1 Sleep Disorders Center, Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA.
2 Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
3 Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, USA.
4 Sleep Disorders Center, Fort Belvoir Community Hospital, Ft Belvoir, VA, USA.
5 Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
6 Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA.