Chiropractic + Naturopathic Doctor

Research Review Corner: February 2013

Shawn Thistle   

Features Research

Acupuncture is a popular treatment employed by many chiropractors.

Study Title: Acupuncture for Chronic Pain – Individual Patient Data Meta-Analysis

Author(s): Vickers AJ, Cronin AM, Maschino AC et al.


Publication Information: Archives of Internal Medicine 2012;
172(19): 1444-1453.


Acupuncture is a popular treatment employed by many chiropractors.  Insertion and stimulation of acupuncture needles at certain locations on the body is done to facilitate pain reduction, improve circulation or induce other beneficial health effects.  Originally developed as a component of Traditional Chinese Medicine, many chiropractors successfully utilize acupuncture in a contemporary, physiological/anatomical fashion, with little or no reference to acupuncture’s pre-modern concepts.

One of the most common reasons patients seek acupuncture treatment is for chronic pain.  Although known to produce physiological effects that are related to analgesia, no consensus exists on the exact mechanism(s) involved in acupuncture.  A large number of randomized controlled trials (RCTs) have investigated the effects of acupuncture on chronic pain. Unfortunately, most of them are of low methodologic quality, making meta-analyses of this literature of questionable interpretability and value. 

The authors of this study attempted to improve on this by presenting an individual patient data meta-analysis of RCTs on acupuncture for chronic pain, including only high-quality studies.  Individual patient data meta-analyses are superior to the use of summary data (which is the customary method) because they enhance data quality, enable different forms of outcomes to be combined, and allow use of statistical techniques that can increase precision of the results.


Studies Included:

·       82 studies were identified, of which 31 were deemed eligible for inclusion in this review

·       11 of the studies employed a sham control, 10 used a no acupuncture group, and 10 were three-armed studies – using both a sham and a no acupuncture group

Clinical Heterogeneity in Control Groups:  

In the 11 sham RCTs, the sham treatment included acupuncture needles inserted superficially, sham devices featuring needles that retract into the handle rather than penetrate the skin, and non-needle approaches, such as deactivated electrical stimulation or detuned laser. Co-interventions also varied, with no additional treatment other than analgesics in some RCTs, whereas in other studies, acupuncture and sham groups received a course of additional treatment (like exercise).  Similarly, the no-acupuncture control groups varied – including ‘usual care’, mere advice to “avoid acupuncture”, attention controls (such as group education sessions), and “guidelined” care (advice as to specific drugs and doses).


  • Raw patient data was obtained from 29 of the 31 studies – including a total of 17922 patients
  • Patients in all RCTs had access to analgesics and other standard treatments for pain
  • Acupuncture was statistically superior to sham acupuncture and no treatment in all analyses (P< 0.001)
  • Effect sizes were larger when comparing acupuncture to no treatment, versus comparing acupuncture to sham acupuncture – (0.37, 0.26, and 0.15 in comparison with sham versus 0.55, 0.57, and 0.42 in comparison with no-acupuncture control for musculoskeletal pain, osteoarthritis, and chronic headache, respectively)
  • In RCTs comparing acupuncture to no acupuncture, the effect size did vary, which seems at least partly explicable in terms of the type of control employed.  To illustrate, as might be expected, acupuncture had a smaller benefit in patients who received a program of ancillary care (such as physical therapist-led exercise) than patients who received usual care



Inclusion Criteria:

·      Randomized controlled trials including at least one group receiving acupuncture and 1 group receiving a sham/placebo/no acupuncture control treatment

·      Patients had to have one of four conditions – non-specific back or neck pain, shoulder pain, chronic headache, or osteoarthritis—with the additional criterion that the current episode of pain must be of at least four weeks duration for musculoskeletal disorders

·      There was no restriction on the type of outcome measure, but it was specified that the primary end point must be measured more than one month after the initial acupuncture treatment

·      Only studies where allocation concealment was deemed adequate were included to remove a common source of potential bias.

 Assessment of Study Quality

The authors contacted the primary investigators of each included RCT to obtain raw data.  The RCTs were graded as having a low likelihood of bias if:

·      The adequacy of blinding was checked by direct questioning of patients; and

·      No important differences were found between groups, or the blinding method had previously been validated as able to maintain blinding.

Randomized controlled trials with a high likelihood of bias from un-blinding were excluded from the meta-analysis. The sensitivity analysis included only RCTs with a low risk of bias.

Sometimes it’s best to let the authors describe this: “Each RCT was reanalyzed by analysis of covariance with the standardized principal end point (scores divided by pooled standard deviation) as the dependent variable, and the baseline measure of the principal end point and variables used to stratify randomization as covariates. This approach has been shown to have the greatest statistical power for RCTs with baseline and follow-up measures.  The effect size for acupuncture from each RCT was then entered into a meta-analysis using the metan command in Stata software (version 11; Stata Corp).” (pg. 1445)

 Study Strengths:

·       The authors employed an exhaustive search strategy, established clear, justifiable and specific inclusion criteria (prior systematic review inclusion criteria were quite broad2), and assessed included studies for relevant sources of bias

·       They also validated study eligibility, used appropriate statistical techniques and conducted a wide range of sensitivity analyses

Most important, by establishing a wide-ranging collaboration, the authors obtained raw data from 29 of 31 eligible trials, allowing data to be pooled and analyzed at the individual level.


·       Because the comparisons between acupuncture and no-acupuncture cannot be blinded, both performance and response bias are possible

·       The meta-analyses combined different end points, such as pain and function, measured at different times. The authors did address this, and the results did not change when the analysis was restricted to pain end points measured at a specific follow-up time, 2 to 3 months after randomization.

·       Another potential criticism of this paper is that the authors relied on fixed effects models that are less conservative than random-effects models, more likely to yield statistical significance, and less appropriate when the goal is to generalize beyond included studies (but, they did conduct the analysis with both methods and found few differences).



1)   Benedetti F, Mayberg HS,Wager TD, Stohler CS, Zubieta J-K. Neurobiological mechanisms of the placebo effect. J Neurosci. 2005; 25(45):10390-10402.

2)   Furlan AD, van Tulder MW, Cherkin DC et al. Acupuncture and dry-needling for low back pain. Cochrane Database Syst Rev. 2005; (1): CD001351.




In addition to practising full time in Toronto, Dr. Shawn Thistle is founder and president of Research Review Service Inc., an online, subscription-based service designed to help busy practitioners integrate current, relevant scientific evidence into their practice ( Shawn also recently launched The Epicurean Scholar, which offers continuing education seminars combined with gourmet food and wine events (  Dr. Thistle graduated from CMCC (where he lectures in the Orthopedics Department) and holds an Honours Degree in Kinesiology from McMaster University. He also holds a certificate in Contemporary Medical Acupuncture from McMaster University, and is a Certified Active Release Techniques (ART®) Provider and Functional Range Release®/Functional Anatomical Palpation® instructor and provider.

Print this page


Stories continue below