Longitudinal Cognitive Dysfunction in Patients with Obstructive Sleep Apnea Syndrome After Transient Ischemic Attack
Obstructive Sleep Apnea Syndrome (OSAS) is a condition characterized by repetitive episodes of partial or complete upper airway obstruction during sleep. This leads to recurrent arterial hypoxemia and sleep fragmentation. In middle-aged patients, untreated OSAS can cause impairments in attention, vigilance, certain aspects of memory, and executive function. Transient Ischemic Attack (TIA), on the other hand, is characterized by a transient episode of neurological dysfunction caused by focal brain ischemia. While TIA does not result in persistent deficits by definition, it significantly increases the risk of long-term cognitive impairment. OSAS is an independent risk factor for TIA. However, the extent and persistence of cognitive impairment following TIA in OSAS patients remain unclear. This study aims to explore the characteristics and influencing factors of cognitive function in OSAS patients within two years after a TIA event.
The study enrolled 163 patients with moderate to severe OSAS who were admitted to the Stroke Unit of Shengli Oilfield Central Hospital between 2012 and 2017. The inclusion criteria were: (i) patients aged 45 years or older with predominant OSAS exhibiting an apnea-hypopnea index (AHI) of at least 20/hour; (ii) an event of neurological symptoms within seven days. Exclusion criteria included: (i) patients with other sleep disorders such as rapid eye movement sleep behavior disorder; (ii) mini-mental state examination scores less than 24; (iii) patients with intracerebral space-occupying lesions or other neurological diseases that could impact cognitive or respiratory function; (iv) patients with major depression; (v) the presence of acute or chronic cardiopulmonary diseases affecting pulmonary function; and (vi) patients with contraindications for magnetic resonance imaging (MRI) or those who developed incident stroke during follow-up. Additionally, 134 patients with moderate to severe OSAS but without TIA were recruited as a control group.
Baseline neuropsychological assessments, basic clinical features, vascular risk factors, the Hospital Anxiety and Depression Scale (HADS), and MRI were evaluated within seven days after admission, at six months, and at two years follow-up. All patients were scored according to the ABCD2 scoring method.
The results showed no significant difference between OSAS patients with and without TIA in age, sex, education level, sleep parameters, mean score of the HADS-D, and presence of vascular risk factors. For OSAS patients with TIA, cognitive domains including executive function, attention, and information processing speed decreased continuously at baseline, six months, and two years follow-up, while other cognitive functions remained stable. There was a significant association of TIA event with decline in executive function, attention, and information processing speed in OSAS patients. Multiple linear regression analysis revealed that age and ABCD2 scores were adverse risk factors for executive dysfunction. Age, hypertension, Fazekas score, and ABCD2 scores were adverse risk factors for attention dysfunction and reduced information processing speed.
The study found that moderate and severe OSAS patients showed functional impairment in multiple cognitive domains in the first two years after TIA. Working memory remained relatively intact, but cognitive domains including attention, executive function, and information processing speed were severely impaired. The study suggests that long-term hypoxemia and sleep fragmentation can lead to widespread microstructural brain tissue damage and permanent neuronal damage, which are the pathological basis of cognitive dysfunction. Acute ischemic lesions may disrupt networks involved in cognitive processing and further accelerate cognitive decline. Vascular risk factors are associated with reduced performance on cognitive screening tasks. The presence of vascular risk factors such as hypertension and low-density lipoprotein cholesterol, along with age, were associated with reduced performance in executive function, attention, and information processing speed. The ABCD2 score, which also heavily loads on vascular risk factors, was associated with cognitive decline.
In summary, the decline in cognitive function, including attention, executive function, and information processing speed, in OSAS patients is a dynamic process, especially in the first two years after TIA. Early onset and persistent cognitive impairment are more likely to occur in moderate and severe OSAS patients with TIA. Long-term management of vascular risk factors may reduce the risk of cognitive impairment.
doi.org/10.1097/CM9.0000000000001428
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