1. Department of Medicine, University of Toronto, Toronto, Ontario, Canada;
2. Department of Physiology, University of Toronto, Toronto, Ontario, Canada;
3. Lilly Research Laboratories, Windlesham, Surrey, United Kingdom;
4. Division of Sleep Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; and
5. Division of Pulmonary and Critical Care, University of California at San Diego, San Diego, California