Obstructive sleep apnoea (OSA) is a condition characterised by repetitive upper airway obstruction during sleep, leading to oxygen desaturations and arousals from sleep. Classical symptoms include snoring, apnoeic and gasping episodes, unrefreshed sleep and excessive daytime sleepiness, and inability to concentrate at work. Sufferers may also report nasal obstruction, dry mouth and throat, morning headaches, inability to concentrate at work and poor memory.

Patients may present to General Practitioners with other symptoms like chronic sore throat and dry throat, especially in the morning because the snoring and mouth breathing result in repetitive stress injury. Nocturia and erectile dysfunction are also associated with OSA. Hypertension in the young and refractive hypertension should raise alarm bells on the possibility of OSA.

OSA is associated with hypertension, ischaemic heart disease, heart attack, premature all-cause mortality, sudden death, cardiac arrhythmias, stroke, type 2 diabetes, poor neurocognitive function and poor quality of life and work productivity.

These medical consequences have postulated to be the result of sleep fragmentations with sympathetic system activation during sleep and oxidative stress injury from repetitive oxygen desaturation and reoxygenation, resulting in a state of inflammation. The degree of oxygen desaturation has been shown to be associated with quality of life measures and cardiac arrhythmias.

The International Diabetes Federation recommends that patients with type 2 diabetes be screened for OSA and vice versa. With the Ministry of Health ‘declaring war’ on diabetes, this is an area that cannot be ignored for us to win this war.

The pathophysiology of OSA is multifactorial and linked to obesity. Known predispositions include:

• Male gender
• Older age group
• Patients with allergic rhinitis and nasal obstruction
• Family history of snoring and sleep apnoea
• Small jaw and retrusive maxilla

Fat deposit around the parapharyngeal airway, in the tongue and soft palate likely interact in the development of OSA in obese individuals. OSA itself can predispose individuals to obesity because of sleep deprivation, daytime somnolence, disrupted metabolism, and craving for high caloric food because of the leptin resistance.

PREVALENCE OF OSA IN SINGAPORE

Obstructive sleep apnoea is a highly prevalent disease in Singapore. It is estimated that 3 in 10 middle-aged Singaporean males have obstructive sleep apnoea.

The prevalence of obesity (defined as a body mass index of 30kg/m²) in Singapore is increasing. In 2004, it was 6.9% for the Singapore population between the ages of 18 to 69 and in 2014, it had risen to 8.6%. As such, the prevalence and incidence of OSA is likely to see further increase.

DIAGNOSIS

The diagnosis and treatment of OSA requires the clinician’s awareness of its potential to cause a spectrum of neurocognitive symptoms in patients who may be unaware that their sleep is disturbed. For patients who present with classic symptoms of OSA, a sleep study can be performed to determine its severity.

A multidisciplinary team including respiratory physicians, Ear, Nose Throat (ENT) specialists, dental specialists and sleep technicians manages patients in a holistic way. Regardless of the severity, patients’ quality of life is affected by this condition.

At the Singapore General Hospital (SGH) Sleep Disorders Centre, patients can undergo an in-laboratory polysomnogram. This will record the patients’ brainwaves to stage muscle tone, eye movement to stage sleep, airflow through nose or mouth and chest and abdominal movement to score respiratory events, electrocardiogram (ECG) to look to arrhythmias and limb leads to look for leg movements.

In Figure 1, it shows a typical polysomnogram for a patient with obstructive sleep apnoea. There is apnoea and oxygen desaturations.

For those who have a high pretest probability of OSA, taking into consideration patients’ presenting symptoms and BMI, we can do an ambulatory sleep study (Figure 2). This ambulatory sleep study is cheaper, has a shorter waiting time, and allows patients to do the test in their own home environment without disturbing their natural sleep pattern.

At SingHealth, a centre of excellence, the SingHealth Duke-NUS Sleep Centre, was set up to specifically look at the care of patients with sleep disorders, including OSA, in SingHealth’s different practice sites.

TREATMENT

1. Sleep hygiene and lifestyle modification
The treatment of OSA requires a holistic team approach. Patients will be advised on sleep hygiene and maintaining a healthy lifestyle with modifications like having a regular exercise regime, and cutting down smoking or alcohol consumption. Oral pharyngeal and tongue exercises have also been shown to be useful.

2. Positive airway pressure
Although not curative, the nasal positive airway pressure device is the initial treatment of choice for most patients because of its non-invasiveness and efficacy. It acts like a pneumatic splint to maintain airway patency during sleep.

