Why do some people die in their sleep and is there any way to prevent it?

Some may worry about dying in their sleep – but luckily, unless you have a certain medical condition, the chance of this happening is relatively low.

There are many reasons why someone can die in their sleep, but they usually center around our three most important organs.

"Sleep death is usually related to the heart, lungs or brain," Dr Milind Sovani, a consultant in respiratory medicine at Nottingham University Hospitals NHS Trust, told Newsweek.

When we sleep, we are less likely to be able to respond to signals that might indicate that something is wrong with these organs.

"If I'm standing up and there's a 10-second pause in my heartbeat, I'm going to pass out and hit the floor hard and somebody's going to hear it," cardiologist Jack Flyer told the Wall Street Journal, adding that when you're sleeping, you just can't react to your symptoms."

According to Sumit Chuh, medical director of the Cedars-Sinai Heart Rhythm Center, sudden cardiac arrest (SCA) is responsible for 90 percent of sudden and unexpected deaths during sleep, also known as nocturnal deaths.

People at higher risk of SCA include those with coronary artery disease, an enlarged heart, or an irregular heartbeat (often rapid, also called ventricular fibrillation).

An SCA is when the heart suddenly stops beating, which in turn cuts off blood flow to major organs and can lead to death – 22 per cent happen between 10pm and 6am.

Obstructive sleep apnea (OSA) can also play a role in sudden sleep death. People with OSA may be more than 2.5 times more likely to experience sudden cardiac death between 12 a.m. and 6 a.m. than those without obstructive sleep apnea.

OSA involves a narrowing of the muscles in the airways, briefly stopping a person's breathing. This causes a lack of oxygen and in turn increases heart rate and blood pressure, which Dr. Sumit Chuh says increases the risk of SCA.

However, OSA itself is often not the cause of sudden death in sleep. It is most often associated with sudden death at night when another condition worsens, such as a heart problem.

Epilepsy is a common condition affecting the brain in which people experience repeated seizures. For people whose seizures cannot be fully controlled with medication, sudden death in epilepsy (SUDEP) is the leading cause of death. Although the reasons for SUDEP are not entirely clear, it often occurs at night, and some research suggests that sleep may increase the risk of it occurring.

A stroke can also be responsible for sudden death at night. About 25 percent of strokes occur during sleep, and conditions like OSA can also increase the risk. They occur when a clot or rupture of a blood vessel prevents blood from reaching the brain.

Without oxygen supply, brain cells die and parts of the body that have affected the control areas of the brain can no longer function properly, which can eventually become fatal.

For those with medical conditions that may increase the risk of sleep death, it is recommended that they speak to a doctor, who will be able to take into account factors such as lifestyle and family history. For everyone else, according to Dr. Chuh, the risk of sudden death is relatively low.

To keep this risk low, doctors recommend taking care of your health, getting enough sleep and exercise, and eating a healthy diet.