Table 3.

Loadings for the First Two Principal Components in WHAS-I and Framingham, Obtained From the HRV Correlations Reported in Table 2

	WHAS-I		Framingham
	PC1	PC2	PC1	PC2
VLF	.33	.76	.39	.51
LF	.42	.17	.41	.30
HF	.43	−.29	.44	−.26
SDNN	.44	.21	.39	.41
pNN50	.41	−.27	.40	−.45
RMSSD	.42	−.43	.41	−.45
% Variation explained	76.3	13.3	74.6	17.4

Note: HRV = heart rate variability; WHAS-I= Women's Health and Aging Study-I; PC = principal components; VLF = very low frequency; LF = low frequency; HF = high frequency; SDNN = standard deviation of N-N intervals; pNN50 = proportion of all N-N intervals that are larger than 50 ms; RMSSD = root-mean-squared differences of successive N-N intervals.