World Stroke Day: NIMHANS study finds that part of sleep apnoea burden is a consequence of stroke

Sleep apnoea, a disorder in which breathing stops briefly during sleep, is common in stroke patients.
| Photo Credit: YANYONG

While it is known that sleep apnoea – a disorder in which breathing stops briefly during sleep – is common in stroke patients, the question whether this disorder is a cause or a consequence of stroke had not been established. A recent study by NIMHANS researchers has now found that a substantial part of severe sleep apnoea improves over the course of time on its own, indicating that at least a part of the burden of this disorder is a consequence of stroke.

Funded by the Indian Council of Medical Research (ICMR), the study has been accepted for publication in Annals of Indian Academy of Neurology (AIAN), the official journal of the Indian Academy of Neurology.

To evaluate the proportion, severity, type, and evolution of sleep-disordered breathing and arousals in ischemic stroke patients, a team of doctors from the Department of Neurology at NIMHANS, studied 105 stroke patients aged above 50, using polysomnography (PSG) that studies brain waves together with sleep time breathing pattern. The study was done twice – initially within one month of stroke and a follow-up study three months after.

Improve in sleep abnormalities

“Of the 105 patients studied, 88% had sleep apnoea, while 38% had severe sleep apnoea. In the follow-up study, 26% had sleep apnoea, while 12% had severe sleep apnoea. While waking up after sleep onset and brief arousals during sleep were high in patients during the first examination, these abnormalities improved substantially in the follow-up study. This indicates that at least a part of the sleep apnoea burden is a consequence of stroke,” said P.R. Srijithesh, Additional Professor of Neurology at NIMHANS, who is the lead author of the paper.

“The study also found a novel laterality in sleep efficiency in patients with stroke-related damage in the right side of the brain. These patients were found to have difficulty in initiating sleep, and would appear drowsy in the morning because of a poor night sleep,” the doctor told The Hindu on Monday. October 29 is observed as World Stroke Day.

“Further research involving sleep studies at longer follow-ups is necessary to know whether the trajectory of improvement continues in patients. This is important as currently, most patients with stroke are not evaluated for sleep apnea. If the condition persists and is indeed a risk factor for stroke as reported by earlier studies, it is an issue that needs to be addressed by the scientific community,” Dr. Srijithesh explained.

Snoring, a risk factor

Meanwhile, doctors have recognised snoring as a vital risk factor for stroke.

While all those who snore loudly do not necessarily have sleep apnoea, many with this disorder may not have snoring. While snoring and sleep apnoea are closely related, this does not mean that a person who snores has sleep apnoea, doctors said.

N.K. Venkataramana, founder-chairman and director-neurosciences at Brains Super Speciality Hospital, said breathing pauses during sleep can lead to a drop in the oxygen concentration in the blood. “The number of such episodes at night can vary from person to person. This increases the risk of stroke, given the significant duration of hypoxia or decreased level of oxygen that can cause damage to the brain as well as the increased risk of blood coagulation,” he said.

Amit Kulkarni, senior consultant and lead-neurology and stroke at Sakra World Hospital, said apart from conventional stroke risk factors such as diabetes, hypertension, high cholesterol, smoking, excessive alcohol consumption, obesity, and heart rhythm problems, obstructive sleep apnoea is a modifiable risk factor for stroke.