Session S22.3

Changes in Detrended Fluctuation Indices with Aging in Healthy and Congestive Heart Failure Subjects

O Barquero-Pérez*, JP Marques de Sá, JL Rojo-Álvarez, R Goya-Esteban

Instituto de Engenharia Biomédica
Porto, Portugal

Detrended Fluctuations Analysis (DFA) aims to quantify the fractal correlation properties of Heart Rate Variability (HRV). However, the physiological meaning of DFA indices and its relationship with aging have not yet been completely established.
Given that a loss of complexity in the physiological regulation of elderly subjects has been reported in the literature, we hypothesize that DFA indices could be modified by aging.
Hurst exponent (H exponent), and DFA indices alpha1 and alpha2 were used to asses the temporal correlation properties of HRV. The H exponent was estimated by using DFA, for comparison purposes. We analyzed the data from 24-hour Holter monitoring in healthy subjects (72 recordings, 20-78 years old) and in Congestive Heart Failure (CHF) subjects (44 recordings, 22-79). First, the discrimination capabilities of these indices to distinguish between the young (from 20 to 50 years) and the elderly (from 51 to 80 years) groups were studied. Second, the dependence of these indices on aging was analyzed, by using linear regression of the indices vs. age.
The H exponent and alpha2 allowed to significantly discriminate between young and elderly groups in healthy subjects. The mean+-std for alpha2 were 1.005+-0.052 in the young group, and 1.089+-0.065 in the elderly group, whereas for the H exponent they were 0.042+-0.043 in the young group, and 0.124+-0.046 in the elderly group. All three indices had no significant differences in CHF subjects. Though alpha1 was found in the literature and in our results to be the best DFA index discriminating healthy from pathological subjects, it showed no significant variation between young and elderly. The H exponent and alpha2 could have a linear relationship with age, and just in healthy subjects. Both indices had a variation of 0.0023 units per year. In CHF subjects there was no evidence of a linear relationship of DFA indices with age.
Significant discrimination capabilities between young and elderly groups have been found in alpha2 and H exponent. Also, changes in these values are related with aging in healthy subjects, but not in CHF patients. Therefore, the loss of complexity with age has the effect of a steady increase in alpha2 and H exponent due to the breakdown of long-term correlation, however preserves the fractal correlations properties quantified by alpha1.

(Abstract Control Number: 163)