating,” says Dr Morrell. “It’s like putting a pillow over somebody’s face and asking them to breathe.”

Extreme fatigue is not the only effect of sleep apnoea. Waking up after each ‘apnoea’ (period without breathing) causes a surge in blood pressure and heart rate around twice as great as that caused by spontaneous waking. Cumulatively, these surges can lead to high blood pressure, meaning an increased risk of cardiovascular disease, including stroke and heart attacks, and memory problems.

Dr Morrell and colleagues set out to investigate what factors in the body affect these surges. In a study of young adults they made a surprising discovery: the size of the surge in blood pressure and heart rate was not affected by respiratory factors such as low blood oxygen or a blocked airway, which can occur in obstructive sleep apnoea.

The researchers recognised that there was a lack of data about these surges in older people. When they studied healthy over-60s, they found that the surge in heart rate and blood pressure after waking was lower than in younger people, suggesting that it decreases with age.

The implications of this finding aren’t clear – a lower surge could mean that the cardiovascular impacts of sleep apnoea are reduced in older people. Alternatively, given that many older people have ‘stiff’ arteries that predispose to heart disease, the effects of sleep apnoea on the risk of stroke or heart attacks could still be substantial.

The National Institute for Health and Clinical Excellence (NICE) guidelines published in 2008 recommend CPAP for adults with moderate-to-severe sleep apnoea. As Dr Morrell’s work shows, the causes and consequences of sleep apnoea are different in older people, so we can’t assume that CPAP will be as effective for elderly patients.

Dr Morrell has recently been awarded funding from the UK NHS Health Technology Assessment Programme for PREDICT, a UK-wide, randomised controlled trial of CPAP in people over 65 with sleep apnoea. The primary outcome measure of the trial is an improvement in sleepiness, but the study will also include a measure of cost-effectiveness, to ensure that the economic impact of the findings can be calculated.

With a research portfolio that combines studies of respiratory physiology with investigations into the clinical consequences, particularly in older people, Dr Morrell is building on our understanding of obstructive sleep apnoea and helping to guide future treatments. Thanks to her work, people such as Mr Govan can get a good night’s sleep at last.

Selected references

Peppard PE et al. The impact of obesity on oxygen desaturation during sleep-disordered breathing. Am J Respir Crit Care Med 2009;180(8):788-93.
Goff EA et al. The cardiovascular response to arousal from sleep decreases with age in healthy adults. Sleep 2008;31(7):1009-17.
Morrell MJ, Badr MS. Effects of NREM sleep on dynamic within-breath changes in upper airway patency in humans. J Appl Physiol 1998;84(1):190-9.

 

“You can’t breathalyse for sleepiness”

The exhaustion caused by sleep apnoea can make everyday tasks life-threatening ones. Research suggests that the condition is associated with an increased risk of road-traffic accidents. One study found that drunk healthy people performed better on a driving stimulator than sober people with sleep apnoea.

Bus and lorry drivers are at a particular risk of sleepiness-related accidents. These professions often involve long stretches of monotonous driving and shift work, which can increase sleepiness. Such sedentary jobs also encourage weight gain, a risk factor for sleep apnoea.

“Most patients can overcome sleepiness except when doing something boring, such as driving,” says Dr Mary Morrell from the Royal Brompton Hospital, London. “The problem is you can’t breathalyse for sleepiness – we don’t have good objective measures for it.”

Some researchers stress the need for that kind of measure. Dr Charles George, University of Western Ontario, Canada, writes: “Not all cases [of sleep apnoea] are sleepy or have crashes and more data are needed for society to establish and accept a ‘safe’ sleep apnea cutoff for driving, akin to that for alcohol.”

References

George CFP. Sleep apnoea, alertness, and motor vehicle crashes. Am J Respir Crit Care Med 2007;176(10):954-6.
Sleep apnoea and road accidents, Behind the Medical Headlines

Image credit: A still from our Understanding Obstructive Sleep Apnoea film.
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