Home : Research : Stroke : Case-Controlled Study
Chiropractic Manipulation and Stroke: A Population-Based Case-Controlled Study
This
one will need to be paid attention to throughout the profession as it has
the potential of being the most important collection and analysis of data
in the adjustment-stroke discussion.
A retrospective analysis was done using records from 1993-1998 in Ontario. 582 cases of vertebrobasilar artery accident were reported during that time. The cases were age and sex matched to four controls from the Ontario population with no history of stroke at the event date. The analysis showed that in patients under the age of 45 VBA cases were 5 times more likely than controls to have visited a chiropractor within one week of the VBA. No associations were found in the above 45 age group.
The conclusions were: "While our analysis is consistent with a positive association in young adults, potential sources of bias are also discussed. The rarity of VBAs makes this association difficult to study despite high volumes of chiropractic treatment. Because of the popularity of spinal manipulation, high-quality research on both its risks and benefits is recommended."
Anthony Rosner, Ph.D. has offered his thoughts in a news release presented by the Foundation for Chiropractic Education and Research. The full discussion of Dr. Rosner and the references used to support his argument are available online, at no cost, at FCER.
Rosner states "The latest study, from the University of Toronto and the Sunnybrook and Women's College Health Sciences Centre and published in Stroke, has turned the heat up a notch or two. It presents 582 cases with a diagnosis of vertebrobasilar dissection (VBA) or occlusion over the 6-year period from January 1993 through December 1998, age and sex matching these to 4 controls each lacking this diagnosis from the Ontario population. The study documents use of chiropractic services from public health insurance billing records. Of those patients aged less than 45 years, VBA cases appeared to be 5 times more likely than controls to have visited a chiropractor within 1 week of the VBA, although no significant associations were found for those aged >45 years. In the younger cohort, VBA cases were 5 times as likely to have had 3 or more visits with a cervical diagnosis in the month before the actual occurrence of the VBA.
Unfortunately, this argument appears to be somewhat of a red herring. It also suffers from a paucity of numbers, for when the focus is reduced to the most heralded cohort of the study (patients aged less than 45 years), only 6 had cervical manipulations within 1 week of their VBA against a background figure of 1 from a matched cohort which did not have a vascular event. That would leave 5 incidences that would appear to be attributable to the chiropractic visit over a 5-year period, or 1 per year.
The
fact remains that Rothwell's own data clearly indicate that vast preponderance
(over 95%) of VBA stroke victims did not visit the chiropractor's office within
the year preceding the vascular event, and nearly another 3% saw a chiropractor
from 1 month to 1 year preceding the stroke. What needs to be emphasized is
that no less than 68 everyday activities have been shown to disrupt cerebral
circulation. Among those activities, 18 (childbirth, interventions by surgeon
or anesthetist during surgery, calisthenics, yoga, overhead work, neck extension
during radiography, neck extension for a bleeding nose, turning the head while
driving a vehicle, archery, wrestling, emergency resuscitation, star gazing,
sleeping position, swimming, rap dancing, fitness exercise, beauty parlor
events, and Tai Chi) have actually been associated with vascular accidents
but are decidedly non-manipulative.
Assuming that VBAs are the result of blunt trauma may actually exonerate most cervical adjustments as the causative agent. Peak elongations of the vertebral artery during neck manipulative treatments have recently been shown to be at most about 11% of the elongations observed at the arterial failure limit; in fact, these elongations are consistently lower than those seen during routine range of motion and diagnostic testing. What is becoming more and more apparent is that VBAs must be considered to be the result of cumulative events over an extended period of time rather than recent visits to the chiropractor.
Simply expressed, this argument states that a subset of stroke patients who had sought chiropractic treatment for neck pain were already well on the way to experiencing a VBA accident. Rothwell's study omitted the most obvious and convincing control group--which would have been to include a cohort of patients with neck pain seeking treatment by practitioners other than chiropractors, such as allopathic physicians. Like a perfect sham procedure in a clinical trial, this particular control would have accounted for all variables except the fact that the patient visited a chiropractor rather than another practitioner. Clearly, this design would have more directly tracked the development of VBAs and avoided the highly conjectural and suspiciously political attempt to lay the blame directly to chiropractic manipulation, as has been done in the studies of inferior design cited earlier.
Instead of becoming too obsessed with Rothwell's single-digit numbers of cases and to put this matter in the proper perspective, one should be forever cognizant of the fact that death rates following cervical manipulation calculate to be anywhere between 1/100-1/400, the rates seen in the use of NSAIDs for similar conditions. Death rates from lumbar spine operations have been reported to be 300 times higher than the rate produced by cerebrovascular accidents in spinal manipulation. For cervical surgeries, recent death rates have been estimated to be 700-fold greater. As Rome has pointed out, risks for "virtually all" medical procedures ranging from the taking of blood samples, use of vitamins, drugs, "natural" medications, and vaccinations are routinely accepted by the public as a matter of course.
Until these lifestyle risks are properly bundled into a study of the proper design, the public will continue to misunderstand the true etiology of vertebrobasilar artery accidents, being led instead to chase arguably less than 3% of the total number of reported VBAs down a rabbit hole which has been labeled "The Chiropractor's Office." One also hopes that having to respond to this increasing number of studies based on a paucity of cases does not become the centerpiece of the chiropractic agenda.
An abstract regarding the above titled article appeared in the June 27,
2001 issue of JAMA, Volume 285, Number 24, page 3071.
The full article is available online for a fee of $15.00 at AHA
Journals
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