[1] Providence Vet Affairs Med Ctr, Providence, RI USA
[2] Brown Univ, Warren Alpert Med Sch, Providence, RI 02912 USA
[3] Univ Ottawa, Ottawa Hosp Res Inst, Ottawa, ON, Canada
[4] McMaster Univ, Hamilton, ON, Canada
[5] Vet Affairs Puget Sound Hlth Care Syst, Seattle, WA USA
[6] Univ Washington, Seattle, WA 98195 USA
[7] Johns Hopkins Univ, Sch Med, Baltimore, MD USA
[8] St Louis Univ, St Louis, MO 63103 USA
[9] Lewis Katz Sch Med, Philadelphia, PA USA
[10] Imperial Coll, Natl Heart & Lung Inst, London, England
[11] Rhein Westfalische TH Aachen Univ, Univ Hosp Aachen, Aachen, Germany
[12] Univ Toronto, Sunnybrook Hlth Sci Ctr, Toronto, ON, Canada
[13] Univ Michigan, Ann Arbor, MI 48109 USA
[14] Univ Illinois, Chicago, IL USA
[15] Univ Buffalo, Jacobs Sch Med & Biomed Sci, Buffalo, NY USA
[16] Cornell Univ, Med Ctr, New York, NY 10021 USA
[17] Univ Colorado, Coll Nursing, Anschutz Med Campus, Denver, CO 80202 USA
[18] Univ Leicester, Univ Hosp Leicester Natl Hlth Serv Trust, Leicester, Leics, England
[19] Royal Brompton & Harefield Natl Hlth Serv Fdn Tru, London, England
[20] Univ Zurich, Dept Epidemiol, Zurich, Switzerland
[21] Univ British Columbia, Vancouver, BC, Canada
[22] Brigham & Womens Hosp, 75 Francis St, Boston, MA 02115 USA