All healthcare disciplines are associated with risks of injury or death. Rare but sensational occurrences are often exploited by the media, leading the public to believe that rare events are commonplace. In contrast, common occurrences are often under reported, leading the public to have higher confidence in the safety of certain healthcare disciplines and procedures.
How Safe Is Medical Care?
The risks of medical healthcare (allopathic healthcare) were shockingly revealed in 1994 when Harvard’s Lucian Leape, MD, indicated that medical error was responsible for 180,000 deaths per year (1, 2). Dr. Leape’s analogy was that this was “the equivalent of three jumbo-jet crashes every 2 days,” killing all on board (2). Dr. Leape’s revelation was published in the prestigious Journal of the American Medical Association, and titled:
Error in Medicine
Four years after Dr. Leape’s headlines pertaining to error in medicine, Jason Lazarou, MD (neurologist) and colleagues from the University of Toronto published a study in the Journal of the American Medical Association titled (3):
Incidence of Adverse Drug Reactions in Hospitalized Patients
A Meta-analysis of Prospective Studies
The objective of this study was to estimate the incidence of serious and fatal adverse drug reactions (ADR) in hospital patients. Serious ADRs were defined as those that required hospitalization, were permanently disabling, or resulted in death. The authors performed a meta-analysis of 39 prospective studies done in the United States over a period of 32 years on the incidences of Adverse Drug Reactions (ADRs). The goal of this study was to “estimate injuries incurred by drugs that were properly prescribed and administered.” If the event was determined to be a “Possible ADRs” it was excluded from this study. The authors noted:
“We estimated that in 1994 overall 2,216,000 (1,721,000-2,711,000) hospitalized patients had serious ADRs and 106,000 (76,000-137,000) had fatal ADRs, making these reactions between the fourth and sixth leading cause of death.”
“We have found that serious ADRs are frequent and more so than generally recognized. Fatal ADRs appear to be between the fourth and sixth leading cause of death. Their incidence has remained stable over the last 30 years.”
“It is important to note that we have taken a conservative approach, and this keeps the ADR estimates low by excluding errors in administration, overdose, drug abuse, therapeutic failures, and possible ADRs. Hence, we are probably not overestimating the incidence of ADRs.”
This study on ADRs excluded medication errors “to show that there are a large number of serious ADRs even when the drugs are properly prescribed and administered.”
“The incidence of serious and fatal ADRs in US hospitals was found to be extremely high.”
The incidence of hospital adverse drug reactions detailed in the Lazarou and colleague’s study is stunning:
Importantly, these numbers require additional discussion. These statistics pertain only to hospitalized patients; they did not assess similar such events occurring outside of the hospital setting, in locations such as nursing homes, extended care facilities, at home, etc.
Additionally, and more startling, these deaths and serious adverse events occurred as a consequence of taking the correct drug for the correct diagnosis in the correct dosage. As such, these deaths and serious adverse events are not considered to be as a consequence of error. Rather, they are considered to be “fallout” of a health care delivery discipline that is heavily dependent upon pharmacology.
Dr. Leape’s premise of “Error in Medicine” was updated in 2016, showing that the problem has not improved in the past two decades. Published in the British Medical Journal, Johns Hopkins University School of Medicine professor Martin A. Makary (MD, MPH) and research fellow Michael Daniel (medical student) produced an article titled (4):
The Third Leading Cause of Death in the United States
This title is misleading, and lay publications were mislead into believing that medical error was the 3rd leading cause of yearly death in the United States. The article clearly notes that the 3rd leading cause of death in the United States is error in hospitals. Once again, the data did not assess medical error deaths occurring outside of the hospital setting, in nursing homes, extended care facilities, at home, etc. Nor did it assess “fallout” deaths either in the hospital or outside the hospital setting.
In this study, Makary and Daniel analyzed the scientific literature on hospital medical errors to identify its contribution to US deaths. In their appraisal of the magnitude of the problem, they note:
“We calculated a mean rate of death from [hospital] medical error of 251,454 a year.”
“We believe this understates the true incidence of death due to medical error because the studies cited rely on errors extractable in documented health records and include only inpatient deaths.”
[Hospital] “medical error is the third biggest cause of death in the US and therefore requires greater attention.”
As noted, the 251,000 deaths from medical error underestimates the actual number because it represents only medical error deaths that occur in the hospital setting. Medical error deaths occurring in non-hospital facilities or at home are not included in the estimated number.
