[1] Univ Washington, Dept Hlth Serv, Seattle, WA 98195 USA
[2] Univ Washington, Dept Radiol, Seattle, WA 98195 USA
[3] Univ Washington, Dept Neurol Surg, Seattle, WA 98195 USA
[4] Univ Washington, Dept Pharm, Seattle, WA 98195 USA
[5] Oregon Hlth & Sci Univ, Dept Family Med, Portland, OR 97201 USA
[6] Oregon Hlth & Sci Univ, Dept Med, Portland, OR 97201 USA
[7] Oregon Hlth & Sci Univ, Dept Publ Hlth & Prevent Med, Portland, OR 97201 USA
[8] Oregon Hlth & Sci Univ, Ctr Res Occupat & Environm Toxicol, Portland, OR 97201 USA
[9] Kaiser Permanente Ctr Hlth Res, Portland, OR USA