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Dartmouth Atlas of Health Care


The Dartmouth Atlas Project (DAP) began in 1993 as a study of health care markets in the United States, measuring variations in health care resources and their utilization by geographic areas: local hospital market areas, regional referral regions, and states. More recently, the research agenda has expanded to reporting on the resources and utilization among patients at specific hospitals. DAP research uses very large claims databases from the Medicare program and other sources to define where Americans seek care, what kind of care they receive, and to correlate increasing expenditures and the supply of health providers and services with health outcomes.

The Dartmouth Institute
Data Years Available: 
Available for 1994 onward.
Annual or periodic, depending on indicator.
Mode of Collection: 
This is a "secondary" data source. The original data come from the Centers for Medicare and Medicaid Services (CMS) administrative and claims data, U.S. Census population data.
Selected Content: 
The database contains information on Medicare spending and on Medicare utilization of selected services, providers, and facilities, by state, local, and regional market areas; by selected subpopulations of Medicare beneficiaries, including decedents and chronically ill beneficiaries; and by providers. The database also allows users to compare quality measures across hospitals.
Population Covered: 
Medicare beneficiaries between the ages of 65 and 99 years with full Part A and Part B entitlement are included in the database. Persons enrolled in managed care organizations are excluded from the analysis.

Indicators are created from Medicare claims and administrative data. The percentage of Medicare deaths occurring in a hospital was computed using “death in a hospital” (discharge status B in the Medicare Provider Analysis and Review (MEDPAR) file) as the numerator event. For the percentage of Medicare deaths who were admitted to an intensive care unit (ICU) in the last 6 months of life, the numerator event was “death in a hospital with admission to an ICU within 6 months of the death date, “ using MEDPAR files. Rates were age, sex, and race adjusted and were expressed as a percentage of deaths. Medicare decedents are identified by their ZIP code of residence. Total ICU days measures intensive care days (which includes medical, surgical, trauma, and burn care) and coronary care days to produce a total ICU days measure. Intermediate care or step-down units are also included.

Response Rates and Sample Size: 

The data are from the MEDPAR file, a 100% sample of inpatient claims. The file includes one record for each hospital stay by a Medicare beneficiary, including data on dates of admission and discharge, diagnoses, procedures, and Medicare reimbursements to the hospital.

Interpretation Issues: