Each year, the VA-Medicare Data Merge Initiative creates
a file, known as the VHA cohort, containing Social Security
Numbers (SSNs) of veterans known to the VA as eligible
or potentially eligible to receive healthcare through the
VHA. This file is submitted to the Centers for Medicare
and Medicaid Services (CMS), who extract Medicare enrollment
and claims data for these SSNs.
The VHA cohort includes veterans who:
• have obtained healthcare services from
the VHA since 1992,
• have enrolled in the VHA, or
• are receiving compensation or pension benefits
from the VA.
Multiple data sources are used in the creation of the
VHA cohort. The cohort is cumulative and is updated
annually to add SSNs from the most recent source data. A
list of the source files used to create the VHA cohort
for each year is available: "Source
files for the VHA cohort by year". For each
source file, the list contains: the file name, the file
type, a link to file documentation, and the calendar year
in which SSNs that are new to the cumulative VA cohort
contained in the specific source file could first appear
in the Medicare data.
The VHA cohort has grown from over 6 million veterans
in 1999 to over 12 million in 2003.
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