Abstract

Background

Fibromyalgia is characterised by persistent, widespread pain; sleep problems; and fatigue. Transcutaneous electrical nerve stimulation (TENS) is the delivery of pulsed electrical currents across the intact surface of the skin to stimulate peripheral nerves and is used extensively to manage painful conditions. TENS is inexpensive, safe, and can be self‐administered. TENS reduces pain during movement in some people so it may be a useful adjunct to assist participation in exercise and activities of daily living. To date, there has been only one systematic review in 2012 which included TENS, amongst other treatments, for fibromyalgia, and the authors concluded that TENS was not effective.

Objectives

To assess the analgesic efficacy and adverse events of TENS alone or added to usual care (including exercise) compared with placebo (sham) TENS; no treatment; exercise alone; or other treatment including medication, electroacupuncture, warmth therapy, or hydrotherapy for fibromyalgia in adults.

Search methods

We searched the following electronic databases up to 18 January 2017: CENTRAL (CRSO); MEDLINE (Ovid); Embase (Ovid); CINAHL (EBSCO); PsycINFO (Ovid); LILACS; PEDRO; Web of Science (ISI); AMED (Ovid); and SPORTDiscus (EBSCO). We also searched three trial registries. There were no language restrictions.

Selection criteria

We included randomised controlled trials (RCTs) or quasi‐randomised trials of TENS treatment for pain associated with fibromyalgia in adults. We included cross‐over and parallel‐group trial designs. We included studies that evaluated TENS administered using non‐invasive techniques at intensities that produced perceptible TENS sensations during stimulation at either the site of pain or over nerve bundles proximal (or near) to the site of pain. We included TENS administered as a sole treatment or TENS in combination with other treatments, and TENS given as a single treatment or as a course of treatments.

Data collection and analysis

Two review authors independently determined study eligibility by assessing each record and reaching agreement by discussion. A third review author acted as arbiter. We did not anonymise the records of studies before assessment. Two review authors independently extracted data and assessed risk of bias of included studies before entering information into a 'Characteristics of included studies' table. Primary outcomes were participant‐reported pain relief from baseline of 30% or greater or 50% or greater, and Patient Global Impression of Change (PGIC). We assessed the evidence using GRADE and added 'Summary of findings' tables.

Main results

We included eight studies (seven RCTs, one quasi‐RCT, 315 adults (299 women), aged 18 to 75 years): six used a parallel‐group design and two used a cross‐over design. Sample sizes of intervention arms were five to 43 participants.

Two studies, one of which was a cross‐over design, compared TENS with placebo TENS (82 participants), one study compared TENS with no treatment (43 participants), and four studies compared TENS with other treatments (medication (two studies, 74 participants), electroacupuncture (one study, 44 participants), superficial warmth (one cross‐over study, 32 participants), and hydrotherapy (one study, 10 participants)). Two studies compared TENS plus exercise with exercise alone (98 participants, 49 per treatment arm). None of the studies measured participant‐reported pain relief of 50% or greater or PGIC. Overall, the studies were at unclear or high risk of bias, and in particular all were at high risk of bias for sample size.

Only one study (14 participants) measured the primary outcome participant‐reported pain relief of 30% or greater. Thirty percent achieved 30% or greater reduction in pain with TENS and exercise compared with 13% with exercise alone. One study found 10/28 participants reported pain relief of 25% or greater with TENS compared with 10/24 participants using superficial warmth (42 °C). We judged that statistical pooling was not possible because there were insufficient data and outcomes were not homogeneous.

There were no data for the primary outcomes participant‐reported pain relief from baseline of 50% or greater and PGIC.

There was a paucity of data for secondary outcomes. One pilot cross‐over study of 43 participants found that the mean (95% confidence intervals (CI)) decrease in pain intensity on movement (100‐mm visual analogue scale (VAS)) during one 30‐minute treatment was 11.1 mm (95% CI 5.9 to 16.3) for TENS and 2.3 mm (95% CI 2.4 to 7.7) for placebo TENS. There were no significant differences between TENS and placebo for pain at rest. One parallel group study of 39 participants found that mean ± standard deviation (SD) pain intensity (100‐mm VAS) decreased from 85 ± 20 mm at baseline to 43 ± 20 mm after one week of dual‐site TENS; decreased from 85 ± 10 mm at baseline to 60 ± 10 mm after single‐site TENS; and decreased from 82 ± 20 mm at baseline to 80 ± 20 mm after one week of placebo TENS. The authors of seven studies concluded that TENS relieved pain but the findings of single small studies are unlikely to be correct.

