Urinary free cortisol (UFC) levels and heart rate variability parameters of subjects with and without obstructive sleep apnoea
| oAHI <2 | oAHI ≥2 | p-value | |
| UFC µg·24 h–1 | 36 (1–157) | 46 (12–171) | 0.7¶ |
| Mean RR interval ms | 802.3 (598.3–1182.4) | 758.7 (605.2–1006.3) | 0.02¶ |
| SDNN ms | 96.9 (34.6–198.7) | 94.5 (39.6–177.2) | 0.3¶ |
| Mean HR beats·min−1 | 75.88±9.79 | 80.20±9.66 | 0.008# |
| LF bands % | 15.5 (5.4–30.5) | 17.0 (8.3–40.4) | 0.07¶ |
| HF bands % | 21.4 (3.2–63.2) | 20.2 (2.3–54.4) | 0.4¶ |
| LF/HF band ratio | 0.707 (0.168–2.963) | 0.962 (0.242–12.215) | 0.05¶ |
Data are presented as median (range) or mean±sd, unless otherwise stated. oAHI: obstructive apnoea-hypopnoea index; UFC: urinary free cortisol; SDNN: standard deviation of RR intervals (normal sinus-to-normal sinus interbeat intervals); HR: heart rate; LF: low-frequency; HF: high-frequency. #: independent sample t-test; ¶: Mann–Whitney U-test. p≤0.05 was considered statistically significant.