A Cochrane review [Abstract] 1 included 7 studies with a total of 220 subjects. High-frequency TENS was shown to be effective for the treatment of dysmenorrhoea by four small trials (pain relief: OR 7.2, 95% CI 3.1 to 16.5; 2 trials, n= 106). Pain was reduced by a WMD of 45.0 (95% CI 22.5 to 67.5; 1 trial) on a VAS. Low-frequency TENS was found to be no more effective in reducing pain than placebo TENS (OR 1.48, 95% CI 0.43 to 5.08)
A systematic review 2 assessed TENS and heat therapy for pain relief. 6 studies on TENS and 3 studies on heat therapy were included. On the PEDRO quality scale, the trials methodological quality was 4.8 out of 10 for TENS and 6.3 out of 10 for heat therapy. TENS and heat therapy both showed evidence of pain reduction, but no study included quality of life as an outcome. Meta-analysis was not possible due to substantial heterogeneity in included studies.
A study 3 randomly assigned 134 participants into the intervention group (TENS) and the sham group (sham TENS). The primary outcome was measured by the Numeric Rating Scale (NRS). A total of 122 participants completed the study. Compared to sham TENS, TENS showed a greater effect in pain relief with regard to the NRS (P < .01), duration of relief from dysmenorrheal pain (P < .01), and number of ibuprofen tablets taken (P < .01). However, no significant differences in the quality of life, measured by the WHOQOL-BREF score, were found.
Comment: The quality of evidence is downgraded by limitations in study quality (unclear allocation concelament and blinding).
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