I’m going to be commenting on a couple of articles related to a bit of a fight going on in the UK between the British Chiropractic Association (BCA) and, well, a lot of people who are keen to have a bit of a go at them. The BCA recently sued a journalist for libel after he described chiropractic treatment as “bogus” ( http://bit.ly/h1Ux3). They won, and ever since there’s been a bit of to and fro between the BCA and various journalists and scientists.
Recently New Scientist ( http://bit.ly/unO7B) published an article which cited 2 studies outlining the saftey of neck manipulation. I’m going to review one here.
The reason people think neck manipulation might be unsafe relates not to all those Arnold Schwarzenegger movies where he goes around breaking necks every 5 minutes, but to the theory that in the combined movement of neck extension and rotation the vertebral artery can become occluded and maybe dissect (VAD), resulting in a stroke. There has not been a study which has proven this hypothesis to be correct to my knowledge, but the theory exists nonetheless.
In the study, published in Spine (one of the most reputable journals going around), they looked at the risk of having a stroke after seeing a Chiropractor and compared it to the risk of having a stroke after seeing your General Practitioner (GP). This may sound like an odd choice, but the results help us understand something very important.
They looked at the total number of cases of stroke admitted to hospitals in Ontario in a ten year period. There were 818 cases in “a population of more than 100 million person-years” – roughly 0.00000818%, so this is incredibly rare.
Was there an increased risk after seeing a Chiropractor compared to a GP? No. As Richard Brown wrote when summarising the findings, (http://bit.ly/ugEee) “the incidence of stroke after chiropractic was no greater than after a consultation with a general practitioner“.
The reason for this, as postulated by the authors of the Spine article, is that the symptoms of vertebral artery dissection (VAD) are normal symptoms you would consult a manual therapist (Osteopath, Chiropractor) or GP about, that is, neck pain and headache. The authors of the Spine study think that any association between having seen a practitioner and having a stroke would be due to the probability that you have already had the VAD and are on your way to having a stroke, not anything anyone you saw did to you.
In their words, “We found no evidence of excess risk of VBA stroke associated chiropractic care compared to primary care.” Which is a pretty compelling finding when you think about it – of all the people admitted to hospitals in that region in a 10 year period, despite the paranoia about neck manipulation that exists, it seems it is no more dangerous to go and have a chat to your GP than it is to have your neck adjusted.
Update: It might even be more dangerous to go to a GP – “Hospital tells man to take Panadol for broken neck” http://bit.ly/jhMcT
Risk of Vertebrobasilar Stroke and Chiropractic Care: Results of a Population-Based Case-Control and Case-Crossover Study
Cassidy, J David DC, PhD, DrMedSc; Boyle, Eleanor PhD; Côté, Pierre DC, PhD; He, Yaohua MD, PhD; Hogg-Johnson, Sheilah PhD; Silver, Frank L. MD, FRCPC; Bondy, Susan J. PhD
Spine: 15 February 2008 – Volume 33 – Issue 4S – pp S176-S183
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.