How Safe Are Pain Medications?
The primary reason people seek chiropractic care is for pain. Chiropractic is considered an alternative therapy for pain management, and especially for spinal pain (5, 6). An important study looking at some of the risks associated with the chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs) for pain was published by M. Michael Wolfe, MD, and colleagues, from Stanford’s Medical School and Boston University School of Medicine, and published in the New England Journal of Medicine in 1999. The article was titled (7):
Gastrointestinal Toxicity of
Nonsteroidal Anti-inflammatory Drugs
The authors make the following points:
“It has been estimated conservatively that 16,500 NSAID-related deaths occur among patients with rheumatoid arthritis or osteoarthritis every year in the United States.”
“If deaths from gastrointestinal toxic effects of NSAIDs were tabulated separately in the National Vital Statistics reports, these effects would constitute the 15th most common cause of death in the United States.”
“Yet these toxic effects remain largely a ‘silent epidemic,’ with many physicians and most patients unaware of the magnitude of the problem.”
“Furthermore, the mortality statistics do not include deaths ascribed to the use of over-the-counter NSAIDs.”
The authors note that Cox-2 inhibitors (a prescription form of NSAID) have been available in the US since February 1999, in the hope that they will have a reduced capacity to cause injury to the gastroduodenal mucosa. However, Cox-2 inhibitors are also known to cause defects in renal function, alter the regulation of bone resorption, impair female reproductive physiology, and increase the rate of thrombotic events in patients with increased risk of cardiovascular disease.
In 2003, researchers from the University of Queensland, Australia, published a study in the Journal Spine, titled (8):
Chronic Spinal Pain:
A Randomized Clinical Trial Comparing
Medication, Acupuncture, and Spinal Manipulation
In this study, the spinal manipulation was performed by licensed chiropractors (two visits per week). The medications used were Celebrex or Vioxx, both prescription NSAIDs. The acupuncture (also two visits per week) was performed by an experienced acupuncturist. The study evaluated 115 chronic neck and back pain patients. The treatment interventions extended over a 9-week period. These authors made the following observations and statements:
“Adverse reactions to nonsteroidal antiinflammatory (NSAID) medication have been well documented.”
“Gastrointestinal toxicity induced by NSAIDs is one of the most common serious adverse drug events in the industrialized world.”
“The newer COX-2-selective NSAIDs are less than perfect, so it is imperative that contraindications be respected.”
There is “insufficient evidence for the use of NSAIDs to manage chronic low back pain.”
“The highest proportion of early (asymptomatic status) recovery was found for manipulation (27.3%), followed by acupuncture (9.4%) and medication (5%).”
“Manipulation yielded the best results over all the main outcome measures.”
“The consistency of the results provides evidence that in patients with chronic spinal pain, manipulation, if not contraindicated, results in greater short-term improvement than acupuncture or medication.”
“The results of this efficacy study suggest that spinal manipulation, if not contraindicated, may be superior to needle acupuncture or medication for the successful treatment of patients with chronic spinal pain syndrome.”
“Medication apparently did not achieve a marked improvement in chronic spinal pain and caused adverse reactions in 6.1% of the patients.”
“In summary, the significance of the study is that for chronic spinal pain syndromes, it appears that spinal manipulation provided the best overall short-term results, despite the fact that the spinal manipulation group had experienced the longest pretreatment duration of pain.”
Highlights of this study show that chiropractic spinal manipulation is five times more effective than prescription NSAIDs in the treatment of chronic low back and neck pain, and the results from spinal manipulation were accomplished without any reported adverse events. In contrast, for the patients taking the drugs, more experienced an adverse event (6.1%) than those who became asymptotic (5%) over the nine-week clinical trial.
Importantly, when this study was published in 2003, Vioxx had been on the market since 1999, four years. The following year, 2004, Vioxx was pulled off the market due to an unacceptable incidence of fatal heart attacks and strokes (9, 10). It has since been established that in the five years that Vioxx was on the market it caused more US deaths (about 60,000) than the Viet Nam war did in 10 years (about 58,000).
How Safe Is Chiropractic?
The most sensational adverse event with a supposed link to chiropractic spinal manipulation is vertebral artery dissection. Allegations of vertebral artery dissection caused by chiropractic spinal manipulation have appeared in the published literature for decades. However, recent large critical reviews of the topic have appeared in the scientific literature, and they question the causation between cervical spine manipulation and cervical artery dissection. Some of this literature is reviewed below.
