Baseline characteristics of the study participants
| OSA group | CPAP group (before treatment)# | Healthy volunteers | p-value¶ | |
| Subjects n | 60 | 32 | 29 | |
| Age years | 54±8 | 55±7 | 55±6 | 0.865 |
| Male n (%) | 50 (83.3) | 26 (81.2) | 24 (82.5) | 0.969 |
| Body mass index kg·m−2 | 28.5±4.6 | 27.4±4.8 | 27.4±5.0 | 0.463 |
| Smoking habit n (%) | 0.987 | |||
| Current smoker | 21 (35.0) | 12 (37.5) | 10 (34.5) | |
| Former smoker | 21 (35.0) | 12 (37.5) | 10 (34.5) | |
| Never smoker | 18 (30.0) | 8 (25.0) | 9 (31.0) | |
| ESS | 10.8±4.5 | 10.7±4.4 | 4.1±3.6 | <0.001 |
| Daytime sleepiness (ESS ≥10) | 33 (55.0) | 20 (62.5) | 1 (3.4) | <0.001 |
| AHI events·h−1 | 55.1±18.2 | 54.3±17.9 | 2.7±1.2 | <0.001 |
| Oxygen desaturation index events·h−1 | 49.6±22.3 | 49.5±19.9 | 1.9±1.1 | <0.001 |
| Sleep time with SpO2 <90% % | 33.1±29.0 | 31.8±29.1 | 2.3±2.8 | 0.004 |
| Sleep time with SpO2 <80% % | 5.6±9.6 | 6.1±8.5 | 0 | 0.117 |
| Low nocturnal SpO2 % | 77.6±6.9 | 77.2±7.0 | 87.6±2.3 | <0.001 |
| Mean nocturnal SpO2 % | 89.9±4.0 | 89.3±4.3 | 92.3±1.5 | 0.102 |
| Obstructive events % | 88.7±6.6 | 87.2±6.4 | 86.0±6.4 | 0.343 |
| Systolic blood pressure mmHg | 121.6±10.5 | 123.0±10.2 | 122.8±11.5 | 0.807 |
| Diastolic blood pressure mmHg | 74.6±6.4 | 75.6±6.5 | 75.7±6.5 | 0.693 |
| White cell count mm−3 | ||||
| Total | 7.60±1.27 | 7.63±1.25 | 7.77±1.33 | 0.834 |
| Neutrophils | 5.02±0.95 | 4.89±0.91 | 5.03±1.04 | 0.785 |
| Lymphocytes | 1.93±0.56 | 2.10±0.63 | 2.09±0.61 | 0.314 |
| Monocytes | 0.50±0.14 | 0.51±0.13 | 0.48±0.09 | 0.690 |
| Haemoglobin g·dL−1 | 13.6±1.2 | 13.7±1.3 | 14.0±1.2 | 0.392 |
| Cholesterol total mg·dL−1 | 186.6±41.9 | 182.6±52.7 | 183.9±40.4 | 0.938 |
| HDL-cholesterol mg·dL−1 | 52.5±7.0 | 50.6±5.8 | 49.0±4.4 | 0.089 |
| LDL-cholesterol mg·dL−1 | 122.7±36.9 | 121.5±47.9 | 122.6±35.7 | 0.992 |
| Triglycerides mg·dL−1 | 142.9±40.8 | 138.4±46.2 | 136.1±18.4 | 0.789 |
Data are presented as mean±sd, unless otherwise stated. OSA: obstructive sleep apnoea; CPAP: continuous positive airway pressure; ESS: Epworth Sleepiness Scale; AHI: apnoea-hypopnea index; SpO2: arterial oxygen saturation measured by pulse oximetry; HDL: high-density lipoprotein; LDL: low-density lipoprotein. #: baseline values of the treated patients with OSA refer to the diagnostic time, before starting treatment with CPAP; ¶: comparisons between groups were performed by an ANOVA or Chi-squared test.