Table 3.

The regression coefficient (β) estimates and SE of major population attributes on mean, amplitude and acrophase of the circadian periodic curves of HRV from random-effects meta-analysis

		HRV Indices
		Frequency-domain variables			Time-domain variables
Population Attributesa		Log HF (ms2)	Log LF (ms2)	LF/HF ratio	SDNN (ms)	RMSSD (ms)	HR (BPM)
		β(SE)	β(SE)	β(SE)	β(SE)	β(SE)	β(SE)
Ageb	Mc	−0.01(0.02)	0.02(0.01)	0.006(0.002)**	0.95(0.54)	0.26(0.54)	0.91(0.21)**
	Âc	0.03(0.01)**	0.004(0.005)	0.004(0.001)**	0.42(0.25)	0.93(0.33)**	0.22(0.15)
	θc	0.04(0.18)	−0.48(0.28)	0.41(0.16)**	−0.14(0.21)	−0.17(0.18)	0.23(0.08)**
Male	Mc	0.04(0.08)	0.18(0.05)**	0.02(0.009)	8.07(2.37)**	1.08(2.35)	2.24(0.91)**
	Âc	−0.004(0.004)	0.05(0.02)*	−0.009(0.006)	4.97(1.08)**	1.38(1.46)	1.05(0.64)
	θc	1.61(0.81)*	0.52(1.22)	0.38(0.72)	−0.65(0.89)	1.05(0.80)	0.49(0.36)
Non-Hispanic white	Mc	0.03(0.09)	0.12(0.06)**	0.01(0.01)	4.45(2.80)	0.58(2.79)	−1.39(1.08)
	Âc	−0.05(0.05)	0.02(0.03)	−0.01(0.01)	1.13(1.27)	−0.02(1.72)	0.19(0.75)
	θc	0.59(0.96)	1.80(1.44)	−0.34(0.85)	2.23(1.05)*	0.52(0.95)	−0.60(0.43)

Abbreviations: Â, amplitude, BPM, beats per minute; CIs, confidence intervals; HF, high frequency power; HRV, heart rate variability; LF, low frequency power; Log, logarithm; M, mean; 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; θ, acrophrase time.

^aAll variables were added into the same model.

^bAge was analyzed as a continuous variable; thus the regression coefficient correspond to the changes for every 1-year increase in age

^cM, Â, and θ : parameters of the cosine periodic curve mean, amplitude, and acrophase; 1 unit of θ corresponds to 30-minute, with a positive θ of 2 unit indicating 1-hour later.

p-value :

^*p<0.05;

^**p<0.01