Evolution of obstructive sleep apnea after ischemic stroke

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Oulu University Hospital auditorium 10

Topic of the dissertation

Evolution of obstructive sleep apnea after ischemic stroke

Doctoral candidate

MD Jaana Huhtakangas

Faculty and unit

University of Oulu Graduate School, Faculty of Medicine, Medical Research Center Oulu

Subject of study

Faculty of Medicine


Docent Pirkko Brander, Helsinki University Hospital


Professor Riitta Kaarteenaho, University of Oulu

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Evolution of sleep apnea after stroke

Sleep apnea is more common among stroke patients than we know. The doctoral thesis of MD Jaana Huhtakangas pointed out, that sleep apnea prevalence was over 90 % among stroke patients. Aftre six months follow-up, the prevalence of sleep apnea still remained high, and sleep apnea was aggravated in most of the stroke patients.

The prevalence of slee apnea among stroke patients is unkown because sleep recording is not usually performed on stroke patients.

Stroke is a common disease causing marked burden to both public health and economy and in Finland, the costs of stroke are approximately 1.1 billion euros annually. Sleep apnea is a risk factor for stroke, and approximately 7 % of sleep apnea patients experience stroke.

The final analysis included 204 adult stroke patients. Over half of study patients underwent thrombolysis treatment and others were treated without thrombolysis. Cardiorespiratory polygraphy was carried out at ward soon after diagnosis of stroke and sleep recording was repeated at home after a six-month follow-up. The total prtevalence of sleep apnea in this study was 91.2% on admission to hospital. Only nine study patients had previous sleep apnea diagnosis before stroke and almost all study patients had new sleep apnea diagnosis. The stroke patients with thrombolysis treatment had more (96.4 %) and severe sleep apnea than those without thrombolysis treatment. After six months follow-up, the prevalence of sleep apnea slightly increased (92.7 %) and aggravated in two thirds of the stroke patients.

The unattended portable monitor was a feasible tool to screen for sleep apnea in the acute phase of stroke. Both automatic scoring and manual scoring pointed out excellent agreement in arterial oxyhemoglobin decrease of ≥ 4% (ODI4), lowest arterial oxyhemoglobin saturation (SaO2) or percentage of time spent below 90 percent saturation. The automated scoring underestimated the severity of sleep apnea, recognized poorly the type of event, and missed 18.6% of sleep apnea diagnoses.

This study showed, that stroke volume correlated with proportion of time spent below saturation less than 90 %. The larger the ischemic stroke volume, the greater the time spent with saturation below 90%. "We recommend the cardiorespiratory polygraphy to those stroke patients who have arterial oxyhemoglobin saturation below 90 % over 10 % of time," Huhtakangas says.

"The screening of sleep apnea among risk groups is not yet common in Finland, but the screening of stroke patients, and especially focusing the screening on risk groups, may prove to be useful for patients, healthcare professionals, and society", Huhtakangas ponders.

In the future, it is also necessary to evaluate which subgroup of stroke patients profits the most from early screening and treatment of sleep apnea. Untreated sleep apnea impairs the recovery from stroke, causes prolonged hospitalization, and increases the risk for a new event and mortality.
Last updated: 1.3.2023