Obstructive Sleep Apnoea (OSA)

Epidemiology and Risk Factors

• Typical demographic: Overweight, middle-aged men with a thick neck circumference (>40 cm). However, OSA also occurs in women, younger adults, and people with normal body habitus .

• Key risk factors:

  • Obesity (particularly central adiposity)

  • Anatomical abnormalities (e.g. high arched palate, retrognathia)

  • Craniofacial structural changes (e.g. in Down syndrome, where risk can be near-universal by adulthood)

  • Family history of OSA

  • Alcohol use

  • Smoking

  • Sedatives and muscle relaxants

Clinical Presentation

Night-time symptoms

• Loud, habitual snoring (often prompting bed partner to leave the bedroom)

• Witnessed apnoeas (bed partner observes pauses in breathing)

• Gasping, choking, or snorting awakenings

• Frequent nocturnal awakenings

• Nocturia

• Nocturnal sweating

Daytime symptoms

• Excessive daytime sleepiness (EDS)—patients may present with unintentional napping, difficulty staying awake when reading or watching TV, or near-miss motor vehicle accidents

• Morning headaches

• Poor concentration, irritability, mood changes

• Decreased libido or erectile dysfunction

Comorbidities

• Hypertension (particularly younger-onset hypertension)

• Arrhythmias (e.g. atrial fibrillation)

• Cardiovascular disease, cerebrovascular disease

• Diabetes mellitus

• Thyroid disease

• Down syndrome (high prevalence of OSA)

• Obesity

Untreated OSA is also associated with a higher risk of motor vehicle accidents due to excessive daytime sleepiness .

Screening Tools

Several validated questionnaires help identify high-risk individuals and guide referral for sleep studies:

• Berlin Questionnaire

• STOP-Bang (Snoring, Tiredness, Observed apnoeas, high blood Pressure, BMI, Age, Neck circumference, Gender)

• OSA-50 (focuses on obesity, snoring, apnoea, age)

• Epworth Sleepiness Scale (ESS): Measures subjective daytime sleepiness. An ESS ≥8 is considered significant, prompting further evaluation.

Under Medicare Benefits Schedule (MBS) criteria, a GP can directly order a sleep study for patients with an ESS ≥8 plus a high-risk result on one of the validated screening tools .

Diagnosis

Formal diagnosis requires an overnight sleep study (polysomnography), which may be:

• Home-based (unattended): Suitable for most patients with straightforward suspected OSA.

• In-laboratory (attended): Indicated if there is:

  • Comorbid neuromuscular disease, heart failure, or significant respiratory disease

  • Suspected respiratory failure or parasomnias

  • Intellectual or physical disability preventing at-home testing

  • Unsuitable home environment

  • Prior failed home-based study

  • Strong preference for a supervised study

Key Indices in Sleep Studies

• Apnoea–Hypopnoea Index (AHI): Number of apnoeas + hypopnoeas per hour of sleep.

  • AHI >5 = diagnostic for OSA (provided clinical context)

  • AHI >30 = severe OSA

• Hypoxic Burden: Measured by the percentage of total sleep time with SpO₂ <90% (P90) or total time below 90% (T90).

  • P90 or T90 ~1–5% suggests moderate disease

  • P90 >5% suggests more severe disease

A single AHI threshold does not always capture the full clinical picture; daytime sleepiness, comorbid conditions, and the presence or absence of significant hypoxaemia all guide management decisions.

Classification of OSA Severity

• Mild: AHI 5–15 events/hour

• Moderate: AHI 15–30 events/hour

• Severe: AHI >30 events/hour

Additional markers include the degree of daytime sleepiness, clinical impairment, and comorbidities—these factors often trump purely numerical thresholds.

Management of OSA in Adults

General (Conservative) Measures

All patients benefit from conservative interventions, which may be sufficient for those with mild disease and minimal daytime symptoms:

• Weight reduction: Even modest weight loss can significantly reduce apnoeic events.

• Smoking cessation: Improves nasal mucosal inflammation and reduces upper airway oedema.

