Clinical manifestations and consequences

The symptoms of OSAS can be classified as those manifesting during sleep and those present during wakefulness (table 1). The most common complaint is excessive daytime sleepiness (EDS). However, EDS is not present in all patients with OSA and consideration should be given to other causes of diurnal sleepiness, such as shift work, medication and alternative diagnoses – periodic limb movement disorder and narcolepsy, for example.

During sleep While awake
Loud snoring/snorting Daytime sleepiness
Witnessed apnoeas by bed partner Non-restorative sleep
Awakening with choking Lack of concentration
Nocturnal restlessness Cognitive deficits
Vivid, strange or threatening dreams Changes in mood
Gastro-oesophageal reflux Morning headaches
Insomnia with frequent awakenings Dry mouth
Nocturia (urination at night) Impotence or decreased libido
Hypersalivation, teeth grinding  
Diaphoresis (sweating)  
Table 1 – Symptoms of obstructive sleep apnoea syndrome. Adapted from Riha, 2010, with permission from the publisher.

Nocturnal symptoms of OSAS are generally reported by a bed partner. The most common are snoring (which is almost always a feature), snorting, choking attacks terminating a snore, and witnessed apnoeas. Apnoeic episodes are reported by about 75% of bed partners.

A number of clinical features are associated with OSAS (table 2), but the predictive value of any single one for diagnosis is limited and not all will co-exist in the same patient. History and clinical examination alone (including blood pressure and BMI) can predict the presence of OSAS in only 50% of patients attending a sleep disorders clinic: definitive diagnosis requires overnight investigation.

Obesity (particularly central, BMI >30 kg·m-2)
Large neck circumference (>40 cm)
Small mandible, small maxilla
Retrognathia (back-set jaw)
Dental malocclusion, overbite
Reduced nasal patency
High and narrow hard palate
Elongated and low-lying uvula
Enlarged tonsils and adenoids
Macroglossia (large tongue)
Table 2 – Clinical features of obstructive sleep apnoea syndrome. BMI: body mass index. Adapted from RIHA, 2010, with permission from the publisher.

Recording and measuring sleep and breathing during the night

Previously, the most widely used method for the diagnosis of OSAS was detailed overnight polysomnography (PSG), but simpler diagnostic investigations are increasingly being used and these often take place in the patient’s home rather than in hospital. PSG remains the gold standard by which most newer developments in the measurement of breathing during sleep are assessed. PSG simultaneously monitors:

  • nasal and/or oral airflow

  • thoraco-abdominal movement

  • snoring

  • electroencephalogram (EEG)

  • electro-oculogram (EOG)

  • electromyogram (EMG)

  • oxygen saturation

Video recording of any abnormal movements may help identify other disorders. For accurate interpretation, manual scoring of the PSG recording is necessary, using guidelines for the interpretation of the EEG (sleep trace) and for the scoring of respiratory and other events.

Simplified recording systems are increasingly used (respiratory PSG or polygraphy). These measure airflow, respiratory effort, oxygen saturation and heart rate, but not EEG. Their advantages are greater capacity of service, lower cost and better portability and convenience to patients, who can set up the equipment in their own homes. Overnight oximetry is sometimes used as a screening test for identifying patients with OSAS but there are significant limitations to using oximetry alone.

Assessing daytime sleepiness

Sleepiness is difficult to define objectively and a wide variety of behavioural, performance-related, electrophysiological and questionnaire-based tests have been used. The most widely used and best validated and pragmatic scale for assessing daytime sleepiness is the Epworth Sleepiness Scale (ESS). This asks the subject to grade the likelihood of falling asleep in each of eight everyday situations (each scored from 0 to 3). An ESS score of greater than 11 out of 24 generally indicates abnormal daytime sleepiness, irrespective of age. However, as with any subjective measurement, the ESS can be prone to misinterpretation by the patient and, of course, a high score may be due to causes other than OSAS.


OSAS is an independent risk factor for hypertension and is associated with an increased risk of cardiovascular disease, abnormal glucose metabolism, depression and sleepiness-related accidents.

OSAS is not generally recognised as a specific cause of death and therefore is not routinely reported on death certificates. However, a number of databases are being created to document OSAS – in France and Denmark, for instance. The association with cardiovascular, cerebrovascular and metabolic disorders implies that OSAS contributes to increased morbidity and mortality in the general population.

Untreated OSAS increases the rate of road traffic accidents and work-related and domestic accidents. A recent meta-analysis has shown that most medical conditions confer an increased risk of a driving accident (between 1.2–2-fold compared to the healthy population). By contrast, OSAS was associated with a large increase in risk of a motor vehicle accident, with a relative risk of 3.7; this was second only to age and sex as a general risk factor.

Undiagnosed OSAS results in higher medical costs than those incurred by age- and sex-matched healthy individuals and the more severe the disease, the greater the medical cost. Even a single road accident due to sleepiness caused by OSAS can incur considerable health costs.

There has been no comprehensive evaluation of the financial burden of OSAS across Europe. However, reports from several countries have evaluated healthcare consumption, cost-effectiveness/utility of treatment and treatment costs. These are summarised in the further reading list. Table 3 illustrates the comparative cost-effectiveness of treating OSAS compared to ‘doing nothing’ across four different countries.

See the entire Sleep breathing disorders Chapter