The Association Between Medical Costs and Participation in the Vitality Health Promotion Program Among 948,974 Members of a South African Health Insurance Company. - Patel, Deepak N.; Lambert, Estelle V.; Roseanne da Silva; Greyling, Mike; Nossel, Craig; Noach, Adam; Derman, Wayne; Gaziano, Thomas (American Journal of Health Promotion, 2010)