Developmental changes in heart period and high-frequency heart period variability from 4 months to 4 years of age

Cardiac measures of heart period and high-frequency heart period variabilit y increasingly employed as dependent variables in studies of social and emo tional development in infancy and childhood. This study describes significa nt developmental increases in these a longitudinal sample assessed at 4. 9, 14. 24 ands 48 months of age. In addition, developmental changes in the ch aracteristics of the heart period poll er spectra are described. these chan ges have implications for the quantification of high-frequency? heart perio d variability in infancy and childhood First, shorter analysis? sis epoch l engths may he used for younger infants. Second, the commonly used high-freq uency band for infants (0.24-1.04Hz) appears to reach its practical limit a t an age of around four years. Findings are discussed in relation to the de sign of developmental psychophysiological studies. (C) 2000 John Wiley & so ns, Inc.