Chiropractic Care and VBA Stroke – Major New Study Reports No Association
Kosloff T, Elton D et al. (2015) Chiropractic Care and the Risk of Vertebrobasilar Stroke: Results of a Case-Control Study in U.S. Commercial and Medicare Advantage Populations. Chiropractic and Manual Therapies; 23:19. (Appendix A)
1. Well, here we go. A new large independent study using a database of approximately 39 million members in the US reports no causal relationship between chiropractic cervical manipulation and vertebrobasilar artery ( VBA) stroke. Importantly, it provides the first independent support for the Cassidy, Boyle et al. study and its conclusion that neck manipulation may be associated in time with stroke but does not cause it.
The study is from Kosloff, Elton et al., researchers from the managed care organization United Health Group in Minnesota and is just published and available free online in Chiropractic and Manual Therapies. Points are:
Data came from commercially insured (35,726,224 members) and Medicare (3,188,825) cases during the three years January 2011 to December 2013. Using the case-control method, the 1,829 VBA stroke patients (1,159 from the commercially insured sample, 670 from the Medicare) were compared with 7,319 similar but non-stroke control patients (4 controls for each stroke patient).
Exposure periods were the 0-30 days prior to the date of hospital admission for VBA stroke, and there was analysis at 1, 3,7,14 and 30 days prior to:
- Chiropractic visits.
- Primary care physician (or GP) visits.
Kosloff, Elton et al. conclude that “there was no association between chiropractic visits and VBA stroke found for the overall sample or for samples stratified by age” (4/1/bottom). In contrast “there is an association existing between GP visits and VBA stroke incidents regardless or length of hazard period (4/2/2).
The likelihood or odds ratio of there being an association between a stroke and a GP visit “increase dramatically from 1-30 days to 1-1 day” which is consistent with “the hypothesis that patients are more likely to see a GP for symptoms related to vertebral artery dissection closer to the index date of their actual stroke.” (6/1/3)
“Overall, our results increase confidence in the findings of (the Cassidy, Boyle et al. study) which concluded there was no excess risk of VBA stroke associated with chiropractic care compared to primary care” (6/2/2).