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Eur Spine J. 2008 Apr; 17(Suppl 1): 176–183.
Published online 2008 Feb 29. doi: 10.1007/s00586-008-0634-9
PMCID: PMC2271108

Risk of Vertebrobasilar Stroke and Chiropractic Care

Results of a Population-Based Case-Control and Case-Crossover Study
J. David Cassidy,corresponding author1,2,3,4 Eleanor Boyle,1,2 Pierre Côté,1,2,3,4,5 Yaohua He,1,2 Sheilah Hogg-Johnson,3,5 Frank L. Silver,6,7 and Susan J. Bondy3
Author information Copyright and License information Disclaimer

Abstract

Study Design

Population-based, case-control and case-crossover study.

Objective

To investigate associations between chiropractic visits and vertebrobasilar artery (VBA) stroke and to contrast this with primary care physician (PCP) visits and VBA stroke.

Summary of Background Data

Chiropractic care is popular for neck pain and headache, but may increase the risk for VBA dissection and stroke. Neck pain and headache are common symptoms of VBA dissection, which commonly precedes VBA stroke.

Methods

Cases included eligible incident VBA strokes admitted to Ontario hospitals from April 1, 1993 to March 31, 2002. Four controls were age and gender matched to each case. Case and control exposures to chiropractors and PCPs were determined from health billing records in the year before the stroke date. In the case-crossover analysis, cases acted as their own controls.

Results

There were 818 VBA strokes hospitalized in a population of more than 100 million person-years. In those aged <45 years, cases were about three times more likely to see a chiropractor or a PCP before their stroke than controls. Results were similar in the case control and case crossover analyses. There was no increased association between chiropractic visits and VBA stroke in those older than 45 years. Positive associations were found between PCP visits and VBA stroke in all age groups. Practitioner visits billed for headache and neck complaints were highly associated with subsequent VBA stroke.

Conclusion

VBA stroke is a very rare event in the population. The increased risks of VBA stroke associated with chiropractic and PCP visits is likely due to patients with headache and neck pain from VBA dissection seeking care before their stroke. We found no evidence of excess risk of VBA stroke associated chiropractic care compared to primary care.

Keywords: vertebrobasilar stroke, case control studies, case crossover studies, chiropractic, primary care, complications, neck pain

Footnotes

Supported by Ontario Ministry of Health and Long-term Care. P.C. is supported by the Canadian Institute of Health Research through a New Investigator Award. S.H.-J. is supported by the Institute for Work & Health and the Workplace Safety and Insurance Board of Ontario.

The opinions, results, and conclusions are those of the authors and no endorsement by the Ministry is intended or should be inferred.

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

University Health Network Research Ethics Board Approval number 05-0533-AE.

Reprinted with permission from Lippincott Williams & Wilkins, Cassidy JD, Boyle E, Côté P, et al., Risk of Vertebrobasilar Stroke and Chiropractic Care, Results of a Population-Based Case-Control and Case-Crossover Study, SPINE, Volume 33, Number 4S, pp S176–S183

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