Electroencephalography Theta/Beta Ratio Decreases in Patients with Severe Obstructive Sleep Apnea

Figures & data

Table 1 Demographic and Clinical Characteristics of All the Participants

Variables	Control (n = 42)	OSA (n = 100)	t/χ^2-value	p-value
Demographics
Age (years)	52.1 ± 8.0	51.5 ± 7.2	0.508^a	0.612
Male (n, %)	19, 45.2%	63, 63%	3.824^b	0.051
BMI (kg/m^2)	25.3 ± 3.7	28.8 ± 4.3	−4.535^a	<0.001
ESS	4.93 ± 5.4	6.8 ± 4.8	−1.944^a	0.054
Comorbidities
Hypertension (n, %)	10, 23.8%	53, 53%	10.211^b	0.001
Diabetes (n, %)	5, 11.9%	21, 21%	1.636^b	0.201
CAD (n, %)	2, 4.8%	4, 4%	0.042^b	0.837
Arrhythmia (n, %)	2, 4.8%	9, 9%	0.743^b	0.389

Notes: Data are expressed as mean ± standard deviation or n (%) values; ^aWas for independent t-test; ^bWas for χ² test.

Abbreviations: OSA, obstructive sleep apnea; BMI, body mass index; ESS, Epworth Sleepiness Scale; CAD, coronary artery disease.

Table 2 Polysomnographic Characteristics of All the Participants

Variables	Control (n = 42)	OSA (n = 100)	t-value	p-value
Respiration
AHI (events/h)	3.0 ± 2.0	61.1 ± 18.2	−31.452	<0.001
AI (events/h)	0.5 ± 0.6	38.8 ± 25.3	−14.912	<0.001
HI (events/h)	2.5 ± 1.9	21.7 ± 17.2	−11.023	<0.001
LSaO2(%)	91.0 ± 2.2	75.4 ± 9.3	15.819	<0.001
ArI	10.5 ± 6.3	46.0 ± 21.0	−15.325	<0.001
Sleep stage, %
REM (%)	23.9 ± 32.8	15.1 ± 5.6	2.610	0.010
N1 (%)	14.4 ± 6.0	29.1 ± 13.4	−9.006	<0.001
N2 (%)	63.7 ± 7.6	54.5 ± 12.9	5.258	<0.001
N3 (%)	2.9 ± 5.2	1.2 ± 3.1	1.940	0.058
Sleep and wake time
Sleep latency (min)	21.8 ± 23.0	12.5 ± 16.8	2.681	0.008
REM latency (min)	108.4 ± 62.6	150.6 ± 88.1	−3.231	0.002
SE (%)	82.4 ± 12.3	82.9 ± 9.9	−0.220	0.826
TST (min)	417.3 ± 75.7	428.3 ±81.4	−0.750	0.455

Note: Data are expressed as mean ± standard deviation.

Abbreviations: OSA, obstructive sleep apnea; AHI, apnea hypopnea index; ArI, arousals per hour; LSaO2, lowest oxygen saturation; TST, total sleep time; SE, sleep efficiency; REM, rapid eye movement; N1, non-REM (NREM) stage 1; N2, NREM stage 2; N3, NREM stage 3; R, REM stage.

Table 3 Comparison of Relative Spectral Power and Frequency Band Ratios Between OSA and Control Groups

