Why was this study done?
When faced with neck pain and headaches, patients sometimes choose to visit a chiropractor for help. In the past, there have been reports linking chiropractic care with vertebrobasilar artery (VBA) stroke. This type of stroke is caused by a blockage or injury to the vertebrobasilar artery that passes through the base of the skull and the vertebrae of the spine. This study looked at the association between VBA strokes and chiropractic visits, and compared it with visits to primary care physicians and VBA strokes.
How was the study done?
Researchers examined cases of VBA strokes in Ontario between 1993 and 2002 using data obtained from the Canadian Institute for Health Information and the Ontario Health Insurance Plan (OHIP). Chiropractor and primary care physician visits were determined from health billing records in the year before the stroke date. More than 100 million person-years of data were analyzed for this study.
What did the researchers find?
Over the study period, 818 people were admitted to Ontario hospitals for VBA stroke. Of these cases, four per cent had visited a chiropractor within 30 days of their hospital visit. About 53 per cent had visited a primary care provider over the same time span. For patients under the age of 45, researchers found a link between VBA stroke and visits to a chiropractor. However, this same link was also present for those who saw a primary care physician, regardless of age. In patients 45 years or older, there was no increased risk of VBA stroke and chiropractor visits.
What are some strengths and weaknesses of the study?
One strength of this study was that it looked at an entire population over a nine-year period. However, when using health records, cases can be misclassified, and the databases do not always provide clinical details for the specific causes of a stroke, some which may or may not have been related to the vertebrobasilar artery.