Table S1.
Brief description of research studies investigating the effects of chiropractic therapy on hypertension
| First author, year | Participants | Study design | Control group | Type of CMT | Results | Limitations |
| Bakris et al 200788 | 50 patients with stage 1 hypertension subdivided in treated (25) and controls (25) | Double blind, placebo controlled. Duration: 8 weeks |
Treatment vs placebo | Atlas/Upper cervical chiropractic adjustment | Systolic BP (treatment: -17+/-9 mmHg vs placebo: -3+/-11 mmHg, P<0.0001) Diastolic BP (treatment: -10+/-11 mmHg vs placebo: -2+/-7 mmHg, P=0.002). No adverse effects recorded |
Should be confirmed in a larger trial |
| Toms 201290 | 42 patients subdived in 3 groups: 12 hypotensive, 12 nomiotensive, 18 prehypertensive or stage 1 or stage 2 hypertensive | Cohort study. Duration: 1 treatment | Pre-treatment vs posttreatment | Atlas orthogonal upper cervical adjustment | Hypotensive group: systolic BP (+13.83mmHg, p<0.0001); diastolic BP (+8.83, p=0.0003). Nomiotensive group: systolic BP (- 3.92, p= 0.1107); diastolic BP (-1.58, p=0.2486). Pre-hypertensive + hypertensive groups: systolic BP(-20.22mmHg, p<0.0001); diastolic BP (-6.83mmHg, p<0.0001). No adverse effects recorded. |
Absence of a specific control group. Follow-up measurements did not measure the duration of the effects |
| Toms 201491 | 20 participants ( 10 placebo group, 10 therapeutic group) | Placebo-controlled, randomized, prospective longitudinal cohort study. Duration: 6 weeks |
Controls vs treatment | Atlas orthogonal upper cervical chiropractic care | Systolic BP (-12.2mmHg, p<0.05); Diastolic BP (-7.2; p<0.05) | The effect on the diastolic values were not significant after 4 weeks |
| Ward et al 201292 | 48 nomiotensive college students (24 controls, 24 treated) | Single blind, randomized controlled trial. Duration: 24h | Controls vs treatment | Atlas cervical break | No significant differences before and after chiropractic care compared to head turn and no contact control | Non-hypertensive patients |
| Knutson 200194 | 110 patients (80 in test one, 30 in test two) | Comparison study | Test 1: controlled clinical trial with a treatment group and a control group. Test 2: controlled clinical trial with subjects as controls | Vectored upper cervical care | Test 1: Significant decrease in systolic blood pressure (p<0.001); Test 2: No significant decrease in systolic blood pressure | Lack of randomization, blinding, manipulated control group |
| Kessinger et al 201995 | 130 patients subdivided in 3 groups: 54 with low pulse pressure (<40mmHg), 29 with medium pulse pressure (40 49mmHg), 47 with high pulse pressure (>49 mmHg) | Observational comparison study | Pre-treatment vs posttreatment | Knee chest upper cervical | Pulse pressure (-8.9mmHg, p<0.01) in patients with hypertension | Lack of randomization, not a clinical trial |
| Plaugher et al 200297 | Subdivided in 3 groups: 9 undertook chiropractic, 8 a brief massage, 6 untreated. Study duration: 2 months | comparison trial with 3 parallel groups. Duration: 2 months | Chiropractic group vs brief massage/untreated groups | Gonstead technique | BP decreased in all 3 groups (largest change in control group) | Small cohort |
| Roffers, Huber et al 201199 | 331 subjects subdivided in control (108), sham adjustment (117), treatment (106) | Randomized control trial. Duration: 1 treatment | Treatment vs control/placebo | Specific thoracic (T5- Tl) chiropractic treatment | Systolic and diastolic BP decreased significantly (p<0.0001) in the treatment group. No significant changes in the placebo and control groups | The authors did not collect hypertensive medication history and current usage. The trial was not double-blind. Anxiety might have increased the systolic and diastolic scores before treatment |
| Roffers, Stiles et al 2011100 | 331 subjects subdivided in control (108), sham adjustment (117), treatment (106) | Randomized control trial. Duration: 1 treatment | Treatment vs control/placebo | Cervical (C3 to occiput CO) chiropractic adjustment | Systolic and diastolic BP decreased significantly (p<0.0001) in the treatment group. No significant changes in the placebo and control groups | The authors did not collect hypertensive medication history and current usage. The trial was not double-blind. Anxiety might have increased the systolic and diastolic scores before treatment |
| Scott et al 2007105 | 20 healthy chiropractic students subdivided in chiropractic adjustment (10), control group(10) | Randomized control trial. Duration: 1 treatment | Treatment vs control | Cervical HVLA | A single cervical adjustment had no effect on systolic or diastolic BP | No hypertensive patients, small cohort |
| Goertz et al 2016107 | 51 participants with prehypertension or stage 1 hypertension. Treatment group (24), control group (27) | Randomized placebo- controlled clinical trial. Duration: 6 weeks | Treatment vs control | Toggle recoil upper cervical chiropractic | Sham group: systolic BP (-4.2 mmHg), diastolic BP (-1.6 mmHg). Treatment group: systolic BP (0.6 mmHg); diastolic BP (0.7 mmHg). The difference was not statistically significant. No serious adverse events noted | Patients in treatment group treated with antihypertensive medications were not washed out. The sham procedure was not validated for BP studies |
| Goertz et al 2002108 | 140 subjects with high to normal BP or stage I hypertension subdivided in diet group (69) and chiropractic group (71) | Randomized doubleblind controlled trial. Duration: 4 weeks | Chiropractic treatment vs diet treatment | High velocity, short- lever impulse/force applied directly to a joint space | Systolic/diastolic BP average decrease in control group (-4.9/-5.6 mmHg). Systolic/diastolic BP decrease in treated group (-3.5/-4.0 mmHg). No statistically significant changes among groups | Lack of a no treatment control group |