SGH Sleep Disorders Centre provides a one-stop patientcentric service for trying the different masks and positive airway pressure, and trouble-shooting for patients.

Positive airway pressure use has been shown to eliminate snoring, obstructive events and improve sleep quality, improving patients’ quality of life. Patients feel refreshed the next day and have decreased daytime sleepiness. Using positive airway pressure can reduce the risk of hypertension, ischaemic heart disease, heart failure, type 2 diabetes, stroke, and vehicle accidents.

For positive airway pressure, patients have to be fitted with either the nasal mask, nasal pillow or full face mask. Positive airway pressure technology has come a long way and most patients currently can be on autotitrating airway pressure. For obese patients, if the pressure requirement is too high or if they have obesity hypoventilation syndrome, they may need bilevel positive airway pressure.

However, positive airway pressure device is limited by patient acceptance and long-term compliance. Overall the longterm compliance is about 30-40%. It is therefore important for us to have other modalities of treatment that are able to help these patients.

OSA in obesity may be cured with sufficient lifestylemediated or surgical weight loss, depending on patients’ airway size, skeletal makeup and how much the weight contributes to OSA.

At SGH, the Sleep Centre works closely with the SGH LIFE Centre to help effect weight loss and maintenance of the weight loss through its team of experienced endocrinologists, nutritionists, psychologists, and metabolic/bariatric surgeons. The patients will be thoroughly assessed and an individualised program will be tailored to suit them.

3. Dental Appliances and Upper Airway Surgery
Surgical modifications of the airway can be performed to reduce nasal obstruction and obstruction of the upper airway by tissues such as tonsils, long redundant soft palate, bulky lymphoid tissue tongue through various surgical techniques, including the use of robot to reach the tongue base area.

Multiple level surgeries can be performed safely and help improve outcomes compared to single level surgery. Similarly, skeletal surgeries can be done to enlarge the airway and increase tension on the tissue.

MULTI-INSTITUTION COLLABORATION

The Sleep Apnoea Surgery Service in the Department of ENT, SGH, brings together dental specialists and ENT surgeons to offer a comprehensive treatment for patients.

In addition to the different treatment options, patients with severe obstructive sleep apnoea or with cardiac arrhythmias on sleep study will be referred to the National Heart Centre Singapore (NHCS) for coronary artery assessment. This is based on studies done by SGH Sleep Disorders Centre and NHCS showing an association between the severity of OSA and coronary artery calcium deposit in the coronary artery, reflecting coronary artery disease.

Similarly, a research collaboration between Singapore National Eye Centre (SNEC) and SGH Sleep Disorders Centre found an association between the severity of OSA and normal tension glaucoma and patients with severe OSA will be referred to SNEC for assessment.

HOW GPs CAN HELP

Obstructive sleep apnoea is a common and serious condition in Singapore. Its pathogenesis is multifactorial and linked to obesity.

General Practitioners have an important role to play in case identification for patients with classical and nonclassical symptoms. A holistic treatment using a multidisciplinary team approach is important to improve patient outcomes and give patient the best treatment. Preventive cardiology assessment needs to be done for patients with severe OSA.

GPs can call for appointments through the GP Appointment Hotline at 6321 4402 (SGH), 6788 3003 (CGH), 6472 2000 (SKH), 6294 4050 (KKH) for more information.

By: Dr Toh Song Tar, Senior Consultant, Department of Otolaryngology; Director, Sleep Disorders Centre, Singapore General Hospital; Head, SingHealth Duke-NUS Sleep Centre

Dr Toh Song Tar is a Senior Consultant in the Department of Otolaryngology and Director, Sleep Disorders Centre, Singapore General Hospital (SGH). He is Chief, Sleep Apnoea Surgery Service and Deputy Head (Research) in the department. He is also Head of the SingHealth Duke-NUS Sleep Centre. He is an appointed Adjunct Assistant Professor and Senior Clinical Lecturer of the National University of Singapore, Yong Loo Lin School of Medicine, as well as Adjunct Assistant Professor at the Duke-NUS Medical School.

He is trained as a console-surgeon in performing transoral robotic surgery (TORS) using the da Vinci robot for obstructive sleep apnoea (OSA). He and his team have vast experience in this field, having done the most cases of TORS for OSA, in Singapore and Southeast Asia to-date. 

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