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Review
. 2021 Oct 4;57(10):1060.
doi: 10.3390/medicina57101060.

Does TENS Reduce the Intensity of Acute and Chronic Pain? A Comprehensive Appraisal of the Characteristics and Outcomes of 169 Reviews and 49 Meta-Analyses

Carole A Paley  1   2 , Priscilla G Wittkopf  1 , Gareth Jones  1 , Mark I Johnson  1
Affiliations
Review

Does TENS Reduce the Intensity of Acute and Chronic Pain? A Comprehensive Appraisal of the Characteristics and Outcomes of 169 Reviews and 49 Meta-Analyses

Carole A Paley et al. Medicina (Kaunas). .

Abstract

Background and Objectives: Uncertainty about the clinical efficacy of transcutaneous electric nerve stimulation (TENS) to alleviate pain spans half a century. There has been no attempt to synthesise the entire body of systematic review evidence. The aim of this comprehensive review was to critically appraise the characteristics and outcomes of systematic reviews evaluating the clinical efficacy of TENS for any type of acute and chronic pain in adults. Materials and Methods: We searched electronic databases for full reports of systematic reviews of studies, overviews of systematic reviews, and hybrid reviews that evaluated the efficacy of TENS for any type of clinical pain in adults. We screened reports against eligibility criteria and extracted data related to the characteristics and outcomes of the review, including effect size estimates. We conducted a descriptive analysis of extracted data. Results: We included 169 reviews consisting of eight overviews, seven hybrid reviews and 154 systematic reviews with 49 meta-analyses. A tally of authors' conclusions found a tendency toward benefits from TENS in 69/169 reviews, no benefits in 13/169 reviews, and inconclusive evidence in 87/169 reviews. Only three meta-analyses pooled sufficient data to have confidence in the effect size estimate (i.e., pooled analysis of >500 events). Lower pain intensity was found during TENS compared with control for chronic musculoskeletal pain and labour pain, and lower analgesic consumption was found post-surgery during TENS. The appraisal revealed repeated shortcomings in RCTs that have hindered confident judgements about efficacy, resulting in stagnation of evidence. Conclusions: Our appraisal reveals examples of meta-analyses with 'sufficient data' demonstrating benefit. There were no examples of meta-analyses with 'sufficient data' demonstrating no benefit. Therefore, we recommend that TENS should be considered as a treatment option. The considerable quantity of reviews with 'insufficient data' and meaningless findings have clouded the issue of efficacy. We offer solutions to these issues going forward.

Keywords: analgesia; efficacy; meta-analysis; neuromodulation; pain; pain management; systematic review; transcutaneous electric nerve stimulation (TENS).

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Conflict of interest statement

All authors have completed the ICMJE uniform disclosure form and declare the following: C.A.P., G.J., and P.G.W. declare no competing interests; M.I.J. reports that he has received royalties from Oxford University for his book TENS: Research to support clinical practice, and M.I.J.’s employer has received support from Glaxo-SmithKline, TENSCare Ltd., and LifeCare Ltd., for expert consultancy services. All authors were involved in conducting reviews that were considered for inclusion in the work submitted for publication. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 4
Figure 4
Tally of systematic reviews and meta-analyses for any outcome and for pain intensity (continuous data) according to pain condition (n = 154).
Figure 10
Figure 10
Conclusions of systematic reviews. Tally of our categorisation of conclusions of authors according to pain condition (n = 154).
Figure 11
Figure 11
Plots of effect sizes and 95% confidence intervals for different pain conditions during or immediately post TENS. Overall effect size SoC = Standard of care; IFT = interferential therapy; * indicates not versus placebo control. Pain conditions have been highlighted in colour (right hand column).
Figure 11
Figure 11
Plots of effect sizes and 95% confidence intervals for different pain conditions during or immediately post TENS. Overall effect size SoC = Standard of care; IFT = interferential therapy; * indicates not versus placebo control. Pain conditions have been highlighted in colour (right hand column).
Figure 1
Figure 1
Flow chart of search and screening process.
Figure 2
Figure 2
Flow chart summarising the sequence of analyses. Key: SMD, standardised mean difference; MD, mean difference; DRB, difference relative to baseline; Dabs, difference absolute (not relative to baseline); (+) authors’ judgement—evidence tends toward benefit, (−) authors’ judgement—evidence tends toward no benefit (?) authors’ judgement—inconclusive.
Figure 3
Figure 3
Characteristics of the 169 included reviews. Tally of (a) types of review according to our categorization of conclusions of authors, (b) duration of pain according to our categorization of conclusions of authors, and (c) pain condition.
Figure 3
Figure 3
Characteristics of the 169 included reviews. Tally of (a) types of review according to our categorization of conclusions of authors, (b) duration of pain according to our categorization of conclusions of authors, and (c) pain condition.
Figure 3
Figure 3
Characteristics of the 169 included reviews. Tally of (a) types of review according to our categorization of conclusions of authors, (b) duration of pain according to our categorization of conclusions of authors, and (c) pain condition.
Figure 5
Figure 5
Tally of the size of the total sample of pooled data points in meta-analyses of pain intensity continuous data (n = 37).
Figure 6
Figure 6
Tally of comparators in meta-analyses of pain intensity continuous data (n = 37).
Figure 7
Figure 7
Characteristics of the 35 analyses of pain intensity (continuous data) versus a comparator. Inner ring: Tally of type of effect size estimate (SMD = standardised mean difference, MD = mean difference). Outer ring: Tally of type of outcome (DAbs = absolute difference between groups, DRB = relative difference between groups i.e., difference in change from baseline).
Figure 8
Figure 8
Tally of our judgement of outcome based on our criteria for sufficient data for all reviews (n = 169).
Figure 9
Figure 9
Conclusions of systematic reviews. Tally of our categorisation of conclusions of authors according to pain duration (n = 154).
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