J Manipulative Physiol Ther 2014 (Mar); 37 (3): 143–154 ~ FULL TEXT
Paula A Weigel, Jason Hockenberry, PhD, Suzanne E. Bentler, PhD, Fredric D. Wolinsky, PhD
Candidate for PhD,
Department of Health Management and Policy,
College of Public Health,
The University of Iowa, Iowa City, IA.
OBJECTIVES: The comparative effect of chiropractic vs medical care on health, as used in everyday practice settings by older adults, is not well understood. The purpose of this study is to examine how chiropractic compares to medical treatment in episodes of care for uncomplicated back conditions. Episodes of care patterns between treatment groups are described, and effects on health outcomes among an older group of Medicare beneficiaries over a 2-year period are estimated.
METHODS: Survey data from the nationally representative Survey on Assets and Health Dynamics among the Oldest Old were linked to participants' Medicare Part B claims under a restricted Data Use Agreement with the Centers for Medicare and Medicaid Services. Logistic regression was used to model the effect of chiropractic use in an episode of care relative to medical treatment on declines in function and well-being among a clinically homogenous older adult population. Two analytic approaches were used, the first assumed no selection bias and the second using propensity score analyses to adjust for selection effects in the outcome models.
RESULTS: Episodes of care between treatment groups varied in duration and provider visit pattern. Among the unadjusted models, there was no significant difference between chiropractic and medical episodes of care. The propensity score results indicate a significant protective effect of chiropractic against declines in activities of daily living (ADLs), instrumental ADLs, and self-rated health (adjusted odds ratio [AOR], 0.49; AOR, 0.62; and AOR, 0.59, respectively). There was no difference between treatment types on declines in lower body function or depressive symptoms.
CONCLUSION: The findings from this study suggest that chiropractic use in episodes of care for uncomplicated back conditions has protective effects against declines in ADLs, instrumental ADLs, and self-rated health for older Medicare beneficiaries over a 2-year period.
Copyright © 2014 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.
KEYWORDS: Activities of Daily Living, Chiropractic, Episode of Care, Medicare, Mobility Limitation
From the FULL TEXT Article
The therapeutic and restorative benefit of chiropractic on functional abilities has been well established in clinical efficacy studies. [1-15] However, what is not known is the comparative effectiveness of chiropractic vs other common medical treatments for similar clinical conditions over time, especially among Medicare beneficiaries receiving their care in everyday practice settings. For uncomplicated back conditions (eg, strains and sprains, and nonspecific back disorders), Medicare patients have a variety of provider choices, including doctors of chiropractic (DCs), physical therapists, internists, neurologists, interventional pain providers, and orthopedists to name a few. Understanding which providers and treatments Medicare beneficiaries seek, how often they seek those treatments, and the effect of that care on health outcomes would inform clinicians and policy makers alike about the comparative effectiveness of various treatments for uncomplicated back conditions provided in everyday settings.
Investigating how chiropractic care is delivered to Medicare beneficiaries in everyday practice is especially important because treatment patterns there deviate substantially from those delivered under controlled clinical trial conditions, where the intent is to prove treatment efficacy. [16, 17] As a result, the health effects that a patient actually realizes from chiropractic may differ from effects observed in more controlled research settings. Furthermore, understanding how chiropractic care episodes compare to medical care episodes on patient-reported health outcomes sheds light on whether the therapeutic benefits patients perceive is the same, better, or worse. 
Functional health changes are measured by the number of limitations in activities of daily living (ADLs), instrumental ADLs (IADLs), and lower body function (LBFs), and changes in well-being are measured by self-rated health and depressive symptoms. The 3 functional measures are standard disability indicators, and the 2 well-being measures are closely associated with future functional decline, dependency, and mortality. [19-26] Slowing the rate of functional decline, disability, and dependency among community-dwelling older adults reduces the threat of institutionalization and preserves autonomy and well-being, both of which are long-standing public health policy goals in the United States. 
In this study, we use Medicare provider claims linked to a national longitudinal survey of community-dwelling older adults to examine the use of chiropractic and medical treatments in back care episodes that are comparable based on clinical presentation. The purpose of this study is 2-fold: to describe back care episodes in terms of visit patterns and duration among a clinically homogeneous population of older Medicare beneficiaries and to examine whether care episodes involving chiropractic visits result in the same, better, or worse changes in functional health and well-being relative to medical-care-only episodes.
