The long-term outcome of transcutaneous electrical nerve stimulation in the treatment for patients with chronic pain: a randomized, placebo-controlled trial.

Background: Transcutaneous electrical nerve stimulation (TENS) is an easy to use analgesic intervention. However, long-term randomized placebo-controlled studies with treatment periods of more than 3 months have not been executed to date. The aim of our study is to explore the long-term (1 year) time course of the treatment effects of TENS compared to placebo (sham TENS). Method: We performed a randomized placebo-controlled trial in patients with chronic pain (165), referred to a multidisciplinary pain center of a university hospital. Main outcome measures are the proportion of patients satisfied with treatment result and willing to continue treatment, pain intensity, pain disability, and perceived health status. Results: Survival analysis of time courses of proportions of satisfied patients revealed no significant differences (P = 0.79; log-rank test) for TENS treatment compared to sham TENS. After 1 year, 30% (24/81) of the patients of the TENS group and 23% (19/82) of the sham TENS group were satisfied with treatment result. These patients experienced a mean overall improvement of 62.7% (n = 43). This effect was not significantly different between both groups. For satisfied patients, there were no differences in pain intensity or disability and perceived health status between the TENS and sham TENS group. Conclusions: Transcutaneous electrical nerve stimulation and sham TENS show similar effects in patients with chronic pain over a period of 1 year. We found support for a long sustained placebo effect.