Nine RCTs were included: 1 long-term electrical stimulation study, 2 interferential therapy studies, and 6 maximal stimulation studies. Only one study evaluated the effect on urge incontinence.
The studies varied in terms of the sample size (n=14 to n=56); the drop-out rates (0 to 27%); whether or not they reported any information on patient adherence; whether electrical intervention was compared with placebo, control or another intervention; what equipment and regimens were used; and how PFM strength was measured.
PFM strength (6 studies).
One study did not provide any data. Two studies (one interferential and one maximal stimulation study) demonstrated a significant improvement in strength when compared with placebo. Three studies failed to find any significant improvements.
Self reported outcomes (6 studies).
One study using a visual analogue assessment scale demonstrated a significant improvement after interferential stimulation when compared with placebo. Another study demonstrated a significant improvement in most of the self-reported outcome measures used, compared with a control group. Four studies failed to find any significant improvement in the self-reported variables.
Leakage or urodynamic assessment (7 studies).
Two of the 9 studies failed to measure leakage or urodynamic variables. Five studies measured leakage, of which 4 used pad testing before and after treatment. All demonstrated a significant improvement after electrical stimulation. One study measured the number of leakage episodes.
Four studies measured urodynamic variables. One study demonstrated an improvement in some urodynamic measures after electrical stimulation, whilst the remaining 3 studies failed to demonstrate any significant improvements.
Side-effects (5 studies).
Side-effects were reported in 4 out of the 9 studies. These included vaginal irritation and infection, pain, discomfort, and urinary tract infections. One study reported that no side-effects were found. In one of the larger studies, side-effects were reported in around half of the women in either group.