[1] Univ Calif Davis, Dept Publ Hlth Sci, Davis, CA 95616 USA
[2] Univ Calif San Diego, Div Biostat & Bioinformat, San Diego, CA 92103 USA
[3] Univ Calif San Francisco, Dept Radiol & Biomed Imaging, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, Dept Epidemiol & Biostat, San Francisco, CA 94143 USA