Cognitive Function and Quality of Life in Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a serious health condition affecting 9-36% of the global population, associated with significant systemic morbidity that profoundly impacts general health and quality of life (QoL) beyond the immediate symptoms of sleep disruption. Among the serious repercussions of OSA is neurocognitive impairment, which extends beyond impaired attention to include deficits in memory, executive functions, and visuo-constructive performance. Various pathophysiological links between OSA and cognitive impairment have been proposed, including sleep fragmentation, intermittent hypoxia, and apnea-related cerebral hypoperfusion.

Although OSA has been linked to poorer health-related QoL, fewer studies have investigated cognitive impairment as a factor that potentially explains this diminished QoL. This study aims to comprehensively compare the cognitive performance of patients with OSA to that of matched healthy controls, and to verify the correlation between health-related QoL (derived from the SF-36) and multiple domains of neurocognitive function.

Participants enrolled in the study will undergo a series of structured evaluations:

• Clinical & Socio-economic Evaluation: A structured interview will capture clinical data including sleep symptoms, comorbidities, and medication use. Anthropometric measurements (BMI, neck, and waist circumferences) will be taken, and excessive daytime sleepiness will be assessed using the Epworth Sleepiness Scale. Baseline cardiopulmonary status will be evaluated via pulmonary function testing (spirometry), radiological assessment (Chest X-Ray and Transthoracic Echocardiography), and routine laboratory tests (CBC, ABG, electrolytes, thyroid function, and lipid profile).
• Diagnostic Polysomnography (PSG):All participants will undergo a full-night, supervised, in-laboratory diagnostic PSG at the Sleep Medicine Unit. Physiological parameters will be continuously monitored to score sleep stages and respiratory events, allowing researchers to accurately classify OSA severity based on the Apnea-Hypopnea Index (AHI).
• Cognitive Function Assessment: Within 10 days of the diagnostic PSG, participants will complete a computerized neurocognitive test battery using the Psychology Experiment Building Language (PEBL) software. The assessment will evaluate specific cognitive domains using the following tools:
• Attention: Assessed via a 10-Minute Psychomotor Vigilance Task (PVT) for sustained attention, and a Four-choice Test for selective attention.
• Memory: Assessed via a Memory Span Test targeting working memory, short-term memory, and visual processing.
• Executive Function: Assessed via the Wisconsin's Card Sorting Test to evaluate mental flexibility, problem-solving, and abstraction-reasoning.
• Quality of Life and Psychological Assessment: Participants will complete standardized questionnaires to evaluate their overall well-being and mood. These include the Short Form-36 Health Survey (SF-36) for general QoL, the Calgary Sleep Apnea Quality of Life Index (SAQLI) for disease-specific QoL, and the Beck Depression Inventory (BDI) to explore the potential impact of depressive symptoms on cognitive function and QoL.

Inclusion criteria

• Patients Group: Age > 18 years.
• Patients Group: Meeting the AASM diagnostic criteria for OSA.
• Control Group: Age and sex-matched community members related to the patients.
• Control Group: Education level, social status, and comorbidity-matched people.

Exclusion criteria

• Patients Group: OSA patients who are compliant on PAP therapy (> 4 hours, > 5 nights/week) for ≥ 6 months.
• Patients Group: Inability to comprehend and/or co-operate with the instructions provided by the investigators during neurocognitive function assessment.
• Patients Group: History of neurological comorbidities with potential cognitive impairment (previous cerebrovascular stroke, dementia).
• Patients Group: Patients who are maintained on medications that potentially impair cognitive performance (histamine receptor antagonist, antipsychotic, antidepressant, or mood stabilizer drugs).
• Patients Group: Use of alcohol, or illicit drugs that interfere with cognitive function (cannabis, opioids, amphetamine or equivalents).
• Control Group: Intermediate or high-risk of having undiagnosed OSA as assessed by the STOP-BANG questionnaire.