TABLE 2. Association Between Depression and Heart Rate Variability Indices During 24 Hour and Daytime Observations.

	24 Hour HRV				Daytime HRV
	Not Depressed (CES-D <8) n = 776	Depressed (CES-D ≥8) n = 131	p Unadjusted	p Adjusteda	Not Depressed (CES-D <8) n = 776	Depressed (CES-D ≥8) n = 131	p Value Unadjusted	p Adjusteda
VLF-HRV	6.92 ± 0.64	6.79 ± 0.62	.036	.13	6.72 ± 0.63	6.61 ± 0.63	.059	.14
LF-HRV	5.87 ± 0.83	5.78 ± 0.82	.26	.53	0.57 ± 0.78	5.47 ± 0.79	.17	.25
HF-HRV	4.81 ± 1.04	4.74 ± 1.04	.49	.61	4.42 ± 1.03	4.35 ± 0.96	.49	.64
Total power	9.55 ± 0.58	9.51 ± 0.52	.46	.70	9.09 ± 0.60	9.10 ± 0.57	.94	.57
SDNN	124.7 ± 35.5	121.9 ± 31.3	.41	.69	98.3 ± 30.3	98.3 ± 29.0	.98	.55
RMSSD	27.5 ± 20.8	26.8 ± 21.9	.72	.90	23.9 ± 18.4	22.4 ± 13.8	.39	.56
PNN50	6.01 ± 8.84	5.27 ± 7.58	.37	.50	4.81 ± 8.71	3.98 ± 6.15	.29	.42
DFA1 <1.0	247 (31.8%)	43 (32.8%)	.82	.98	233 (30.0%)	53 (40.5%)	.017	.017
HRT onset >0	109 (14.0%)	17 (13.0%)	.74	.86	40 (5.2%)	4 (3.1%)	.30	.24
HRT slope	130 (17.0%)	24 (18.5%)	.69	.58	123 (15.9%)	20 (15.3%)	.98	.92
Heart rate	73.8 ± 9.0	73.9 ± 7.4	.92	.66	79.2 ± 10.2	79.4 ± 8.4	.91	.70

HRV = heart rate variability; CES-D = Centers for Epidemiological Studies Depression scale; VLF = very low frequency; LF = low frequency; SDNN = standard deviation of the NN intervals; RMMSD = square root of mean square successive difference of NN intervals; PNN50 = percent of successive NN interval differences >50 ms; DFA₁ = detrended fluctuation analysis for the short-term fractal scaling exponent; HRT = heart rate turbulence.

Units: VLF, LF, HF and total power HRV in ln ms²; SDNN and RMSSD in ms; and PNN50 in %; HRT onset >0%.

HRT slope, <3 ms/beat; heart rate, beats/min.

^aAdjusted for age, sex, systolic blood pressure, diabetes, body mass index, physical activity (kcal/wk), and use of β-adrenergic blocking agents.

Data are presented as mean ± standard deviation or N and (%).