A sleep burden index that considers multiple sleep-wake disturbances (SWDs) predicts subsequent cardiocerebrovascular events during the 2 years after a stroke, preliminary results on an ongoing study suggest.
The index, which combines sleep duration, sleep disordered breathing, restless leg syndrome (RLS), insomnia, and sleep duration, is a better predictor of new events than a single sleep disorder alone.
With further evidence of its usefulness, “the sleep burden index could be integrated into clinical routine,” Simone B. Duss, PhD, of the department of neurology at Bern (Switzerland) University Hospital, told a press briefing.
The findings were presented online at the Congress of the European Academy of Neurology 2020, which transitioned to a virtual meeting because of the COVID-19 pandemic.
Sleep-wake disorders are very common in stroke patients and may preexist or appear de novo as a consequence of brain damage, said Dr. Duss. “They may also be a result of medical, psychological, or environmental challenges these patients face after a stroke.”
There’s “clear evidence” that sleep disordered breathing is a risk factor for stroke, and negatively affects stroke outcome if left untreated, said Dr. Duss.
But for other SWDs, such as insomnia, RLS, and long and short sleep duration, “the evidence is less compelling,” she said. “However, some studies still suggest they influence stroke risk and outcome.”
Experts believe that sleep disturbances after a stroke lead to sleep fragmentation, as well as decreased slow wave sleep and REM sleep.
“This negatively affects inflammatory neuroprotective and synaptic plasticity processes during the recovery process of a stroke,” said Dr. Duss. “In the end, this results in worse outcomes with regard to recurrent events but also in activities of daily living and mood.”
The new analysis aimed to assess the impact of sleep-wake disturbances on recurrent events and outcomes following a stroke or transient ischemic attack (TIA). It included 438 patients with acute stroke (85%) or TIA (15%). The mean age of the study population was 65 years, and 64% were male.
Researchers used the National Institutes of Health Stroke Scale (NIHSS) to assess stroke severity. At admission, the mean NIHSS score was 4. Most strokes (77.2%) were supratentorial.
About one-fifth of stroke patients and one-third of TIA patients had experienced a previous event.
Researchers used functional outcome scores to assess the clinical course of the stroke or TIA. In addition, they regularly asked patients about recurrence of cardiocerebrovascular events.
Investigators assessed sleep disordered breathing during the acute phase of stroke, so within the first few days, using respirography. They collected information on the presence of other sleep-wake disturbances from questionnaires and clinical interviews at 1 month, 3 months, 1 year, and 2 years after the event.
About 26% of subjects showed severe sleep disordered breathing, “meaning that they had more than 20 apnea-hypopnea events per hour,” said Dr. Duss.
More than a quarter of patients reported subclinical symptoms of insomnia (measured using the Insomnia Severity Index), and up to 10% reported severe insomnia symptoms corresponding to the clinical diagnosis of insomnia, she said.
About 9% of patients in the acute phase of stroke, and 6% in the more chronic phase, fulfilled the diagnostic criteria of RLS.