[1] Univ Utah, Div Pulm & Crit Care Med, 701 Wintrobe,26 North 1900 East, Salt Lake City, UT 84132 USA
[2] Vanderbilt Univ, Med Ctr, Div Allergy Pulm & Crit Care Med, Nashville, TN USA
[3] Univ Utah, Div Epidemiol, Salt Lake City, UT USA
[4] Harvard Med Sch, Dept Populat Med, Boston, MA USA
[5] Harvard Pilgrim Hlth Care Inst, Boston, MA USA
[6] Dept Vet Affairs Med Ctr, Salem, VA USA
[7] Brigham & Womens Hosp, Dept Med, Boston, MA USA
[8] VA Salt Lake City Hlth Care Syst, Salt Lake City, UT USA
[9] Brigham & Womens Hosp, Boston, MA USA