Reading multifractal spectra: Aging by multifractal analysis of heart rate

Abstract

The method of effective reading of multifractal properties is proposed. The method consists in the analysis of a given signal together with the analysis of an integrated signal. A practical way to separate monofractal-type signals from other signals is given. The method is applied to 24-hour ECG recordings of RR-interbeat intervals to assess the effect of aging on autonomic regulation of the heart in healthy adults. Heart rate variability is evaluated by multifractal analysis in the VLF band. A switch from mono- to multifractality is observed between diurnal and nocturnal parts of series in the group of young adults. With aging the multifractal structure of nocturnal signals declines. The observed changes can be related to the circadian alternation in the central mechanisms controlling the cardiovascular system which becomes impaired with advance in age in human. Indices for age impairment of autonomic regulation are proposed.