Investigating the Role of Obstructive Sleep Apnea on Depressive Symptoms in the UAE

Abstract

In the UAE, there are limited studies conducted to look at the association between depression and obstructive sleep apnea (OSA). Due to the overlapping symptoms between both disorders, depression is usually misdiagnosed when it is correlated with OSA. The early detection of the overlapping symptoms between OSA and depression can enhance the individual's health quality and decrease the associated healthcare expenses. Identifying shared biomarkers between OSA and depression within signals obtained from sleep recordings will allow for a faster and more efficient diagnosis of the comorbidity. Phase coherence between respiratory sinus arrhythmia (RSA) and respiration (λ RSA-RESP) has been proposed as an alternative measure for assessing vagal activity and slow-wave sleep (SWS). The aim of this thesis is to assess: 1) The changes in phase coherence between respiratory sinus arrhythmia (RSA) and respiratory movement in relation to variations in heart rate variability (HRV) and respiratory frequency in OSA patients with and without MDD. 2) Phase coherence of RSA as a function of sleep stages in OSA patients with and without MDD and how it differs from healthy subjects. 3) Slow-wave brain activity and its correlation with phase coherence between RSA and respiration in OSA patients with and without MDD and how they differ from healthy subjects. Overnight electroencephalogram (EEG), electrocardiograms (ECG), and breathing using plethysmography were recorded from 118 subjects, including 38 healthy individuals (control), 40 OSA subjects with MDD (OSAD+) and 40 OSA subjects without MDD (OSAD-). The interbeat intervals (RRI) and respiratory movement were extracted from ECG. RRI and respiration were resampled at 10 Hz, and the band passed filtered (0.10–0.4 Hz) before the Hilbert transform was used to extract instantaneous phases of the RSA and respiration. Subsequently, the λ RSA-RESP between RSA and Respiration and Heart Rate Variability (HRV) features were computed. Amplitude of RSA (ARSA) and respiratory frequency (fR) were quantified as well. Slow wave activity was computed by the amplitude envelope of the delta EEG (δ-wave) (0.5–4 Hz). The results showed that λ RSA-RESP was significantly increased in the OSAD+ group compared to the OSAD- group during NREM and REM sleep. These variations in λ RSA-RESP could not be attributed to variations in ARSA or fR, as no significant difference was found between OSAD+ and OSAD- groups in these variables. However, this increase was accompanied by a decrease in the low frequency (LF) component of HRV and the sympathovagal balance measured by the LF HF ratio. The findings suggest that depression might have lowered the sympathetic activity when accompanied by OSA, allowing for stronger synchronization between RSA and respiration. In addition, the results showed that overnight λ RSA-RESP was significantly greater, while HRV was significantly lower in OSAD+ compared to OSAD-. Also, overnight δ-wave activity was greater in OSAD- compared to both OSAD+ and control groups. Using auto- and cross-correlation analyses, it was found that overnight profiles of λ RSA-RESP and δ-wave were correlated only in healthy individuals compared to OSAD+ and OSAD-, indicating that sleep apnea may only have an impact on this cortical-cardiorespiratory correlation, rather than depression. The findings suggest that λ RSA-RESP and SWS activity appear to be biomarkers for assessing depression in OSA patients, whereas their correlation pattern can serve as a marker for only OSA. This could enhance diagnostic precision and provide valuable insights into the complex physiological mechanisms underlying the corambid of OSA and MDD.

Date of Award	2024
Original language	American English
Supervisor	AHSAN Khandoker (Supervisor)