Effects of Wearable Transcutaneous Electrical Nerve Stimulation on Fibromyalgia: A Randomized Controlled Trial

Abstract

Purpose: Fibromyalgia is a chronic condition characterized by widespread pain and interference with daily activities. The aim of this study is to assess the benefit of transcutaneous electrical nerve stimulation (TENS) for persons diagnosed with fibromyalgia.

Patients and methods: Adults meeting diagnostic criteria for fibromyalgia were randomized in a double-blind trial to receive either an active (n=62) or sham (n=57) wearable TENS device for 3-months. Subjects were classified as having lower or higher pain sensitivity by Quantitative Sensory Testing (QST). Patient Global Impression of Change (PGIC, primary outcome) and secondary efficacy measures including Fibromyalgia Impact Questionnaire (FIQR), Brief Pain Inventory (BPI) and painDETECT questionnaire (PDQ) were assessed at baseline, 6-weeks and 3-months. Treatment effects were determined by a mixed model for repeated measures (MMRM) analysis of the intention-to-treat (ITT) population (N=119). A pre-specified subgroup analysis of pain sensitivity was conducted using an interaction term in the model.

Results: No differences were found between active and sham treatment on PGIC scores at 3-months (0.34, 95% CI [-0.37, 1.04], p=0.351) in the ITT population. However, in subjects with higher pain sensitivity (n=60), PGIC was significantly greater for active treatment compared to sham (1.19, 95% CI [0.24, 2.13], p=0.014). FIQR total score (-7.47, 95% CI [-12.46, -2.48], p=0.003), FIQR pain item (-0.62, 95% CI [-1.17, -0.06], p=0.029), BPI Interference (-0.70, 95% CI [-1.30, -0.11], p=0.021) and PDQ (-1.69, 95% CI [-3.20, -0.18], p=0.028) exhibited significant improvements for active treatment compared to sham in the ITT population. Analgesics use was stable and comparable in both groups.

Conclusion: This study demonstrated modest treatment effects of reduced disease impact, pain and functional impairment from wearable TENS in individuals with fibromyalgia. Subjects with higher pain sensitivity exhibited larger treatment effects than those with lower pain sensitivity. Wearable TENS may be a safe treatment option for people with fibromyalgia.

Clinicaltrialsgov registration: NCT03714425.

Keywords: clinical trial; fibromyalgia; neuromodulation; non-pharmacological treatment; transcutaneous electrical nerve stimulation; wearable.

Figure 1

CONSORT diagram with intention-to-treat.

Figure 2

Loading weights for the first QST principal component. PPT1, PPT at trapezius muscle. PPT2, PPT at thumb joint. Cuff, cuff pressure at gastrocnemius, P1, 1st of 10 punctate stimuli delivered once per second rated on 0–100 pain scale. P5, 5th of 10 punctate stimuli. P10, last of 10 punctate stimuli. CPT1, cold pressor test at 15 seconds following hand immersion into cold water bath (pain 0–100). CPT2, 30-second after sensation following 15 seconds of hand immersion in cold water bath (pain 0–100). The first component can be interpreted as an index of pain sensitivity.

Figure 3

Comparisons of PGIC scores at 3-months (A). Comparisons of baseline to 3-month change scores in pain intensity (FIQR pain item) (B). Error bars indicate SE. Δ, treatment effect (Active - Sham). Treatment comparisons based on MMRM analyses of ITT population and of the lower and higher pain sensitivity subgroups. Subgroup analysis p-value is for the treatment by pain sensitivity interaction term in the subgroup MMRM model.

Figure 4

Change in FIQR total score (A) and FIQR pain item (B) from baseline to 6-weeks and 3-months. Error bars indicate SE. Δ, treatment effect (Active - Sham). Both treatment arms exhibit improvement from baseline to 6-weeks, however the group difference small and not significant. Between 6-weeks and 3-months, the active treatment arm continues to improve while the sham arm regresses or stays flat, leading to a significant group difference at the study endpoint.

Figure 5

Comparison of pain intensity reduction responder rates, based on FIQR pain item, in the ITT population and for the lower and higher pain sensitivity subgroups. Responder rates for a moderate (≥30%) reduction in pain intensity (A). Responder rates for a substantial (≥50%) reduction in pain intensity (B). Error bars indicate SE. Δ, treatment effect (Active - Sham). Responder rates based on logistic regression analyses. Subgroup analysis p-value is for the treatment-by-pain sensitivity interaction term in the subgroup logistic regression model.