• Avoidance of alcohol and sedatives: These worsen pharyngeal muscle relaxation and increase apnoeic episodes.

• Optimise sleep hygiene: Adequate and regular sleep minimises daytime fatigue and helps reduce apnoea severity.

• Intranasal corticosteroids: Especially helpful in reducing nasal congestion and improving airflow.

• Positional therapy:

  • Avoid supine sleeping if the patient has positional OSA. Simple measures (e.g. tennis ball sewn into the back of the pyjama top) may help.

  • Elevating the head of the bed (5–8 cm) can reduce rostral fluid shift, thus improving airway patency.

Continuous Positive Airway Pressure (CPAP)

CPAP is the gold-standard, most effective therapy for moderate to severe OSA, or mild OSA with significant daytime symptoms . It delivers pressurised air to keep the airway patent throughout sleep.

• Indications:

  • Severe OSA (AHI >30 or P90 >5%)

  • Moderate OSA (AHI 15–30 or P90 1–5%) with daytime sleepiness or other clinically significant issues (e.g. poorly controlled hypertension)

• Benefits:

  • Reduces apnoea/hypopnoea frequency

  • Improves daytime alertness, mood, and quality of life

  • May improve blood pressure control

  • Reduces risk of motor vehicle accidents

• Challenges:

  • Cost of CPAP machines (some patients may rent on trial first)

  • Mask fit and comfort

  • Adherence (motivation, claustrophobia, dryness, air leak)

Troubleshooting common CPAP problems:

• Nasal dryness/congestion: Use intranasal saline spray or switch to a humidified CPAP device.

• Mouth leak/dry mouth: Consider a chin strap or a full-face mask.

• Skin irritation or nasal bridge sores: Adjust mask fit; consider alternative mask interfaces.

• Persistent discomfort or intolerance: Offer short-term anxiolytic if anxiety is a barrier, reduce initial CPAP pressure, or recheck for machine fault or mask leak.

In complex cases or persistent intolerance, a repeat sleep study or referral to a sleep physician is recommended.

Mandibular Advancement Splints (MAS)

A dentist-fitted mandibular advancement splint may help:

• Mild to moderate OSA—especially if the patient cannot tolerate CPAP

• Primary snoring (with minimal apnoea/hypopnoea)

They work by holding the mandible slightly forward, enlarging the retroglossal space. Long-term issues include temporomandibular joint discomfort or occlusal changes. Simple “boil-and-bite” mouthguards are generally not recommended.

Surgical Interventions

• Adenotonsillectomy or nasal surgery: May help if significant hypertrophy or obstruction is identified, or to improve CPAP tolerance.

• Orthognathic surgery (e.g. maxillomandibular advancement): May be considered in patients with severe craniofacial abnormalities.

• Palatal surgery (uvulopalatopharyngoplasty): Historically used, but has poor long-term success in most patients.

• Upper airway pacemaker: Largely experimental and of unclear long-term benefit.

Special Considerations

OSA with Respiratory Disease

• Coexisting COPD or asthma increases risk of nocturnal hypoventilation. Consider advanced or in-laboratory sleep studies (with CO₂ monitoring) if clinically indicated.

• Ensure optimal management of the underlying respiratory condition (e.g. inhalers, smoking cessation, pulmonary rehabilitation).

Down Syndrome

Maintain a high index of suspicion for OSA. Adults with Down syndrome commonly have anatomical risk factors, and the prevalence of OSA approaches 100% by adulthood.

Pregnancy

OSA in pregnancy may be associated with hypertension or pre-eclampsia. Early detection and appropriate management are important.

Complications of Untreated OSA

• Cardiovascular morbidity: Systemic hypertension, arrhythmias (e.g. atrial fibrillation), higher risk of myocardial infarction and stroke

• Neurocognitive dysfunction: Poor concentration, depression, memory impairment

• Increased accident risk: Due to excessive daytime sleepiness

• Metabolic sequelae: Insulin resistance, worsened glycaemic control in diabetes