Four weeks of transcutaneous electrical nerve stimulation (TENS) ease the pain and fatigue associated with movement in women with fibromyalgia (FM), a Phase 2 study showed.
Findings from the study, “A Randomized Controlled Trial of TENS for Movement‐Evoked Pain in Women with Fibromyalgia,” were published in the journal Arthritis & Rheumatology.
Fibromyalgia is a complex disorder characterized by widespread musculoskeletal pain and fatigue. Pharmaceutical therapies have had limited effectiveness, with many people taking multiple drugs and still experiencing pain, limiting their physical activity.
While exercise has been shown to be an effective treatment for FM, individuals still report pain caused by body movements (movement-evoked pain) which limits participation in physical activities.
An alternative is transcutaneous electrical nerve stimulation (TENS), an intervention that delivers a low level of electrical current through the skin via electrodes placed on the body, with the intent of reducing pain.
In animal models, TENS treatment reduced the activity of pain-sensitive nerve cells. As people with FM have a reduced ability to inhibit this activity, TENS may be a useful treatment.
Researchers at The University of Iowa and Vanderbilt University Medical Center initiated the Fibromyalgia Activity Study with TENS (FAST) — a Phase 2 (NCT01888640), placebo-controlled study of the effectiveness of TENS to ease movement-evoked pain and fatigue in women with FM.
Their study enrolled 301 women between the ages of 18 and 70. Of these, 103 were assigned to TENS treatment (active-TENS group), 99 were given a sham TENS treatment that looked identical but delivered a very weak, gradually reducing current (placebo-TENS group), and 99 received no treatment (no-TENS group).
The TENS treatment (and sham treatment) involved placing butterfly-shaped electrodes at the base of the neck (cervicothoracic junction) and the lower back.
All women were assessed before treatment in the first week. Over the following three weeks, active-TENS and placebo-TENS were taken home by participants to use at least two hours each day during physical activity. After a four-week assessment, all were allowed to take the TENS device home for four more weeks.
Pain intensity, either at rest or during body movements, was measured using an 11-point numerical rating system (NRS) that measured pain on a scale of 0 to 10. Movement-evoked pain was determined using the Six-Minute-Walk-Test (6MWT) (the distance a person can walk in six minutes), the Five-Time-Sit-to-Stand test (5TSTS; the time it takes to move from sitting to standing five times).
Pain intensity and interference (pain that interferes with activity) was measured using the Brief Pain Inventory (BPI).
After four weeks, those in the active-TENS group had significantly reduced 6MWT scores compared to before treatment (pre-TENS), and people in the placebo-TENS and no-TENS groups. Significant reductions were also seen in resting pain, and pain intensity and interference with active-TENS for resting pain (NRS).
After the additional four weeks of TENS treatment for all participants, there was a reduction in resting pain and movement-evoked pain. This result was observed regardless of whether participants had previously received TENS treatment or not.
Fatigue, either at rest or during movement, was also measured before and during the 6MWT and 5TSTS tests. In addition, the researchers assessed it via the Multidimensional Assessment of Fatigue (MAF). This 16-item scale measures fatigue according to degree and severity, the distress that it caused, timing of fatigue, and the impact on various daily activities.
After four weeks of active-TENS, when compared to placebo-TENS and no-TENS, there was a significant reduction in movement-evoked fatigue. The MAF assessment also showed significant differences between the active-TENS groups and the two control groups.
An overall assessment of the TENS treatment was measured using the Global Impression of Change (GIC) — an analysis to show whether the patient’s illness has improved or worsened. In the active-TENS groups, 70% of participants reported overall improvement, compared to 31% in the placebo-TENS groups and 9% of those without TENS (no-TENS).
Adverse events related to TENS by reported by 30 women. The most common were pain with TENS (4.8% active-TENS, 4% placebo-TENS, 1% no-TENS), and skin irritation due to electrode use (4.8% active TENS, 1% placebo-TENS, 0% no-TENS).
Given that TENS treatment produces a noticeable feeling of electrical current, its use is not completely blinded and this can introduce bias in patient reporting. To minimize this bias, participants were asked if they could identify the TENS treatment. By comparing the results between those that correctly identified TENS to those who did not, no significant differences were found, suggesting the effectiveness of TENS was not due to this bias.
“Among women with FM and stable medication, 4‐weeks of active‐TENS use compared with placebo‐TENS or no‐TENS resulted in a significant improvement in movement‐evoked pain and other clinical outcomes,“ the team concluded. “Further research is needed to examine effectiveness in a real world, pragmatic setting to establish clinical importance of these findings.”