This report from the Kaiser Family Foundation describes the make-up of the dual eligible population. It explains that this group comprises one of the least healthly groups in both the Medicare and Medicaid systems, resulting in above average spending on their health care.

From the report: 

Medicaid fills in the gaps in Medicare’s benefit package for many low-income Medicare enrollees. These ―dual eligibles are individuals who are entitled to Medicare who are also eligible for some level of assistance from their state Medicaid program. Such assistance ranges from help paying for Medicare’s premiums and cost-sharing, to coverage of benefits not offered under Medicare, such as hearing, vision, dental, and long-term care. Because dual eligibles have significant medical needs and a much higher per capita cost than other beneficiaries, they are of great interest to both Medicare and Medicaid policymakers and to the state and federal governments that finance and manage the programs.

This brief provides an update of the share of total Medicaid enrollment and spending attributable to dual eligibles using data through 2007. It also provides state-level estimates of Medicaid enrollment and expenditures for dual eligibles, together with a breakdown of dual eligible Medicaid expenditures by service category, as well as by age group and Medicaid eligibility group (elderly or disabled under age 65).

Full Report: Dual Eligibles: Medicaid Enrollment and Spending for Medicare Beneficiaries in 2007 (PDF | 1.24 MB)

Kaiser Family Foundation. (2010). Dual eligibles: Medicaid enrollment and spending for Medicare Beneficiaries in 2007. Rousseau, D., Clemans-Cope, L., Lawton, E., Langston, J., Connolly, J., and Howard, J.