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NCT Number: NCT07364318

Cognitive Function in Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and has been increasingly recognized as a contributor to cognitive decline and a potential risk factor for neurodegeneration. Previous studies have identified several associated comorbidities, including vascular dysfunction, metabolic alterations, and neuroinflammatory changes. However, the impact and underlying interplay of these pathophysiological mechanisms remain poorly understood due to the lack of integrated, multidimensional assessment. This prospective, observational, longitudinal cohort study aims to investigate cognition and OSA-related physiological and pathophysiological processes in 100 adults newly diagnosed with OSA, who have no history of chronic diseases (except for overweight and obesity) and are not receiving chronic medication. A subgroup of patients with moderate to severe OSA indicated for positive airway pressure (PAP) therapy will be followed to evaluate its long-term effects on cognitive function and related mechanisms. All participants will undergo polysomnography (PSG), comprehensive neuropsychological assessment, brain MRI with volumetric analysis, biomarker profiling from blood and saliva, and evaluation of endothelial function, baroreflex sensitivity, and gut microbiome composition at baseline and after 12 months. PAP adherence will be continuously monitored. The primary objective of this study is to characterize the profile of cognitive impairment associated with OSA. Secondary exploratory analyses will focus on factors contributing to neurocognitive dysfunction in OSA.

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Key information

Conditions

OSA - Obstructive Sleep Apnea Apnea Cognitive Functions Dyssomnias Nervous System Diseases Respiration Disorders Respiratory Tract Diseases Sleep Apnea Syndromes Sleep Apnea, Obstructive Sleep Disorders, Intrinsic Sleep Wake Disorders

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Observational

Primary location

1st Department of Neurology, Faculty of Medicine, Comenius University and University Hospital Bratislava, Slovakia

Bratislava, 813 72, Slovakia

Location status: Recruiting

Location contact

Peter Musil, PhD.

CONTACT

[email protected]

+421903836788

About this study

  • Background OSA is a multifaceted sleep disorder characterized by repeated episodes of upper airway obstruction during sleep, leading to significant reductions in airflow and oxygenation. Beyond its primary respiratory manifestations, OSA is associated with major comorbidities such as cardiovascular, metabolic, and neurocognitive disorders, affecting overall health and quality of life. Epidemiological data suggest that OSA affects nearly one billion individuals worldwide, yet remains markedly underdiagnosed, particularly in middle-aged and older adults. Chronic intermittent hypoxia and sleep fragmentation have been implicated in the disruption of neural networks involved in attention, executive function, memory, and emotion regulation. Neuroimaging studies further support these findings, revealing region-specific brain alterations such as hippocampal and cortical atrophy, white-matter hyperintensities, and changes in cerebral perfusion and metabolism. These mechanisms may contribute to accelerated brain aging and increase the vulnerability to neurodegenerative processes. With the global rise in dementia and aging populations, identifying modifiable contributors to cognitive decline is critical. Given that OSA is a treatable condition, timely diagnosis and effective management may represent one of the most accessible interventions to prevent or delay cognitive deterioration in vulnerable populations.
  • Aim of the study The primary aim of this study is to perform a detailed cognitive assessment in patients with OSA. The investigators seek to analyze the baseline prevalence, severity, and pattern of cognitive deficits in this population to gain a clearer understanding of the initial cognitive status from which potential therapeutic or disease-related changes may occur. The secondary aims of this study are exploratory. The investigators plan to investigate potential associations between cognitive impairment and a spectrum of PSG, sleep-related, neuroimaging, anthropometric, laboratory, and vascular measures. The investigators aim to compare the sensitivity of the Montreal Cognitive Assessment (MoCA) with that of a comprehensive neuropsychological battery. Furthermore, the investigators will evaluate the longitudinal effects of PAP therapy on cognition and the related processes under investigation.
  • Inclusion criteria Patients with newly diagnosed OSA who have no history of other chronic diseases except for overweight and obesity, are not taking any medication, and are aged between 18 and 65 years.
  • Study methodology This is a prospective, observational, single-centre cohort study conducted at the Sleep Laboratory of the 1st Department of Neurology, Faculty of Medicine, Comenius University and University Hospital Bratislava. One hundred adults with OSA will be examined at baseline and after 12 months. As part of standard clinical care, all participants will undergo overnight diagnostic PSG to confirm the OSA diagnosis and determine its severity. Patients indicated for PAP therapy will start treatment according to clinical indications, with adherence monitored via device memory cards. Additional research assessments include neuropsychological testing, brain MRI with volumetry, blood and saliva biomarker analysis, assessment of vascular functions, anthropometric measurements, oxidative stress evaluation, and gut microbiome analysis. All assessments will be performed by trained research personnel in a standardized order. Participants will first be hospitalized to undergo PSG to confirm the OSA diagnosis. After confirmation, those meeting the inclusion criteria and providing informed consent will be enrolled in the study.
  • What are the possible benefits and risks of participating? Participants may benefit from early detection of cognitive dysfunction, metabolic or vascular abnormalities, and sleep-related pathology. Risks associated with study participation are minimal and primarily related to standard blood sampling and mild discomfort during assessments. No experimental or invasive interventions are applied.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Informed consent.
  • Age 18 - 65 years.
  • Newly diagnosed OSA according to the criteria of the American Academy of Sleep Medicine Guidelines (overnight PSG with an AHI ≥5 events per hour, hypopneas defined by ≥ 10 seconds of airflow reduction accompanied by ≥ 3% desaturation or an arousal).
  • Able to accomplish relevant tests and follow-up.

