title: Risk of Carotid Stroke after Chiropractic Care: A Population-Based Case-Crossover Study.
abstract: BACKGROUND
  Chiropractic manipulation is a popular treatment for neck pain and headache, but may increase the risk of cervical artery dissection and stroke. Patients with carotid artery dissection can present with neck pain and/or headache before experiencing a stroke. These are common symptoms seen by both chiropractors and primary care physicians (PCPs). We aimed to assess the risk of carotid artery stroke after chiropractic care by comparing association between chiropractic and PCP visits and subsequent stroke.
  
  
  METHODS
  A population-based, case-crossover study was undertaken in Ontario, Canada. All incident cases of carotid artery stroke admitted to hospitals over a 9-year period were identified. Cases served as their own controls. Exposures to chiropractic and PCP services were determined from health billing records.
  
  
  RESULTS
  We compared 15,523 cases to 62,092 control periods using exposure windows of 1, 3, 7, and 14 days prior to the stroke. Positive associations were found for both chiropractic and PCP visits and subsequent stroke in patients less than 45 years of age. These associations tended to increase when analyses were limited to visits for neck pain and headache-related diagnoses. There was no significant difference between chiropractic and PCP risk estimates. We found no association between chiropractic visits and stroke in those 45 years of age or older.
  
  
  CONCLUSIONS
  We found no excess risk of carotid artery stroke after chiropractic care. Associations between chiropractic and PCP visits and stroke were similar and likely due to patients with early dissection-related symptoms seeking care prior to developing their strokes.
authors.affiliation: Department of Sports Science and Clinical Biomechanics, Faculty of Health, University of Southern Denmark, Odense, Denmark; Division of Health Care and Outcomes Research, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada; Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada. Electronic address: dcassidy@health.sdu.dk.
authors.forename: J David
authors.initials: JD
authors.lastname: Cassidy
authors.affiliation: Department of Sports Science and Clinical Biomechanics, Faculty of Health, University of Southern Denmark, Odense, Denmark; Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Eleanor
authors.initials: E
authors.lastname: Boyle
authors.affiliation: Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada; Faculty of Health Sciences, University of Ontario Institute of Technology and UOIT-CMCC Centre for Disability Prevention and Rehabilitation, Oshawa, Ontario, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Côté
authors.affiliation: Institute for Work and Health, Toronto, Ontario, Canada; Division of Biostatistics, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Sheilah
authors.initials: S
authors.lastname: Hogg-Johnson
authors.affiliation: Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Bondy
authors.affiliation: Department of Neurology, University of California, Irvine, California.
authors.forename: Scott
authors.initials: S
authors.lastname: Haldeman
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002170:Canada; D016022:Case-Control Studies; D018672:Community Health Planning; D018592:Cross-Over Studies; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008297:Male; D020393:Manipulation, Spinal / Q000009:adverse effects*; D008875:Middle Aged; D019547:Neck Pain / Q000628:therapy; D016017:Odds Ratio; D012306:Risk; D020521:Stroke / Q000453:epidemiology* / Q000209:etiology*; D055815:Young Adult
keywords: Stroke; risk factor; spinal manipulation; stroke prevention