Task 2: Medicaid: History of NHANES and CMS data

Also administered by CMS, Medicaid is a U.S. public health insurance program (Title XIX of the Social Security Act from 1965) covering low-income adults and children and people with certain disabilities. It is jointly funded by the individual states and the Federal government. Each state manages its own Medicaid program within the bounds of minimum Federal requirements. Thus, Medicaid eligible populations and available benefits will vary among states and over time.

Many groups of people are covered by Medicaid depending on the state’s requirements (e.g., age, whether pregnant, disabled, blind, or aged, income level and resources, U.S. citizenship or lawful immigration status).   

A link to the CMS webpage is located in the Resources section.

Where do the Medicaid data come from?

The Medicaid Analytic eXtract (MAX) data are extracted from the Medical Statistical Information System (MSIS) data. MSIS is a database of claims that have been submitted, adjusted and paid by the states. MAX data are organized by CMS into annual calendar year files and include finalized claims. The MAX files, beginning with 1999 data, have been linked with the continuous NHANES files. The range of years of Medicaid data that are linked are described in Course 1, Module 3, Task 2 “NHANES-CMS Linked Data Years of Availability”.

States & services covered

Medicaid is administered by states under general guidelines established by the federal government and is financed jointly by federal and state funds. The Federal Medical Assistance Percentage (FMAP), also called the federal match rate, represents the percent of Medicaid financed by the federal government in each state. The FMAP differs by state and takes into account the average per capita income in a state relative to the national average.   You can find the FMAP for individual states for each federal fiscal year in the Federal Percentages and Federal Medical Assistance Percentages table produced by the Department of Health and Human Services’ Assistant Secretary for Planning and Evaluation.  See the Resources section for the link to this material.

State Medicaid programs must cover mandatory services specified in federal law to receive federal matching funds.  Beneficiaries are entitled to receive the following mandatory services:

Medicaid long-term care services include comprehensive services provided in nursing homes and intermediate care facilities for the mentally retarded (ICF‐MR). Long-term care also includes a wide range of services and supports needed by people to live independently in the community, including home health care, personal care, medical equipment, rehabilitative therapy, adult day care, case management and respite for caregivers.

States are also permitted to cover many services that federal law designates as optional, including dental services, prescription drugs, case management, and hospice services. State variation in Medicaid coverage, with regard to both program eligibility and covered services, results in state differences in enrollment rates and expenditures. Other factors, including the age distribution, the poverty rate, and the Medicaid provider reimbursement rates, also contribute to variation among states in enrollment, service use, and costs. As a result, Medicaid operates as more than 50 distinct programs – one in each state, the District of Columbia, and each of the territories. Consideration of these state-level differences may be necessary for many analyses. State identifiers for NHANES need to be specifically requested in those circumstances. State identifiers are not available in public use data files and must be specifically requested in NCHS Research Data Center proposals.



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