Abstract 133: Comparison of CMS Medicare Beneficiaries Enrolled in Fee-For-Service and Managed Care Programs. The Atherosclerosis Risk In Communities (ARIC) Study
Authors: Kucharska-Newton Anna , Petruski-Ivleva Natalia , Bengston Lindsay , Wright Jacqueline , Stearns Sally , Wruck Lisa 
Published: March 2022

Background:
Healthcare utilization analyses often are conducted with Centers for Medicare and Medicaid (CMS) data from fee-for-service (FFS) Medicare beneficiaries. Although use of preventive care services is greater among beneficiaries in managed care programs compared with those in FFS care, evidence of the effect of managed care enrollment on health outcomes is mixed. We compared the health status of ARIC cohort participants enrolled in FFS to those enrolled in managed care.

Methods:
Data for participants of the ARIC Study cohort were linked with CMS Medicare claims for the years 1991-2012 (N=14,695). Participants missing coverage start date or enrolled prior to 1991 were excluded from analyses (N=2,513). Enrollment in FFS and managed care was ascertained at the start of CMS Medicare coverage. Switch from initial FFS enrollment to managed care was ascertained in follow-up through December 31, 2012. Demographics and comorbidities were ascertained from ARIC clinical examination and follow-up data up to the coverage start date. Mortality was ascertained from start date of CMS Medicare coverage through December 31, 2012; rates were modeled using Poisson regression adjusted for age at time of coverage start. Cox proportional hazard regression models, adjusted for demographic characteristics and comorbidities, were used to examine the hazard ratio of all-cause mortality among those in FFS compared to those enrolled in managed care.

Results:
At the start of Medicare coverage, 10,983 and 1,087 ARIC participants were enrolled in FFS and managed care, respectively. In comparison with managed care beneficiaries, those in FFS at the start of coverage were more likely to be white (91% vs. 73.5%), male (43% vs. 38.5%) and have less than a high school education (20.4 vs. 11.8%). Comorbidity burden was greater among those enrolled in FFS compared to those in managed care. The age-adjusted rate of mortality (per 100,000 person-years; median follow-up 11.2 years) was 5.9 (95% CI 5.7, 6.1) among those in FFS and 3.5 (95% CI 2.9, 4.1) among those in managed care. The mortality hazard ratio, comparing FFS to managed care beneficiaries was 1.29 (95% CI 1.08, 1.55). During the time from coverage start to end of follow-up, 4,200 beneficiaries switched from FFS to managed care. With the exception of gender, education and proportion with a history of cancer, demographic characteristics and comorbidities of beneficiaries who switched vs. those who remained in FFS were comparable. The mortality hazard ratio, assessed from start of coverage through December 31, 2012, was 1.59 (95%CI 1.46, 1.74) among those remaining in FFS, as compared to those who switched to managed care.

Conclusion:
Generalizability of inferences from FFS CMS Medicare data may be limited by a greater observed mortality rate among FFS beneficiaries compared to those in managed care. Further analyses are needed to confirm this finding.