What is it?

Sleep apnoea syndrome refers to breathing pauses lasting more than 10 seconds that occur during sleep. It is usually associated with severe snoring. These pauses may be apnoeas or hypopnoeas (a very significant, but not complete, reduction in airflow) and are generally associated with micro-arousals and oxygen desaturations greater than 3% in the bloodstream.

The severity index most commonly associated with this condition is the Apnoea–Hypopnoea Index (AHI), which includes the two most frequent types of breathing pauses. Overall, most of the population experiences some apnoeas or hypopnoeas during sleep, and up to 5 events per hour is considered normal.

The severity of sleep apnoea is classified as follows:

• Normal: AHI < 5/hour

• Mild: AHI between 5 and 15/hour

• Moderate: AHI between 15 and 30/hour

• Severe: AHI above 30/hour

Like simple snoring (snoring without significant breathing pauses), sleep apnoea mainly affects men (some recent statistics indicate a prevalence of over 20% of the population) and is also closely related to excess weight, although all factors that promote snoring also contribute to the development of this syndrome.

What are the symptoms?

When snoring is complicated by sleep apnoea, it may cause neurocognitive complications, with the most frequent symptom being excessive daytime sleepiness.

This sleepiness results from sleep fragmentation: each apnoea causes a micro-arousal from an electroencephalographic perspective. In other words, the patient does not consciously wake up, but brain function briefly arouses to restart breathing, fragmenting sleep with each apnoea. This disrupts normal nocturnal rest, leading to a persistent sensation of non-restorative sleep, which affects daytime activities.

In undiagnosed or untreated patients, this daytime sleepiness is associated with road traffic accidents and workplace accidents. For the same reason, sleep apnoea may lead to irritability, sudden mood changes, reduced work performance and easy fatigue. In men, this condition is also directly associated with cases of sexual impotence.

The most serious complications in adults are related to cardiovascular diseases. Due to the systematic reduction of blood oxygen levels during sleep and the constant strain placed on cardiac and cerebral function, patients with severe sleep apnoea have a much higher risk of acute myocardial infarction and stroke compared with individuals without this condition.

How is it diagnosed?

The diagnosis of snoring and sleep apnoea syndrome is made through a sleep study called polysomnography. This examination can be performed on an outpatient basis, with the patient taking equipment home to record a full night of sleep, or in a sleep laboratory, which is considered more accurate and reliable but less accessible.

These studies determine the number of respiratory events during sleep and provide additional valuable information, including: snoring intensity, the relationship between snoring and apnoeas with body position, desaturation index, number of micro-arousals (when an electroencephalogram is included), nocturnal heart rate variations, and the presence of complex apnoeas.

Physicians responsible for diagnosing and managing snoring and sleep apnoea are usually specialists in Otolaryngology (ENT), Pulmonology, Psychiatry or Neurology. More recently, a dedicated specialty in Sleep Medicine has been established.

Is there treatment?

In cases of severe sleep apnoea, the first-line and currently most effective treatment is CPAP. This is a device that delivers positive airway pressure during sleep, maintaining constant breathing throughout the night. Technological advances have reduced the size of these devices, making them easier to transport. In addition, the wide variety of available masks allows adaptation to virtually any face type.

However, despite these improvements, 20–30% of patients are unable to tolerate CPAP and prefer alternative solutions. These include the use of mandibular advancement devices or surgical options.

Surgical approaches generally aim to reconstruct the upper airway by widening it. This reconstruction may involve soft tissues (palate, uvula, tonsils, nasal septum or tongue base) or bony structures (bi-maxillary advancement).

More recently, the use of hypoglossal nerve stimulators or implants has opened new possibilities in this field. A small implant allows calibration of the upper airway through a minimally invasive procedure that is fully controllable wirelessly. Results have been very promising, and hypoglossal nerve neurostimulation may represent an effective long-term treatment based on a relatively simple procedure. This surgery is already available in Portugal.