What is sleep apnea?
In short: you are asleep, your throat closes, you stop breathing. Your brain panics and briefly wakes you so the airway opens again, and then it starts over. Ten, thirty, sometimes a hundred times a night.
The medical name is obstructive sleep apnea-hypopnea syndrome (OSAHS). Each pause lasts at least 10 seconds, 20 to 25 seconds on average. The worst part? You remember none of it in the morning.
Illustration being redrawn
An anatomical side-by-side of two sagittal views of the pharynx: on the left the airway open during normal breathing, on the right the obstruction typical of obstructive sleep apnea, with the tongue falling back and blocking the flow of air
anatomie-voies-aeriennes-apnee-obstructive-en · 1200×675px
What I see in the sleep laboratory
Most of the patients who come to us are not there because of "apneas". They come because they are exhausted, because they can no longer concentrate at work, or because their partner cannot take the snoring any more. The link with sleep is not one they make straight away.
The different types of sleep apnea
Obstructive apnea
The muscles of the throat relax during sleep and block the airway. The effort to breathe continues, but no air gets through.
Central apnea
The brain fails to send the right signals to the breathing muscles. The airway is clear, but the effort to breathe is missing.
Mixed apnea
It starts as a central apnea and develops an obstructive component. Rarer, and harder to treat.
This guide deals mainly with obstructive sleep apnea, which accounts for the great majority of diagnosed cases.
Sleep apnea in Belgium
Sleep apnea affects a significant share of the population in Belgium, and remains largely underdiagnosed. The figures speak for themselves:
~20%
of the adult population in Belgium affected
188 500
people in Belgium treated under the NIHDI in 2024
+77%
more people covered in six years (2018 to 2024)
80%
of cases still undiagnosed
More than 188,500 people in Belgium were covered by health insurance in 2024 for obstructive sleep apnea syndrome, which is 77% more than in 2018 (source: NIHDI, June 2025). Yet between 10 and 15% of the population could be affected, the great majority without knowing it.
In Belgium, the NIHDI (INAMI/RIZIV) convention for CPAP treatment is accessed through pulmonologists and accredited sleep centers. Understanding the CPAP convention →
Causes and risk factors
Sleep apnea comes from a combination of anatomical, physiological and behavioral factors. Some cannot be changed; others can be improved.
Anatomical
- • A narrow or receded jaw
- • Enlarged tonsils
- • A large tongue
- • A short, wide neck
- • A deviated nasal septum
Behavioral
- • Excess weight and obesity
- • Drinking alcohol
- • Taking sedatives or sleeping pills
- • Smoking
- • Sleeping on your back
Physiological
- • Reduced muscle tone in the upper airway
- • Chronic inflammation
- • Chronic nasal congestion
- • Gastroesophageal reflux
Cannot be changed
- • Age (over 50)
- • Being male
- • Menopause in women
- • Genetics and facial structure
Health consequences
Untreated sleep apnea is not simply a nuisance. It has serious consequences for health, in the short term and the long term.
Cardiovascular risk
HighHigh blood pressure (50% of patients with apnea), atrial fibrillation (twice the risk in severe apnea), heart failure, heart attack, stroke. Between 60 and 90% of patients whose hypertension resists medication have untreated sleep apnea.
Cognitive effects
ModerateTrouble concentrating and remembering, mood changes, irritability, a higher risk of depression.
Diabetes and metabolism
ModerateWorsened insulin resistance, a higher risk of type 2 diabetes, weight gain through hormonal disruption.
Accidents and sleepiness
At riskThe daytime sleepiness caused by apnea multiplies the risk of a road accident by two to three. It also has legal implications for professional drivers.
Did you know?
Sleep apnea and cardiology: an underestimated link
50 %
of patients with heart failure also have sleep apnea
×2
the risk of atrial fibrillation in severe apnea
60-90 %
of patients whose hypertension resists medication have untreated obstructive apnea
×2
the risk of coronary artery disease and cardiovascular events
Cardiologists play a key part in detecting sleep apnea. If you have resistant high blood pressure, atrial fibrillation or heart failure, ask your cardiologist to assess your risk of apnea: it is part of their training.
If you have a Boston Scientific pacemaker
Some Boston Scientific pacemakers and defibrillators carry ApneaScan™ technology, which analyses chest movement during sleep to detect apnea events. If you have a recent Boston Scientific device, your cardiologist can look at this data at your follow-up. It is one more way to find undiagnosed sleep apnea in cardiac patients.
Sources: Ligue Cardiologique Belge, Fédération Française de Cardiologie, Ottawa Heart Institute, MSD Manuals.
The AHI explained simply
Illustration being redrawn
An infographic explaining the cycle of sleep apnea in four stages: normal breathing, airway obstruction, a drop in blood oxygen, and a brief arousal of the brain. This cycle can repeat from 10 to more than 50 times an hour.
cycle-apnee-sommeil-4-etapes-en · 1200×675px
Theapnea-hypopnea index (AHI) counts the number of apneas and hypopneas per hour of sleep. It is the main measure used to diagnose apnea and to grade how severe it is.
< 5
Normal
No apnea
5 à 15
Mild
Mild apnea
15 à 30
Moderate
Treatment recommended
> 30
Severe
Treatment needed promptly
* In Belgium, the NIHDI CPAP convention is open from an AHI of 15 or more, or 5 or more with associated symptoms. Ask your doctor for an assessment of your own situation.
How is sleep apnea diagnosed?
The diagnosis rests on sleep studies carried out in a center or at home. In Belgium, two main tests measure the AHI: respiratory polygraphy (at home) and polysomnography (in a sleep center).
