Research Review By Dr. Shawn Thistle©


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Date Posted:

August 2012

Study Title:

Spinal Manipulation for the Treatment of Hypertension: A Systematic Qualitative Literature Review


Mangum K, Partna L & Vavrek D

Author's Affiliations:

University of Western States, Portland Oregon, USA.

Publication Information:

Journal of Manipulative & Physiological Therapeutics 2012; 35: 235-243.

Background Information:

Hypertension and its related diseases are a significant cause of morbidity and mortality in developed nations. In the United States, hypertension represents over 5% of family medicine diagnoses, and it is the most commonly seen condition in family practice clinics (1). Further, roughly 25% of adults have hypertension, increasing to 50% in the elderly (2). Needless to say, direct and indirect healthcare costs relating to this condition are very high. Although it is not normally the primary reason patients seek care from manual medicine providers, we all have numerous hypertensive patients. As a component of a patient’s overall health, it is something we should all be aware of and monitor, particularly if patients have no one else to do so (in a rural region that is medically underserviced, for example).

To review, we should concern ourselves with blood pressure, as primary hypertension is a modifiable risk factor for numerous health problems including:
  • Coronary heart disease
  • Stroke
  • Angina
  • Peripheral vascular disease
  • Left ventricular & atrial fibrillation
  • Left ventricular hypertrophy
  • Retinopathy
  • Renal failure & end-stage renal disease
  • Dementia
Etiology of Hypertension:

It is well accepted that hypertension is a complicated and multifaceted condition. Some of the known etiologies of hypertension include:
  • Increased sympathetic nervous system activity
  • Overproduction of sodium-retaining hormones and vasoconstrictors
  • Long-term high sodium intake
  • Inadequate dietary intake of potassium and calcium
  • Increased or inappropriate rennin secretion with resultant increased production of angiotensin II and aldosterone
  • Deficiencies of vasodilators, such as prostacyclin, nitric oxide, and the natriuretic peptides
  • Alterations in expression of the kallikrein-kinin system that affect vascular tone and renal salt handling
  • Selective lesions in the renal microvasculature
  • Diabetes mellitus & insulin resistance
  • Obesity
  • Increased activity of vascular growth factors
  • Alterations in adrenergic receptors that influence heart rate
  • Inotropic properties of the heart & vascular tone
  • Altered cellular ion transport
Spinal manipulative therapy (SMT) has been reported to improve hypertension in case reports, anecdotal evidence, and some clinical trials. As always, it is important that we evaluate and understand the overall state of the literature regarding this topic in order to avoid misinterpreting or overemphasizing the results of individual studies when speaking to patients and other healthcare colleagues (which unfortunately, we tend to do sometimes!). With this in mind, the authors of this study undertook the prudent and relevant task of amalgamating and critiquing this body of literature via qualitative systematic review to assess the efficacy of SMT for treating hypertension.

Pertinent Results:

  • Of 208 potential publications, only 10 met inclusion criteria and were analyzed.
  • Risk of bias scores revealed only 2 studies with low risk (one was a pilot study with only 23 subjects [4]), 3 studies with unclear risk, and 5 studies with high risk.
  • Studies with low risk of bias (3, 4) showed a clinical improvement with SMT of -3.5 maximum systolic improvement (95% confidence interval [CI]: -5.7 to -1.3) and -7.1 maximum diastolic improvement (95% CI: -13.2 to -1.0) at any point during follow-up. By comparison, control groups in these same studies reported a -9.7 maximum systolic improvement (95% CI: -21.1 to 1.8) and -9.0 maximum diastolic improvement (95% CI: -16.8 to -1.2) at any time during follow-up. No statistically significant differences between treatment groups were reported when SMT was compared with a light massage or diet.
  • Specifically, one of the studies with low risk of bias by Goertz et al. (reference 3, n = 140) compared a dietary intervention alone to diet intervention combined with SMT. The SMT intervention was described as “diversified adjustments” 3x/week for 4 weeks (total of 12 visits). The follow-up appointments were 24 and 72 hours later. Clinicians treated any spinal dysfunction that was detected upon spinal palpation. Systolic and diastolic reductions in blood pressure were -4.9/-5.6 mm Hg for the diet-only group and -3.5/-4.0 mm Hg for the chiropractic manipulation plus diet group. When compared, these differences were not statistically significant.
  • Studies with unclear risk of bias showed a clinical improvement with SMT of -17.2 maximum systolic improvement (95% CI: -20.7 to -13.7) and -13.0 maximum diastolic improvement (95% CI: -15.4 to -10.6) at any point during follow-up. By comparison, control groups in these same studies reported a -3.2 maximum systolic improvement (95% CI: -7.5 to 1.1) and -4.2 maximum diastolic improvement (95% CI: -8.9 to 0.5) at any time during follow-up. No statistically significant differences between treatment groups were reported improvement when SMT was compared with no treatment, light massage, or sham adjustment.

