People with epilepsy who sleep on their stomach may be at higher risk of sudden unexpected death, scientists have warned.
Epilepsy is a brain disorder that causes repeated seizures and affects an estimated 50 million people worldwide.
"Sudden unexpected death is the main cause of death in uncontrolled epilepsy and usually occurs unwitnessed during sleep," said study author James Tao, from the University of Chicago in Illinois.
People with tonic clonic seizures (formerly known as grand mal seizures) that affect the entire brain are more likely to die suddenly than people with partial seizures that affect an area of the brain.
Researchers reviewed 25 studies that included 253 sudden unexpected death cases where body position was recorded.
They found that 73 per cent of the cases died in the stomach sleep position, whereas 27 per cent died in other sleep positions.
Looking at a subgroup of 88 people, researchers found that people younger than 40 were four times more likely to be found on their stomachs at the time of sudden death than people over 40.
A total of 86 per cent of those under 40 were sleeping on their stomachs, compared to 60 per cent for those over the age of 40.
"We're not sure why this was more common in younger people. It may be that they are more likely to be single and not have anyone with them during a seizure while sleeping," Tao said.
He noted that a person sleeping with someone who has a generalised tonic clonic seizure while on their stomach should help them turn over or on the side during or after the seizure.
"Similar to infant SIDS cases, adults often have an impaired ability to wake up after a seizure, especially a general seizure," Tao said.
"Our findings highlight an important strategy for preventing sudden unexpected death in epilepsy - that 'back is best,'" Tao said.
"Using wrist watches and bed alarms designed to detect seizures during sleep may also help prevent these deaths," Tao added.
The study is published in Neurology, the medical journal of the American Academy of Neurology.
