Geographic Variations in Chiropractic Utilization under Medicare

Longitudinal variations in chiropractic utilization under Medicare have been described, but except for the results of the Medicare Chiropractic Services Demonstration, little is known about geographic variations in the use of chiropractic under Medicare. The purpose of this research project was to identify, describe and map geographic variations in chiropractic utilization under Medicare Part B, which includes outpatient office visits, the most common venue for delivery of chiropractic care. This investigation employed a cross-sectional design to generate statistics descriptive of geographic variations in volumes and rates of chiropractic availability, use and costs, as well as variations in chiropractic provider and user demographics. Selected variables were mapped to demonstrate variations by state and primary care service area. This study employed a 20% representative sample of Medicare Part B claims data for living Medicare beneficiaries aged 65-99 from 2002 to 2008. The claims records were restricted to those filed under the provider specialty code for chiropractic. Medicare data files for beneficiaries, providers and claims were merged together to generate an analytic file, and estimates of volumes and rates were extrapolated from the results of the analysis of the 20% sample. Selected data were then joined with a geographic attributes file and analyzed with geographic information system software. Geographic variations in chiropractic availability, use and costs facilitate the identification of regions of appropriate care, supply-sensitive care (overutilization), and under-utilization of effective care, as well as preference –sensitive care. Appreciation of geographic variation in chiropractic utilization informs planning, resource allocation and quality improvement efforts.