1 Indiana University Center for Aging Research, 1101 W 10th Street, Indianapolis, IN 46214, USA. Electronic address: nkeith@iupui.edu.
2 University of Alabama at Birmingham, 1717 11th Ave S, MT 618, Birmingham, AL 35294-4410, USA. Electronic address: mbaskin@uab.edu.
3 School of Natural Resources, University of Missouri, 105 Anheuser-Busch Natural Resources Building, Columbia, MO 65211, USA. Electronic address: sonjaws@missouri.edu.
4 Department of Family and Preventive Medicine, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA 92093, USA. Electronic address: jsallis@ucsd.edu.