Gender related differences in scaling structure of heart-rate and blood-pressure variability as assessed by detrended fluctuation analysis

Women, which have lower risks of cardiovascular events, are characterized by higher heart rate entropy. Aim of this study is to evaluate whether also the fractal structure of heart rate and blood pressure, as quantified by DFA, differs between men and women. In 33 male and 23 female volunteers, we recorded R-R intervals (RRI) and systolic (S) and diastolic (D) blood pressure (BP) for 10´ in 3 conditions: supine rest, sitting at rest and sitting during exercise. We calculated a spectrum of scale exponent α(t) as function of the time scale t, by DFA. We also calculated traditional spectral indexes for assessing cardiac and vascular autonomic tone. We found gender related differences in α(t) only during supine rest. Women had significantly lower α(t) of RRI at scales <;6 s, and higher α(t) of BP at the longer scales, the difference being significant for DBP at t>;60s. Results may in part be explained by gender differences in cardiac autonomic tone at rest.