[1] Dept Vet Affairs Puget Sound Hlth Care Syst, Seattle, WA USA
[2] Univ Washington, Dept Med, Div Pulm & Crit Care Med, Seattle, WA 98101 USA
[3] Dept Vet Affairs Puget Sound Hlth Care Syst, Seattle Epidemiol Res & Informat Ctr, Seattle, WA USA
[4] Univ Washington, Dept Epidemiol, Seattle, WA 98101 USA
[5] Dept Vet Affairs Med Ctr, Portland, OR USA
[6] Oregon Hlth & Sci Univ, Dept Med, Div Pulm & Crit Care Med, Portland, OR 97201 USA