Obstructive sleep apnoea (OSA) is defined by the British Thoracic Society as the ‘absence of breathing (>10 seconds) during sleep despite continuing respiratory effort, usually due to transient closure of the upper airways (pharynx).
The person wakes up or lightens their sleep to stop these episodes, which can lead to disrupted sleep and potentially excessive sleepiness.
Based on NHS data, between 2006 and 2019, 1 million people have been prescribed CPAP since treatment started in the UK in the early 1990s. However, around 30% of those prescribed discontinue therapy, so approximately 700,000 people in the UK are successfully established on CPAP.
OSA is common, yet up to 85% are undiagnosed and untreated. It is suspected that 1 in 4 adult males and 1 in 6 adult females may have underlying OSA. Undiagnosed OSA is closely associated with serious health problems, including hypertension, diabetes mellitus, stroke, and coronary artery heart disease. It can shorten life expectancy and lead to road collisions caused by undiagnosed sleepy drivers. Some common yet missed symptoms of OSA can be found here.
Causes and risk factors for OSA:
(A) Obesity:
For most adults, if your Body Mass Index (weight in kilograms (kg) by their height in metres (m) squared) is:
- Below 18.5: the underweight range
- 18.5 to 24.9: the healthy weight range
- 25 to 29.9: the overweight range
- 30 to 39.9: the obese range
- 40 or above: the severely obese range
Obesity leads to the deposition of fat in the neck and surrounding structures, which narrows the airways further during sleep. Thus, due to this ‘obstruction’ to normal airflow, inspiratory efforts increase to compensate, leading to partial arousal from sleep and a sudden airway opening. The result is repeated oscillations in the depth of sleep and subsequent fragmentation.
The best way to treat obesity is to eat a healthy, reduced-calorie diet and exercise regularly.
- Eat a balanced calorie-controlled diet as recommended by a GP or weight loss management health professional (such as a dietitian)
- Take up activities such as fast walking, jogging, swimming or tennis for 150 to 300 minutes (2.5 to 5 hours) a week
If lifestyle modifications do not work, certain medications reduce appetite and promote satiety and are available on consultation with a GP and, as a last modality, invasive surgery.
(B) Excessive alcohol intake and smoking:
There are several reasons why alcohol use may make OSA worse:
- i) Higher arousal threshold: Alcohol raises the arousal threshold, making it more difficult to wake up (alcohol depresses the normal functional brain activity). Therefore, breathing obstructions must be longer or more severe to cause an awakening.
- ii) Relaxation of muscles around the airway: Drinking alcohol can relax the mouth and throat muscles. This loss of muscle tone makes it more likely that these loose structures lead to narrowing.
iii) Increased nasal congestion: Alcohol increases blood flow to the nose’s blood vessels, causing a reduction in functional breathing area indirectly increasing the pressure on the airway.
Cigarette smoke contains a lot of irritants and chemicals which act as ‘noxious’ stimuli to the body, resulting in the body fighting back, akin to an infection. This ‘inflammatory soup’ causes damage to the normal elastic tissue of airways to lose their property and become rigid, predisposing to collapse. This inflammation promotes fluid retention that leads to the narrowing of the upper airway and subsequent symptoms of OSA.
(C) Physical and structural factors
- Jaw bone abnormalities: Some people have a receding jaw, which predisposes the tongue to fall back onto the posterior structures of the airway, leading to collapse. Treatment for this condition would be a thorough consultation with a local physician or dentist who could prescribe certain mandibular (the lower jaw bone) advancement devices to wear at sleep.
- Large tongue: A certain percentage of the population has large, bulky tongues, which could lead to airway obstruction during sleep due to reduced muscle tone. Tongue reduction is the most commonly reported surgical treatment for OSA in children with BWS; there are a variety of techniques depending on the type of pathology.
- Tonsillar & adenoid enlargement: Some children have enlarged palatine tonsils (often simply referred to as “tonsils” on the left and right sides at the back of the throat), and others have enlarged adenoids (also called the pharyngeal tonsil, found at the back of the nose). The medical terms for these enlarged tissue areas are “tonsil hypertrophy” and “adenoid hypertrophy.” Sometimes, both are enlarged. Adenoids are not to be confused with nasal polyps. These are benign growths in the membranes lining the nose. They usually only grow in adults. It is also important not to confuse enlarged tonsils with tonsillitis (an inflammation of the tonsils). These are two different medical conditions.
- Deviated nasal septum: Severe deviation of the central bony structure of one’s nose, like S-shaped or C-shaped, along with an increase in the size of the tissue nearby called turbinates, will lead to snoring and sleep disturbances as the airflow becomes turbulent due to reduced passage.
This is usually curable only with surgical intervention to restore the straightness of the bone.
(D) Pregnancy:
During pregnancy, intermittent snoring occurs in more than 50% of women. Snoring and OSA are independently linked to hypertension in pregnancy.
CPAP therapy has been demonstrated to be a safe adjunct for blood pressure management in the group of women with OSA and associated hypertension. Some reports have associated fetal growth reduction with OSA.
However, a firm relationship has yet to be established between OSA, fetal compromise, and pregnancy outcome.
(E) Systemic Diseases:
OSA could present as the initial presentation in various endocrine disorders such as Cushing’s Syndrome, acromegaly & hypothyroidism, which are diseases resulting from abnormal hormone secretion resulting in excessive growth of body tissue in the airway.
Physiological changes resulting from the cycles of reduced airflow lead to increased incidence of heart disease, strokes and even sudden deaths. Hence, it is imperative that all ‘snoring’ is not considered benign and warrants a thorough check-up with the local GP.
How to check for sleep apnoea?
Several diagnostic tools can be useful, including the STOPBANG and Epworth scoring systems.
STOPBANG consists of eight Yes or No questions with a possible highest score of 8. It is easy to use and is a reliable screening tool. Studies have demonstrated that with an increase in the STOPBANG score, there is an increase in the predicted probability and specificity of OSA, which makes the questionnaire ideal for identifying patients at high risk for OSA.
The specificity of STOPBANG is quoted as 43% and 37%, respectively, for moderate and severe OSA, suggesting a high false positive rate.
There are also more thorough investigations to diagnose OSA, revolving around a sleep study known as polysomnography (PSG), which comprises monitoring chest movement, airflow dynamics, heart rate, blood pressure and arterial oxygen saturation.
From the association with modifiable lifestyle factors, interventions aimed at weight loss, smoking cessation, alcohol intake, and increased physical activity may improve the symptoms of OSA.
Concerned you may have sleep apnoea or OSA?
Both OSA and sleep apnoea can profoundly affect your physical and mental well-being. It is important to contact the right doctors and dentists if you think you may be struggling with your sleep or breathing. If left untreated or unchecked, OSA and sleep apnoea can cause other health conditions, such as strokes and hypertension.
As a leading sleep and respiratory physician specialising in OSA and sleep-related breathing disorders, I offer consultations to diagnose and treat these conditions. Please contact me if you have any further queries about OSA or sleep apnoea or would like further advice on the potential treatments available.
