Sleep apnea often goes undiagnosed

Failing to treat sleep apnea can lead to a stroke or heart trouble, writes Elaine Yau

PUBLISHED : Monday, 13 May, 2013, 12:00am
UPDATED : Monday, 13 May, 2013, 10:00am

Six months ago, 11-year-old Henry Leung began to exhibit some strange sleeping behaviour. He would suddenly sit upright, and his mother would have to wake him up and tell him to lie down again. Leung was unable to get any quality sleep. As a result, the Primary Six student often dozed off in class the next day, and was scolded by teachers.

At first his mother didn't think it was too serious. But eventually, when his daytime sleepiness started to affect his learning at school, she took him to see a doctor.

Henry was diagnosed as having sleep apnea, a condition in which the subject's breathing stops abnormally during sleep. His doctor, paediatrician Daniel Ng Kwok-keung, says Henry's condition was particularly severe, with pauses in breathing of more than 100 times an hour, each lasting 10 seconds.

The initial lack of concern about Henry's disrupted sleep is a common reaction among sleep apnea sufferers, doctors say, which explains why the condition often goes undiagnosed.

Jamie Lam Chung-mei, president of the Hong Kong Society of Sleep Medicine and a specialist in respiratory medicine, says that diagnosis is commonly delayed by an average of seven years among children, and 3.3 years for adults.

"Over 90 per cent of sleep apnea patients snore. But not all snorers are sufferers. The condition is usually discovered by the one sleeping next to the patient, as he's not conscious of the snoring," Lam says. "Patients get woken up by intermittent suffocation, but they might not be aware of it.

"They think their poor sleep is caused by stress, and a nap can make up for it. They don't think they need to see the doctor. A previous study showed that those with the condition usually do not report any symptoms to their doctors."

But Lam says delayed diagnosis can have serious repercussions, as research shows a link between sleep apnea and a host of diseases.

Sleep apnea is related to diabetes, stroke, heart disease and high cholesterol
Jamie Lam Chung-mei, Society of Sleep Medicine

"Previously, it was thought that the condition only caused poor sleep. But literature over the past decade shows sleep apnea is related to diabetes, stroke, heart disease and high cholesterol," Lam says.

"During apneic episodes, the patient lacks oxygen. Suffocation lasting moer than 10 seconds triggers the body to wake up. Repeated episodes of blocked oxygen flow will do damage to blood vessels all over the body," Lam says.

"The blood vessel linings will become abrased. Fat will cluster around the abrasions, leading to blocked vessels, stroke, and early organ failures."

A recent research report released by Tzu Chi Hospital in Taiwan showed that sleep apnea increases the risk of brain cancer. The research tracked 225,000 adults for 10 years, with half of them suffering from sleep apnea.

It found that for every 10,000 sleep apnea sufferers, 2.96 people get brain cancer, compared to 1.66 people for non-sufferers. It means that sleep apnea sufferers are 1.47 times more likely to suffer from brain cancer than others.

A study published in March in the Journal of Inflammation, which was conducted by researchers from North Chicago, Pakistan and Canada, showed that treating sleep apnea reduce inflammation.

The team of researchers carried out a meta-analysis which pooled data from two dozen trials involving more than 1,000 patients.

The data showed that treating apnea with continuous positive airway pressure (CPAP, during which a machine delivers positive pressure via a nasal mask to split open the upper airway that is blocked) significantly reduces levels of two proteins associated with inflammation.

The society's figures show that six per cent of the Hong Kong population suffers from the condition, with overweight and elderly people making up the majority. Daniel Ng says 10 per cent of children in Hong Kong have habitual snoring.

"The prevalence of obstructive sleep apnea in children is about 5.8 and 3.8 per cent for boys and girls respectively. The condition in children is usually caused by enlarged tonsils and adenoids which block the upper airway during sleep.

"Children can have surgery to remove the enlarged tonsils and adenoids. Henry is using the CPAP machine now and a tonsillectomy has been arranged for him later this year," Ng says.

"When parents see children tired in the morning, they mistakenly think they exhausted themselves by engaging in too many activities. But parents should seek prompt treatment when they see such symptoms," says Ng.

For adult sufferers, Lam says the condition is mostly caused by obesity. "Obese people have much fat around the neck which makes the airway narrower when they lie down. The air has to squeeze through it, which leads to snoring."

Excessive fat tissue around the neck obstruct breathing and cause the feeling of suffocation. Apnea strikes in deep sleep, when the muscles are most relaxed. "The best solution to the problem is to lose weight. This can cure the condition completely," says Lam.

Lam says she has noticed many more patients with this condition compared to a decade ago. "About 80 per cent of sleep disorders turn out to be sleep apnea. Many patients do not see a doctor for the condition, and they only come to us when they have been struck by a stroke or heart disease," she says.

"Their prolonged periods of obstructed sleep, and frequent waking up with a start, have put their heart under immense stress for a long time," she says.