[1] Mayo Clin, Dept Hlth Sci Res, Div Epidemiol, Rochester, MN 55905 USA
[2] Mayo Clin, Div Biostat, Rochester, MN 55905 USA
[3] Mayo Clin, Dept Urol, Rochester, MN 55905 USA
[4] Merck Res Labs, Blue Bell, PA USA
[5] Univ Michigan, Dept Urol & Epidemiol, Ann Arbor, MI 48109 USA