Singapore clinics seeing more patients with obstructive sleep apnoea

It took Mr Lim Hak Chye, who suffered for more than five years from obstructive sleep apnoea, less than a week to get used to sleeping using the continuous positive airway pressure machine. He now uses it even for his naps.
PHOTO: Singapore clinics seeing more patients with obstructive sleep apnoea

SINGAPORE - More people are waking up to the realisation that a poor night's sleep is not something they have to put up with.

Take, for example, 55-year-old Lim Hak Chye, who suffered for more than five years from obstructive sleep apnoea (OSA), a condition in which the airway collapses and becomes completely blocked during sleep.

When this happens and the body senses the brain is being deprived of oxygen, the sufferer wakes up very briefly to take a gasp of air and begin breathing again.

Mr Lim underwent an overnight sleep study at the Singapore General Hospital (SGH) last year, which found he stopped breathing 113 times in an hour.

It gave him a sense of relief to know the reason he felt like he barely slept at night was because he, indeed, barely slept at all.

More than that, he received a solution which helped him to sleep better.

In recent years, sleep clinics in public hospitals here have been diagnosing more patients, such as Mr Lim, with OSA, amid rising obesity rates and growing awareness of the condition.

At SGH, there has been a 10 per cent increase in cases of severe OSA each year in the past three years.

At the National University Hospital (NUH), doctors diagnosed more than 400 patients with the condition last year, up from about 350 each year in the previous two years.

The KK Women's and Children's Hospital (KKH) and Tan Tock Seng Hospital have also noticed an uptick, although they did not reveal numbers.

The increase has been observed in both adults and children. It is said that 15 per cent of Singapore's population have OSA, although there are no recent studies on its prevalence.

A local study showed OSA occurred in 2.4 per cent of more than 11,000 children aged four to seven years old.

Unfortunately, although there is a cure, it has not solved the problem. People find the treatment of choice onerous and many give up using it.

This is the continuous positive airway pressure (CPAP) machine, which pumps slightly pressurised air into the nose and throat to keep the airway open during sleep.

It is a non-invasive treatment and can address all levels of obstruction, even after surgery. But patients have to wear a mask over the face or nose while they sleep, which many find hard to get used to.

Over the years, these machines have improved. For instance, they are more responsive to the user's needs and are less noisy than older models.

Mr Sam Chow, managing director of SG Medical, distributor of the ResMed brand of CPAP machines, said pressure settings may vary each night during sleep because of factors such as a patient's weight, fatigue level and consumption of alcohol or medicine.

Doctors say many patients refuse to use the machine, citing discomfort and cost as the reasons. The machine, which can cost from $1,000 to $2,500, is not covered by subsidies.

An audit conducted two years ago of more than 500 patients with moderate to severe OSA at SGH discovered that 65 per cent had opted out of treatment. These patients either rejected CPAP from the onset (40 per cent) or did not use the machine beyond a year.

At KKH, a 2009 review found that only 40 per cent of about 50 children reported using the machine for at least four days a week over a minimum period of six months.

Mr Chow urged patients to persevere as most people need a week of using the machine to get used to it enough to get four hours of sleep a night.

In the past three years, his team has been actively calling existing customers to take their machines for servicing and troubleshoot issues such as air leaks. The service is free during the two-year warranty period.

Patients who got accustomed to the device said it made a huge difference.

These days, Mr Lim says he cannot sleep without his machine, using it even for afternoon naps. It took him less than a week to get used to it and he can now sleep uninterrupted for up to seven hours a night.

Besides the machine, patients can opt for other non-invasive treatments, such as oral appliances, which are also worn during sleep.

Mandibular (lower jaw) advancement splints, which cost between $700 and $1,300, can be fitted to the upper and lower teeth and gradually adjusted to move the lower jaw forward to widen the airway.

Dr Mimi Yow, a senior consultant at the department of orthodontics at National Dental Centre Singapore, said this is especially helpful for Asians who are known to have small jaws in relation to the size of their tongues.

Another alternative is to use a tongue-stabilising device. A gentle suction force is applied to the tip of the tongue, preventing it from falling back into the throat and obstructing the airway. The National Dental Centre Singapore began offering this device, which costs $600, last September, and two patients are using them now.

