How far can the effects of subluxation-based chiropractic care reach? It’s a question that goes to the heart of chiropractic as well as its philosophy, art, and science. It’s also been a highly political question, with some chiropractic peak bodies making controversial statements about whether chiropractic could support better immune function. It was a statement that many had opinions on, but one Dr Amy Haas took to it with a systems biology lens in a mammoth paper spanning more than 440 references and ten major areas of physiology.
To say this was no mean feat is an absolute understatement. While Haas collaborated with several big names in chiropractic (from the Foundation for Vertebral Subluxation), reviewing all the available Level XII data and higher on chiropractic care and putting it into a cohesive, chiropractically and scientifically coherent piece that answers core questions as to the validity and reach of chiropractic was an immense task. The result is a paper that will benefit all chiropractors.
Now, let’s be honest from the outset: summarising this paper is an impossible task. Haas’s talent has previously been seen in her hypothesis paper and work on Heart Rate Variability. This paper takes on ten key areas: blood pressure, cortisol, cytokines, heart rate variability, immunity/the immune system, interferon, interleukin, sleep, substance P, and tumour necrosis factor, all through the lens of salutogenesis and systems biology.
If there are themes in this paper that weave throughout the ten themes, its homeostasis and adaptation; its neurology, endocrinology (hormones and chemicals synthesized in the body) and immune systems all interfacing and communicating with each-other with the Central Nervous System that chiropractors care for, interfacing with them all..
The interconnectedness observed across body systems is evident in the side effects prevalent when targeting one symptom or system. This is increasingly being considered by practitioners as we move toward a truly integrated and whole-person approach to care. Chiropractic has been functioning with a holistic approach for a long time. In fact, it is the very essence of the practice. There is a divide in chiropractic opinions about how far-reaching the effects of chiropractic can be – whether limited to neuromuscular symptoms or not. This paper can go a long way to dispelling these disparities – if it can get the attention it deserves.
So What is Salutogenesis Anyway?
Salutogenesis is the study of the origins of health, different to pathogenesis which is the study of factors that lead to disease.
The keywords included in this review of chiropractic literature and the subsequent subtopics that are formed in the results, all include an aspect of salutogenesis. Meaning, if any of these factors, such as blood pressure, sleep, or cortisol, were to become better regulated and return to ‘normal’ from a state of dysregulation, that would represent a positive change in an individual’s health. Haas et al put it best here:
“We present here a compiled database of diverse physiological outcomes reported with chiropractic care, inclusive of diverse methodologies of quantitative and objective evidence, that supports the application of chiropractic adjustment for the promotion of optimal health and function (salutogenesis). The results of these searches are considered in light of the growing field of integrative physiology, and we present several biologically plausible mechanisms that may explain the salutogenic outcomes observed for chiropractic care. The contents of this work may inform the chiropractic field practitioner of multiple levels and types of evidence to be considered in their evidence-informed clinical decision-making process, and may also inform future research agendas for the chiropractic profession.”
So let’s get into the paper
The original literature search used keywords such as chiropractic and spinal manipulation cross-referenced with the keywords autoimmune, blood pressure, cortisol, cytokine, HRV (heart rate variability), immune, interferon, interleukin, sleep, substance P, TGF (tumor growth factor). 133 studies were included in the final review. It then broke down findings for each keyword except for autoimmune and TGF as no suitable articles were available.
Blood Pressure
Its no secret that high blood pressure is connected to many negative health outcomes such as heart disease and stroke. Low blood pressure, however, can also cause its own issues. Therefore, restoring normal regulation of blood pressure would indicate a positive change in an individual’s health.
The review found conflicting reports of the effect of chiropractic care on blood pressure, suggesting the differences in findings were most likely due to differences in how the studies were carried out. Overall, the data did indicate that chiropractic care may play a role in restoring and regulating blood pressure, particularly when correlated with the correction of subluxation in the upper cervical spinal region.
Thirty references were considered in this section of the review, including 14 trials and 6 reviews. One trial was a double-blinded and placebo-controlled study, meaning neither the participants nor the researchers knew which participant was receiving the ‘real’ or ‘sham’ adjustment. The ‘sham’ adjustment was designed to be indistinguishable to the patient from an actual adjustment. This methodology lowers the risk of multiple biases and provides strong control results to compare the experimental results against. There are many other aspects of this study that contributed to it being considered a high quality study, and the results of this report were both statistically and clinically significant. It found that patients who received the actual adjustment, and not the sham, had improved hypertension immediately after the adjustment and it was a change sustained over the course of eight weeks.
The review’s authors suggested that more in-depth research is needed to understand the relationship between upper cervical subluxation and hypertension fully.
Cortisol
Widely referred to as the ‘stress hormone’, cortisol mediates many aspects of the stress response as well as metabolism and inflammation. Individuals stuck in a state of ‘fight or flight’ often have elevated levels of cortisol. Chronic high cortisol due to stress can lead to numerous health concerns. Dysregulated cortisol caused by lifestyle or autoimmune diseases can have serious, complex effects. Returning the body to a state of normal cortisol regulation would restore the body’s ability to influence metabolism, inflammation, and the response to stress.
Eleven studies were included in this section of the review. This included five clinical trials and three reviews. The authors determined that when the evidence from all of these studies were considered together, the findings do provide preliminary evidence that chiropractic care can impact cortisol levels and, subsequently, may impact outcomes such as blood pressure regulation and hormonal, cognitive, metabolic, and immune function.
The pathway by which chiropractic care may affect cortisol regulation has not yet been identified. However, the authors suggest both the autonomic nervous system and the HPA-axis may be possible explanations.