One study found clinically important improvements in Fibromyalgia Impact Questionnaire (FIQ) subscales for work performance, fatigue, stiffness, anxiety, and depression for TENS with exercise compared with exercise alone. One study found no additional improvements in FIQ scores when TENS was added to the first three weeks of a 12‐week supervised exercise programme.

No serious adverse events were reported in any of the studies although there were reports of TENS causing minor discomfort in a total of 3 participants.

The quality of evidence was very low. We downgraded the GRADE rating mostly due to a lack of data; therefore, we have little confidence in the effect estimates where available.

Authors' conclusions

There was insufficient high‐quality evidence to support or refute the use of TENS for fibromyalgia. We found a small number of inadequately powered studies with incomplete reporting of methodologies and treatment interventions.

Author(s)

Mark I Johnson, Leica S Claydon, G Peter Herbison, Gareth Jones, Carole A Paley

Abstract

Plain language summary

TENS for fibromyalgia in adults

Review question

Does transcutaneous electrical nerve stimulation (TENS) relieve pain in adults with fibromyalgia?

Background

Fibromyalgia is a long‐term medical condition that is characterised by long‐lasting widespread pain throughout the body. TENS is a treatment that involves putting pulsed electrical currents across the surface of the skin using two or four electrodes. It is used to manage painful conditions. TENS is inexpensive, can be self‐administered by people with fibromyalgia, and is not associated with any particular side effects. TENS reduces pain during movement so it may be useful in addition to other treatments to help people carry on their normal lives.

Study characteristics

In January 2017, we found eight clinical studies that examined 315 people. We included TENS administered to produce a non‐painful 'tingling' sensation at the site of pain either as a treatment alone or combined with exercise treatment. All studies used TENS in comparison with 'fake' (called placebo or sham) TENS, no treatment, or other treatments such as medicine or hydrotherapy (treatment in water).

Key results

We did not find enough high‐quality studies to allow us to come to any conclusions about the effectiveness of TENS for fibromyalgia pain. Even though seven studies concluded that TENS relieved pain associated with fibromyalgia, the studies were low quality and the findings for measures of pain were inconsistently reported. Studies did not measure most of our outcomes and it was not always clear what aspects of pain were being reported (e.g. present pain, remembered pain, pain severity, etc.). Only one small pilot study found that one 30‐minute treatment of TENS reduced pain on movement during and immediately after treatment; however, there were too few participants observed and it is unknown whether this effect would be maintained over a longer course of TENS treatments. Overall, it is not possible to judge whether TENS reduces pain associated with fibromyalgia. There were no serious side events reported in any of the studies.

Quality of the evidence 
 We rated the quality of the evidence from studies using four levels: very low, low, moderate, or high. Very low‐quality evidence means that we are very uncertain about the results. High‐quality evidence means that we are very confident in the results. The quality of the evidence was very low overall because of a lack of data.

Author(s)

Mark I Johnson, Leica S Claydon, G Peter Herbison, Gareth Jones, Carole A Paley

Reviewer's Conclusions

Authors' conclusions 

Implications for practice 

For people with fibromyalgia

There is no high‐quality evidence to support or refute the use of transcutaneous electrical nerve stimulation (TENS for fibromyalgia. Further high‐quality research is needed before conclusions can be made about the efficacy and safety of TENS.

For clinicians

Whether TENS should be considered as a potential treatment option for fibromyalgia remains a matter for debate. At present, there is insufficient evidence to support or refute the use of TENS for fibromyalgia.

For policy‐makers

Our analysis of seven randomised controlled trials (RCTs) and one quasi‐RCT with 315 adults found insufficient evidence to support or refute the use of TENS for fibromyalgia. Studies had a high risk of bias associated with inadequate sample sizes in treatment arms and there was variability in study methodology and TENS dosage.

