When we think of our own mortality, dying in our sleep in old age often seems like the least frightening, and probably painless, way to go for many of us.
But dying in your sleep can happen at any age, often being a huge shock to friends and family, leaving many questions unanswered.
So, why exactly do people die in their sleep? Are such deaths preventable?
Research suggests that too much or too little sleep is associated with a greater risk of mortality overall, but there is no clear evidence that the amount of sleep contributes to dying in one's sleep.
Most people who die in their sleep do so as a result of common health issues, experts say, and in some cases it is possible to lower our risk of dying overnight.
"Dying in your sleep is usually related to the heart, lungs or brain," Dr. Milind Sovani, a consultant in respiratory medicine (pulmonologist) at the U.K.'s Nottingham University Hospitals NHS Trust, told Newsweek. "Occasionally, people with diabetes can die in their sleep from low glucose levels."
Sometimes, more complicated conditions are a factor, Sovani says, adding that he had a young male patient in his late 30s die in his sleep recently of Pompe Disease, a glucose storage disorder that causes muscle weakness and breathing difficulties.
More commonly, however, conditions that lead to nocturnal deaths can be managed to lower the risk.
The supine position—lying flat on your back—that many people assume while sleeping can affect lung volume, Sovani says, adding that breathing at night can also be affected by conditions such as paralysis of the diaphragm—the muscle that controls breathing.
Neurological conditions such as epilepsy can also pose risks.
People with refractory epilepsy are more prone to a syndrome known as Sudden Unexpected Death In Epilepsy (SUDEP), which is believed to be caused by seizures that affect the body's respiratory, cardiac and electrocerebral functions.
Research published in 2018 in Frontiers in Neurology found that SUDEP was more likely to occur during the night or the early hours of the morning.
Similarly, high blood pressure that is not controlled can raise the risk of strokes, which can be fatal and occur during sleep.
Other conditions that are more likely to worsen at night include heart failure and sleep apnea, which causes the breathing to start and stop during sleep.
People with obstructive sleep apnea, one form of the condition, are more than 2.5 times as likely to experience sudden cardiac death between midnight and 6 a.m., according to a study by the Cleveland Clinic 2017.
The study also found that people over 60 were at highest risk of sudden cardiac death.
Although mild forms of the condition don't always need to be treated, more severe cases can be treated with a device known as a CPAP machine, which pumps air into a mask the sleeper wears over the mouth or nose at night.
Other heart disorders such as arrhythmias, or abnormal heart rhythms, can also be dangerous if not managed, Sovani says. People with these conditions are often fitted with pacemakers or implantable defibrillators; the former uses pulses to prompt the heart to beat at a normal rate, while the latter monitors heart rhythms and delivers a shock if it detects dangerous ones.
Chronic conditions such as hypertension, diabetes and obesity can contribute to overall poor health and raise the likelihood of complications. Managing these conditions and maintaining a healthy lifestyle can help reduce the risks.
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