Long-term health risks

Doctors believe patients would be more receptive to the machine if they were aware of the long-term health consequences of OSA.

OSA affects more men than women, probably because men tend to accumulate fat in the neck when they gain weight, which increases the likelihood of the airway collapsing during sleep.

Dr Mahesh Babu Ramamurthy, head and senior consultant at NUH's division of paediatric pulmonary and sleep, said excess fat in the chest wall also makes breathing less efficient.

Mr Lim has two health disadvantages - he is male and obese with a body mass index of 34.

A healthy BMI for an Asian adult is between 18.5 and 22.9.

Breathing can also be affected by abnormalities in the facial structure, such as large tonsils and adenoids - the most common causes of OSA in children, said doctors.

Tonsils and adenoids are both lymphoid tissues. Tonsils are located on both sides of the back of the throat, while adenoids can be found at the back of the nose. These tissues are largest in relation to the size of the upper airway in children between two and eight years old, which is why OSA is also more prevalent in children in that age group.

These patients have no problem breathing when they are awake, but the challenge is to keep the airway openduring sleep, when the muscles in the upper airway (pharynx) relax and become floppy, said Dr Khoo See Meng, a senior consultant at the division of respiratory and critical care medicine at NUH.

If the problem is severe enough, surgery can be performed on a child to remove the tonsils or adenoids to create more space for him to breathe properly.

Dr Petrina Wong, associate consultant at the respiratory medicine service at the department of paediatrics at KKH, said parents often worry that their child's immunity would be lower without those tissues.

She assured them: "Most children actually fall sick less often after the surgery because they no longer have frequent tonsillitis (inflammation of the tonsils) and are able to sleep and eat better."

Dangers of sleep apnoea

OSA develops differently in children than in adults.

If a child has a chronically blocked nose - due to inflammation of the nasal airways (allergic rhinitis) or sinuses (cavities in the bones of the face around the nose) - he will tend to breathe through his mouth during sleep.

But prolonged breathing through the mouth has been shown to affect a child's facial development, as well as trigger the development of OSA.

Dr Kenny Pang, an ear, nose and throat surgeon at the Asia Sleep Centre at Paragon, said: "With the mouth almost always opened, the palate arches upwards and narrows the nasal cavity. As a result, the adjoining oral cavity has more space to allow the tongue to grow bigger.

"The open mouth also prompts the lower lips to grow thicker and the lower jaw to be more protruding. The teeth may also protrude outwards."

The resulting big tongue and small nasal cavity - along with a less-pronounced nose - predisposes the child to OSA, as well as a spoon-shaped face, he said.

Research has shown that treating nasal-airway obstruction has some impact on reversing these changes, if a child is young enough.

The realisation came too late for 20-year-old national serviceman Yap Kay Hian, whose nasal blockage led to him developing OSA.

He said his parents and two younger siblings do not share his feature of a prominent lower jaw and he was "very surprised" to learn that breathing through his mouth had affected his facial structure.

"It made sense to me because I used to wake up with a dry mouth," said Mr Yap, who had surgery in March this year to clear his nasal passage.

Unlike adults, who experience daytime sleepiness, a child with OSA is more likely to exhibit daytime inattention and hyperactivity, leading to problems in school.

Research has also shown that OSA is a risk factor for hypertension, stroke and heart failure in adults.

One study in medical journal The Lancet showed that the risk of dying from cardiovascular problems was nearly three-fold higher in men with untreated severe OSA, compared with healthy men.

Doctors said during the frequent breathing pauses which lower oxygen levels in the blood, the nervous system activates what is often dubbed the fight-or-flight response during times of stress - increasing a person's heart rate and blood pressure and making the heart work harder.

Dr Leow Leong Chai, consultant at the department of respiratory and critical care medicine at SGH, said overseas studies have shown that 85 per cent of resistant or hard-to-treat hypertension patients have undiagnosed OSA.

At NUH, 105 patients admitted for a heart attack underwent overnight sleep studies between January 2007 and April 2008.

It was found that 42 per cent of them had undiagnosed severe OSA. The study, published in the Journal Of Clinical Sleep Medicine in 2011, also revealed that the incidence of major adverse events, such as stroke, was also much higher in those with severe OSA.

Therefore, doctors urge patients to take sleep-disordered breathing seriously to prevent even worse health problems from cropping up.

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