Table 1.
Distribution characteristics of heart rate variability indices
| Heart period (ms) |
lnHF (ln-ms2) |
lnLF (ln-ms2) |
ln(LF/HF) (ln-ratio) |
SDNN (ms) |
rMSSD (ms) |
|
|---|---|---|---|---|---|---|
| n | 417 | 417 | 417 | 417 | 417 | 417 |
| mean | 945.85 | 9.84 | 10.42 | 0.58 | 27.17 | 37.49 |
| median | 938.86 | 9.89 | 10.42 | 0.56 | 25.09 | 34.76 |
| Standard deviationa | 126.98 | 0.92 | 0.73 | 0.92 | 11.78 | 16.54 |
| Coefficient of variation (%) | 13.42 | 9.35 | 7.01 | -b | 43.36 | 44.12 |
| Skewness | 0.38 | 0.01 | 0.11 | 0.19 | 1.22 | 1.24 |
| Kurtosis | 0.26 | 0.32 | -0.21 | 0.71 | 1.91 | 2.04 |
| Fifth percentile | 748.53 | 8.39 | 9.24 | -0.90 | 12.4 | 16.98 |
| 95th percentile | 1171.68 | 11.37 | 11.58 | 2.12 | 50.99 | 69.95 |
HF: high frequency component; LF: low frequency component; rMSSD: root mean square of successive differences; SDNN: standard deviation of normal-to-normal intervals. Skewness is a measure of symmetry of distribution. Negative or positive skewness is indicated when the left or right tail of the histogram is longer, respectively. The skewness of a normally distributed data set is zero. Kurtosis is a measure of whether the distribution curve is peaked (positive) or flat (negative) relative to the normal distribution. The kurtosis of a normally distributed data set is zero. aStandard deviation of interindividual variation; bthe coefficient of variation of ln(LF/HF) was not calculated because it was occasionally negative.