Here’s why some people die in their sleep

• Sudden cardiac arrest can occur during sleep, sometimes without warning.

• Sleep apnoea and stroke can also create serious health risks, while seizures can rarely lead to SUDEP.

• The exact cause of a death during sleep requires medical assessment; sleep itself is not necessarily the cause.

For many people, sleep is a time for the body to rest and recover. But in some cases, a person can die while asleep because of a serious medical condition affecting the heart, brain or breathing.

Dying in one's sleep does not necessarily mean the person had a known illness or that sleep itself caused the death. Some life-threatening conditions can occur suddenly, while others may remain undiagnosed for years.

Here are some possible causes.

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One of the major causes of sudden death is cardiac arrest, which happens when the heart suddenly stops pumping blood effectively.

According to the American Heart Association, cardiac arrest can occur because of dangerous abnormal heart rhythms. It can also be associated with conditions such as previous heart damage, a thickened heart muscle and certain inherited electrical abnormalities.

Cardiac arrest can happen with little or no warning, which means a person may experience it while asleep.

It is important to distinguish cardiac arrest from a heart attack. A heart attack occurs when blood flow to part of the heart muscle is blocked, while cardiac arrest is an electrical problem that causes the heart to stop pumping properly. A heart attack can, however, sometimes lead to cardiac arrest.

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Sleep apnoea is a condition in which breathing repeatedly stops and starts during sleep.

The National Heart, Lung, and Blood Institute says common signs include loud snoring, gasping for air and repeated pauses in breathing. Untreated sleep apnoea can increase the risk of serious problems, including heart attack and stroke.

This is why persistent loud snoring, nighttime gasping or excessive daytime sleepiness should not simply be dismissed as normal sleeping habits.

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A stroke occurs when blood flow to part of the brain is blocked or when a blood vessel in the brain ruptures.

A stroke can happen at any time, including during sleep. Some people only realise they have suffered a stroke when they wake up with symptoms such as weakness, numbness, difficulty speaking or problems with balance. These are medical emergencies and require immediate attention.

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People with epilepsy can, in rare cases, experience Sudden Unexpected Death in Epilepsy (SUDEP).

The exact cause is still not fully understood. Research has focused on breathing problems, dangerous heart rhythms and changes in brain function following a seizure. SUDEP occurs most often during sleep, when a seizure may go unwitnessed.

The risk is higher among people whose seizures are poorly controlled, making appropriate epilepsy treatment and seizure control important.

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Sudden death during sleep can also be associated with other serious conditions, including certain inherited heart disorders, blood clots, severe respiratory problems and other medical emergencies.

Because there can be several possible causes, the exact reason someone died in their sleep cannot reliably be determined simply by looking at the circumstances. A medical examination, and sometimes an autopsy, may be necessary to establish the cause.

Certain symptoms should not be ignored, particularly persistent chest pain, unexplained fainting, severe breathing problems, repeated nighttime gasping, unexplained seizures or symptoms suggesting a stroke.

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For someone who becomes unresponsive and is not breathing normally, emergency medical help should be sought immediately and CPR started if appropriate. Cardiac arrest can be fatal within minutes without treatment, but rapid CPR and use of an automated external defibrillator (AED), when available, can improve the chance of survival.

Ultimately, dying in one's sleep is not a single medical condition. It is a description of when a death occurs. The underlying cause may involve the heart, brain, breathing or another serious health problem.