Exclusion criteria

  • History of any chronic disease other than overweight and obesity.
  • Severe psychiatric condition that could affect cognitive functions.
  • Chronic use of medication or nicotine that may affect the study results.
  • Prior neuropsychological assessment less than 6 months before the start of the research.
  • Prior therapy for OSA (i.e., CPAP, upper airway surgery, or oral appliance).
  • Motor or sensory deficits that would significantly complicate test administration.
  • Patients who do not have Slovak as their native language actively used in daily communication.
  • Considered by the study team as not suitable for enrollment based on clinical judgment.

Treatment and study plan

Primary outcomes

  1. Rey Auditory - Verbal Learning Test (RAVLT)

    Time frame: Baseline

    Measure of verbal episodic memory, encompassing immediate recall, learning across trials, delayed recall, and recognition.

    Units: total number of correctly recalled words (0-75); z-score. Higher scores indicate better performance.

  2. Figure Copy Task

    Time frame: Baseline

    A visuoconstructional task used to assess visual perception, spatial planning, and visual memory.

    Units: score 0-24 points; z-score. Higher scores indicate better performance.

  3. Controlled Oral Word Association Test (COWAT)

    Time frame: Baseline

    A verbal fluency task requiring rapid generation of words beginning with specified letters. It assesses phonemic fluency, executive function, and lexical retrieval.

    Units: number of correct words generated per minute; z-score. Higher scores indicate better performance.

  4. Category Fluency Test

    Time frame: Baseline

    A semantic fluency measure where subjects list as many words from a given category. It evaluates semantic memory and executive retrieval processes.

    Units: number of correct words generated per minute; z-score. Higher scores indicate better performance.

  5. Trail Making Test (TMT)

    Time frame: Baseline

    A two-part test evaluating processing speed, visual search, attention, and task-switching.

    Units: completion time in seconds; z-score. Shorter completion times indicate better performance.

  6. The Stroop Color and Word Test

    Time frame: Baseline

    Measure of selective attention, processing speed, cognitive flexibility, and inhibitory control.

    Units: completion time in seconds; z-score. Shorter completion times indicate better performance.

  7. Digit Span

    Time frame: Baseline

    A working memory test comprising forward and backward recall of digit sequences. Assesses attention, concentration, and short-term memory.

    Units: total score (0-14 points); z-score. Higher scores indicate better performance.

  8. Montreal Cognitive Assessment (MoCA)

    Time frame: Baseline

    General cognition screening targeting attention, executive function, memory, language, visuospatial abilities, and orientation.

    Units: total score (0-30 points); ≥26 = normal cognition. Higher scores indicate better performance.

  9. Generalized Anxiety Disorder 7-item scale (GAD - 7)

    Time frame: Baseline

    A 7-item self-report questionnaire to screen and assess the severity of generalized anxiety disorder. Items are rated on a 4-point scale. Units: total score (0-21 points); cut-off ≥ 10. Higher scores indicate greater anxiety symptom severity.

