What causes sleep apnoea? 

Sleep apnoea is a relatively common condition where your breathing stops and starts while you sleep, which can lead to significant daytime fatigue and other health complications if left untreated. The most frequent form is obstructive sleep apnoea (OSA), which occurs when the walls of the throat relax and narrow during sleep, temporarily blocking the airway. Understanding why this happens is a vital step in managing the condition and improving your long-term health outcomes through lifestyle changes or medical intervention. 

What We’ll Discuss in This Article 

• The primary physical causes of airway obstruction during sleep 

• Common lifestyle factors that increase the risk of sleep apnoea 

• How physical attributes and genetics contribute to the condition 

• The impact of age and gender on sleep-disordered breathing 

• Specific medical conditions linked to an increased risk of OSA 

• The difference between obstructive and central sleep apnoea 

The Mechanics of Airway Obstruction 

Sleep apnoea is primarily caused by the muscles in the throat relaxing too much during sleep, which leads to a narrowed or completely blocked airway. Obstructive sleep apnoea (OSA) is caused by the walls of the throat relaxing and narrowing during sleep, which interrupts normal breathing. When the brain senses this drop in oxygen levels, it briefly rouses you from sleep to reopen the airway, often with a snort or gasp. While you may not remember these awakenings, they can happen many times an hour, preventing you from reaching the deep, restorative stages of sleep. 

Several factors can cause these throat muscles to become overly relaxed or the airway to be naturally narrower. For many people, a combination of physical anatomy and lifestyle triggers creates the perfect environment for these obstructions to occur. Because the body is working harder to breathe throughout the night, the heart and lungs are put under additional strain, which is why identifying the underlying cause is essential for effective treatment. 

Lifestyle Factors and Weight 

Excess weight is the most significant preventable cause of obstructive sleep apnoea in adults. Being overweight, particularly having a large neck, is a major risk factor for sleep apnoea because extra tissue can put pressure on the airway. This excess fat around the throat and neck area physically narrows the space through which air can pass. Furthermore, abdominal fat can push up against the diaphragm, reducing lung volume and making the airway more likely to collapse when you lie down. 

Other lifestyle choices also contribute to the relaxation of throat muscles. Alcohol acts as a sedative and causes the muscles in the back of the throat to relax more than usual, significantly worsening snoring and apnoea events. Similarly, smoking causes inflammation and fluid retention in the upper airway, which restricts airflow. Certain medications, especially those used for anxiety or sleep, can have a similar effect on muscle tone, making airway collapse more frequent during the night. 

Physical Attributes and Anatomy 

In many cases, the way your body is built plays a significant role in whether you develop sleep apnoea. Some individuals are born with a naturally narrower airway or have physical traits that make obstruction more likely. For example, a recessed lower jaw (micrognathia) can cause the tongue to fall further back during sleep, blocking the throat. Large tonsils or adenoids are also a primary cause of sleep apnoea in children and some adults, as they physically take up space in the airway. 

Physical Attribute	Impact on Sleep Apnoea
Large Neck Circumference	Extra tissue increases pressure on the airway walls.
Nasal Polyps	Blockages in the nose make breathing through the mouth more likely, increasing throat collapse.
Deviated Septum	Restricted nasal airflow can worsen the vacuum effect in the throat during inhalation.
Large Tongue	Can easily slide back and block the upper airway during deep sleep.

Age, Gender, and Medical Conditions 

The risk of developing sleep apnoea increases as you get older, partly because the muscles in the throat tend to lose some of their tone and elasticity over time. Men are also more likely to be diagnosed with the condition than women, though the risk for women increases significantly after the menopause. This is thought to be due to changes in hormone levels that previously helped maintain airway stability during sleep. 

Certain medical conditions are also closely linked to a higher incidence of sleep apnoea. Individuals with Type 2 diabetes, high blood pressure (hypertension), or a history of stroke are at a much higher risk. In some rarer cases, known as central sleep apnoea, the cause is not a physical blockage but a failure of the brain to send the correct signals to the muscles that control breathing. This form is often associated with heart failure or neurological conditions. 

Conclusion 

Sleep apnoea is primarily caused by the throat muscles relaxing and blocking the airway, with excess weight and neck circumference being the most common risk factors. Physical anatomy, lifestyle habits such as alcohol consumption, and underlying medical conditions all contribute to the severity of the condition. Addressing these causes through medical guidance and lifestyle adjustments can significantly improve sleep quality and cardiovascular health. If you experience severe, sudden, or worsening symptoms, call 999 immediately. 

Authority Snapshot (E-E-A-T Block) 

This article was created to provide the public with clear, factual information on the causes of sleep apnoea based on UK medical standards. It has been written by the MyPatientAdvice Medical Content Team and reviewed by Dr. Stefan Petrov, a UK-trained physician with experience in general medicine and emergency care. The content is strictly aligned with NHS and NICE clinical guidance to ensure accuracy and patient safety.