TABLE 5

Covariate-adjusted regression analysis to investigate the effect of covariates on selected heart rate variability parameters

	HF_NU		LF_NU		Mean RR		SDNN
	β±se	t-stat	β±se	t-stat	β±se	t-stat	β±se	t-stat
Sex	−0.048±0.002***	−23.2	0.035±0.002***	19.0	0.038±0.002***	23.7	0.009±0.000***	20.0
Age	−0.000±0.000	−3.1	−0.001±0.000***	−17.4	0.002±0.000***	29.9	−0.000±0.000***	−6.0
BMI	0.001±0.000***	9.4	−0.002±0.000***	−20.3	−0.004±0.000***	−49.4	−0.000±0.000***	−17.1
ESS	0.001±0.000***	5.5	−0.000±0.000	−3.2	−0.000±0.000	−0.9	0.000±0.000***	4.8
Hypothyroidism	0.017±0.003***	5.0	−0.018±0.003***	−5.8	−0.000±0.003	−0.2	−0.007±0.001***	−8.8
Arrhythmias	0.090±0.004***	22.5	−0.073±0.004***	−20.7	0.073±0.003***	23.9	0.036±0.001***	39.5
Hypertension	0.006±0.002	2.8	−0.018±0.002***	−9.3	0.002±0.002	1.1	−0.007±0.001***	−14.7
COPD	−0.004±0.004	−1.1	−0.033±0.003***	−10.0	−0.080±0.003***	−28.0	−0.011±0.001***	−13.1
DesSev	−0.015±0.000***	−32.2	0.005±0.000***	11.8	−0.008±0.000***	−23.5	0.004±0.000***	39.7

Sex and all comorbidities are considered as categorical variables in the regression model. BMI: body mass index; ESS: Epworth Sleepiness Scale; COPD: chronic obstructive pulmonary disease; DesSev: desaturation severity; β: estimated coefficient for the regression model; t-stat: t-statistic for a test that the coefficient is zero; HF_NU: normalised power in the high-frequency band (HF/(HF+LF)); LF_NU: normalised power in the low-frequency band (LF/(HF+LF)); SDNN: standard deviation of RR intervals (artefacts corrected). ***: p<0.001.