Frequency‑Specific Regional Homogeneity Alterations and Cognitive Function in Obstructive Sleep Apnea Before and After Short-Term Continuous Positive Airway Pressure Treatment

Figures & data

Figure 1 Schematic of recruiting procedures for the OSA patients in this study.

Table 1 Population and Clinical Characteristics of Particpants

Charateristic	HC Groups (N=21)	Pre-CPAP OSA (N=21)	Post-CPAP OSA (N=21)	P^a value	P^b value
Gender (male/female)	20/1	210/1	20/1	n/a	n/a
Age, years	40.1±8.6	40.1±8.4	n/a	1.000	n/a
BMI, Kg/m^2	21.1±1.5	27.3±3.8	27.2±4.0	<0.001	0.770
Education, years	10.1±3.6	12.4±3.8	n/a	0.033	n/a
AHI, /h	2.5±1.9	48.4±19.5	n/a	<0.001	n/a
Nadir SaO2, %	94.0±3.27	69.8±13.6	n/a	<0.001	n/a
SaO2 < 90%	0.3±0.2	15.0±17.4	n/a	<0.001	n/a
ESS, scores	2.8±1.9	10.8±5.1	7.5±3.9	<0.001	0.004
MoCA, scores	27.5±1.5	23.1±3.0	24.9±2.8	<0.001	0.004
MoCA: visual space and execution	4.4±0.7	3.6±0.9	3.8±1.0	<0.001	0.384
MoCA: naming	3.0±0.2	2.9±0.3	2.8±0.5	0.306	0.162
MoCA: delayed memory	4.0±1.0	1.9±1.3	3.0±1.2	<0.001	<0.001
MoCA: attentional function	5.7±0.7	5.2±1.2	5.3±1.4	0.553	0.833
MoCA: language	2.8±0.54	2.3±0.7	2.1±0.7	0.02	0.214
MoCA: abstract	1.9±0.5	1.6±0.7	1.5±0.7	0.057	0.428
MoCA: orienteering	6.0±0.2	5.5±1.0	5.8±0.5	0.352	0.261
HAMA, scores	4.4±2.3	7.1±4.9	4.0±3.7	<0.001	<0.001
HAMD, scores	3.1±1.5	4.4±2.4	2.9±1.8	<0.001	0.026
PSQI, scores	1.6±1.1	6.4±3.6	4.3±2.5	<0.001	0.010

Notes: P^a, two-sample t-test between pre-CPAP OSA patients and HCs; P^b, pair t-test between post- and pre-CPAP OSA patients. SaO2 < 90%, percentage of total sleep time spent at oxygen saturation less than 90%.

Abbreviations: ESS, Epworth sleepiness scale; MoCA, Montreal Cognitive Assessment; HAMA, Hamilton Anxiety Scale; HAMD, Hamilton Depression Scale; PSQI, Pittsburgh Sleep Quality Index.

Figure 2 The MoCA score were changed between post- and pre-CPAP OSA patients. (A) Each OSA patient changes. (B) The mean value of MoCA.

Figure 3 The ESS score were changed between post- and pre-CPAP OSA patients. (A) Each OSA patient changes. (B) The mean value of ESS.

Figure 4 Highly similar spatial distribution patterns of ReHo were found at the group level for healthy controls (A) and OSA patients (pre-CPAP (B) and post-CPAP (C)) in the typical frequency band (0.01–0.1 Hz), slow-4 frequency band (0.027–0.073 Hz), and slow-5 frequency band (0.01–0.027 Hz).

Table 2 Significant Altered ReHo in Typical Frequency Band (0.01–0.1 Hz) Between the Pre-CPAP OSA Patients and HC Groups (Two Sample t-Test)

Brain Regions	BA	MNI Coordinates			t-Scores	Cluster Size
		X	Y	Z
Brainstem	/	3	−36	−51	4.935	462
Right inferior temporal gyrus, fusiform	20	39	−15	−33	4.394	202
Left inferior temporal gyrus, fusiform	20	−23	−9	−40	4.224	315
Right inferior parietal lobule	40	51	−21	36	−4.076	122

Note: All clusters were reported with a voxel-level threshold of P < 0.01, GRF correction, and cluster-level of P < 0.05, two tailed.

Figure 5 Two-sample t-test in the typical frequency band (0.01–0.08 Hz) (A). The results were obtained by a 2×2 two-way ANOVA analysis (group: baseline OSA patients and HC; frequency band: slow-4 and slow-5), Main effects of group (B); Main effects of frequency band (C); Interaction between frequency bands and groups (D). The post hoc two-sample t-test for the slow-4 frequency band (0.027–0.073 Hz) (E) and slow-5 frequency band (0.01–0.027 Hz) (F). All results were reported at voxel-level p < 0.01 and cluster-level p < 0.05, GRF corrected.

