Nocturnal Mean Oxygen Saturation Is Associated with Secondary Polycythemia in Young Adults with Obstructive Sleep Apnea, Especially in Men

Figures & data

Table 1 Baseline Clinical, Laboratory, and Polysomnographic Data of All Participants

Variables	Total (n = 605)	Men (n = 383)	Women (n = 222)	P Value*
Age (year)	30.52 ± 7.21	32.39 ± 7.19	27.30 ± 6.03	<0.001
BMI (kg/m^2)	32.48 ± 6.07	32.21 ± 6.30	32.95 ± 5.62	0.148
Neck circumference (cm)	41.51 ± 4.01	42.40 ± 3.70	39.97 ± 4.06	<0.001
AHI (events/h)	19.70 (4.70–57.75)	40.00 (11.80–67.60)	6.05 (1.38–16.00)	<0.001
ODI (events/h)	26.30 (6.40–61.40)	43.05 (13.15–69.40)	8.10 (2.35–27.80)	<0.001
Mean SpO2 (%)	93.66 ± 4.45	92.78 ± 4.43	95.08 ± 4.12	<0.001
TS90 (%)	2.30 (0.10–21.44)	7.95 (0.40–30.93)	0.10 (0.00–1.90)	<0.001
RBC count (10^3/μL)	4.81 ± 0.47	5.00 ± 0.41	4.49 ± 0.40	<0.001
HGB (g/L)	144.17 ± 14.00	150.92 ± 11.16	132.51 ± 10.23	<0.001
HCT (%)	42.55 ± 3.95	44.42 ± 3.17	39.32 ± 2.94	<0.001
Polycythemia-HGB, n (%)	39 (6.45)	34 (8.88)	5 (2.25)	0.001
Polycythemia-HCT, n (%)	26 (4.30)	24 (6.27)	2 (0.90)	0.002
Smoking, n (%)	87 (14.38)	87 (22.72)	0 (0.00)	<0.001
Hypertension, n (%)	134 (22.15)	118 (30.81)	16 (7.21)	<0.001

Notes: Measurement data are presented as mean ± standard deviations or median with inter-quartile range if variables were not normally distributed. *Men vs women.

Abbreviations: BMI, body mass index; AHI, apnea–hypopnea index; ODI, oxygen desaturation index; Mean SpO₂, mean oxygen saturation; TS90, percentage of sleep duration with SpO₂ < 90%; RBC, red blood cell; HGB, hemoglobin; HCT, hematocrit.

Table 2 Baseline Clinical, Laboratory, and Polysomnographic Data of Male and Female Participants Stratified by OSA Severity Status

	Men				Women
Variables	Control (n = 53)	Mild-to-Moderate OSA (n = 110)	Severe OSA (n = 220)	P Value	Control (n = 102)	Mild-to-Moderate OSA (n = 88)	Severe OSA (n = 32)	P Value
Age (year)	28.70 ± 7.55	29.86 ± 7.60	34.55 ± 6.06*,^†	<0.001	25.94 ± 5.28	27.45 ± 5.88	31.19 ± 7.04*,^†	<0.001
BMI (kg/m^2)	33.38 ± 5.08	32.85 ± 7.23	31.61 ± 6.02	0.084	31.81 ± 5.06	33.20 ± 5.27	35.90 ± 7.10*,^†	0.001
Neck circumference (cm)	41.73 ± 2.52	42.49 ± 3.75	42.53 ± 3.92	0.368	39.00 ± 3.49	40.26 ± 4.15*	42.40 ± 4.59*,^†	<0.001
AHI (events/h)	2.00 (0.95–3.15)	14.25 (8.60–22.43)*	64.70 (49.93–74.23)*,^†	<0.001	1.30 (0.60–2.53)	11.05 (7.20–16.45)*	65.90 (46.53–85.98)*,^†	<0.001
ODI (events/h)	4.50 (1.65–10.40)	13.60 (7.10–26.80)*	65.55 (50.65–79.25)*,^†	<0.001	3.20 (1.00–8.83)	10.60 (5.08–28.93)*	85.10 (52.40–110.50)*,^†	<0.001
Mean SpO2 (%)	95.88 ± 1.45	95.26 ± 2.33	90.86 ± 4.66*,^†	<0.001	96.39 ± 1.46	95.72 ± 1.70	88.90 ± 7.98*,^†	<0.001
TS90 (%)	0.00 (0.00–0.35)	0.85 (0.10–3.70)*	24.50 (10.30–43.50)*,^†	<0.001	0.00 (0.00–0.10)	0.30 (0.00–2.58)*	26.35 (4.30–45.30)*,^†	<0.001
RBC count (10^3/μL)	4.91 ± 0.40	4.93 ± 0.38	5.05 ± 0.42*,^†	0.009	4.40 ± 0.31	4.54 ± 0.42*	4.64 ± 0.55*	0.004
HGB (g/L)	148.17 ± 10.66	148.92 ± 9.46	152.59 ± 11.79*,^†	0.003	132.20 ± 9.16	132.60 ± 10.57	133.25 ± 12.55	0.874
HCT (%)	43.70 ± 3.09	43.77 ± 2.71	44.91 ± 3.32*,^†	0.002	39.08 ± 2.63	39.35 ± 2.67	39.98 ± 4.29	0.315
Polycythemia-HGB, n (%)	2 (3.77)	5 (4.55)	27 (12.27)^†	0.025	1 (0.98)	2 (2.27)	2 (6.25)	0.215
Polycythemia-HCT, n (%)	1 (1.89)	1 (0.91)	22 (10.00)^†	0.002	1 (0.98)	0 (0.00)	1 (3.13)	0.275
Smoking, n (%)	8 (15.09)	22 (20.00)	57 (25.91)	0.174	/	/	/	/
Hypertension, n (%)	9 (16.98)	28 (25.45)	69 (31.36)*	0.091	7 (6.86)	14 (15.91)*	7 (21.88)*	0.040