In 2008, Dr. David Cassidy and colleagues published the most comprehensive study at that time pertaining to the risk of vertebral artery dissection as related to chiropractic cervical spine manipulation. The article was published in the journal Spine, and titled (11):
Risk of Vertebrobasilar Stroke and Chiropractic Care:
Results of a Population-Based Case-Control and Case-Crossover Study
This study included all residents of Ontario, CAN, over a period of 9 years, amounting to 109,020,875 person years of observation. Associations between chiropractic visits and vertebral artery dissection versus primary care physician (PCP) visits and vertebral artery dissection were compared.
The authors noted:
“We found no evidence of excess risk of vertebral artery stroke associated with chiropractic care.”
“Neck pain and headache are common symptoms of vertebral artery dissection, which commonly precedes vertebral artery stroke.”
“The increased risks of vertebral artery stroke associated with chiropractic and primary care physicians visits is likely due to patients with headache and neck pain from vertebral artery dissection seeking care before their stroke.”
“Because patients with vertebrobasilar artery dissection commonly present with headache and neck pain, it is possible that patients seek chiropractic care for these symptoms and that the subsequent vertebral artery stroke occurs spontaneously, implying that the association between chiropractic care and vertebral artery stroke is not causal.”
“Our results suggest that the association between chiropractic care and vertebral artery stroke found in previous studies is likely explained by presenting symptoms attributable to vertebral artery dissection.”
In January of 2011, the Journal of Manipulative and Physiological Therapeutics published a population-based case series using administrative health care records of all Ontario, CAN, residents hospitalized with vertebral artery stroke between April 1, 1993, and March 31, 2002, titled (12):
A Population-based Case-series of Ontario Patients who
Develop a Vertebrobasilar Artery Stroke After Seeing a Chiropractor
These authors note:
“The current evidence suggests that association between chiropractic care and vertebrobasilar artery (VBA) stroke is not causal. Rather, recent epidemiological studies suggest that it is coincidental and reflects the natural history of the disorder.”
“Because neck pain and headaches are symptoms that commonly precede the onset of a VBA stroke, these patients might seek chiropractic care while their stroke is in evolution.”
Also in January 2011, The Open Neurology Journal published an “open access” editorial by Drs. Dean Smith and Gregory Cramer, titled (13):
“Spinal Manipulation is Not an Emerging Risk Factor for Stroke
Nor is it Major Head/Neck Trauma. Don’t Just Read the Abstract!”
Dean L. Smith is Clinical Faculty, Department of Kinesiology and Health, Miami University, Oxford, Ohio, and Gregory D. Cramer is Professor and Dean of Research, National University of Health Sciences, Lombard, Illinois. Their editorial includes:
We would like to address two points in this letter:
1) The current best-evidence indicates no causal relationship between spinal manipulation (‘chiropractic maneuver’ in the paper) and vertebrobasilar artery (VBA) stroke, and,
2) Spinal manipulation or ‘chiropractic maneuvers’ are not major head/neck trauma as suggested in abstract of this article.
“First, evidence is mounting that the association between spinal manipulation and stroke is coincidental rather than causal and reflects the natural history of the disorder.”
“The largest population-based study to date was conducted by Cassidy et al. and included all vertebrobasilar artery (VBA) strokes in Ontario, Canada over a period of 9 years. The authors found no evidence of excess risk (i.e. no risk) of VBA stroke associated with chiropractic care.”
“The prevailing hypothesis is that patients with vertebral artery dissections often have initial symptoms that cause them to seek care from a chiropractic or medical physician and the stroke is independent of their visit.”
“The latest scientific evidence questions whether spinal manipulation is a risk factor at all for cervical artery dissection.”
“Chiropractic spinal manipulations may very well be a demerging risk factor for stroke since there may not be any risk.”
“The evidence, albeit limited to date, suggests that spinal manipulative treatments produce stretches of the vertebral artery that are much smaller than those that are produced during normal everyday movements, and thus they appear harmless.”
“Spinal manipulations delivered by licensed chiropractors do not fulfill the criteria for major trauma and should not be considered major trauma.”