  10. Patient´s Health Questionnaire (PHQ - 9)

    Time frame: Baseline

    A 9-item scale assessing depression severity based on DSM IV criteria. Items are rated on a 4-point scale.

    Units: total score (0-27 points); cut-off ≥ 10. Higher scores indicate greater depressive symptom severity.

  11. Rey Auditory - Verbal Learning Test (RAVLT) 12 moths

    Time frame: Change from baseline to 12 months

    Measure of verbal episodic memory, encompassing immediate recall, learning across trials, delayed recall, and recognition.

    Units: total number of correctly recalled words (0-75); z-score. Higher scores indicate better performance. Assessments will be performed after 12 months.

  12. Figure Copy Task 12 months

    Time frame: Change from baseline to 12 months

    A visuoconstructional task used to assess visual perception, spatial planning, and visual memory.

    Units: score 0-24 points; z-score. Higher scores indicate better performance. Assessments will be performed after 12 months.

  13. Controlled Oral Word Association Test (COWAT) 12 months

    Time frame: Change from baseline to 12 months

    A verbal fluency task requiring rapid generation of words beginning with specified letters. It assesses phonemic fluency, executive function, and lexical retrieval.

    Units: number of correct words generated per minute; z-score. Higher scores indicate better performance. Assessments will be performed after 12 months.

  14. Category Fluency Test 12 months

    Time frame: Change from baseline to 12 months

    A semantic fluency measure where subjects list as many words from a given category. It evaluates semantic memory and executive retrieval processes.

    Units: number of correct words generated per minute; z-score. Higher scores indicate better performance.

    Assessments will be performed after 12 months.

  15. Trail Making Test (TMT) 12 months.

    Time frame: Change from baseline to 12 months

    A two-part test evaluating processing speed, visual search, attention, and task-switching.

    Units: completion time in seconds; z-score. Shorter completion times indicate better performance.

    Assessments will be performed after 12 months.

  16. The Stroop Color and Word Test 12 months.

    Time frame: Change from baseline to 12 months

    Measure of selective attention, processing speed, cognitive flexibility, and inhibitory control.

    Units: completion time in seconds; z-score. Shorter completion times indicate better performance.

    Assessments will be performed after 12 months.

  17. Digit Span 12 months.

    Time frame: Change from baseline to 12 months

    A working memory test comprising forward and backward recall of digit sequences. Assesses attention, concentration, and short-term memory.

    Units: total score (0-14 points); z-score. Higher scores indicate better performance.

    Assessments will be performed after 12 months.

  18. Montreal Cognitive Assessment (MoCA) 12 months.

    Time frame: Change from baseline to 12 months

    General cognition screening targeting attention, executive function, memory, language, visuospatial abilities, and orientation.

    Units: total score (0-30 points); ≥26 = normal cognition. Higher scores indicate better performance.

    Assessments will be performed after 12 months.

  19. Generalized Anxiety Disorder 7-item scale (GAD - 7) 12 months.

    Time frame: Change from baseline to 12 months

    A 7-item self-report questionnaire to screen and assess the severity of generalized anxiety disorder. Items are rated on a 4-point scale. Units: total score (0-21 points); cut-off ≥ 10. Higher scores indicate greater anxiety symptom severity.

    Assessments will be performed after 12 months.

  20. Patient´s Health Questionnaire (PHQ - 9) 12 months.

    Time frame: Change from baseline to 12 months

    A 9-item scale assessing depression severity based on DSM IV criteria. Items are rated on a 4-point scale.

    Units: total score (0-27 points); cut-off ≥ 10. Higher scores indicate greater depressive symptom severity.

    Assessments will be performed after 12 months.

Secondary outcomes

  1. Apnea-Hypopnea Index (AHI)

    Time frame: Baseline

    A polysomnographic measure representing the number of apneas and hypopneas per hour of sleep.

    Units: events per hour. Higher scores indicate more severe OSA.

  2. Apnea-Hypopnea Index (AHI) 12 months

    Time frame: 12 months

    A polysomnographic measure representing the number of apneas and hypopneas per hour of sleep.

