Prior to this research, there was no data on the incidence of sleep apnea among Finnish ischemic stroke patients, because sleep apnea screening is not normally carried out on such patients.
Ischemic strokes are a common and economically significant illness for which the annual economic costs in Finland are approximately EUR 1.1 billion. Sleep apnea is one of the factors which increases susceptibility to ischemic strokes, and approximately 7% of sleep apnea patients later develop cerebral vascular disorder.
A total of 204 adult ischemic stroke patients took part in the study. Slightly more than half of them received thrombolytic therapy and the rest were treated without this. Cardiorespiratory polygraphy, a type of sleep apnea evaluation, was carried out on the patients immediately after diagnosis of the ischemic stroke, and this was then repeated at the patient's home six months later.
During the initial phase, 91.2% of the patients were diagnosed with sleep apnea. Of the patients examined, only nine had been found to have sleep apnea before the ischemic stroke, which means that most of the sleep apnea cases were new. Patients treated with thrombolytic therapy had more sleep apnea (96.4%) during the initial cardiorespiratory polygraphy and it was more severe than for the others.
Over the six-month observation period, the incidence of sleep apnea increased slightly (92.7%) and became severe for two thirds of the patients.
Taking measurements with a portable cardiorespiratory polygraphy device during the acute phase of the ischemic stroke was found to function well as a method for screening for sleep apnea. Both the automatic result and the manually assessed nocturnal recording result were very consistent with each other when the criteria assessed were a drop in oxygen saturation of four percentage points per hour, the lowest blood oxygen saturation or oxygen saturation below 90% during the night. However, the automatic analysis underestimated the severity of sleep apnea, detected poorly the type of breathing interruption, and failed to identify 18.6% of sleep apnea diagnoses.
The study showed that the size of the ischemic stroke was connected with the deterioration of oxygen saturation during the night. The ischemic stroke correlated with the period when the oxygen saturation was less than 90%.
‘Based on the study, we recommend carrying out sleep apnea screening for ischemic stroke patients with oxygen saturation levels that are below 90% over 10% of the time,’ says Huhtakangas.
‘Screening of sleep apnea high-risk groups is not yet common practice in Finland, but screening of ischemic stroke patients and especially particular high-risk groups could prove useful for patients, health care professionals and society as a whole,’ Huhtakangas believes.
The future challenge is to find out how to identify those ischemic stroke patients who benefit from immediate treatment of sleep apnea. Untreated sleep apnea affects the rehabilitation of these patients, prolongs their hospital stay and increases the risk of death and of ischemic stroke recurrence.
Last updated: 2.12.2019