[1] Boston Coll, William F Connell Sch Nursing, Chestnut Hill, MA 02467 USA
[2] Johns Hopkins Univ, Sch Med, Baltimore, MD USA
[3] Univ Penn, Perelman Sch Med, Dept Biostat & Epidemiol, Philadelphia, PA USA
[4] Natl Univ Hosp Iceland, Landspitali, Dept Resp Med & Sleep, Reykjavik, Iceland
[5] Univ Iceland, Fac Med, Sch Hlth Sci, Reykjavik, Iceland
[6] Univ Penn, Perelman Sch Med, Ctr Sleep & Circadian Neurobiol, Dept Med,Div Sleep Med, Philadelphia, PA USA