1. Epidemiology and Public Health Group, University of Exeter Medical School, RILD Level 3, Royal Devon & Exeter Hospital, Exeter, EX2 5DW, UK
2. Department of Community Medicine and Health Care, Connecticut Institute for Clinical and Translational Science, Institute for Systems Genomics, University of Connecticut Health Center, CT 06269, USA
3. Center for Demography of Health and Aging, University of Wisconsin, Madison, WI 53706, USA
4. UConn Center on Aging, University of Connecticut, Farmington, CT 06030, USA
5. Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Level 3, Royal Devon & Exeter Hospital, Exeter, UK
6. La Follette School of Public Affairs and the Department of Sociology, University of Wisconsin, Madison, WI 53706, USA
7. College of Public Health, University of Iowa, Iowa City, IA 52242, USA
8. National Institute on Aging, Baltimore, MD 21224, USA