This study was built upon a previously developed algorithm to define episodes of chiropractic care for back problems.  Applying this algorithm to a nationally representative sample of older Medicare beneficiaries resulted in 1057 individuals having clinically similar presentations of back problems occurring in between 2 interviews that were all 2 years apart. The pattern of chiropractic care episodes closely aligned with reports from other studies demonstrating chiropractic efficacy and was also consistent with research that showed little overlap between care provided by DCs and care provided by medical providers during back episodes. [1, 2, 17, 33, 47-49] Within an average chiropractic care episode, only 1 of 9 visits was to a nonchiropractic provider, reflecting the fact that individuals clearly had strong preferences for either chiropractic care or medical care, but not an admixture of the two.
Without adjusting for potential selection bias into chiropractic vs medical care episodes, our findings revealed no statistically significant differences between chiropractic treatment and medical care only in single, nonrecurring episodes of back conditions over a 2-year period. After reweighting the data for individual propensities to use chiropractic vs medical care, however, we observed a protective effect of chiropractic against declines in ADLs, IADLs, and declines in self-rated health. The propensity score weighted model results are particularly interesting because they statistically balanced the groups using propensity scores to remove the preexisting functional and self-rated health advantages among individuals choosing chiropractic care, and the effect of chiropractic care on function and health became significantly protective. These results suggest that when chiropractic care is delivered in practice at care levels comparable to those used in clinical trials and relative to the types of services delivered within an episode of medical care only, chiropractic confers significant and substantial benefits to older adult functional ability and self-rated health.
We found no differential effects on declines in LBF or depressive symptoms between chiropractic and medical services only episodes. This indicates that although chiropractic care was not significantly more beneficial for these health outcomes, chiropractic care did provide comparable benefits compared with medical care only on these 2 health outcomes.
There are several limitations to this study, the first of which concerns the clinical homogeneity of the sample. We assumed that our sample selection criteria that identified only those individuals presenting to clinicians with any of the 29 back conditions for a single episode of care in between the contiguous survey interviews resulted in homogeneity in terms of the nonspecificity, complexity, and chronicity of their conditions. Medicare claims, however, are simply not sufficiently granular to empirically demonstrate this assumption.
A second limitation pertains to how the episodes of care were defined. The algorithm used here operated under a 60-day gap between sequential claims to determine the end of an episode and the start of a new one. In previous sensitivity analyses using different gap lengths, we examined the effect on episode duration and provider distribution and found shorter gaps left many imaging claims unlinked to other services. Although future studies might find that different claims-bundling strategies for defining episodes of care result in different mean episode characteristics, our results are consistent with other research, particularly among the AHEAD sample.
A third limitation with our analysis is combining episodes of care containing medical and chiropractic services with chiropractic-only episodes of care. These types of episodes may be very different from one another in their effect on health. Moreover, the episode descriptives for chiropractic-integrated care illustrate a greater number of chiropractic services and longer episode duration than those in the pure chiropractic services-only episodes, indicating the possibility of more complex back conditions. Thus, heterogeneity resulting from combining these episode types may resulted in underestimating the magnitude of the beneficial effect of chiropractic.
A fourth limitation to this study is the temporal relationship between the effect of treatment for back care and the ascertainment of health outcomes. We did not account for the timing of the back treatment within the 2-year window between survey interviews. This creates the possibility that other factors besides back problems may influence responses to the survey questions measuring ADLs, IADLs, LBFs, self-rated health, and depressive symptoms.
An additional limitation is that although we have addressed selection bias by using propensity score methods, this approach may not have adjusted for unobserved confounders that could affect the care episode type and health outcome relationship (eg, a preference for health that drives other unobserved behaviors affecting functional ability). As a result, selection bias may still be affecting the protective effects of chiropractic care that we observed.
This study provides evidence of the comparative effectiveness of chiropractic care relative to medical-only services on the functional health of older adults during acute episodes of back care. Our results are the first to show the importance of examining chiropractic use within an episode of care in traditional practice settings, rather than focusing on visit frequency alone. Moreover, we evaluated the effects of the treatments received during the episodes on ADLs, IADLs, and LBFs, which are critically important measures that inform patients, clinicians, and payers about the benefits and harms of certain treatments relative to others. Given the literature supporting a minimally effective chiropractic treatment level for back problems, this research provides additional support that such therapeutic levels are indeed beneficial in terms of protecting older persons from functional declines and self-rated health over as much as 2 years.
Chiropractic episodes were longer in duration and contained more
visits to providers than those that were medical-only episodes.
Chiropractic care episodes are protective against 2-year declines
in ADLs among older adults.
Chiropractic care episodes are protective against 2-year declines
in LBF among older adults.
No comparative benefit or harm of chiropractic episodes on declines
in instrumental ADLs, self-rated health, and depressive symptoms among older adults.