The authors identified a limitation to consider in that there was a lack of clinically significant patient outcomes reported relating to the changes in cortisol. Future studies investigating the effect of chiropractic care on cortisol levels should incorporate clinical endpoints, as well as research that focuses on the specific pathway by which spinal adjustment can affect cortisol regulation.
Cytokine, Interleukins, Interferons, TNF, Substance P
The researchers separated each of these terms into individual results sections, but for the sake of brevity we have grouped them together to discuss the significance of the findings. Changes to cytokines, interleukins, interferons, TNF, and substance P with chiropractic care may have a simple biomechanical pathway with potential for both local and widespread effects.
All of these small molecules are important messengers of the nervous, immune, and endocrine systems, responsible for mediating inflammation and other cell functions when released. The findings from these sections of the review suggest that foundational evidence does exist that chiropractic care may alter the levels of these messaging molecules, but further research into the clinical significance of these changes and further substantiate these early observations.
Heart Rate Variability
We have discussed Heart Rate Variability (HRV) many times in different blogs, digging into its use and the different perceptions of its role in chiropractic research. While it is still debated whether it is a sufficient standalone biomarker of autonomic activity or whether it should only be utilised in conjunction with other measures, it is thought to provide an indication of the adaptability of the nervous system and cardiovascular system. HRV is derived from the changes in the time intervals between heartbeats. A high level of variability suggests a greater ability of the autonomic nervous system to adapt to the stressors it encounters, and a lower level of variability, thus indicating a diminished ability to adapt. The authors of the review highlight the previous correlations that have been made between abnormally low levels of HRV and future poor health outcomes.
Twenty-nine references were included in this section of the review, including twelve larger studies (cohort, RCT) and five reviews. There were many differences in measurement conditions across the studies so drawing a definitive conclusion is difficult. Considering all of the evidence together with the limitations, these studies suggest chiropractic care and the correction of vertebral subluxation may enhance adaptability and resilience, as measured by HRV. Further research is needed for this measure of adaptability, specifically to overcome the technical challenges of quantifying and standardising HRV.
“The emerging field of research exploring the impact of chiropractic care on HRV contains both clues and opportunities for the broader-reaching effects of chiropractic care to be discovered and understood”
Immunity/Immune System
Examining the relationship that ‘immunity’ has with anything is a complex task, as many interactions and systems can influence the immune system’s activity. The researchers included some key terms in their literature search that directly related to immunity, such as ‘cytokine’ and ‘interleukin’, and discussed these in greater detail. This section of the review assessed other aspects of immune function and the evidence that exists relating to chiropractic care and its impact on immunity.
Twenty-seven references were included in this section of the review, including five research trials and 10 reviews. Across these references, there was evidence of changes in blood markers, lymphocytic activation, antibody secretion, and functional improvement of autoimmune and infectious diseases following chiropractic care. Overall these data are supportive of chiropractic care impacting immune adaptability. The current literature suggests chiropractic care can impact a range of immune and neuroimmune biomarkers, potentially explaining the improvements in immunity observed following courses of chiropractic care. The authors suggest future research should be directed at enhancing our understanding of the effects of vertebral subluxation on immune outcomes and the relationship between chiropractic care and immune health.
Sleep
We are all familiar with how great a decent night’s sleep is, although we may not experience them as much as we’d like. In recent years, the emphasis on the importance of high quality and sufficient quantity of sleep has increased, as researchers continue to learn just how vital sleep is to our body and mind. Disordered sleep has been connected to multiple metabolic, cardiovascular, immune, and inflammatory consequences, and is correlated with an increased risk of all-cause mortality.
The researchers identified a collection of twenty-nine papers that suggest chiropractic care improves sleep. It is not yet clear which types of sleep disturbances and challenges are best helped by chiropractic care and whether any specific subluxation patterns are causative of sleep difficulties. The authors highlight the need for clarity in these areas and suggest that the restoration of normal sleep patterns by correcting subluxation could reduce the global social and economic burden of poor sleep.
Many explanations may exist as to why correcting subluxation may improve sleep quantity, quality, and the processes occurring during sleep, such as decreased anxiety, improved heart rate variability, and improved blood pressure.
“Considered together, this body of literature provides supportive evidence that spinal adjustments modulate NEI supersystem-mediated clinical outcomes”
Conclusion
There’s a lot of information in this incredible paper, all viewed through a chiropractically sound paradigm of subluxation and salutogenesis. No single blog post could adequately capture what this means though, so make sure you clear yourself an hour to read this paper yourself. It’s well worth it.
In next week’s blog, we will chat with Dr Haas about what this paper means for the profession.
The ASRF would like acknowledge the valuable work of the Foundation for Vertebral Subluxation, as contributing significantly to the research around the role of chiropractic in immune function, and to the project discussed in this article.
References
- Haas, A., Chung, J., Kent, C., Mills, B., & McCoy, M. (2024). Vertebral Subluxation and Systems Biology: An Integrative Review Exploring the Salutogenic Influence of Chiropractic Care on the Neuroendocrine-Immune System. Curēus, https://www.cureus.com/articles/229791-vertebral-subluxation-and-systems-biology-an-integrative-review-exploring-the-salutogenic-influence-of-chiropractic-care-on-the-neuroendocrine-immune-system?utm_medium=email&utm_source=transaction&fbclid=IwAR2qsPT3_HxfvQT2gK8ZJbfbc13l0YISKe86vvQM5dtUJhdclcryg3ESihE#!/.
