What Causes Sleep Apnoea? Risks and Treatments

What causes sleep apnoea is a question that affects millions of people in the UK, many of whom are unaware they have the condition. Sleep apnoea occurs when the upper airway repeatedly collapses during sleep, disrupting breathing and fragmenting rest throughout the night. The causes range from excess body weight and anatomical features to neurological factors and lifestyle habits such as alcohol use. Understanding what drives the condition is essential, as it directly shapes which treatments are most effective and when urgent medical assessment is needed.

What actually causes sleep apnoea?

Sleep apnoea is most commonly caused by excessive relaxation of throat muscles during sleep, allowing soft tissue to collapse and block the upper airway. Central sleep apnoea, a less common form, results from the brain failing to signal breathing muscles correctly.

Sleep apnoea is caused by the repeated partial or complete collapse of the upper airway during sleep, which interrupts normal breathing. In the most common form, obstructive sleep apnoea (OSA), the muscles of the throat and soft palate relax excessively during sleep, allowing the surrounding soft tissue to fall inward and narrow or block the airway. This triggers a brief arousal from sleep as the brain detects falling oxygen levels, restoring muscle tone and reopening the airway, often with a loud snore or gasp. Because these arousals are usually very brief, most people have no memory of them, yet they can occur dozens or even hundreds of times each night.

A less common form, central sleep apnoea, arises not from a physical obstruction but from a failure of the brain to send the correct signals to the muscles that control breathing. This is more often associated with underlying neurological conditions, heart failure or the use of certain medicines, including opioids.^[1][5] Because the cause differs from OSA, management of central sleep apnoea focuses on treating the underlying condition and may involve specialist ventilation strategies rather than standard CPAP. A third type, complex or mixed sleep apnoea, combines features of both.

Several structural factors can predispose the airway to collapse. A narrow jaw, enlarged tonsils or adenoids, a large tongue, or a naturally small upper airway all reduce the space available for airflow. Nasal congestion, whether from allergies, a deviated nasal septum or chronic rhinitis, can promote mouth breathing and further destabilise the airway. Alcohol and sedative medicines relax throat muscles beyond their usual resting tone, which is why symptoms often worsen after drinking.^[3] Understanding the underlying mechanism matters because it directly informs which treatment is most likely to be effective for an individual. The NHS and NICE both provide detailed information on OSA definitions and management for patients and clinicians.

Who is most at risk of developing sleep apnoea in the UK?

Excess body weight is the single strongest modifiable risk factor for OSA, with men, older adults, smokers, and those with a family history also at significantly higher risk. Certain anatomical features and conditions such as hypothyroidism further increase susceptibility.

Excess body weight is the single strongest modifiable risk factor for obstructive sleep apnoea, with fatty deposits around the neck and throat narrowing the upper airway and increasing the likelihood of collapse during sleep. NHS guidance indicates that OSA is significantly more prevalent in people with obesity, and weight loss is consistently associated with a reduction in symptom severity. That said, sleep apnoea also affects people of a healthy weight, particularly those with certain anatomical features or other risk factors.

Men are approximately twice as likely as women to develop OSA, though the gap narrows after the menopause, suggesting that female sex hormones offer some degree of protection.^[8][3] Age is also an independent risk factor, as muscle tone throughout the body, including in the throat, naturally declines with age. Middle-aged and older adults therefore carry a higher background risk.

Other recognised risk factors include:

• A family history of sleep apnoea, pointing to a genetic contribution to airway anatomy and respiratory control

• Smoking, which causes upper airway inflammation and fluid retention in the throat^[9]

• Alcohol consumption, particularly in the hours before sleep

• Nasal congestion from any cause, including allergic rhinitis

• Hypothyroidism and acromegaly, both of which can alter soft tissue around the airway^[4][3]

• Pregnancy, especially in the third trimester, when weight gain and hormonal changes increase risk

Certain ethnic groups, including people of South Asian and Black African or Caribbean heritage, may have anatomical features that increase susceptibility even at lower body weights, though UK-specific prevalence data by ethnicity remain limited.

Anyone with persistent snoring, witnessed apnoeas, or unexplained daytime sleepiness should discuss these symptoms with their GP promptly. People with multiple risk factors, or where a bed partner has observed breathing pauses during sleep, should not delay seeking assessment.

How does sleep apnoea affect your body and overall health?

Untreated sleep apnoea raises the risk of hypertension, coronary heart disease, stroke, and type 2 diabetes through repeated oxygen drops and sympathetic nervous system surges each night. It also causes daytime sleepiness that may legally require DVLA notification and cessation of driving.

Untreated sleep apnoea places significant strain on the cardiovascular system, raising the risk of high blood pressure, coronary heart disease, stroke and atrial fibrillation. Each apnoea episode causes a transient drop in blood oxygen saturation and a surge in sympathetic nervous system activity, which repeatedly stresses the heart and blood vessels throughout the night. NICE guidance and NHS clinical resources recognise OSA as an independent risk factor for hypertension, and effective treatment has been shown to produce modest but meaningful reductions in blood pressure in some patients.^[11][13]

The fragmented, non-restorative sleep that results from repeated arousals leads to excessive daytime sleepiness, impaired concentration and slowed reaction times. This has direct safety implications for driving. If you have OSA and your sleepiness is likely to affect your ability to drive safely, you must stop driving and notify the Driver and Vehicle Licensing Agency (DVLA). You may be able to drive again once your condition is controlled and your doctor confirms it is safe to do so. Drivers of lorries, buses or other Group 2 vehicles face stricter rules and should check the DVLA's current guidance on fitness to drive.^[17] Employers and patients alike should be aware of these obligations.

