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Methods Inf Med 2004; 43(01): 26-29
DOI: 10.1055/s-0038-1633418
Original Article
Schattauer GmbH

Decreased Fractal Correlation in Diurnal Physical Activity in Chronic Fatigue Syndrome

K. Ohashi
1   Educational Physiology Laboratory, Graduate School of Education, The University of Tokyo, Japan
,
G. Bleijenberg
2   The Netherlands Fatigue Research Group Nijmegen, Department of Medical Psychology and Internal Medicine, University Hospital Nijmegen, Nijmegen, The Netherlands
,
S. van der Werf
2   The Netherlands Fatigue Research Group Nijmegen, Department of Medical Psychology and Internal Medicine, University Hospital Nijmegen, Nijmegen, The Netherlands
,
J. Prins
2   The Netherlands Fatigue Research Group Nijmegen, Department of Medical Psychology and Internal Medicine, University Hospital Nijmegen, Nijmegen, The Netherlands
,
L. A. N. Amaral
3   Department of Chemical Engineering, Northwestern University, Evanston, IL, USA
,
B. H. Natelson
4   Department of Neurosciences, New Jersey Medical School, East Orange, NJ, USA
,
Y. Yamamoto
1   Educational Physiology Laboratory, Graduate School of Education, The University of Tokyo, Japan
4   Department of Neurosciences, New Jersey Medical School, East Orange, NJ, USA
5   PRESTO, Japan Science and Technology Corporation, Saitama, Japan
› Author Affiliations
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Publication History

Publication Date:
07 February 2018 (online)

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Summary

Objectives: Our objectives were to study the temporal correlation of physical activity time series in patients with chronic fatigue syndrome (CFS) during normal daily life and to examine if it could identify the altered physical activity in these patients.

Methods: Fractal scaling exponents of diurnal and nocturnal physical activity time series in 10 CFS patients and 6 healthy control subjects (CON) were calculated by the detrended fluctuation analysis (DFA) and the wavelet transform modulus maxima (WTMM) method. We hypo-thesized that, due to their illness- and/or fatigue-induced resting episodes, altered physical activity patterns in CFS patients might be observed at the interruption of activity bursts. Thus, we further developed a new method, the wavelet transform negative modulus maxima (WTNMM) method, which could evaluate the temporal correlation at the interruption of activities. We compared the fractal scaling exponents for CFS and CON by each method.

Results: Both for CFS and CON, we found the fractal time structures in their diurnal physical activity records for at least up to 35 minutes. No group difference was found in nocturnal activities. The WTNMM method revealed that, in diurnal activities, CFS patients had significantly (p <0.01) smaller fractal scaling exponent (0.87 ± 0.03) compared to controls (1.01 ± 0.03). Such a difference was identified neither by the DFA nor WTMM method.

Conclusions: CFS patients had more abrupt interruptions of voluntary physical activity during diurnal periods in normal daily life, probed by the decreased correlation in the negative modulus maxima of the wavelet-transformed activity data, possibly due to their exaggerated fatigue.

Keywords

Chronic fatigue syndrome - physical activity - detrended fluctuation analysis - wavelet transform modulus maxima method