For funders

The safety profile and ease of use of TENS compares favourably to alternative treatments because it can be self‐administered and is inexpensive and readily available without prescription. In some countries, TENS needs to be prescribed by a healthcare practitioner to claim reimbursement from social security or health insurance companies.

Implications for research 

General

This review has identified the need for high‐quality research with long‐term follow‐up investigating the use of TENS for fibromyalgia pain. All the studies included in this review had design limitations such as inadequate sample sizes, outcome measures, and follow‐up.

Design

As with previous Cochrane Reviews on TENS, we found a small number of inadequately powered studies with incomplete reporting of methodologies and treatment interventions. The CONSORT statement for non‐pharmacological treatments should be adopted to report all aspects of study design and subsequent reporting (Boutron 2008). A comprehensive review of TENS methodologies by Bennett 2011 provides detailed criteria and operational guidelines to aid the design of future RCTs on TENS. Pain, Palliative and Supportive Care (PaPaS) guidance suggests that a sample size of 200 participants per treatment arm is necessary for a low risk of bias in RCTs so much larger sample sizes per treatment arms are needed in the future. The study by Dailey 2013 included in this review has been used to inform the design of a phase II randomised, double‐blind, placebo‐controlled, multicentre clinical study that plans to recruit 360 participants with fibromyalgia and a protocol for this study has been published (Noehren 2015). It is expected that the findings will be available in a future update of this review. For meta‐analyses, the PaPaS template protocol for the evaluation of drugs for neuropathic pain recommends that at least 500 participants would be needed to measure the magnitude of a treatment effect adequately for comparisons in which the number needed to treat for an additional beneficial outcome (NNTB) is four or above (Moore 1998).

To assess the effects of TENS on chronic pain long‐term studies of a minimum of six weeks, but ideally more than six months, are necessary to monitor the decline in people who continue to use TENS long term. Ideally, TENS should be self‐administered at home with people using TENS regularly throughout the day whenever they are in pain and for at least 30 minutes at a time whenever possible. In such studies, barriers to effective long‐term TENS use should be evaluated and resolved before the start of the TENS intervention. Gladwell 2015a suggested that a learning phase should be incorporated into future studies to allow people to maximise the complex pattern of TENS usage. This could be achieved during a 'run‐in' period in an enriched enrolment randomised withdrawal design whereby all participants initially receive active TENS to titrate dosage and optimise TENS technique (Moore 2013c). Participants who do not achieve benefits or experience adverse events (or both) are withdrawn from the study and the remaining participants randomised to receive active or placebo TENS to determine efficacy. Blinding of participants to active and placebo TENS becomes a challenge in such a design because participants become aware of sensations generated by TENS in the run‐in phase. However, electrotherapeutic devices that do not produce sensations during stimulation are available (e.g. microcurrent) and information about them can be used in briefing information to create uncertainty about the need for TENS sensation for beneficial effects (see Johnson 2014, p. 170) This, coupled with the use of credible sham (no current) TENS devices, can effectively blind participants (Rakel 2010). Blinding can be monitored post‐intervention using simple questions such as 'do you believe your TENS device was functioning properly?' (Deyo 1990). Monitoring TENS usage in home studies can be achieved using electronic monitoring devices to assure participant compliance with the recommended TENS treatment protocol and TENS usage can also be used as an outcome measure (Pallett 2014).

To ensure high‐quality evidence in future studies ‐ in addition to having an adequate sample size, adequate dose, and a credible sham device ‐ researchers should consider measuring pain both during use of TENS and afterwards and also monitoring ongoing use of TENS. A health economic assessment would also be useful to enable a cost‐benefit analysis to be produced.

Measurement

Future studies should use pain outcomes recommended by IMMPACT. The primary outcome should be the number of participants reporting at least a 30% or 50% reduction in pain intensity while TENS is switched on. Concurrent analgesia should be standardised and monitored. However, evaluating TENS using a unidimensional pain scale is likely to overlook other potential benefits such as 'distraction from pain,' alleviation of other unpleasant sensations (e.g. muscle tension or spasm), reduction in medication consumption, and improvements in function (Gladwell 2015b). These should be considered important secondary outcomes.

Get full text at The Cochrane Library