FormalPara Key Summary Points

Why carry out this study?

Electromyographic biofeedback (EMG-BF) can be regarded as an adjuvant to pelvic floor muscle training (PFMT) for the management of stress urinary incontinence.

This meta-analysis aimed to compare the efficacy of PFMT with and without EMG-BF on the cure and improvement rate, PFM strength, urinary incontinence score, and quality of sexual life for the treatment of SUI or PFD.

What was learned from the study?

PFMT combined with EMG-BF achieves better outcomes than PFMT alone in SUI or PFD management. Still, randomized controlled trials in different countries are still necessary to confirm the results.

Digital Features

This article is published with digital features, including a summary slide, to facilitate understanding of the article. To view digital features for this article go to https://doi.org/10.6084/m9.figshare.14787660.

Introduction

Urinary incontinence is the involuntary loss of urine and affects approximately 50% of women at some point in their lifetime, with an increasing incidence in older age [1,2,3,4,5]. Stress urinary incontinence (SUI) occurs during physical exertion, effort, coughing, or sneezing [1]. In women under 65 years old, SUI is slightly more common, whereas women over 65 years old are more likely to have mixed incontinence. Deficient or inadequate pelvic floor muscle (PFM) function is an etiological factor in SUI development [6,7,8,9]. Urinary incontinence directly impacts the quality of life, general and sexual, in women [5, 10]. If left unmanaged, urinary incontinence is more likely to worsen than improve [11].

Conservative treatment, recommended by the International Continence Society as first-line therapy, consists of an assessment of pelvic floor strength and functional use of PFM training (PFMT) [4, 5, 12,13,14]. PFMT increases the contraction and holding strength, coordination, velocity, and endurance of the PFMs to keep the bladder elevated during rises in intra-abdominal pressure, maintain adequate urethral closure pressure, and support and stabilize the pelvic organs [4, 12,13,14].

Furthermore, clinicians can assess the myoelectric activation of these muscle groups and train them using electromyographic biofeedback (EMG-BF) [15, 16]. EMG-BF can be regarded as an adjuvant to PFMT and is designed to assess muscle integrity and to allow both patient and physical therapist to observe correct PFM contraction and relaxation, thus facilitating neuromuscular learning or re-adaptation in the setting of pelvic floor dysfunction (PFD) [15, 16]. A meta-analysis in 2011 suggested that EMG-BF might benefit PFMT but that additional studies were required [16]. Since 2011, new studies were published around the world.

This meta-analysis aimed to compare the efficacy of PFMT with and without EMG-BF on the cure and improvement rate, PFM strength, urinary incontinence score, and quality of sexual life for the treatment of SUI or PFD.

Methods

Literature Search

This systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [17]. PubMed, EMBASE, the Cochrane Library, Web of Science, Wanfang, and CNKI were systematically searched for studies published up to January 2021 using the MeSH terms of “Pelvic Floor Disorders”, “Urinary Incontinence, Stress”, and “Women”, and “electromyographic biofeedback”, “female”, as well as relevant keywords. This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors.

Eligibility Criteria

The eligibility criteria were (1) diagnosis of SUI or PFD, (2) intervention and control: BF + PFMT vs. PFMT, (3) outcomes: cure and improve rate, symptom-related score, pelvic floor muscle strength change, and sexual life quality, (4) study type: randomized controlled trials (RCTs) or nonrandomized controlled trials (nRCTs), and (5) published in English or Chinese. The exclusion criteria were (1) overlapping publications, (2) single-arm study, case report, case series, or review, or (3) incomplete reported data for this meta-analysis.

Data Extraction and Quality Assessment

The selection and inclusion of studies were performed in two stages by two independent reviewers (Yuping Lan and Xiaoli Wu). The retrieved records were first screened on the basis of the titles/abstracts, and the full-text papers were then examined for eligibility. Disagreements were resolved by a third reviewer (Xiu Zheng).

Data including authors, publication year, study design, country, sample size, mean age, diagnostic criteria, intervention methods, instrument model, follow-up, outcomes, radiographic outcomes, and criteria for success were extracted by two authors (Xiaoli Wu and Xiaohong Yi). Discrepancies were resolved by discussion with a third author (Ping Lai).

The risk of bias of the RCTs was assessed using the Cochrane risk of bias tool [18]. The nRCTs were assessed using the Risk of Bias in Non-Randomized Studies of Interventions (ROBINS-I) assessment tool [19].

Statistical Analysis

The odds ratios (ORs) and their associated 95% confidence intervals (CIs) were used to determine the value of dichotomous data. Continuous data were evaluated using standardized mean differences (STDs) and their corresponding 95% CIs using the Mantel–Haenszel method. In all cases, P values less than 0.05 were considered statistically significant. A sensitivity analysis was conducted to obtain a solid conclusion and to evaluate the stability of the results. Cochran’s Q statistic (P < 0.10 indicated evidence of heterogeneity) was used to assess heterogeneity among studies [20]. When significant heterogeneity (P < 0.10) was observed, the random-effects model was used to combine the effect sizes of the included studies; otherwise, the fixed-effects model was adopted [18]. All analyses were performed using STATA SE 14.0 (StataCorp, College Station, TX, USA).

Results

Study Selection and Characteristics

Figure 1 presents the flowchart of the search process. The initial search yielded 341 records. After removal of the duplicates, 275 records were screened, and 218 were excluded. Then, 57 articles were assessed for eligibility, and 36 were excluded (missing data, n = 8; inappropriate outcome, n = 28).

