Table 4.

Adjusted R² (coefficient of determination) for linear regression models fit to explain specific HRF parameters by the principal components of HRV

HRF Parameter	R 2
	WBS	Controls
PIP	0.620	0.331
PIPH	0.437	0.257
PIPS	0.955	0.952
W 0	0.481	0.460
W 1	0.812	0.154
W 2	0.225	0.299
W 3	0.431	0.392

Heart rate variability (HRV) and heart rate fragmentation (HRF) parameters were log-transformed. Models were adjusted for age and sex. PIP, percentage of inflection points in NN time series; PIP^H, percentages of hard inflection points in NN time series; PIP^S, percentages of soft inflection points in NN time series; W_j, percentage of “words” with j inflection points; WBS, Williams–Beuren syndrome.