| Holt et al 2010109 |
70 patients subdivided in treated (35) and control (35) groups | Randomized controlled clinical trial. Duration: 1 treatment | Treatment vs control | Diversified | Systolic blood pressure (-3.9 mmHg, p=0.002) | Average changes in blood pressure were not clinically significant |
| McKnight et al 198828 | 75 students undergoing routine chiropractic care (53 treated, 22 control group) | Nonrandomized controlled clinical trial. Duration: 1 treatment | Treatment vs control | Cervical adjustment via Gonstead method | Systolic BP (-2.8 mmHg, p<0.01), diastolic BP (-2.6 mmHg, p<0.01) were statistically significantly lower than the controls | Average changes in blood pressure not clinically significant |
| McMasters et al 201329 | 24 prehypertensive or hypertensive stage 1, with or without medication | Nonrandomized. Duration: 23 visits | Pre-treatment vs posttreatment | Adjustments from a full spine exam | Average systolic/diastolic BPs (no statistically significant pre/post differences for pre-hypertensive patients, p>0.05). Average systolic BP (-12.8 mmHg, p=0.009), average diastolic BP (-7.6, p=0.0012) for stage 1 hypertensive patients |
The patients were not randomized. No control group. High dropout rate. Lack of accounting of confounding determinants of hypertension (diet, exercise) |
| Schwartzbauer et al 1997104 | 21 male university baseball players aged 19-23 (9 treated, 12 controls) | Longitudinal study with control group. Duration: 14 weeks |
Treatment vs control | Upper cervical | No statistically significant differences recorded for blood pressure in controls or treated subjects | Small sample size |
| Morgan et al 1985110 | 29 randomly selected subjects | Randomized placebo- controlled trial. Duration 18 weeks | Treatment vs control | Osteopathic spinal manipulation, occipito-atlantal and thoracolumbar | No significant difference in the BP after manipulation | Small sample size |
| Win et al 2015111 | 10 asymptomatic normotensive volunteers + 10 normotensive patients with acute neck pain | Randomized controlled, cross-over. Duration: 1 treatment | Pre-treatment vs posttreatment for both groups | Upper or lower cervical, using high velocity, low amplitude | Systolic BP (-11 mmHg, p<0.05) in asymptomatic normotensive volunteers. Systolic BP (-10 mmHg, p<0.05) in normotensive patients with acute neck pain |
Small sample size. No control or sham group. Lack of control over variables (diet, exercise) |
| Nansel et al 1991112 | 24 healthy, asymptomatic, nonsmoking males (12 treated, 12 controls) | Nonrandomized. Duration: 1 treatment | Treatment vs control | Unilateral lower cervical spinal adjustment | No significant differences between adjusted and non-treated subjects in blood pressure | Small sample size, nonhypertensive subjects |
| Welch et al 2008® | 40 patients of 21-55 years old, non-hypertensive, no history of heart disease | Randomized trial. Duration: 1 treatment | Pre-treatment vs posttreatment | Diversified cervical segment adjustment or a diversified thoracic segment adjustment | Diastolic BP (-5.6 mmHg, p=0.038) only after cervical adjustments. No significant reductions for thoracic adjustments | Non-hypertensive patients |
| Wickes 1980115 | 20 normotensive individuals | Double blind. Duration: 1 treatment | Pre-treatment vs posttreatment | Thoracolumbar spinal manipulation | Systolic BP (+4.0 mmHg) 5 minutes post-manipulation | Non-hypertensive patients |
| Yates et al 198823 | 21 hypertensive patients (7 treatment, 7 placebo, 7 no treatment) | Randomized placebo- controlled trial. Duration: 1 treatment | Treatment vs placebo/control | Adjusting instrument to thoracic spine (Activator) | Systolic and diastolic blood pressure decreased significantly in the active treatment condition | Small sample size |
| Younes et al 2017116 | 17 patients with acute back pain (10 treatment, 7 placebo) | Randomized placebo- controlled trial. Duration: 1 week | Treatment vs placebo | Osteopathic spinal manipulation therapy | No significant differences in the blood pressure | Small sample size, nonhypertensive patients |
| Ward et al 2013117 |
36 healthy chiropractic college students with less than 32% body fat | 3-arm randomized single-blind controlled trial. Duration: 1 treatment | Treatment vs placebo/control | Anterior thoracic manipulation of T1-4 | No statistically significant or clinically relevant difference was shown amongst any between-group or within-group cardiovascular dependent variables | Non-hypertensive patients |
| Ward et al 2015118 | 50 hypertensive patients | Single blind, controlled trial. Duration: 1 treatment | Treatment vs control | Upper thoracic spinal manipulative therapy | Short-term cardiovascular physiology is not affected by upper thoracic spine SMT in hypertensive individuals to a clinically relevant level | Small sample size, the researchers did not include in the exclusion criteria, severe cardiovascular conditions or non-cardiovascular medications that could impact the cardiovascular system |
| Watanabe et al 2007119 | 11 young healthy adults | Pre/post test comparison. Duration: 1 treatment | Pre-treatment vs posttreatment | Mechanically stimulate cervical manipulation | Significant reductions in BP after application of the mechanical stimulus in the supine posture (p<0.05). The reduction peaked at 20 seconds post-stimulation. | Non-hypertensive subjects, small sample size |
| Dimmick et al 2006120 | 70 Patients (35 treatment, 35 control) | Nonrandomized, matched pair, controlled clinical trial | Treatment vs control | McTimoney technique of chiropractic manipulation | No significant difference between controls and treatment group | Possible selection bias, lack of blinding |