Research continues to suggest the blood pressure-lowering benefits of the chiropractic adjustment. The latest study concluded that specific instrument-assisted adjustments to the thoracic spine (T1-T5) positively affected blood pressure, pulse rate and classification of high blood pressure compared to placbebo manipulation or no intervention.
Researchers randomly assigned 290 adults with and without hypertension to one of three groups for comparison: an active group, a placebo group and a control group. The active group received instrument-assisted manipulation to T1-T5, while the placebo group received the identical manipulative procedure, except the adjusting instrument was set not to deliver any force. The control group received no intervention (manipulation) whatsoever. Both patients and clinicians were blinded as to whether they were receiving / delivering active or placebo adjustments.
The primary finding following instrument-assisted manipulation to T1-T5 was a reduction in blood pressure (both systolic and diastolic BP) of approximately 7 percent compared to baseline measurements. Neither of the other subject groups achieved this reduction. Active intervention also improved blood pressure classification in many cases. (All subjects were classified at baseline as normotensive, prehypertensive, stage 1 hypertensive or stage 2 hypertensive.) The study authors described the impact of active intervention on these classifications as follows:
"Systolic and diastolic BP, pulse rate, and BP classification decreased significantly only in the active treatment group. No significant changes occurred in the placebo treatment and control groups. ... By category, 46% of [active treatment] subjects improved in early hypertensive or prehypertensive classification – about 4 times more than placebo and 2.65 times better than the controls. Similarly, 51% of Stage I and 57% of Stage II hypertensive patients improved, also better than placebo and control subjects."
In summarizing their findings, the researchers stated: "This RCT demonstrated that specific thoracic segmental manipulation had at least a transient effect in decreasing blood pressure and pulse rate. BP measurements are notoriously unstable and shift over the course of the day and according to patient apprehension and discomfort. The observed treatment improvement in blood pressure and pulse rate represents a somatovisceral reflex worthy of further investigation."
- Roffers SD, et al. A somatovisceral reflex of lowered blood pressure and pulse rate after spinal manipulative therapy in the thoracic region. Asian J Multidiscipl Studies, June 2015;3(6).