When a person breathes, the air from the atmosphere travels from the nostril and passes the nose and back of the throat before it reaches the lungs where gaseous exchange takes place.

Snoring is the sound produced by turbulence created by air flows through the narrowed soft passages of the nose and the back of the throat. Snoring is not usually worrisome unless it prevents sleep.

The soft tissues of the throat and tongue may collapse on the back of the throat, blocking air flow and consequent breathing difficulties.

This condition is called obstructive sleep apnoea (OSA).

There are two types of breathing interruptions in OSA: apnoea in which the throat muscles relax, causing a total blockage of the airway and lasting about 10 seconds; and hypopnoea in which there is partial airway blockage of about 10 seconds.

The term 'obstructive' is used to distinguish OSA from rarer types of sleep apnoea like central sleep apnoea in which the brain 'forgets' to breathe during sleep.

During episodes of OSA, the body does not get sufficient oxygen. This leads to the affected individuals moving from deep sleep to lighter sleep, or even awakening, to re-establish normal breathing.

When they get back to deep sleep, episodes of apnoea and hypopnoea recur.

OSA is not an uncommon condition affecting more men than women.

In a community study of 1,611 adults between the ages of 30 and 70 years, Kamil M.A., Teng C.L. and Hassan S.A. reported that 7% of respondents were clinically suspected to have OSA (8.6% males and 5.1% females). The prevalence of habitual snoring, breathing pauses and excessive sleepiness during the day were 47.3%, 15.2% and 14.8% respectively.

The predictors of habitual snoring were older age groups, Chinese, Indians, smokers, obesity and sedative usage. (Snoring And Breathing Pauses During Sleep In The Malaysian Population, Respirology 2007)

Risk factors

Obesity is a major risk factor for OSA because there is extra strain placed on the throat muscles by excessive fat which is thought to narrow air passages.

Other risk factors are those above 40 years old, male, large neck (circumference of more than 43 cm), consumption of sedatives as well as medical conditions like allergies, sinsusitis, nasal tumours and underactive thyroid (hypothyroidism).

Alcohol consumption prior to bed time, smoking, menopause, sildenafil (Viagra) intake and a family history are suspected risk factors.

People with OSA are at increased risk of developing high blood pressure. Judgement and reaction time are impaired, leading to increased risk of accidents which may be life threatening.

Clinical features

As OSA progresses, affected individuals show symptoms of sleep deprivation such as poor memory and concentration, mood changes like irritability and anxiety, depression, decreased sexual drive, excessive daytime sleepiness and erectile dysfunction in men.

There is no recollection of the sleep interruption but affected individuals wake up feeling they did not have a good night's sleep. OSA may lead to medical problems like high blood pressure, coronary artery disease, stroke, memory loss, confusion and psychiatric conditions.

If one has excessive daytime sleepiness, it would be useful to request another person to observe oneself when asleep. They may be able to note the episodes of breathlessness.

Each cycle of OSA lasts 20 seconds to three minutes. It is common to have five episodes per hour per night.

Medical attention should be sought particularly if there is excessive daytime sleepiness, irritability, loss of concentration and depression. After taking a history, the doctor will perform a physical examination to exclude the medical conditions listed previously.

A referral to a specialist may be necessary. Treatment will be prescribed for medical conditions diagnosed.

Severe cases will be referred to a sleep laboratory in which several body functions are monitored overnight. The results of these tests will assist in determining the severity of OSA if it is present.

The severity of OSA is defined by the number of episodes per hour per night: mild (5 to 14 episodes per hour), moderate (15 to 30 episodes) and severe (more than 30 episodes).

Management

Lifestyle changes are useful in successful treatment of mild to moderate OSA. They include reducing weight, smoking cessation, avoiding alcohol in the evening and avoiding sedatives.

A useful measure is to sleep on the side as snoring is more likely when sleeping on the back. The obese may benefit from sleeping in an upright position.

Continuous positive airway pressure (CPAP), which is an apparatus that assists breathing during sleep, is useful for moderate to severe OSA or if there is no response to lifestyle changes.

It is a device with a mask that fits tightly over the nose and mouth and is held in place by straps. The mask is connected to a blower that delivers compressed air to prevent the soft tissue in the nose and throat from collapsing, thus keeping the airway open during sleep. Side effects like nasal dryness, nose bleeds, sore throat and skin abrasions were common with the earlier versions of CPAP.

However, the newer versions include a humidifier which has reduced the side effects considerably. If there is discomfort, adjustments can be made to the device to make it more comfortable.

There is usually marked improvement with CPAP, which has been reported to be useful for about 95% of people with OSA.

Oral devices are used in mild OSA or those who do not tolerate CPAP. They are small devices placed in the mouth to keep the throat open during sleep.

The side effects are increased salivation, toothache and gum pain. Its use is limited because it is difficult to predict its response in individual patients.

Central nervous system (CNS) stimulants may be prescribed for a short term in those who have severe daytime sleepiness or those on CPAP who have residual daytime sleepiness.

They make the person feel more alert and awake. Its side effects include blurring of vision, dizziness and depression.

As the CNS stimulants are potentially addictive, long term use is not recommended.

Surgery is considered when other treatments are unsuccessful and the quality of life is severely affected by OSA. It is recommended if there is a specific abnormality causing the OSA.

There are various procedures that include tonsillectomy, adenoidectomy and tracheostomy.

Tracheostomy is the most effective surgical procedure but it is disfiguring and decreases the quality of life.

It is only done for those with severe OSA when all other treatments fail.

Somnoplasty is a procedure that involves using radiofrequency energy to reduce the tissue volume of the soft palate which is at the back of the throat.

There are reports of improvement after the procedure but snoring recurred in about 40%. Larger and long-term studies are needed before it can be accepted as a treatment modality.

Prevention

There are several measures that can prevent or reduce the likelihood of OSA.

They include: appropriate eating and weight control; regular exercise; ceasing cigarette smoking as nicotine relaxes the muscles that keep the airway open; avoiding alcohol and medicines like sedatives and sildenafil before bed time; sleeping on the side; raising the head of the bed by 10 to 15 cm; and prompt treatment of breathing problems due to colds or allergies.

> Dr Milton Lum is member of the board of Medical Defence Malaysia. This article is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organisation the writer is associated with.

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