Key Facts

Obstructive sleep apnoea (OSA) is characterised by repetitive partial (hypopnoea) or complete (apnoea) collapse of the upper airway during sleep, resulting in intermittent hypoxia, hypercapnia, and sleep fragmentation.

Epidemiology

• Prevalence: ~4% of middle-aged men, ~2% of middle-aged women (symptomatic OSA)
• Affects up to 20-30% of the population when asymptomatic disease is included
• Vastly underdiagnosed: estimated 80% of moderate-severe cases undiagnosed
• Strong association with obesity (present in >70% of OSA patients)
• Increasing prevalence due to obesity epidemic

Aetiology

Anatomical factors:

• Obesity (increased pharyngeal fat deposition)
• Retrognathia, micrognathia
• Macroglossia
• Tonsillar/adenoidal hypertrophy (especially children)
• Nasal obstruction (polyps, deviated septum)
• Neck circumference >43cm (men), >41cm (women)

Non-anatomical factors:

• Male sex (hormonal influence; changes post-menopause)
• Age >50
• Alcohol, sedatives, muscle relaxants
• Hypothyroidism, acromegaly
• Neuromuscular disorders
• Genetic factors

Pathophysiology

• During sleep, pharyngeal dilator muscle tone decreases
• In OSA, pharyngeal anatomy is already compromised (fat deposition, structural factors)
• Upper airway collapses during inspiration → apnoea/hypopnoea
• Progressively increasing respiratory effort → arousal from sleep → airway reopens
• Cycle repeats hundreds of times per night
• Consequences: intermittent hypoxia → sympathetic activation → oxidative stress → endothelial dysfunction → cardiovascular disease

Symptoms (Nocturnal)

• Loud snoring (reported by bed partner)
• Witnessed apnoeas (bed partner sees breathing stops)
• Choking/gasping during sleep
• Restless sleep, frequent awakenings
• Nocturia

Symptoms (Daytime)

• Excessive daytime somnolence (most important symptom)
• Unrefreshing sleep
• Morning headaches
• Poor concentration and memory
• Irritability, mood changes
• Reduced libido/erectile dysfunction

Clinical Signs

• Obesity (BMI >30)
• Large neck circumference
• Retrognathia, high-arched palate
• Enlarged tonsils, macroglossia
• Nasal obstruction
• Hypertension (often resistant)

Red Flags

• Falling asleep while driving or operating machinery
• Severe desaturation on oximetry (<80%)
• Severe OSA (AHI >30) with comorbidities
• Children: OSA with failure to thrive, behavioural problems, cor pulmonale
• Resistant hypertension (OSA is the commonest secondary cause)

Bedside

• Epworth Sleepiness Scale (ESS): ≤10 normal; 11-14 mild; 15-18 moderate; >18 severe sleepiness
• STOP-BANG questionnaire: screening tool (Snoring, Tired, Observed apnoeas, Pressure/BP, BMI >35, Age >50, Neck >40cm, Gender male); ≥3 = high risk
• BMI and neck circumference: measure at assessment

Sleep Studies

• Pulse oximetry (overnight): screening; oxygen desaturation index (ODI) — number of >4% desaturations per hour
• Limited channel home sleep study: nasal flow, oximetry, respiratory effort — most commonly used in UK
• Polysomnography (PSG): gold standard; records EEG, EOG, EMG, airflow, respiratory effort, oximetry, ECG, body position; distinguishes obstructive from central events

Severity Classification (AHI)

• Mild: AHI 5-14
• Moderate: AHI 15-29
• Severe: AHI ≥30

Bloods

• TFTs: exclude hypothyroidism
• HbA1c: diabetes screening
• FBC: polycythaemia
• ABG: if OHS suspected (daytime hypercapnia)

Additional

• ECG: arrhythmias, LVH
• BP monitoring: often hypertensive
• ENT assessment: if anatomical obstruction (nasal polyps, tonsillar hypertrophy)

Non-pharmacological

• Weight loss: 10% weight loss can reduce AHI by ~50%; most important lifestyle modification
• Sleep position: avoid supine sleeping (positional therapy; tennis ball technique)
• Alcohol avoidance: especially in evening (relaxes pharyngeal muscles)
• Sedative avoidance: benzodiazepines, opioids
• Sleep hygiene: regular sleep schedule, avoid sleep deprivation
• DVLA notification: must inform DVLA if excessive sleepiness while driving; driving restriction until treated and ESS normalised

Pharmacological

• Limited role for pharmacotherapy in OSA
• Treat contributing conditions: hypothyroidism, allergic rhinitis (intranasal corticosteroids)

CPAP (Continuous Positive Airway Pressure)

• First-line for moderate-severe OSA (AHI ≥15), or mild OSA with significant symptoms/cardiovascular comorbidity
• Pneumatic splinting of upper airway via nasal/full-face mask
• Typical pressures: 5-15 cmH₂O (auto-titrating CPAP most common)
• Compliance: aim ≥4 hours/night for ≥70% of nights
• NICE TA139: CPAP recommended for moderate-severe OSA
• Benefits: reduces ESS, improves QoL, reduces BP, may reduce cardiovascular events

Surgical/Interventional

• Mandibular advancement device (MAD): for mild-moderate OSA or CPAP intolerance; custom-made preferred (NICE TA139)
• Tonsillectomy/adenoidectomy: first-line in children with OSA
• Uvulopalatopharyngoplasty (UPPP): rarely used; limited efficacy in adults
• Maxillomandibular advancement: for severe OSA with craniofacial abnormality
• Hypoglossal nerve stimulation: emerging therapy for moderate-severe OSA intolerant of CPAP (Inspire device)
• Bariatric surgery: if morbid obesity (BMI >40 or >35 with comorbidities); significant improvement in AHI

Referral Criteria

• All suspected OSA: sleep service referral for diagnostic study
• ENT: if anatomical obstruction
• Bariatric surgery: morbid obesity
• Complex cases: specialist sleep centre

• Untreated moderate-severe OSA: increased cardiovascular mortality (HR ~2-3)
• Untreated OSA increases RTA risk 2-7 fold
• CPAP normalises ESS and reduces cardiovascular risk when used consistently
• CPAP compliance >4 hours/night needed for cardiovascular benefit
• Weight loss of 10% can halve AHI; bariatric surgery can cure OSA in >60%
• Children: excellent outcomes with adenotonsillectomy (~80% cure rate)
• OSA contributes to resistant hypertension; treating OSA reduces BP by ~3-5 mmHg

OSA Severity Classification

Epworth Sleepiness Scale

DVLA Guidance