Efficacy and Safety of Transcutaneous Electrical Nerve Stimulation (TENS) for Acute and Chronic Pain: A Systematic Review and Meta-Analysis (Meta-TENS)

Background: Uncertainty about the benefit of transcutaneous electrical nerve stimulation (TENS) to relieve pain is long-standing. We systematically reviewed the efficacy and safety of TENS for acute and chronic pain.  Methods: We searched 10 databases from inception for randomised controlled trials (RCTs) that evaluated TENS administered using pulsed currents above sensory detection threshold at or close to the site of pain versus placebo and other treatments in adults. We meta-analysed mean pain intensity during or immediately after TENS and proportions of participants achieving > 30% or > 50% relief of pain (PROSPERO - CRD42019125054).  Findings: We included 381 RCTs with 24532 participants. TENS reduced pain intensity compared with placebo [91 RCTs, 92 samples, n = 4841, standardised mean difference (SMD) = -0·96 [95% CI, -1·14, -0·78], I² = 88%], and compared with various treatments used in standard of care [61 RCTs, 61 samples, n = 3155, SMD = -0·72 [95% CI, -0·95, -0·50], I² = 88%]. Methodological and clinical characteristics did not modify the effect. Levels of evidence were downgraded because of a considerable number of small sized trials contributing to imprecision in magnitude estimates. Data was limited for other outcomes. Adverse events were mild and not different to comparators [18 RCTs, n = 805, 63/95 events, risk ratio, irrespective of severity, = 0·73 [95% CI, 0·36, 1·48], I² = 66%). Interpretation: There is moderate-certainty evidence that TENS reduces pain intensity during and immediately after stimulation compared with placebo. There were no serious adverse events. Funding Statement: The review was funded by an Investigator Sponsored Study grant from GlaxoSmithKline. The funder had no role in study design, data collection, data analysis, data interpretation, or writing of the report. Declaration of Interests: Prof. Mark I. Johnson (taken from ICMJE form): Dr. Johnson reports grants from GlaxoSmithKline, during the conduct of the study; other from GlaxoSmithKline, other from TENSCare, other from Actegy Ltd , personal fees from Oxford University Press, other from LifeCare Ltd, other from GlaxoSmithKline, other from Eurocept Pharmaceuticals, outside the submitted work; and I was involved in conducting studies [see manuscript] that were considered for inclusion in the work submitted for publication. We declare no competing interests: Dr Carole Paley, Dr Gareth Jones, Dr Mathew R. Mulvey, and Dr Priscilla Wittkopf.