Daytime Hypercapnia Impairs Working Memory in Young and Middle-Aged Patients with Obstructive Sleep Apnea Hypopnea Syndrome

Figures & data

Figure 1 A flow chart illustrating the study sample and design.

Abbreviations: PtcCO₂, transcutaneous partial pressure of carbon dioxide; DSB, Digit Span Backward; CANTAB, Cambridge Neuropsychological Test Automated Battery; OSAHS, Obstructive sleep apnea hypopnea syndrome.

Table 1 Baseline and Clinical Data in the Hypercapnic and Normocapnic Groups

Variables	Hypercapnic Group(N=45)	Normocapnic Group(N=86)	P-value
PtcCO2, mmHg	51.40(47.70,58.10)	39.20(37.20,40.90)	<0.001
Age, years	41.18±7.80	39.49±6.61	0.194
Sex(male)	44(97.8%)	81(94.2%)	0.664
Education, years	16.00(15.00,16.00)	16.00(12.00,16.00)	0.990
Snoring, years	10.00(5.00,10.00)	6.00(3.00,10.00)	0.063
BMI, kg/m2	27.04(25.86,29.73)	26.56(24.91,29.41)	0.437
Smoking	16(35.6%)	23(26.7%)	0.295
Drinking	13(28.9%)	18(20.90%)	0.309
Common symptoms, n (%)
Poor memory	19(42. %2)	31(36.0%)	0.490
Morning fatigue	32(71.1%)	44(51.2%)	0.028
Dry mouth	31(68.9%)	54(62.8%)	0.487
Daytime sleepiness	33(73.3%)	45(52.3%)	0.020
Nocturia	25(55.6%)	44(51.2%)	0.633
Complications, n (%)
Hypertension	10(22.2%)	20(23.3%)	0.894
Diabetes	0(0.0%)	1(1.2%)	1.000
Fatty liver	1(2. 2%)	1(1.2%)	1.000

Abbreviations: PtcCO₂, transcutaneous partial pressure of carbon dioxide; BMI, body mass index.

Table 2 Polysomnographic Parameters in the Hypercapnic and Normocapnic Groups

Variables	Hypercapnic Group(N=45)	Normocapnic Group(N=86)	P-value
TST, min	408.35±74.03	409.57±75.62	0.930
Sleep efficiency, %	85.00(71.60,89.10)	88.35(79.00,92.00)	0.056
NREM 1 sleep, %	14.50(6.70,21.80)	12.00(6.90,19.40)	0.527
NREM 2 sleep, %	54.13±13.60	52.55±10.73	0.468
NREM 3 sleep, %	8.20(1.10,16.40)	12.70(6.70,18.90)	0.034
REM sleep, %	18.87±5.36	20.55±5.57	0.099
AHI, n/h	46.80(29.50,64.00)	31.00(14.70,55.90)	0.010
ODI, n/h	42.00(21.60,62.40)	21.20(7.50,45.30)	0.003
TS90, %	10.60(1.50,24.30)	1.90(0.20,12.00)	0.014
AvgSaO2, %	94.00(92.00,96.00)	95.00(94.00,96.00)	0.050
LSaO2, %	75.00(61.00,83.00)	81.00(71.00,87.00)	0.059
ArI, n/h	27.30(15.80,40.40)	19.80(9.70,40.20)	0.143

Abbreviations: TST, total sleep time; NREM, non-rapid eye movement; REM, rapid eye movement; AHI, apnea-hypopnea index; ODI, oxygen desaturation index; TS90, percentage of total time with oxygen saturation level < 90%; AvgSaO₂, average arterial oxygen saturation; LSaO₂, lowest arterial oxygen saturation; ArI, arousal index.

Table 3 Results of the Neuropsychological Tasks in the Hypercapnic and Normocapnic Groups

Variables	Hypercapnic Group(N=45)	Normocapnic Group(N=86)	P-value
DSB score	5.00(4.00,6.00)	6.00(5.00,7.00)	0.005
Immediate PRM
Accuracy, %	87.50(79.17,95.83)	91.67(87.50,95.83)	0.056
Response delay, ms	1725.08(1408.50,2277.96)	1574.49(1364.00,1884.92)	0.051
Total task duration, ms	170,497.00(163,259.00,182,362.00)	166,829.50(161,998.00,173,902.00)	0.018
Delayed PRM
Accuracy, %	83.33(75.00,91.67)	91.67(83.33,100.00)	0.020
Response delay, ms	1827.83(1457.50,2066.25)	1569.21(1391.67,1833.50)	0.059
SRM
Accuracy, %	80.00(70.00,90.00)	90.00(80.00,100.00)	0.004
Response delay, ms	1399.50(1259.00,1873.60)	1355.45(1142.40,1720.60)	0.135
SSP score	6.00(5.00,7.00)	7.00(6.00,8.00)	<0.001
SWM
Between errors, n	32.00(30.00,36.00)	29.50(22.00,34.00)	0.002
Strategy score	107.00(104.00,113.00)	104.00(97.00,108.00)	<0.001

Abbreviations: DSB, Digit Span Backward Test; PRM, Pattern Recognition Memory; SRM, Spatial Recognition Memory; SSP, Spatial Span; SWM, Spatial Working Memory.

Figure 2 Results of multivariate logistic regression in verbal working memory (low DSB score).

Abbreviations: BMI, body mass index; AHI, apnea-hypopnea index; TS90, percentage of total time with oxygen saturation level < 90%; AvgSaO₂, average arterial oxygen saturation; LSaO₂, lowest arterial oxygen saturation.

Figure 3 Results of multivariate logistic regression in visual memory. (a) accuracy in the immediate PRM task; (b) accuracy in the delayed PRM task; (c) accuracy in the SRM task.

Abbreviations: BMI, body mass index; TST, total sleep time; SE, Sleep efficiency; REM, rapid eye movement; AHI, apnea-hypopnea index; NREM, non-rapid eye movement; AvgSaO₂, average arterial oxygen saturation; LSaO₂, lowest arterial oxygen saturation; ArI, arousal index.

Figure 4 Results of multivariate logistic regression in spatial memory. (a) SSP task; (b) between errors in SWM task; (c) strategy scores in SWM task.

Abbreviations: BMI, body mass index; ODI, oxygen desaturation index; TST, total sleep time; SE, Sleep efficiency; NREM, non-rapid eye movement; REM, rapid eye movement.