Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1997
Jan;55(1):845-9.
Deviations from uniform power law scaling in nonstationary time series.
Viswanathan GM, Peng CK, Stanley HE, Goldberger AL.
Department of Physics, Boston University, Massachusetts 02215, USA.
A classic problem in physics is the analysis of highly nonstationary time series
that typically exhibit long-range correlations. Here we test the hypothesis that
the scaling properties of the dynamics of healthy physiological systems are more
stable than those of pathological systems by studying beat-to-beat fluctuations
in the human heart rate. We develop techniques based on the Fano factor and
Allan factor functions, as well as on detrended fluctuation analysis, for
quantifying deviations from uniform power-law scaling in nonstationary time
series. By analyzing extremely long data sets of up to N = 10(5) beats for 11
healthy subjects, we find that the fluctuations in the heart rate scale
approximately uniformly over several temporal orders of magnitude. By contrast,
we find that in data sets of comparable length for 14 subjects with heart
disease, the fluctuations grow erratically, indicating a loss of scaling
stability.
PMID: 11541831 [PubMed - indexed for MEDLINE]