Table 3 Significant Altered ReHo in Main Effect of Group (Pre-CPAP OSA and HC Groups)

Brain Regions	BA	MNI Coordinates			F Scores	Cluster Size
		X	Y	Z
Brainstem, Right cerebellum posterior lobe	/	6	−36	−51	48.036	1047
Right inferior temporal gyrus, fusiform	20	39	−15	−36	25.943	87
Left cerebellum posterior lobe	/	−3	−81	−33	31.027	256
Right inferior parietal lobule	40	39	−39	42	23.706	62
Left inferior parietal lobule	40	−39	−42	51	27.021	116

Note: All clusters were analyzed using a two-way ANOVA with a voxel-level threshold of P < 0.01, GRF correction, and cluster-level of P < 0.05, two tailed.

Table 4 Significant Altered ReHo at Specific Frequency Bands Between the Pre-CPAP OSA Patients and HCs (Two Sample t-Test)

Brain Regions	BA	MNI Coordinates			t-Scores	Cluster Size
		X	Y	Z
Slow-5 frequency band (0.01–0.027 Hz)
Brainstem, Right cerebellum posterior lobe	/	6	−36	−51	5.554	1756
Right superior temporal gyrus	22	57	−21	3	−4.34	81
Left precentral gyrus	4,6	−33	−15	46	−5.096	97
Left inferior parietal lobule	40	−39	−42	−54	−4.646	112
Slow-4 frequency band (0.027–0.073 Hz)
Brainstem	/	−6	−36	−48	4.563	262
Right cerebellum posterior lobe	/	30	−51	−42	4.226	110
Right inferior temporal gyrus, fusiform	20	3	−24	−18	4.241	193
Left inferior temporal gyrus, fusiform	20	−24	−9	−39	4.635	110
Right inferior parietal lobule	40	30	−48	48	−4.004	61

Note: All clusters were reported with a voxel-level threshold of P < 0.01, GRF correction, and cluster-level of P < 0.05, two tailed.

Table 5 Significant Altered ReHo at Typical Frequency Band (0.01–0.1 Hz) Between the Post-CPAP OSA Patients and Pre-CPAP OSA (Paired Sample t-Test)

Brain Regions	BA	MNI Coordinates			t-Scores	Cluster Size
		X	Y	Z
Left middle temporal gyrus, inferior temporal gyrus	21	−51	3	−21	4.863	105
Right superior temporal gyrus, middle temporal gyrus	22	48	−33	6	6.762	97
Bilateral supplementary motor area	6	3	−15	63	4.022	110
Right cerebellum posterior lobe	/	42	−84	−33	−4.495	206
Left superior frontal gyrus	10	−9	66	30	−4.230	78
Right inferior parietal lobule	39	42	−54	33	−5.08	206
Left inferior parietal lobule	40	−42	−81	39	−4.35	134
Right middle frontal gyrus	9	33	39	48	−4.017	83

Note: All clusters were reported with a voxel-level threshold of P < 0.01, GRF correction, and cluster-level of P < 0.05, two tailed.

Table 6 Significant Altered ReHo at Specific Frequency Bands Between the Post- and Pre-CPAP OSA (Paired Sample t-Test)

Brain Regions	BA	MNI Coordinates			t-Scores	Cluster Size
		X	Y	Z
Slow-5 frequency band (0.01–0.027 Hz)
Left middle temporal gyrus	37	−54	−66	6	4.201	78
Right precentral gyrus	6	45	−6	33	4.958	112
Right middle frontal gyrus	6	27	−18	51	5.459	135
Right supplementary motor area	6	9	−12	72	4.197	64
Left precentral gyrus	6	−27	−18	69	4.211	61
Left cerebellum posterior lobe	/	−42	−66	−39	−3.892	60
Right medial frontal gyrus	32	12	39	30	−4.474	64
Right inferior parietal lobule	40	57	−54	33	−5.291	237
Left inferior parietal lobule	40	−51	−60	45	−3.791	94
Slow-4 frequency band (0.027–0.073 Hz)
Right superior temporal gyrus	22	48	−33	6	5.082	103
Right supplementary motor area	6	6	−21	48	4.436	67
Left superior frontal gyrus	10	−15	66	12	−3.709	90

Note: All clusters were reported with a voxel-level threshold of P < 0.01, GRF correction, and cluster-level of P < 0.05, two tailed.

Figure 6 Pair sample t-test in the typical frequency band (0.01–0.08 Hz) (A), the slow-4 frequency band (0.027–0.073 Hz) (B), and slow-5 frequency band (0.01–0.027 Hz) (C) between pre- and post-CPAP OAS patients. The CPAP treatment-related changes of the ReHo in the three different frequency bands in OSA patients (D). All results were reported at voxel-level p < 0.01 and cluster-level p < 0.05, GRF corrected.

Figure 7 Mean ReHo z-value of HC, pre- and post-CPAP OSA patients in altered brain regions, which were compared before and after CPAP treatment in OSA patients in three different frequency band. (A) typical frequency band; (B) slow-4 band; (C) slow-5 band.

Figure 8 In the pre-CPAP OSA patients, significant correlations between the mean ReHo z-value with between-subgroup differences (pre-CPAP OSA patients vs HC groups) and clinical assessment.

Abbreviations: ReHo, regional homogeneity; IPL, inferior parietal lobule; ITG, inferior temporal gyrus; Fus, Fusiform; MoCA, Montreal cognitive assessment; ESS, Epworth sleepiness scale.