1. Margret and H. A. Rey Institute for Nonlinear Dynamics in Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
2. Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital, Boston, Massachusetts
3. Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
4. Epidemiological Cardiology Research Center, Department of Epidemiology and Prevention and Department of Medicine, Cardiology Section, Wake Forest School of Medicine, Winston-Salem, North Carolina
5. Department of Epidemiology, University of Washington, Seattle, Washington