    Units: events per hour. Higher scores indicate more severe OSA. Assessments will be performed after 12 months.

  3. Positive Airway Pressure (PAP) Therapy Adherence

    Time frame: 12 months

    Objective measure of treatment compliance obtained from PAP device data. Units: average hours of use per night. Higher scores indicate better adherence to therapy. Assessments will be performed after 12 months.

  4. Pittsburgh Sleep Quality Index (PSQI)

    Time frame: Change from baseline to 12 months

    A self-rated questionnaire comprising 19 items that evaluate sleep quality and disturbances over a one-month interval.

    Units: global PSQI score (0-21 points); cut-off ≥ 5. Higher scores indicate poorer overall sleep quality.

  5. Epworth Sleepiness Scale (ESS)

    Time frame: Change from baseline to 12 months

    An 8-item self-report questionnaire measuring habitual daytime sleepiness in common situations.

    Units: total score (0-24 points); cut-off ≥ 10. Higher scores indicate greater daytime sleepiness.

  6. Brain Volumetry

    Time frame: Change from baseline to 12 months

    Quantitative assessment of total and regional brain volumes will include total brain volume, gray and white matter volumes, hippocampal volume, cortical thickness, and other regional volumetric measures.

    Units: mL; changes in volumes reflect structural brain alterations.

  7. Body Mass Index (BMI)

    Time frame: Change from baseline to 12 months

    BMI calculated as weight (kg) divided by height squared (m²). Units: kg/m². Higher values indicate greater adiposity.

  8. Apolipoprotein E (APOE)

    Time frame: Baseline

    Genotype Genetic biomarker associated with neurodegenerative risk. Units: genotype category (ε2/ε2, ε2/ε3, ε2/ε4, ε3/ε3, ε3/ε4, ε4/ε4). ε4 allele presence indicates higher vulnerability to cognitive decline.

  9. Plasma Neurofilament Light Chain (pNfL)

    Time frame: Change from baseline to 12 months

    A biomarker of neuroaxonal injury. Units: pg/mL. Higher concentrations indicate greater neuronal damage.

  10. Total cholesterol

    Time frame: Change from baseline to 12 months

    Measure of circulating total cholesterol, representing the combined cholesterol content within all lipoprotein classes.

    Units: mmol/L. Higher values reflect a more adverse lipid profile.

  11. Trolox Equivalent Antioxidant Capacity (TEAC)

    Time frame: Change from baseline to 12 months

    Measure of total antioxidant capacity in plasma and saliva. Units: mmol Trolox equivalents/L. Lower TEAC values indicate reduced antioxidant defense and increased susceptibility to oxidative stress.

  12. Reactive Hyperemia Index (RHI)

    Time frame: Change from baseline to 12 months

    Measure of endothelial function assessed by pulse amplitude tonometry. RHI reflects the vasodilatory response of peripheral arteries following temporary occlusion.

    Units: ratio. Lower values indicate worse endothelial function.

  13. Baroreflex Sensitivity

    Time frame: Change from baseline to 12 months

    Indicator of autonomic cardiovascular regulation measured via Finometer. Units: ms/mmHg. Higher values indicate better baroreflex control.

  14. Gut Microbiome Composition

    Time frame: Change from baseline to 12 months

    Analysis of microbial diversity and abundance from stool samples. Units: Shannon index and Bray-Curtis dissimilarity. Lower alpha diversity and altered beta diversity indicate dysbiosis.

Study contacts

Contact information is provided by the study sponsor or research team.

Branislav Kollar, prof. MD PhD. MPH.

CONTACT

[email protected]

+421 948 334 417

Stela Biathova, MA

CONTACT

[email protected]

+421 905 218 668

Sponsors and collaborators

Lead sponsor

Comenius University

Other

Collaborators

  • Slovak Academy of Sciences
  • University Hospital Bratislava

Registry information

Official study title

Cognitive Function and Pathophysiological Mechanisms in Adults With Obstructive Sleep Apnea: Long-term Impact of Positive Airway Pressure Therapy

Acronym: CUFM1DN

Important dates

Study start
2024
Primary completion
2027
Study completion
2027
First posted
Jan 23, 2026
Registry last updated
Jan 23, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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