Notes: Data are presented as mean ± standard deviations or median with inter-quartile range if variables were not normally distributed. *P <0.05 vs the control group; ^†P <0.05 vs the mild-to-moderate OSA group.

Abbreviations: OSA, obstructive sleep apnea; BMI, body mass index; AHI, apnea–hypopnea index; ODI, oxygen desaturation index; Mean SpO₂, mean oxygen saturation; TS90, percentage of sleep duration with SpO₂< 90%; RBC, red blood cell; HGB, hemoglobin; HCT, hematocrit.

Table 3 Correlations Between Polysomnographic Parameters and RBC Count, HGB, and HCT in Male and Female Participants

	Men			Women
Variables	RBC Counts	Hemoglobin	Hematocrit	RBC Counts	Hemoglobin	Hematocrit
Age (year)	−0.068, 0.184	0.117, 0.022	0.023, 0.659	−0.048, 0.473	−0.045, 0.504	−0.068, 0.316
BMI (kg/m^2)	0.152, 0.003	−0.067, 0.194	0.019, 0.715	0.228, 0.001	0.007, 0.915	0.097, 0.150
AHI (events/h)	0.212, <0.001	0.211, <0.001	0.212, <0.001	0.226, 0.001	0.028, 0.683	0.094, 0.164
ODI (events/h)	0.238, <0.001	0.182, <0.001	0.200, <0.001	0.285, <0.001	0.132, 0.050	0.193, 0.004
Mean SpO2 (%)	−0.344, <0.001	−0.304, <0.001	−0.362, <0.001	−0.303, <0.001	−0.219, 0.001	−0.274, <0.001
TS90 (%)	0.283, <0.001	0.258, <0.001	0.290, <0.001	0.245, <0.001	0.125, 0.064	0.175, 0.009

Notes: Data are Spearman’s coefficients (rho, P value).

Abbreviations: BMI, body mass index; AHI, apnea–hypopnea index; ODI, oxygen desaturation index; Mean SpO₂, mean oxygen saturation; TS90, percentage of sleep duration with SpO₂< 90%; RBC, red blood cell.

Table 4 Comparison of Clinical, Laboratory, and Polysomnographic Data in OSA Patients with or Without Polycythemia

