Skip to main content
. Author manuscript; available in PMC: 2012 Jul 12.
Published in final edited form as: N Engl J Med. 2012 Jan 12;366(2):150–157. doi: 10.1056/NEJMsa1104273

Figure 1. Example of Study Populations and Timelines or a Case Plan That Added a Fitness-Membership Benefit in 2004 and Its Matched Control Plan.

Figure 1

Shown is the study timeline for a case plan that introduced a fitness benefit in 2004 and its matched control plan. For case plans that introduced the fitness benefit in 2005, earlier enrollees were defined as those enrolled before 2005, and new enrollees as those enrolled in 2005 or 2006. All case and control plans participated in Medicare from 2002 through 2008. All beneficiaries were continuously enrolled from the time of entry into the plan until the follow-up health-status assessment in 2008. HOS denotes Health Outcomes Survey.