The biomechanics of cervical spine manipulation and vertebral artery stress is important. The world leader on this type of biomechanical assessment is Walter Herzog, PhD, from the University of Calgary, CAN. In 2012, Dr. Herzog and colleagues published a study in the Journal of Electromyography and Kinesiology titled (14):
Vertebral Artery Strains During High-speed,
Low Amplitude Cervical Spinal Manipulation
Dr. Herzog notes that spinal manipulative therapy (SMT) is recognized as an effective treatment modality for many back, neck and musculoskeletal problems. Yet, one of the major issues of the use of SMT is its safety, especially with regards to neck manipulation and the risk of stroke. It has been assumed [wrongly as per this study] that the vertebral artery (VA) experiences considerable stretch during extension and rotation of the neck, which may lead to occlusions and damage to the VA, predisposing the patient to stroke. Therefore, this study presents the first ever data on the mechanics between C2/C1 during cervical SMT performed by chiropractic clinicians.
The authors compared the results of human VA strains during high-speed, low-amplitude SMTs administered by qualified chiropractic clinicians and compared them to the strains encountered during full range of motion (ROM) tests. They used a total of 3,034 segment strains obtained during SMTs and 2,380 segment strains obtained during full ROM testing, making this is an extensive study. Dr. Herzog and colleagues conclude:
“VA strains obtained during SMT are significantly smaller than those obtained during diagnostic and range of motion testing, and are much smaller than failure strains.”
“We conclude from this work that cervical SMT performed by trained clinicians does not appear to place undue strain on VA, and thus does not seem to be a factor in vertebro-basilar injuries.”
“In summary, the maximal strain values for the ROM testing at each segmental level were always greater than the corresponding strain values for the SMTs, suggesting that neck SMTs impose less stretch than turning your head, or extending your neck while looking up at the sky.”
“Therefore, based on the mechanical tests performed here, one should be able to conclude that stretching of VA during neck SMTs does not cause any damage of the VAs.”
“The VA is never really strained during spinal manipulative treatments but that the VA is merely taking up slack as the neck and head are moved during SMT, but that there is no stress and thus no possibility for microstructural damage.”
“The results from this study demonstrate that average and maximal VA strains during high-speed low-amplitude cervical spinal manipulation are substantially less than the strains that can be achieved during ROM testing for all vertebral artery segments.”
“We conclude that cervical spinal manipulations, as tested here, are safe from a mechanical point of view for normal, healthy VA.”
In 2015, a study was published in the journal Chiropractic & Manual Therapies, and titled (15):
Chiropractic Care and the Risk of Vertebrobasilar Stroke:
Results of a Casecontrol Study in U.S. Commercial
and Medicare Advantage Populations
The main purpose of this study was to replicate the casecontrol epidemiological design study published by Cassidy, et al. in 2008 (11), and to investigate the association between chiropractic care and vertebral artery stroke; and compare it to the association between recent primary care physician (PCP) care and vertebral artery stroke. The authors assessed commercially insured and Medicare Advantage (MA) health plan members in the U.S. The data set included health plan members located in 49 of 50 states (excluded North Dakota) and encompassed national health plan data for 35,726,224 commercial and 3,188,825 MA members. Hence, this study looked at approximately 39 million people, making this the largest casecontrol study to investigate the association between chiropractic manipulation and vertebral artery stroke. These authors concluded:
“There was no association between chiropractic visits and VBA stroke found for the overall sample, or for samples stratified by age.”
“We found no significant association between exposure to chiropractic care and the risk of vertebral artery stroke. We conclude that manipulation is an unlikely cause of vertebral artery stroke.”
“Our results increase confidence in the findings of a previous study , which concluded there was no excess risk of vertebral artery stroke associated with chiropractic care compared to primary care.”
In 2016, a study from the Department of Neurosurgery, Penn State Hershey Medical Center, and the Department of Neurosurgery, Johns Hopkins University School of Medicine, was published in the journal Cureus, and titled (16):
Systematic Review and Meta-analysis of Chiropractic Care
and Cervical Artery Dissection:
No Evidence for Causation
The authors note that case reports and case control studies have suggested an association between chiropractic neck manipulation and cervical artery dissection (CAD), but a causal relationship has not been established. These authors evaluated the evidence related to this topic by performing a systematic review and meta-analysis of published data on chiropractic manipulation and cervical artery dissection (CAD). These authors state:
“We found no evidence for a causal link between chiropractic care and CAD. This is a significant finding because belief in a causal link is not uncommon, and such a belief may have significant adverse effects such as numerous episodes of litigation.”
“In spite of the very weak data supporting an association between chiropractic neck manipulation and CAD, and even more modest data supporting a causal association, such a relationship is assumed by many clinicians. In fact, this idea seems to enjoy the status of medical dogma.”