The work of P.S.R. is supported by the US National Institute on Minority Health and Health Disparities of the US National Institutes of Health (grant number R01 MD015395), and by the US National Institute of Arthritis and Musculoskeletal and Skin Diseases (grant number P30 AR072582). The work of S.S.L. is supported by the National Center for Chronic Disease Prevention and Health Promotion (grant number U01 DP006698).