A dangerous type of snoring known as sleep apnoea can cause stroke by decreasing blood flow, raising blood pressure and harming the brain’s ability to modulate these changes, researchers reported yesterday.
The study may help explain why people with sleep apnoea are more likely to have strokes and to die in their sleep, the team led by Vahid Mohsenin of Yale University in Connecticut said.
“Three years ago we showed that patients with sleep apnoea ... they die or have strokes three times more than people with a comparable age or risk factors without sleep apnoea,” Dr Mohsenin said.
“We asked the question of why they have a higher risk for stroke.”
Writing in the Journal of Applied Physiology, Dr Mohsenin and colleagues said they tested 48 middle-aged men and women, 22 of whom had sleep apnoea but who were otherwise healthy. They checked blood pressure and used ultrasound to monitor blood flow in the brain.
They had the volunteers do a blood pressure test in which they squatted and then stood suddenly.
“We found that patients with sleep apnoea had difficulty compensating for the change in blood pressure,” Dr Mohsenin said. “They actually had decreased blood flow to brain.”
He said this showed the damage caused by sleep apnoea continues throughout the day.
“When you are up and around and experience changes in your blood pressure, or during the night when you have fluctuations in blood pressure due to apnoea, they have a hard time compensating for that,” Dr Mohsenin said.
“It is a carryover effect.”
Now, Dr Mohsenin said, his team will test whether statin drugs, known to reduce inflammation, can restore the lost brain function in sleep apnoea sufferers.
The patients will also later be treated using airway pressurization masks, or CPAP.
“The important thing is to recognise sleep apnoea early on so there won’t be any significant damage to the brain,” he said.
During sleep apnoea episodes, the upper airway becomes blocked, hindering or stopping breathing and causing blood oxygen levels to drop and blood pressure to rise. The person eventually awakens and begins breathing, restoring normal blood oxygen and blood flow to the brain.
Symptoms of sleep apnoea include feeling tired and needing a nap even after eight hours of sleep, loud snoring that disturbs others and snorting that indicates breathing has stopped.
Using an airway pressurisation mask can help the brain restore normal function, Dr Mohsenin said, although no study has shown it lowers the rate of strokes.
Reuters