1 Sleep Disorders Center, Walter Reed National Military Medical Center, Bethesda, Maryland.
2 Uniformed Services University of the Health Sciences, Bethesda, Maryland.
3 Department of Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland.
4 Sleep Disorders Center, Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland.
5 Walter Reed Army Institute of Research, Silver Spring, Maryland.