Table 2.

Summary statistics for frequency domain, time domain, and nonlinear heart rate variability across the two heart rate groups

	Mean value ± standard deviation
Parameter	Normal HR (n = 43)	Bradycardia HR (n = 25)	P valueKruskal-Wallis test	P valuet test
Frequency domain analysis
Total power	1817 ± 1460	2411 ± 1724	0.113	0.155
HF	367 ± 530	401 ± 290	0.038∗	0.34
LF	448 ± 404	621 ± 572	0.135	0.19
HF ln	5.27 ± 1.09	5.720 ± 0.827	0.038∗	0.06
LF ln	5.695 ± 0.960	6.086 ± 0.831	0.135	0.082
HF norm	47.7 ± 65.0	40.7 ± 12.6	0.488	0.498
LF norm	56.3 ± 19.0	56.8 ± 12.8	0.975	0.898
LF/HF	2.24 ± 2.10	1.75 ± 1.36	0.661	0.249
Time domain analysis
SDNN	40.5 ± 15.4	48.7 ± 15.1	0.038∗	0.038∗
RMSSD	26.2 ± 14.5	33.6 ± 13.0	0.007∗	0.034∗
Nonlinear analysis
DFA α1	1.013 ± 0.296	1.057 ± 0.247	0.537	0.513
DFA α2	0.938 ± 0.178	0.923 ± 0.132	0.642	0.688
DFA32	91.4 ± 42.2	129.0 ± 72.1	0.01∗	0.023∗
ApEN	1.112 ± 0.236	1.181 ± 0.199	0.242	0.203

∗Significant at P < 0.05.

HR indicates heart rate; for other abbreviations, see Table 1.