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Use of Chiropractic Spinal Manipulation in Older Adults Is Strongly Correlated With Supply

Whedon, James M. DC, MS*; Song, Yunjie PhD*; Davis, Matthew A. DC, MPH*; Lurie, Jonathan D. MD, MS

doi: 10.1097/BRS.0b013e31825762b7
Health Services Research
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Study Design. Retrospective cross-sectional analysis of administrative data.

Objective. To examine the relationship between regional chiropractic supply and both use and utilization intensity of chiropractic services among Medicare beneficiaries.

Summary of Background Data. Numerous studies have documented trends and patterns in the utilization of chiropractic services in the United States, but little is known about geographic variation in the relationship between chiropractic supply and utilization.

Methods. We analyzed Medicare claims data for services provided by chiropractic physicians in 2008. We aggregated the data to the hospital referral region level and used small area analysis techniques to generate descriptive statistics. We mapped geographic variations in chiropractic supply, use and utilization intensity (treatments per user), and quantified the variation by coefficient of variation and extremal ratio. We used Spearman rank correlation coefficient to correlate use with supply. We used a logistic regression model for chiropractic use and a multiple linear regression model for chiropractic utilization intensity.

Results. The average regional supply of chiropractic physicians was 21.5 per 100,000 adult capita. The average percentage of beneficiaries who used chiropractic was approximately 7.6 (SD, 3.9). The average utilization intensity was 10.6 (SD, 1.8). Regional chiropractic supply varied more than 14-fold, and chiropractic use varied more than 17-fold. Chiropractic supply and use were positively correlated (Spearman ρ, 0.68; P < 0.001). A low back or cervical spine problem was strongly associated with chiropractic use (odds ratios, 21.6 and 14.3, respectively). Increased chiropractic supply was associated with increased chiropractic use (odds ratio, 1.04) but not with increased chiropractic utilization intensity.

Conclusion. Both the supply of chiropractors and the utilization of chiropractic by older US adults varied widely by region. Increased chiropractic supply was associated with increased chiropractic use but not with increased chiropractic utilization intensity. Utilization of chiropractic care is likely sensitive to both supply and patient preference.

In a retrospective cross-sectional analysis of Medicare data, regional chiropractic supply varied more than 14-fold and chiropractic use varied more than 17-fold. Chiropractic supply and use were positively correlated. Chiropractic supply was associated with chiropractic use (odds ratio, 1.04) but not with number of chiropractic visits per user.

*The Dartmouth Institute for Health Policy & Clinical Practice, Lebanon, NH

Department of Orthopaedic Surgery and The Dartmouth Institute, Lebanon, NH.

Address correspondence and reprint requests to James M. Whedon, The Dartmouth Institute for Health Policy & Clinical Practice, 30 Lafayette St., Lebanon, NH 03756; E-mail: james.m.whedon@dartmouth.edu

Acknowledgment date: January 20, 2012. First revision date: March 13, 2012. Acceptance date: March 19, 2012.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Grant funds were received to support this work.

One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: e.g., honoraria, gifts, consultancies, royalties, stocks, stock options, decision-making position.

© 2012 Lippincott Williams & Wilkins, Inc.