Graduation Semester and Year

2015

Language

English

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Bioengineering

First Advisor

Khosrow Behbehani

Abstract

Obstructive sleep apnea (OSA) is one of the most prevalent sleep related breathing disorders, with an estimated amount 17% of affected adults in the U.S. Research has linked OSA to mood and cognitive disorders, including Alzheimer’s disease. Structural changes in the brain have also been found to be associated with OSA. Several studies have shown deterioration of cognition in OSA patients because of structural and physiological changes due to apnea. The purpose of this research is to study the correlational relationships between cognitive measures and 1) quantitative measures of sleep quality; 2) measures of sleep disordered breathing; and 3) hypoxia resulting from apnea. Fifteen subjects (AHI 60.1±28.3, BMI of 34.3±7.0, ages 53±6.9 years) who were suspected of having OSA participated in an overnight study (4.90±1.68 hours) in an accredited sleep lab. Nocturnal polysomnography was used to identify multiple quantitative measures of sleep quality, disordered breathing, and hypoxia. A computerized neurocognitive testing battery was used to obtain measures of cognitive function. It was found that the composite memory aspect of cognition was significantly correlated with AHI (ρ value= -0.7216 p-value= 0.0024), arousals (ρ value= -0.5998 p-value= 0.0181), total number of events (ρ value= -0.6052 p-value= 0.0168), time in obstructive sleep apnea (in mins) (ρ value= -0.5735 p-value= 0.0254), and the percentage of total sleep time subjects spent in any type of sleep disordered breathing event (ρ value= -0.6589 p-value= 0.0076). In addition to the composite memory, verbal memory- correct hits immediate scores were significantly correlated with AHI (ρ value= -0.5314 p-value= 0.0415) and BMI (ρ value= 0.5368 p-value= 0.0391); verbal memory was sensitive to AHI (ρ value= -0.6386 p-value= 0.0104); visual memory- correct hits immediate was significantly correlated with the total number of events the subjects experienced throughout the night (ρ value= -0.5139 p-value= 0.0501), and Stroop test- commission errors were correlated with the percentage of sleep time spent in REM sleep (ρ value= 0.6830 p-value= 0.005). No significant correlations were found with hypoxia. This study showed that the current globally accepted method of quantifying the severity of apnea, AHI, is still a good indicator with several measures of cognition. While some metrics of hypoxia and the rates of duration of only OSA throughout the night were not significant with cognitive measures, some absolute metrics of time, duration rates of all events, and sleep fragmentation did show relationships with composite memory and other subset domains of cognition.

Keywords

Sleep apnea, Hypoxia, Cognition, Cognitive function, Memory, Sleep disordered breathing, Hypopnea, Apnea duration, Obstructive sleep apnea, OSA

Disciplines

Biomedical Engineering and Bioengineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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