Correlated and uncorrelated regions in heart-rate fluctuations during sleep.

Armin Bunde,1 Shlomo Havlin,1,2 Jan W. Kantelhardt,1 Thomas Penzel,3 Jorg-Hermann Peter,3 and Karlheinz Voigt3 1Institut fur Theoretische Physik III, Justus-Liebig-Universitat, D-35392 Giessen, Germany 2Department of Physics and Gonda-Goldschmied-Center for Medical Diagnosis, Bar-Ilan University, Ramat-Gan 52900, Israel 3Zentrum fur Innere Medizin und Institut fur Physiologie, Philipps-Universitat, D-35033 Marburg, Germany (Received 18 November 1999)