	Total OSA			Severe OSA			Total OSA			Severe OSA
Variables	Without Polycythemia–HGB (n = 414)	With Polycythemia–HGB (n = 36)	P Value	Without Polycythemia–HGB (n = 223)	With Polycythemia–HGB (n = 29)	P Value	Without Polycythemia–HCT (n = 426)	With Polycythemia–HCT (n = 24)	P Value	Without Polycythemia–HCT (n = 229)	With Polycythemia–HCT (n = 23)	P Value
Age (year)	31.62 ± 7.17	33.53 ± 5.98	0.123	34.07 ± 6.32	34.52 ± 6.05	0.717	31.65 ± 7.17	33.92 ± 5.31	0.057	34.12 ± 6.37	34.09 ± 5.36	0.980
BMI (kg/m^2)	32.45 ± 6.33	33.47 ± 6.85	0.356	31.89 ± 6.18	34.17 ± 7.10	0.068	32.39 ± 6.28	35.02 ± 7.44	0.049	31.88 ± 6.12	34.95 ± 7.59	0.072
AHI (events/h)	34.40 (13.38–66.53)	54.50 (36.45–76.38)	<0.001	64.70 (48.90–75.80)	65.00 (49.20–82.25)	0.660	34.40 (13.25–66.18)	65.15 (47.40–80.23)	<0.001	64.70 (48.60–75.95)	65.60 (50.70–81.10)	0.720
ODI (events/h)	42.40 (13.10–70.00)	53.40 (33.40–75.60)	0.001	68.30 (51.70–81.35)	61.20 (49.00–81.88)	0.279	42.40 (13.30–69.13)	64.30 (49.00–81.98)	<0.001	66.85 (51.18–81.28)	64.80 (48.50–83.50)	0.761
Mean SpO2 (%)	93.20 ± 4.15	87.48 ± 7.87	<0.001	91.15 ± 4.45	86.64 ± 8.18	<0.001	93.15 ± 4.25	85.83±7.70	<0.001	91.12 ± 4.61	85.73 ± 7.87	<0.001
TS90 (%)	6.60 (0.40–27.10)	29.45 (5.55–54.38)	<0.001	24.10 (9.20–42.98)	37.90 (18.55–58.55)	0.018	6.60 (0.50–27.10)	44.45 (21.74–63.08)	<0.001	24.05 (9.20–42.90)	47.30 (21.38–63.20)	0.006
RBC count (10^3/uL)	4.84 ± 0.42	5.53 ± 0.47	<0.001	4.92 ± 0.40	5.62 ± 0.39	<0.001	4.85 ± 0.43	5.70 ± 0.39	<0.001	4.93 ± 0.40	5.69 ± 0.40	<0.001
HGB (g/L)	144.30 ± 12.28	170.58 ± 5.57	<0.001	147.37 ± 11.64	171.34 ± 5.86	<0.001	144.94 ± 12.67	172.42 ± 5.82	<0.001	147.89 ± 11.91	172.48 ± 5.94	<0.001
HCT (%)	42.65 ± 3.38	49.44 ± 3.72	<0.001	43.50 ± 3.20	50.31 ± 2.69	<0.001	42.74 ± 3.42	51.24 ± 2.26	<0.001	43.59 ± 3.19	51.23 ± 2.31	<0.001

Notes: Data are presented as mean ± standard deviations or median with inter-quartile range if variables were not normally distributed.

Abbreviations: OSA, obstructive sleep apnea; BMI, body mass index; AHI, apnea–hypopnea index; ODI, oxygen desaturation index; Mean SpO₂, mean oxygen saturation; TS90, percentage of sleep duration with SpO₂< 90%; RBC, red blood cell; HGB, hemoglobin; HCT, hematocrit.

Table 5 Odds Ratio Estimates from Logistic Regression Analysis for the Risk Factors for Polycythemia in Men

	Men with Polycythemia–HGB			Men with Polycythemia–HCT
Independent Variables	Odds Ratio	95% Confidence Interval	P Value	Odd Ratio	95% Confidence Interval	P Value
Age (year)	1.006	0.936–1.081	0.874	1.021	0.933–1.117	0.655
BMI (kg/m^2)	1.042	0.966–1.124	0.288	1.070	0.978–1.169	0.140
AHI (events/h)	1.018	0.982–1.056	0.325	1.015	0.972–1.060	0.491
ODI (events/h)	0.982	0.950–1.015	0.290	0.981	0.943–1.021	0.342
Mean SpO2 (%)	0.802	0.689–0.934	0.004	0.786	0.665–0.929	0.005
TS90 (%)	0.987	0.947–1.028	0.516	0.994	0.949–1.040	0.784
Smoking	0.426	0.177–1.025	0.057	0.420	0.148–1.197	0.104
Hypertension	1.306	0.525–3.247	0.566	0.809	0.291–2.247	0.684

Abbreviations: BMI, body mass index; AHI, apnea–hypopnea index; ODI, oxygen desaturation index; Mean SpO₂, mean oxygen saturation; TS90, percentage of sleep duration with SpO₂< 90%; RBC, red blood cell; HGB, hemoglobin; HCT, hematocrit.

Figure 1 ROC curves for HBG and HCT to predict nocturnal hypoxemia defined with as mean SpO₂ < 90% in patients with obstructive sleep apnea. (A) In men; (B) In women.