. Author manuscript; available in PMC: 2015 Dec 1.

Published in final edited form as: Clin Auton Res. 2014 Oct 31;24(6):265–273. doi: 10.1007/s10286-014-0257-7

Table 2.

The means and their 95% CI of the cosine periodic regression parameters for each HRV index

	Cosine Periodic Parameters

HRV Indices	Mean (95% CI)	Amplitude (95% CI)	Acrophase (95%CI)^†
Frequency-domain Variables
Log HF (ms²)	6.16 (6.08–6.24)	0.68 (0.64–0.73)^*	2:45 (2:30–3:15) AM
Log LF (ms²)	6.65 (6.59–6.70)	0.33 (0.31–0.35)^*	6:15 (5:45–7:00) AM
LF/HF Ratio	1.10 (1.11–1.09)	0.10 (0.09–0.11)^*	12:45 (12:15–1:00) PM
Time-domain Variables
SDNN (ms)	91.9 (89.5–94.2)	16.8 (15.8–17.9)^*	6:00 (5:30–6:30) AM
RMSSD (ms)	57.8 (55.5–60.1)	19.9 (18.4–21.3)^*	3:00 (2:30–3:15) AM
Heart Rate (BPM)	77.2 (76.2–78.1)	14.0 (13.3–14.6)^*	1:30 (1:15–1:45) PM

Abbreviations: BPM, beats per minute; CIs, confidence intervals; HF, high frequency power; HRV, heart rate variability; LF, low frequency power; Log, logarithm; RMSSD, square root of the mean of the sum of the squares of differences between adjacent RR intervals; SDNN, standard deviation of all RR intervals.

: P value <0.0001 for non-zero amplitude test of the HRV variables.

^†

: Calculated as the unit to peak ± 2 standard errors, and translated into clock time.