Chiropractic care A VBA stroke risk? Study title: Risk of Vertebrobasilar Stroke and Chiropractic Care Results of a Population-Based Case-Control and Case-Crossover Study Author: Cassidy JD et al. Publication information: Spine, 2008; 33(4S): S176–S183. Summary: Below THANKS TO DR. MICHAEL HANELINE, DC, MPH, FROM PALMER COLLEGE OF CHIROPRACTIC WEST, FOR PROVIDING THIS REVIEW. N Dr.Shawn Thistle is the founder and president of Research Review Service Inc., an online, subscription- based service designed to help busy practitioners to integrate current, relevant scientific evidence into |their practice. Shawn graduated from CMCC and holds an Hon- ours Degree in Kinesiology from McMaster University. He also holds a certificate in Contemporary Medi- cal Acupuncture from McMaster University, and is a Certified Active Release Techniques (ART®) Pro- vider. For more information about the Research Review Service, visit www.researchreviewservice.com. eck pain is a widespread problem that is treated most commonly by medical physicians, physical therapists and chiropractors. Approximately 12 per cent of adults in Canada, and the United States, (U.S.) visit chiropractors annually, al- though Canadian chiropractic patients tend to be younger and have fewer health problems than those in the U.S. Numerous clinical trials, and a few systematic reviews, which point to the effectiveness of manual therapy, have been carried out, but too few subjects have been included to as- sess the risk of rare adverse events. Vertebrobasilar artery (VBA) stroke is a rare neurological event that has been reported to occur very infrequently following cervical manipulation and other neck-related activi- ties, as well as spontaneously. Reports of VBA stroke in association with chiropractic care have mainly been derived from case reports and a few case-control studies. Researchers have therefore questioned whether the relationship is causal, primarily because most of the patients in these studies presented for care complaining of neck pain and headache, which are very common early symptoms of VBA dissection that can lead to VBA stroke. The purpose of this study was to test the assumption that the reason VBA stroke pa- tients have a higher rate of chiropractic care preceding the event is that they seek care when already experiencing VBA-related symptoms. To do this, the authors compared rates among neck pain patients who received chiropractic care versus those who received care by primary care physicians (PCPs). If the rates of care preceding VBA stroke were high in both groups, it would lend support to the assumption. To strengthen the study’s fi ndings, two different research designs were utilized – popu- lation-based case-control and case-crossover designs - both using the same cases. Cases and controls were derived from the same source population, which included all residents of Ontario covered by the publicly funded Ontario Health Insurance Plan (OHIP) over the nine-year period extending from 1993 to 2002. All patients who were hospitalized with VBA strokes during this period were included as cases. For each case, four age and sex- matched controls were randomly selected from the Registered Persons Database. The case- crossover study made comparisons using four control periods of time that were randomly chosen from the year before the date of the VBA stroke. Cases were considered to be exposed if they had reimbursed ambulatory encounters with chiropractors or PCPs for a neck-related disorder during the one-year period before the index date from the OHIP database. PERTINENT RESULTS OF THIS STUDY: The study included 818 cases and 3,164 matched controls. The mean age of all subjects was 63 years and 63 per cent were male. There was a higher proportion of comorbid conditions – e.g. hypertension, heart disease, and diabetes – among cases. 12 • CANADIAN CHIROPRACTOR | APRIL 2008 www.canadianchiropractor.ca Shawn Thistle, BKin (Hons), DC, CSCS
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