8.2.3 Sleep apnoea
Definitions and prevalence
Sleep apnoea is present on overnight monitoring in 9 per cent of adult women and 24 per cent of adult men. Sleep apnoea syndrome (excessive daytime sleepiness in combination with sleep apnoea on overnight monitoring) is present in 2 per cent of women and 4 per cent of men. Some studies suggest a higher prevalence in transport drivers.
Obstructive sleep apnoea (OSA) involves repetitive obstruction to the upper airway during sleep, caused by relaxation of the dilator muscles of the pharynx and tongue and/or narrowing of the upper airway, and resulting in cessation (apnoea) or reduction (hypopnoea) of breathing.
Central sleep apnoea refers to a similar pattern of cyclic apnoea or hypopnoeas caused by oscillating instability of respiratory neural drive, and not due to upper airways factors. This condition is less common than OSA and is associated with cardiac or neurological conditions. It may also be idiopathic. Hypoventilation associated with chronic obstructive pulmonary disease (COPD) or chronic neuromuscular conditions may also interfere with sleep quality causing excessive sleepiness.
Sleep apnoea assessment
Clinical features. Common clinical features of sleep apnoea include:
- habitual snoring during sleep
- witnessed apnoeic events (often in bed by a spouse/partner) or falling asleep inappropriately (particularly during non-stimulating activities such as watching television, sitting reading, travelling in a car, when talking with someone)
- feeling tired despite adequate time in bed.
Poor memory and concentration, morning headaches and insomnia may also be presenting features.
The condition is more common in men and with increasing age. Physical features commonly include obesity (BMI greater than 35), a thick neck (greater than 42 cm in men, greater than 41 cm in women) and a narrow oedematous (‘crowded’) oropharynx. The presence of type 2 diabetes and difficult-to-control high blood pressure should also increase the suspicion of sleep apnoea. However, the condition may be present without these features.9
Subjective measures of sleepiness.10 Determining excessive daytime sleepiness is a clinical decision, which may be assisted with clinical tools. Subjective measures include tools such as the Epworth Sleepiness Scale (ESS) or equivalent. The responses to eight questions relating to the likelihood of falling asleep in certain situations are scored and summed. A score of 0–10 is within the normal range. Mild to moderate self-reported sleepiness (ESS score of 11–15) may be associated with a significant sleep disorder but only a small increase in crash risk.5 Scores of 16–24 are consistent with moderate to severe excessive daytime sleepiness and are associated with an increased risk of sleepiness-related motor vehicle crashes (odds ratio 3:15). Such tests rely on honest completion by the driver, and there is evidence that incorrect reporting may occur in some settings.11 The tools are therefore just one aspect of the comprehensive assessment.
A history of frequent self-reported sleepiness while driving or motor vehicle crashes caused by sleepiness also indicates a high risk of motor vehicle crashes (odds ratio 5:13).
Objective measures of sleepiness. Objective measures include the Maintenance of Wakefulness Test (MWT).12 Excessive sleepiness on the MWT is related to impaired driving performance.
Screening tools, which combine questions and physical measurements (e.g. the Multivariate Apnoea Prediction Questionnaire), have been evaluated for screening people for sleep disorders in a clinic setting. Their efficacy for screening large general populations remains under evaluation.
Referral and management. People in whom sleep apnoea, chronic excessive sleepiness or another medical sleep disorder is suspected should be referred to a specialist sleep physician for further assessment, investigation with overnight polysomnography and management. Referral to a sleep specialist should also be considered for any person who has unexplained daytime sleepiness while driving, or who has been involved in a motor vehicle crash that may have been caused by sleepiness. Kits for home assessment are widely available.
A person found to be positive for moderate to severe OSA on polysomnography, but who denies symptoms and declines treatment, may be offered an MWT (the MWT should include a drug screen and utilise a 40-minute protocol). For those with a normal MWT, the driver licensing authority may consider a conditional licence without OSA treatment subject to review in one year.
Commercial vehicle drivers. Commercial vehicle drivers who are diagnosed with OSA syndrome and require treatment are required to have annual review by a sleep specialist to ensure that adequate treatment is maintained. For drivers who are treated with CPAP, it is recommended that they should use CPAP machines with a usage meter to allow objective assessment and recording of treatment compliance. An assessment of sleepiness should be made and an objective measurement of sleepiness should be considered (MWT), particularly if there is concern regarding persisting sleepiness or treatment compliance. Mandibular splints with a usage meter are also acceptable.13