Clinical Application & Conclusions:

Overall, the state of the literature on the efficacy of SMT for treating hypertension is not as strong as some of our colleagues would lead us to believe. Although some case studies have reported successful outcomes, larger trials have not been as promising when comparing SMT to other treatment options such as effleurage massage, or even waiting for 5 minutes! The biological plausibility of SMT as a treatment for hypertension remains controversial and requires further study. Remember, hypertension is a multifaceted problem, so it is unlikely to have a one treatment cure! Therefore, clinicians should not strictly employ SMT as a standalone therapy for hypertension at the expense of other therapeutic options (i.e. dietary modifications, exercise, some anti-hypertensive medications etc.).

Having said that, we shouldn’t abandon this topic just yet, since the literature on this topic is varied, of general low quality, and subject to design flaws and moderate/high risks of bias. Future studies will hopefully improve upon these shortcomings and give us a more concrete answer.

Study Methods:

All included articles were rated for bias using the Cochrane Collaboration's tool for assessing risk of bias. This includes an assessment of the likelihood for selection bias (randomization, allocation concealment), performance bias (blinding of patients and caregivers), attrition bias (incomplete outcome data, selective outcome reporting), and detection bias (blinding of outcome assessment).

3 Categories were established to grade bias within the studies:
  1. Low: plausible bias unlikely to seriously alter the results, all quality criteria met.
  2. Unclear: plausible bias that raises some doubt about the results, one or more criteria partially met.
  3. High: plausible bias that seriously weakens confidence in the results, one or more criteria not met.
A meta-analysis was not conducted because studies reporting differing methodologies, types of SMT (ex. Gonstead, Activator, Diversified), frequency of treatment, and time of follow-up were considered too dissimilar.

Inclusion/Exclusion Criteria for Studies:

To be included, studies had to:
  • Include human subjects with HTN
  • Evaluate SMT as a treatment
  • Employ an observational or therapy trial study design
Studies were excluded if they utilized non-human subjects or non-SMT interventions. Literature reviews, letters to the editor, abstracts, non-English studies, and articles that only had subjects who were normotensive were also excluded.

Study Strengths / Weaknesses:

Study Strengths:
  • The authors employed an appropriate search strategy and assessed included studies for relevant sources of bias.
  • The authors clearly delineated their bias rankings for each of the included papers, citing specific short-comings.
The authors were not able to analyze the potential cause and effect relationship in case studies or case series because these types of studies are not of adequate design to address this type of scientific inquiry (these types of studies are important for communications to other clinicians and can contain important information to direct future study design, but in and of themselves, lack the design features necessary for hypothesis testing).

Additional References:

  1. Sloane PD. Essentials of family medicine. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2008.
  2. Hodgson TA, Cai L. Medical care expenditures for hypertension, its complications, and its comorbidities. Med Care 2001; 39:599-615.
  3. Goertz CH, Grimm RH, Svendsen K, Grandits G. Treatment of hypertension with alternative therapies (THAT) study: a randomized clinical trial. J Hypertens 2002; 20: 2063-8.
  4. Plaugher G, Long CR, Meeker WC, Menke JM, et al. Practice-based randomized controlled-comparison clinical trial of chiropractic adjustments and brief massage treatment at sites of subluxation in subjects with essential hypertension: pilot study [randomized controlled trial]. J Manipulative Physiol Ther 2002; 25: 221-39.