[1] Alberta Canc Board, Div Populat Hlth & Informat, Calgary, AB T2N 4N2, Canada
[2] Univ Alberta, Fac Phys Educ & Recreat, Edmonton, AB, Canada
[3] Vanderbilt Univ, Sch Med, Vanderbilt Ingram Canc Ctr, Dept Med,Div Gen Internal Med, Nashville, TN 37212 USA
[4] NCI, Div Canc Control & Populat Sci, Bethesda, MD 20892 USA
[5] Yale Univ, Sch Publ Hlth, Dept Epidemiol, New Haven, CT USA