Study design and participants
The present research’s procedures were approved by the university’s Ethical Board. Every patient offered informed written consent. Patients with ischemia stroke admitted to the Neural Psychiatric Disorders and Mental Health Centre of Anhui Province between January 2020 and May 2021 were invited to participate in our study. The inclusive criteria were as follows: (1) 18 to 75 years of age; (2) ischemic stroke proven via computed tomography (CT) and/or magnetic resonance imaging (MRI) and diagnosed by a neurologist; (3) NIHSS score between 1 and 5 at admission, defined as minor ischemic stroke; and (4) admission between 1 and 7 days after stroke onset.
Patients were excluded if they had (1) serious medical conditions, including respiratory failure and advanced CHF; (2) a history of any cognition impairment or psychiatric comorbidity before the stroke; (3) central sleep apnea, complex sleep apnea, or previously diagnosed OSA; or (4) refusal to participate in all testing. Data on demographic and clinical characteristics, including medical history, medications, and stroke details, were collected. Overnight polysomnography (PSG) was conducted to assess for OSA, and a set of neuropsychological assessments was conducted to evaluate cognitive function.
Sleepiness was assessed using the Epworth Sleepiness Scale (ESS) before performing PSG. Each stroke sufferer received PSG using the Alice 6 Diagnosis Platform, Respironics, America for one night at the sleep lab in our department. PSG was conducted over 8 h within 7 days of stroke onset. The parameters investigated included airflow (sensed by both thermistor and pressure transducer), six electroencephalographic leads (F3, F4, C3, C4, O1, and O2), electrooculographic, electrocardiographic, electromyographic (chin and leg muscles) measurements, thoracoabdominal respiratory effort, snoring, body position, blood oxygen saturation, and pulse rate.
Apnea was defined as air flow cessation ≥ 90% lasting for ≥ 10 s. Apnea with ongoing chest and abdomen effort, no chest and abdomen movements, and with initial lack of motion followed by respiratory effort were categorized as obstructive, central, and mixed apneas. Hypopnea was defined as a reduction in air flow or a reduction of thoracic and abdominal movement amplitude of 50% for ≥ 10 s with an oxygen desaturation ≥ 3%. The apnea hypopnea index (AHI) was the average of apneas and hypopneas per hour of sleep. The clinical diagnosis of OSA was made in patients with an AHI ≥ 5 by PSG . The sufferers were grouped into the no OSA group (AHI < 5), which served as the control group in this research, mild OSA group (AHI 5–15), and moderate-to-severe OSA (MS OSA) group (AHI ≥ 15).
The PSG parameters of sleep structure variables (arousal index, sleep efficiency, total sleep time (TST), proportion (%) of sleep duration in stage 3 sleep, and proportion (%) of sleep duration in the rapid eye movement (REM) stage) and hypoxia and disordered breathing (proportion (%) of nighttime spent with an oxyhemoglobin saturation < 90% (TSat90), lowest SpO2, average SpO2, and oxygen desaturation index (ODI)) of all patients were collected.
Every patient ompleted a set of standardized neuropsychology assessments to evaluate global cognition and clinical symptoms within 7 days after stroke. All tests were carried out in a quiet and separate room outside the stroke unit. These assessments included the following:
the CAVLT was utilized to assess functions of memory, including instantaneous memory, delayed memory, and recognition memory functions;
the Digital Span Test (DST), which includes forward and backward tests, used as a tool for investigating verbal attention and working memory;
the Montreal Cognitive Assessment (MoCA) was utilized to assess multiple cognition domains, such as short-term memory, attention and work memory, visual spatial capability, executive function, concentration, linguistic skill, and spatiotemporal orientation;
the Hamilton Anxiety Rating Scale (HAMA) was used to evaluate the severity of depressive symptoms;
the Hamilton Rating Scale for Depression (HAMD) was used to evaluate anxiety; and
the Stroop Color Word Test (SCWT), which comprises the Stroop color, word, and interference tests, was employed to evaluate executive function.
All data were analyzed via SPSS 23.0 (America). Standard descriptive statistics were used to summarize the clinical characteristics and sleep and cognitive assessments of all participants. The differences in the clinical characteristics, polysomnography parameters, and cognitive assessment among the 3 groups were analyzed via ANOVA. The post hoc (LSD) tests for multiple comparisons were also performed to compare the difference of polysomnography parameters and cognitive functions among the 3 groups. A binary logistic regression analysis with the “enter” approach was utilized to forecast OSA on the foundation of the AHI and potential predictors. Furthermore, the patients were classified into two groups that exhibit cognition damage (MoCA < 26) and normal cognition function (MoCA ≥ 26). The polysomnography predictor of cognitive impairment based on MoCA in stroke patients was also evaluated by a logistic regression analysis with adjustments for confounding covariates. p < 0.05 was used to signify statistical significance.