Beyond cardiovascular and cognitive effects, sleep apnoea is associated with:

• Type 2 diabetes, partly through disrupted glucose metabolism and insulin resistance caused by intermittent hypoxia

• Depression and anxiety, which may both result from and contribute to poor sleep quality

• Erectile dysfunction and reduced libido

• Non-alcoholic fatty liver disease

• Worsening of pre-existing asthma or COPD

Children with OSA may present differently from adults, with behavioural problems, poor school performance and growth difficulties rather than obvious daytime sleepiness.^[20] If a child snores loudly, breathes through the mouth at night or is unusually restless during sleep, a GP referral for assessment is appropriate. Children are commonly referred to paediatrics or ENT services; where enlarged tonsils or adenoids are identified as a contributing factor, adenotonsillectomy is often considered as part of the treatment plan.

What treatments are available for sleep apnoea in the UK?

CPAP therapy is the NICE-recommended first-line treatment for moderate to severe OSA, keeping the airway open via pressurised air delivered through a mask during sleep. Mandibular advancement devices, lifestyle changes, and surgery are validated options for milder cases or those who cannot tolerate CPAP.

Continuous positive airway pressure (CPAP) therapy is the most effective treatment for moderate to severe obstructive sleep apnoea and is recommended by NICE (TA139) as the first-line intervention for eligible patients. CPAP works by delivering a continuous stream of pressurised air through a mask worn during sleep, acting as a pneumatic splint that keeps the upper airway open and prevents collapse. When used consistently, it eliminates most apnoea episodes, restores normal sleep architecture and reduces associated cardiovascular and daytime symptoms. CPAP devices are available on the NHS following a formal sleep study and diagnosis, typically arranged through a respiratory or sleep medicine clinic. Diagnosis is usually made via a home sleep apnoea test or, where indicated, an in-laboratory polysomnography study.

For people with mild to moderate OSA, or those who cannot tolerate CPAP, a mandibular advancement device (MAD) is a clinically validated alternative. These custom-fitted dental appliances hold the lower jaw slightly forward during sleep, increasing the space behind the tongue and reducing airway collapse. NICE guidance supports their use in appropriate patients, and they are available through some NHS dental and sleep services as well as privately.

Lifestyle modifications form an important part of management for all severity levels:

• Weight loss, which can substantially reduce OSA severity in people with overweight or obesity

• Avoiding alcohol and sedative medicines, particularly in the evening

• Positional therapy for people whose apnoeas occur predominantly when sleeping on their back

• Treating nasal congestion with appropriate medicines or, where indicated, surgery

Surgical options, including tonsillectomy, uvulopalatopharyngoplasty and, in selected cases, maxillomandibular advancement, are considered when anatomical factors are prominent and other treatments have failed or are unsuitable. In carefully selected adults at specialist centres, hypoglossal nerve stimulation is an option assessed under NICE interventional guidance. For people with qualifying BMI, referral for bariatric surgery in line with NICE obesity guidance may also be considered as part of a broader weight management plan.

For people exploring weight management as part of their OSA treatment plan, Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support. Weight-management medicines are only prescribed where clinically appropriate following a consultation. Anyone who suspects they have sleep apnoea should speak to their GP in the first instance, as a formal diagnosis requires an overnight sleep study before treatment can be initiated.

Scientific References

1. Tramadol 50 mg capsules – Summary of Product Characteristics.
2. HTG455: Hypoglossal nerve stimulation for moderate to severe obstructive sleep apnoea – evidence overview.
3. Sleep apnoea.
4. Central Sleep Apnea in Renal and Endocrine Disease.
5. Update on the Pathophysiology, Aetiology and Management of Central Sleep Apnoea.
6. Central sleep apnea: pathophysiologic classification.
7. Guideline scope: Obstructive sleep apnoea/hypopnoea syndrome (GID-NG10098).
8. Expert consensus on the diagnosis and treatment of obstructive sleep apnea in women.
9. Interaction between smoking and obstructive sleep apnea.
10. Restless legs syndrome in pregnancy: frequency, sleep quality, and questionnaire-defined risk of obstructive sleep apnea syndrome.
11. NG202: Obstructive sleep apnoea/hypopnoea syndrome and obesity hypoventilation syndrome in over 16s.
12. NG202 Chapter 1: Obstructive sleep apnoea/hypopnoea syndrome – recommendations.
13. Influence and implications of the renin-angiotensin-aldosterone system in obstructive sleep apnea: an updated systematic review and meta-analysis.
14. Effect of CPAP therapy on blood pressure in patients with OSA.
15. Effect of CPAP on Blood Pressure in Patients With Resistant Hypertension and Obstructive Sleep Apnea.
16. Excessive sleepiness and driving.
17. Miscellaneous conditions: assessing fitness to drive.
18. Obstructive sleep apnoea and type 2 diabetes mellitus.
19. Obstructive sleep apnoea and glucose dysregulation in type 2 diabetes: a systematic review of the literature.
20. The impact of obstructive sleep apnea on growth in patients with syndromic and complex craniosynostosis: a retrospective study.
21. TA139: Continuous positive airway pressure for the treatment of obstructive sleep apnoea/hypopnoea syndrome.
22. IPG598: Hypoglossal nerve stimulation for moderate to severe obstructive sleep apnoea.

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