a. Comparison of Relative Spectral Power and Frequency Band Ratios Between OSA and Control Groups During NREM Sleep.
	Control (n = 42)	OSA (n = 100)	t-value	p-value	Cohen’s d
Delta (1–4Hz)	0.670 ± 0.060	0.679 ± 0.093	−0.607	0.545	0.106
Theta (4–8 Hz)	0.167 ± 0.036	0.149 ± 0.041	2.375	0.019	0.455
Alpha (8–12Hz)	0.096 ± 0.031	0.093 ± 0.037	0.437	0.663	0.085
Sigma (12–15Hz)	0.043 ± 0.018	0.045 ± 0.021	−0.533	0.595	0.099
Beta (15–20Hz)	0.025 ± 0.008	0.033 ± 0.020	−3.693	<0.001	0.461
NREM-TAR	1.866 ± 0.588	1.760 ± 0.549	1.028	0.306	0.189
NREM-TBR	7.599 ± 3.615	5.335 ± 2.402	4.378	<0.001	0.805
EEG slowing	5.577 ± 1.893	5.686 ± 2.710	−0.238	0.812	0.044
b. Comparison of Relative Spectral Power and Frequency Band Ratios Between OSA and Control Groups During REM Sleep.
Delta (1–4Hz)	0.582 ± 0.113	0.630 ± 0.124	−2.163	0.032	0.397
Theta (4–8 Hz)	0.210 ± 0.060	0.174 ± 0.060	3.251	0.001	0.600
Alpha (8–12Hz)	0.120 ± 0.054	0.105 ± 0.045	1.795	0.075	0.314
Sigma (12–15Hz)	0.042 ± 0.016	0.043 ± 0.023	−0.233	0.816	0.047
Beta (15–20Hz)	0.046 ± 0.019	0.049 ± 0.024	−0.602	0.548	0.132
REM-TAR	1.937 ± 0.604	1.813 ± 0.569	1.161	0.247	0.214
REM-TBR	5.344 ± 2.886	4.119 ± 1.963	2.517	0.015	0.539
EEG slowing	4.506 ± 2.670	5.213 ± 3.479	−1.179	0.240	0.217
c. Comparison of Relative Spectral Power and Frequency Band Ratios Between OSA and Control Groups During Total Sleep.
Delta (1–4Hz)	0.664 ± 0.061	0.676 ± 0.095	−0.748	0.456	0.139
Theta (4–8 Hz)	0.169 ± 0.037	0.151 ± 0.042	2.488	0.014	0.443
Alpha (8–12Hz)	0.098 ± 0.030	0.094 ± 0.037	0.565	0.573	0.114
Sigma (12–15Hz)	0.043 ± 0.018	0.045 ± 0.021	−0.574	0.567	0.099
Beta (15–20Hz)	0.026 ± 0.009	0.034 ± 0.020	−2.534	0.012	0.457
TS-TAR	1.851 ± 0.548	1.756 ± 0.533	0.961	0.338	0.177
TS-TBR	7.180 ± 3.107	5.143 ± 2.201	4.297	<0.001	0.815
EEG slowing	5.443 ± 1.860	5.609 ± 2.639	−0.371	0.711	0.068

Note: Data are expressed as mean ± standard deviation.

Abbreviations: TAR, theta/alpha ratio; TBR, theta/beta ratio; EEG slowing, (delta+theta)/(alpha+sigma+beta).

Figure 1 Comparisons of the relative spectral power during NREM sleep, REM sleep and total sleep between OSA patients and controls. *p < 0.05. Bars denote mean ± standard deviation.

Figure 2 Comparisons of the frequency band ratios (TAR and TBR) during NREM sleep, REM sleep and total sleep between OSA patients and controls. *p< 0.05. Bars denote mean ± standard deviation.

Table 4 Correlation Analyses Between AHI, Relative Spectral Power and Frequency Band Ratios of All the Participants

	NREM Sleep		REM Sleep		Total Sleep
	r	p-value	r	p-value	r	p-value
Delta (1–4Hz)	0.079	0.351	0.203	0.016	0.093	0.274
Theta (4–8 Hz)	−0.162	0.054	−0.237	0.005	−0.175	0.038
Alpha (8–12Hz)	−0.095	0.261	−0.174	0.038	−0.105	0.212
Sigma (12–15Hz)	−0.044	0.602	−0.064	0.447	−0.037	0.661
Beta (15–20Hz)	0.229	0.006	−0.020	0.809	0.204	0.015
TAR	−0.009	0.916	−0.029	0.728	−0.002	0.978
TBR	−0.324	<0.001	−0.162	0.054	−0.312	<0.001

Abbreviations: TAR, theta/alpha ratio; TBR, theta/beta ratio.

Table 5 Correlation Between Arousal Index, Relative Spectral Power and Frequency Band Ratios of All the Participants

	NREM Sleep		REM Sleep		Total Sleep
	r	p-value	r	p-value	r	p-value
Delta (1–4Hz)	0.147	0.080	0.289	0.000	0.162	0.054
Theta (4–8 Hz)	−0.241	0.004	−0.336	0.000	−0.255	0.002
Alpha (8–12Hz)	−0.166	0.049	−0.248	0.003	−0.179	0.033
Sigma (12–15Hz)	−0.055	0.514	−0.084	0.318	−0.049	0.562
Beta (15–20Hz)	0.234	0.005	−0.040	0.634	0.207	0.014
TAR	0.008	0.924	−0.020	0.817	0.015	0.860
TBR	−0.344	<0.001	−0.204	0.015	−0.338	<0.001

Abbreviations: TAR, theta/alpha ratio; TBR, theta/beta ratio.