Is β- amyloid a reliable marker for assessing neurocognitive functions in middle-aged OSAS patients??

Obstructive sleep apnea syndrome (OSAS) is a condition defined by recurrent episodes of airflow cessation or significant reduction during sleep, resulting in fragmented sleep patterns and intermittent hypoxemia. These physiological disturbances are known to contribute to cognitive deficits, including impairments in attention, memory, and overall cognitive function. In parallel, amyloid beta (β-Amyloid, Aβ) has gained prominence as a crucial biomarker in Alzheimer's disease pathogenesis, raising interest in its potential role in the early detection of neurocognitive dysfunction. This study aims to explore the association between plasma Aβ levels, neurocognitive performance, and polysomnographic parameters in middle-aged patients diagnosed with OSAS.

This prospective, cross-sectional study was conducted over a four-month period in a sleep disorders clinic. Patients who diagnosed as OSA in polysomnographic evaluation with no pre-existing neurocognitive conditions and possessed at least a primary school education were included. The study participants were evaluated using Montreal Cognitive Assessment (MoCA) test and Epworth Sleepiness Scale (ESS). Morning fasting blood samples were collected to measure plasma total Aβ levels.

A total of 126 individuals (mean age: 54.7 ± 7.5 years; 53 females, 42%) participated in the study. Based on their apnea-hypopnea index (AHI), patients were categorized into two groups: Group 1 (AHI < 15, 23.8% mild OSA) and Group 2 (AHI ≥ 15, moderate-severe OSA, 76.2%). The mean MoCA scores were 25 ± 7 in Group 1 and 24 ± 6 in Group 2. Following multivariable adjustment, reduced sleep duration, lower mean nocturnal oxygen saturation, and prolonged time with SpO2 below 90% (T90%) were significantly correlated with lower MoCA scores. Serum Aβ concentrations were notably elevated in patients with severe OSAS, exhibiting a negative correlation with MoCA scores and slow wave sleep stage. Additionally, serum Aβ levels showed a direct correlation with both AHI and oxygen desaturation index (ODI), while an inverse correlation was found with minimum oxygen saturation.

Neurocognitive impairment was common in OSAS patients. Elevated serum Aβ levels were found to be directly associated with OSA severity, and OSA-related hypoxemia was linked to diminished cognitive function.