Table 3.

Linear regression analysis of HRV indices on RDI over REM, wakefulness and sleep Stage 1–3 after adjusting for age and BMI (statistically significant postulated relationships in bold)

		RDI
		Men (n = 221)			Women (n = 67)
	Indices
Sleep state	(log-transformed)	β*	(SE*)	P-value	β*	(SE*)	P-value
R	LHR	−0.18	(0.14)	0.190	0.06	(0.27)	0.237
	LHRra	−0.25	(0.14)	0.069	0.10	(0.25)	0.702
	HFP	0.26	(0.20)	0.200	0.76	(0.47)	0.109
	HFPra	0.31	(0.20)	0.128	0.73	(0.47)	0.124
	mRRI	−0.09	(0.02)	< 0.001	−0.06	(0.04)	0.147
W	LHR	0.21	(0.17)	0.212	0.03	(0.27)	0.927
	LHRra	0.16	(0.16)	0.318	0.13	(0.27)	0.626
	HFP	−0.67	(0.23)	0.004	−0.20	(0.40)	0.627
	HFPra	−0.62	(0.23)	0.007	−0.22	(0.41)	0.583
	mRRI	−0.10	(0.03)	< 0.001	−0.07	(0.04)	0.128
S1	LHR	0.03	(0.13)	0.825	0.74	(0.26)	0.005
	LHRra	−0.04	(0.12)	0.733	0.75	(0.25)	0.004
	HFP	−0.15	(0.19)	0.419	−0.18	(0.42)	0.660
	HFPra	−0.11	(0.19)	0.553	−0.17	(0.42)	0.688
	mRRI	−0.09	(0.02)	< 0.001	−0.06	(0.04)	0.166
S2	LHR	0.05	(0.14)	0.703	0.66	(0.24)	0.007
	LHRra	−0.02	(0.13)	0.899	0.67	(0.22)	0.004
	HFP	0.01	(0.19)	0.953	0.10	(0.43)	0.812
	HFPra	0.06	(0.19)	0.755	0.09	(0.42)	0.834
	mRRI	−0.10	(0.02)	< 0.001	−0.05	(0.04)	0.288
S3	LHR	−0.08	(0.16)	0.615	0.39	(0.28)	0.164
	LHRra	−0.08	(0.16)	0.633	0.49	(0.28)	0.086
	HFP	−0.07	(0.21)	0.752	0.45	(0.44)	0.310
	HFPra	−0.02	(0.21)	0.913	0.27	(0.43)	0.534
	mRRI	−0.11	(0.02)	< 0.001	−0.03	(0.04)	0.529

BMI, body mass index; HRV, heart rate variability; RDI, respiratory disturbance index; HFP, high-frequency power; mRRI, mean R-R interval; LHR, low-to-high frequency ratio; HFPra, HFP respiration-adjusted counterparts; LHRra LFP respiration-adjusted counterparts; R, REM; W, wakefulness.

^*Values are scaled to 10⁻².