Table 1.
Characteristics of the groups classified according to OSA severity using current clinical definitions
| Non-OSA (AHI<5) | Mild OSA (5≤AHI<15) | Moderate (15<AHI≤30) | Severe OSA (AHI≥30) | ||
|---|---|---|---|---|---|
| Variables | (N=561) | (N=505) | (N=478) | (N=1439) | p Value |
| Demographics | |||||
| Age (years) | 39 (30–49) | 42 (34–52) | 44 (35–54) | 42 (35–53) | <0.001§ |
| Female, N (%) | 226 (40.3) | 115 (22.8) | 95 (19.9) | 134 (9.3) | <0.001§ |
| Body mass index (kg/m2) | 23.7 (21.7–25.7) | 25.4±3.2 | 26.0 (24.2–28.1) | 27.7 (25.6–30.0) | <0.001* |
| Neck circumference (cm) | 36.0 (34.0–38.5) | 38.0 (36.0–40.0) | 39.0 (37.0–41.0) | 40.0 (38.5–42.0) | <0.001* |
| Waist circumference (cm) | 86.0 (79.0–92.0) | 91.0 (86.0–96.8) | 94.0 (89.0–99.0) | 98.0 (993.0–104.0) | <0.001* |
| Hip circumference (cm) | 96.0 (81.0–100.0) | 98.0 (94.0–102.0) | 100.0 (96.0–104.0) | 102.0 (98.0–106.3) | <0.001* |
| Waist/hip circumference ratio | 0.90 (0.85–0.94) | 0.93±0.05 | 0.94±0.05 | 0.96 (0.93–1.00) | <0.001* |
| Biochemistry assays | |||||
| Glucose (mmol/L) | 4.97 (4.62–5.30) | 5.13 (4.81–5.55) | 5.25 (4.95–5.68) | 5.39 (5.01–5.95) | <0.001* |
| Insulin (μU/mL) | 7.17 (4.88–9.96) | 8.93 (5.94–13.68) | 10.95 (7.30–15.51) | 13.01 (8.61–19.01) | <0.001* |
| Insulin resistance index | 0.42±0.60 | 0.72±0.68 | 0.92±0.63 | 1.13±0.64 | <0.001# |
| TC (mmol/L) | 4.37 (3.80–5.06) | 4.64 (4.13–5.28) | 4.76 (4.23–5.42) | 4.87 (4.29–5.43) | <0.001* |
| TG (mmol/L) | 1.10 (0.73–1.61) | 1.40 (0.96–1.99) | 1.60 (1.18–2.38) | 1.76 (1.28–2.57) | <0.001* |
| HDL-C (mmol/L) | 1.12 (1.97–1.33) | 1.10 (0.95–1.29) | 1.04 (0.91–1.21) | 1.02 (0.90–1.16) | <0.001* |
| LDL-C (mmol/L) | 2.67 (2.16–3.21) | 2.99 (2.46–3.54) | 3.04 (2.53–3.61) | 3.16 (2.64–3.69) | <0.001* |
| apoA-I (g/L) | 1.08 (0.96–1.24) | 1.08 (0.96–1.21) | 1.04 (0.94–1.17) | 1.03 (0.93–1.15) | <0.001* |
| apoB (g/L) | 0.73 (0.63–0.86) | 0.82 (0.71–0.94) | 0.83 (0.73–0.96) | 0.86 (0.76–0.97) | <0.001* |
| apoE (mg/dL) | 3.83 (3.15–4.84) | 4.09 (3.40–5.10) | 4.38 (3.59–5.33) | 4.48 (3.63–5.60) | <0.001* |
| Lp (a) (mg/L) | 8.50 (4.45–17.1) | 8.60 (4.82–15.30) | 7.80 (4.20–14.73) | 7.80 (4.10–15.60) | 0.14 |
| Dyslipidaemia | |||||
| HyperTC, N (%) | 124 (22.1) | 148 (29.3) | 150 (31.4) | 531 (36.9) | <0.001 |
| HyperTG, N (%) | 124 (22.1) | 179 (35.4) | 222 (46.4) | 771 (53.6) | <0.001 |
| HypoHDL-C, N (%) | 208 (37.1) | 204 (40.4) | 232 (48.5) | 774 (53.8) | <0.001 |
| HyperLDL-C, N (%) | 108 (19.3) | 163 (32.3) | 158 (33.1) | 575 (40.0) | <0.001 |
| HyperapoA-I, N (%) | 378 (67.4) | 364 (72.1) | 377 (78.9) | 1190 (82.7) | <0.001 |
| HyperapoB, N (%) | 14 (2.5) | 28 (5.5) | 30 (6.3) | 119 (8.3) | <0.001 |
| HyperapoE, N (%) | 223 (39.8) | 200 (39.6) | 201 (42.1) | 666 (46.3) | 0.011 |
| Sleep apnoea | |||||
| Apnoea–hypopnea index | 1.3 (0.4–2.8) | 9.2 (6.9–11.7) | 21.7 (18.5–25.8) | 57.7 (44.6–70.4) | <0.001* |
| Mean SaO2 | 97.0 (95.8–97.9) | 95.7 (94.3–96.9) | 95.0 (93.7–96.0) | 92.7 (90.0–94.0) | <0.001* |
| Minimum SaO2 | 93.0 (90.0–96.0) | 87.0 (82.7–90.0) | 82.0 (76.9–86.0) | 71.0 (63.0–79.0) | <0.001* |
| Oxygen desaturation index | 1.4 (0.5–3.4) | 9.6 (6.7–13.8) | 23.8 (17.5–31.2) | 58.1 (44.6–71.9) | <0.001* |
| Arousal index | 12.1 (6.6–20.5) | 18.5 (9.2–29.0) | 23.4 (10.1–33.5) | 37.0 (16.5–57.5) | <0.001* |
| Medical history | |||||
| ESS | 4 (0–8) | 7 (3–10) | 8 (4–11) | 11 (6–15) | <0.001§ |
| Non-smoker, N (%) | 441 (78.6) | 320 (63.4) | 290 (60.7) | 773 (53.7) | <0.001§ |
| Non-drinker, N (%) | 460 (82.0) | 399 (79.0) | 370 (77.4) | 1040 (72.3) | <0.001§ |
| Presence of hypertension, N (%) | 61 (10.9) | 114 (22.6) | 142 (29.7) | 557 (38.7) | <0.001§ |
| Presence of diabetes, N (%) | 28 (5.0) | 54 (10.7) | 64 (13.4) | 313 (21.8) | <0.001§ |
The data are presented as means±SD; skewed data are presented as the median (IQR), and categorical data as the number (percentage). Differences in the baseline characteristics among the four groups were examined using a Kruskal–Wallis H test (*), one-way analysis of variance (ANOVA) (#) or χ2 tests (§) according to the characteristics of the data distribution.
AHI, apnoea–hypopnea index; ESS, Epworth Sleepiness Scale; OSA, obstructive sleep apnoea; TG, triglyceride; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; apoA-I, apolipoprotein A-I; apoB, apolipoprotein B; apoE, apolipoprotein E; Lp(a), lipoprotein(a); SaO2, oxygen saturation; TC, total cholesterol.