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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Recurrent pharyngeal collapse during sleep causing apnoeas (≥10 seconds) and hypopnoeas
- Strongly associated with obesity (BMI >30), male sex, age >40, neck circumference >43 cm
- Diagnosis: sleep study (home pulse oximetry or polysomnography) — apnoea-hypopnoea index (AHI) ≥5/hour
- First-line treatment: continuous positive airway pressure (CPAP) for moderate-severe OSA (AHI ≥15)
- DVLA implications: must not drive if excessive daytime sleepiness — must notify DVLA if condition affects driving
Overview
Obstructive sleep apnoea (OSA) is characterised by repetitive partial (hypopnoea) or complete (apnoea) collapse of the pharyngeal airway during sleep, leading to intermittent hypoxia, sleep fragmentation, and excessive daytime sleepiness. The apnoea-hypopnoea index (AHI) quantifies severity: mild (5–14/hour), moderate (15–29/hour), severe (≥30/hour). The principal mechanism is reduced pharyngeal dilator muscle tone during sleep combined with anatomical narrowing from obesity, macroglossia, retrognathia, or tonsillar hypertrophy. OSA is an independent risk factor for hypertension, cardiovascular disease, stroke, type 2 diabetes, and road traffic accidents.
Epidemiology
OSA affects approximately 2–4% of middle-aged adults, though it is substantially underdiagnosed. It is 2–3 times more common in men than women (though the gap narrows post-menopause). Obesity is the strongest risk factor: ~70% of OSA patients are obese. Other risk factors include increased neck circumference (>43 cm men, >40 cm women), craniofacial abnormalities, tonsillar hypertrophy, hypothyroidism, acromegaly, alcohol, and sedative use. OSA is associated with a 2–7 fold increased risk of road traffic accidents.
Clinical Features
Symptoms
Excessive daytime sleepiness (EDS) — the cardinal symptom; quantified by Epworth Sleepiness Scale (≥11/24 = abnormal)
Loud habitual snoring — often reported by bed partner
Witnessed apnoeic episodes during sleep (partner reports breathing pauses)
Unrefreshing sleep despite adequate duration
Morning headaches (nocturnal hypercapnia)
Nocturia
Poor concentration, memory impairment, irritability
Reduced libido
Signs
Obesity (BMI >30) and increased neck circumference
Crowded oropharynx (Mallampati score III–IV), macroglossia, tonsillar hypertrophy
Retrognathia (recessed jaw)
Hypertension (especially resistant to treatment)
Investigations
First-line
Epworth Sleepiness Scale (ESS)Self-reported questionnaire scoring daytime sleepiness (0–24). ≥11 = excessive sleepiness
Home sleep study (pulse oximetry ± nasal flow)Overnight recording — ≥4% oxygen desaturation index (ODI) ≥15/hour suggests moderate-severe OSA
Second-line
Polysomnography (PSG)Gold standard — measures AHI, oxygen saturation, sleep stages, and respiratory effort. Used if home study equivocal or complex cases
Blood testsTFTs (exclude hypothyroidism), HbA1c (diabetes screening), FBC (polycythaemia from chronic hypoxia)
Specialist
ABGIf obesity hypoventilation syndrome suspected (daytime hypercapnia + hypoxia + obesity + OSA)
Drug-induced sleep endoscopy (DISE)If considering surgical options — identifies site of airway collapse
1
Lifestyle modifications (all patients)
- Weight loss — even 10% weight reduction can significantly improve AHI
- Avoid alcohol and sedatives (especially in the evening)
- Sleep hygiene and positional therapy (avoid sleeping supine)
- Smoking cessation
2
CPAP (moderate-severe OSA, AHI ≥15/hour)
- NICE TA139: CPAP is the first-line treatment for moderate-severe symptomatic OSA
- Delivers continuous positive pressure via nasal or full-face mask, splinting the airway open
- Reduces daytime sleepiness, improves quality of life, and reduces cardiovascular risk
- Compliance is key — minimum 4 hours/night for benefit
3
Alternative treatments (if CPAP intolerant or mild OSA)
- Mandibular advancement device (MAD) — custom-fitted oral appliance for mild-moderate OSA or CPAP intolerance
- Surgery: tonsillectomy (if tonsillar hypertrophy), bariatric surgery (if morbidly obese), uvulopalatopharyngoplasty (limited evidence)
4
DVLA and occupational considerations
- Patients MUST NOT drive if they have excessive daytime sleepiness
- Must notify DVLA — driving licence may be revoked until symptoms controlled (usually with CPAP)
- Group 2 (HGV/bus) drivers: stricter requirements — must demonstrate adequate CPAP compliance
Complications
- Road traffic accidents: 2–7 fold increased risk — medico-legal implications
- Cardiovascular disease: Independent risk factor for hypertension, MI, stroke, AF
- Type 2 diabetes: Associated with insulin resistance
- Pulmonary hypertension: From chronic intermittent hypoxia
- Obesity hypoventilation syndrome: BMI >30 + daytime hypercapnia + OSA — may need non-invasive ventilation (NIV)
UKMLA Exam Tips
- 1Obese patient + daytime sleepiness + loud snoring + witnessed apnoeas = OSA
- 2Epworth Sleepiness Scale ≥11 = excessive daytime sleepiness — investigate with sleep study
- 3CPAP is first-line for moderate-severe OSA (AHI ≥15)
- 4Must not drive with excessive sleepiness — DVLA must be notified — this is a common exam question
- 5Resistant hypertension (on 3+ drugs) = screen for OSA
- 6OSA in children = tonsillar and adenoidal hypertrophy is the most common cause — adenotonsillectomy is first-line
- 7Polycythaemia on FBC in an obese patient = think chronic hypoxia from OSA
practicetest your knowledge on obstructive sleep apnoeaApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — respiratory and beyond.
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Obstructive Sleep Apnoea: guidance by region
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