Key Facts

OSA is a condition in which the upper airway repeatedly collapses during sleep, causing intermittent hypoxia, sleep fragmentation, and excessive daytime somnolence. It has significant cardiovascular, metabolic, and neurocognitive consequences and is a major cause of preventable road traffic accidents.

Epidemiology

• Prevalence: 2-4% of middle-aged adults (estimated >1.5 million in UK)
• Significantly underdiagnosed — 80-90% of cases unrecognised
• Male:female ratio 2-3:1 (narrows after menopause)
• Prevalence increases with obesity (>20% in BMI >30 men)
• More common with increasing age

Aetiology

• Obesity: most important modifiable risk factor; fat deposition around pharynx narrows airway
• Anatomical: retrognathia/micrognathia, large tonsils/adenoids, macroglossia, deviated septum, nasal polyps
• Male sex: different fat distribution, hormonal factors
• Age: loss of muscle tone, weight gain
• Alcohol and sedatives: relax pharyngeal muscles
• Hypothyroidism: myxoedematous tissue, obesity
• Acromegaly: macroglossia, soft tissue overgrowth
• Down syndrome: midface hypoplasia, macroglossia, obesity

Pathophysiology

• During sleep, pharyngeal dilator muscle tone decreases
• In predisposed individuals, the airway narrows or collapses completely
• Apnoea (cessation of airflow ≥10 seconds) or hypopnoea (≥30% reduction in airflow with ≥3% desaturation or arousal)
• Results in intermittent hypoxia, hypercapnia, and repeated arousals from sleep
• Sympathetic nervous system activation → hypertension, cardiovascular disease
• Sleep fragmentation → excessive daytime somnolence, cognitive impairment
• Cyclical pattern: sleep → obstruction → desaturation → arousal → airway opening → sleep → repeat

Nocturnal Symptoms

• Loud snoring (often reported by bed partner)
• Witnessed apnoeas (bed partner observes breathing cessation)
• Gasping/choking episodes during sleep
• Restless sleep
• Nocturia

Daytime Symptoms

• Excessive daytime somnolence (falling asleep during activities)
• Non-refreshing sleep
• Morning headaches
• Poor concentration and memory
• Irritability and mood changes
• Reduced libido

Examination

• BMI (usually >30)
• Neck circumference (>43cm/17 inches in males)
• Mallampati score (III or IV — limited oropharyngeal view)
• Retrognathia/micrognathia
• Tonsillar hypertrophy
• Nasal obstruction
• Blood pressure (often hypertensive)

Red Flags

• Falling asleep while driving (immediate driving cessation, DVLA notification)
• Severe hypoxia (SpO2 <80%) on sleep study
• Coexisting COPD (overlap syndrome — worse hypoxia)
• Cor pulmonale (right heart failure)
• Occupational risk (HGV driver, pilot, machine operator)

Bedside

• Epworth Sleepiness Scale (ESS): validated self-report questionnaire (score 0-24; ≥11 abnormal)
• STOP-BANG questionnaire: screening tool (≥3 = high risk for OSA)
• BMI, neck circumference
• Mallampati score
• Blood pressure
• Pulse oximetry (may show desaturations)

Bloods

• TFTs (exclude hypothyroidism)
• HbA1c (diabetes screening)
• FBC (polycythaemia from chronic hypoxia)
• ABG if obesity hypoventilation syndrome suspected

Sleep Study

• Home sleep study (limited polygraphy): first-line
  • Measures airflow (nasal cannula), respiratory effort (chest/abdominal bands), SpO2, snoring, body position
  • AHI (apnoea-hypopnoea index): mild 5-14, moderate 15-29, severe ≥30 events/hour
  • ODI (oxygen desaturation index): number of ≥4% desaturations per hour
• Polysomnography (PSG): gold standard (in-lab); includes EEG, EMG, EOG; used if diagnostic uncertainty

Imaging

• Not routinely required
• Lateral cephalometry: if surgical planning (mandibular advancement)
• CT/MRI upper airway: if structural cause suspected

Special Tests

• Drug-induced sleep endoscopy (DISE): identifies site of upper airway collapse under sedation (guides surgical planning)

Non-pharmacological

• Weight loss: target 10% body weight reduction (can significantly reduce AHI)
• Positional therapy: avoid supine sleeping (use positional device) for positional OSA
• Alcohol and sedative avoidance (especially before bed)
• Sleep hygiene: regular sleep schedule, avoid caffeine

Pharmacological

• No first-line drug treatment for OSA
• Modafinil: may be considered for residual daytime sleepiness despite adequate CPAP use (specialist use only)
• Treat contributing conditions: hypothyroidism, nasal congestion

CPAP (Continuous Positive Airway Pressure)

• First-line treatment for moderate-severe OSA (AHI ≥15) (NICE TA139)
• Also offered for mild OSA (AHI 5-14) with significant symptoms
• Pneumatic splint holds airway open during sleep
• Reduces AHI to <5 in most patients
• Improves daytime sleepiness, blood pressure, cardiovascular risk, quality of life
• Compliance: critical; minimum 4 hours/night for benefit; long-term adherence 60-70%

Surgical

• Mandibular advancement device (MAD): oral appliance; alternative to CPAP for mild-moderate OSA or CPAP intolerance (NICE TA139)
• Tonsillectomy/adenoidectomy: first-line in children with OSA due to adenotonsillar hypertrophy
• Uvulopalatopharyngoplasty (UPPP): limited evidence; reserved for selected patients
• Maxillomandibular advancement: effective but major surgery
• Hypoglossal nerve stimulation (Inspire device): for moderate-severe OSA intolerant of CPAP
• Bariatric surgery: for morbid obesity with OSA

Referral Criteria

• Sleep clinic/respiratory referral: suspected OSA (ESS ≥11, witnessed apnoeas, excessive sleepiness)
• ENT referral: if upper airway structural cause (nasal obstruction, tonsillar hypertrophy)
• DVLA notification: mandatory if excessive daytime sleepiness affecting driving

• Untreated moderate-severe OSA associated with:
  • 3-6× increased risk of road traffic accidents
  • 2-3× increased risk of hypertension, cardiovascular events, and stroke
  • Increased risk of type 2 diabetes, AF, heart failure
  • Increased all-cause mortality
• CPAP treatment: reduces excessive daytime sleepiness, normalises AHI, reduces BP by 2-3mmHg, reduces cardiovascular events
• Weight loss of 10% can reduce AHI by 26-50%
• Compliance with CPAP is the key determinant of long-term outcomes
• OSA in children: tonsillectomy/adenoidectomy curative in >80%

OSA Severity Classification

STOP-BANG Screening Questionnaire

DVLA and OSA