Urinary free cortisol (UFC) levels and heart rate variability parameters of subjects with and without obstructive sleep apnoea

oAHI <2oAHI ≥2p-value
UFC µg·24 h–136 (1–157)46 (12–171)0.7
Mean RR interval ms802.3 (598.3–1182.4)758.7 (605.2–1006.3)0.02
SDNN ms96.9 (34.6–198.7)94.5 (39.6–177.2)0.3
Mean HR beats·min−175.88±9.7980.20±9.660.008#
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 ratio0.707 (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.