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Table 2 Estimated means of the three cosine periodic regression parameters and their 95% CIs for each HRV index.

From: Insulin resistance and circadian rhythm of cardiac autonomic modulation

  Cosine periodic parameter
HRV index Mean (95% CI) Amplitude (95% CI) Acrophase (95% CI)
Log HF (ms2) 4.36 (4.17-4.54) 0.60 (0.53-0.67)* 4:00(3:00-5:00) AM
Log LF (ms2) 5.36 (5.21-5.52) 0.44 (0.39-0.49)* 5:30(4:30-6:45) AM
LF/HF ratio 3.74 (3.33-4.15) 1.16 (0.98-1.34)* 6:00(4:30-7:15) PM
Log VLF (ms2) 6.95 (6.83-7.07) 0.39 (0.35-0.44)* 8:00(7:00-9:00) AM
SDNN (ms) 60.8 (57.2-64.4) 10.5 (9.3-11.7)* 6:45(5:45-7:30) AM
RMSSD (ms) 28.4 (25.7-31.0) 7.24 (6.10-8.37)* 4:15(3:15-5:15) AM
Heart rate (BPM) 76.6 (74.6-78.6) 10.8 (9.8-11.7)* 2:00(1:45-2:30) PM
  1. 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; VLF, very low frequency power.
  2. *: P value < 0.0001 for zero amplitude test of the HRV indices.
  3. †: Calculated as the unit to peak ± 2 standard errors, and translated into clock time.