Sleep apnea is a condition in which breathing repeatedly stops and restarts during sleep. Obstructive sleep apnea (OSA) — the most common form — occurs when throat muscles relax and block the airway. Central sleep apnea is rarer and involves the brain failing to send correct signals to the breathing muscles. OSA is defined by an Apnea-Hypopnea Index (AHI) of 5 or more events per hour.
Why it's so widely missed
Most people with sleep apnea are undiagnosed because the defining symptom — breathing pauses — happens while they are asleep and unaware. Their partner notices the snoring and gasping; they only know they feel inexplicably tired during the day.
The consequences of untreated OSA extend far beyond tiredness. Nocturnal oxygen dips activate the sympathetic nervous system, raise blood pressure and drive inflammation — increasing the risk of cardiovascular events, type 2 diabetes and cognitive decline over time.
Key symptoms
- Loud, chronic snoring — though not everyone who snores has sleep apnea
- Witnessed pauses in breathing during sleep (a partner's report)
- Waking with a choking, gasping sensation
- Excessive daytime sleepiness despite adequate time in bed
- Morning headaches (from overnight CO₂ retention)
- Difficulty concentrating, memory problems or 'brain fog'
- Frequent night-time urination (nocturia)
- Mood changes — irritability, depression, anxiety
- Dry mouth or sore throat on waking
The STOP-Bang screening questionnaire
STOP-Bang is the most widely used clinical screening tool. One point each for: Snoring loudly, Tired during the day, Observed apnoeas, high blood Pressure, BMI > 35, Age > 50, Neck circumference > 40 cm, male Gender. A score of 3 or more warrants further investigation.
How diagnosis is confirmed: sleep studies
A polysomnography (PSG) is the full overnight sleep study — the gold standard. It monitors brain activity, eye movements, muscle tone, heart rhythm, airflow, chest movement and blood oxygen simultaneously. It can be done in a hospital sleep lab or, increasingly, in the patient's own home with a portable device.
Home sleep apnea tests (HSATs) are simpler — they measure airflow, respiratory effort and oximetry without the neurological channels. They are appropriate for adults with a high pre-test probability of moderate-to-severe OSA and no significant comorbidities. The AHI from a home test uses different denominators, so results are interpreted slightly differently.
| AHI (events/hour) | Severity |
|---|---|
| 5–14 | Mild OSA |
| 15–29 | Moderate OSA |
| ≥ 30 | Severe OSA |
Treatment options
Continuous positive airway pressure (CPAP) — a mask worn during sleep that delivers pressurised air to keep the airway open — is the most effective treatment for moderate to severe OSA. AHI, oxygen saturation and sleepiness typically improve within days of starting.
For mild OSA and positional OSA (worse when lying on the back), mandibular advancement devices and positional therapy are effective alternatives. Weight loss reduces OSA severity meaningfully — every 10% reduction in body weight is associated with a 26% fall in AHI.
"Sleep apnea is not just snoring. It is a cardiovascular and metabolic risk factor that is sitting undiagnosed in millions of people."
Sara Nassereddin, Health Technology Writer, Looms