Fig. 1
figure 1

Flowchart of the search process and included studies

Full size image

Finally, 21 studies were included (Table 1). There were 13 RCTs and eight nRCTs. Seventeen studies were from China, two from Europe, one from Brazil, and one from Turkey. A total of 1967 patients received EMG-BF + PFMT, and 1898 received PFMT alone. When reported, the studies used different diagnostic criteria for SUI and PFD and used different EMG-BF instruments. The follow-up also varied from 1 month to 2 years. Table 2 presents the quality assessment of the included studies. Among the RCTs, six had one item with a high risk of bias, and seven had at least one item with an unclear risk of bias. All eight nRCTs had at least one item with a moderate risk of bias.

Table 1 Characteristics of the included studies
Full size table
Table 2 Quality assessment of the included studies
Full size table

Cure and Improvement Rate

Eleven studies reported the cure and improvement rate of SUI. There was a significant difference between the two groups, favoring EMG-BF + PFMT in patients with SUI (OR 4.82, 95% CI 2.21–10.51, P < 0.001; I2 = 85.3%, Pheterogeneity < 0.001) (Fig. 2A). The analysis of six studies showed a significant benefit with EMG-BF + PFMT in PFD (OR 2.81, 95% CI 2.04–3.86, P < 0.001; I2 = 13.1%, Pheterogeneity = 0.331) (Fig. 2B). Then, a subgroup analysis of the cure and improvement rate of SUI was performed according to follow-up. Five studies reported a follow-up of at least 3 months, and six studies reported a follow-up of less than 3 months. In both cases, there was a benefit of EMG-BF + PFMT in women with SUI (at least 3 months: OR 3.99, 95% CI 1.09–14.58, P = 0.036; I2 = 90.0%, Pheterogeneity < 0.001; less than 3 months: OR 5.87, 95% CI 2.99–11.56, P ≤ 0.001; I2 = 49.1%, Pheterogeneity = 0.080) (Fig. 2C).

Fig. 2
figure 2

Forest plots of the cure and improvement rate. A Stress urinary incontinence. B Pelvic floor dysfunction. C Subgroup analysis of stress urinary incontinence (> 3 months and ≤ 3 months)

Full size image

Quality of Life

Six studies reported quality of life, using three different tools (I-QOL, IIQ-7, and ICIQ-LUTSqol). The three studies that used I-QOL showed benefits of EMG-BF + PFMT on quality of life (SMD 1.47, 95% CI 0.69–2.26, P < 0.001; I2 = 90.1%, Pheterogeneity < 0.001) (Fig. 3A). The two studies and one study that used IIQ-7 and ICIQ-LUTSqol, respectively, did not report significant differences between the two groups (SMD 1.65, 95% CI − 0.17 to 3.48, P = 0.076; I2 = 94.6%, Pheterogeneity < 0.001; SMD 0.04, 95% CI − 0.17 to 0.25, P = 0.376) (Fig. 3A).

Fig. 3
figure 3

Forest plots of the quality of life score. A Urinary incontinence quality of life. B Quality of sexual life

Full size image

Five studies reported the quality of sexual life, using the PISQ-12 and the FSFI. Two studies used the PISQ-12 and showed no difference between the two groups (SMD 0.04, 95% CI − 0.78 to 0.87, P = 0.919; I2 = 84.6%, Pheterogeneity = 0.011) (Fig. 3B). Three studies used the FSFI and showed a benefit of EMG-BF + PFMT on the quality of sexual life (SMD 2.86, 95% CI 0.47–5.25, P = 0.019; I2 = 98.7%, Pheterogeneity < 0.001) (Fig. 3B).

Severity of Urinary Incontinence, PFM Strength, and Urodynamics

Five studies reported the severity of urinary incontinence, using either the ICIQ-UI SF or the ICI-Q-SF scale. For the ICIQ-UI SF, the pooled data showed no significant difference between the two groups (SMD − 0.52, 95% CI − 2.17, 1.12, P = 0.532; I2 = 98.7%, Pheterogeneity < 0.001) (Fig. 4A). For ICI-Q-SF, the pooled data showed a significant difference between the two groups in favor of EMG-BF + PFMT (SMD − 0.62, 95% CI − 1.16, − 0.08, P = 0.024) (Fig. 4A).

Fig. 4
figure 4

Forest plots of A the severity of urinary incontinence, B pelvic floor muscle strength, and C urodynamics

Full size image

Four studies reported PFM strength. The pooled data showed benefits of EMG-BF + PFMT (SMD 1.72, 95% CI 1.08–2.35, P < 0.001; I2 = 91.4%, Pheterogeneity < 0.001) (Fig. 4B).

Six studies reported the urodynamics using three indicators (Qmax, ALPP, and MUCP). For Qmax and MUCP the pooled data showed benefits of EMG-BF + PFMT (Qmax: SMD 0.84, 95% CI 0.57–1.10, P < 0.001; I2 = 0%, Pheterogeneity = 0.420; MUCP: SMD 1.54, 95% CI 0.66–2.43, P = 0.001; I2 = 81.8%, Pheterogeneity = 0.019) (Fig. 4C). For ALPP, the pooled data showed no significant difference between the two groups (SMD 7.37, 95% CI − 6.09–20.83, P = 0.283; I2 = 98.8%, Pheterogeneity < 0.001) (Fig. 4C).

Publication Bias

There was limited evidence of publication bias (Supplementary Fig. S1A), as suggested by Begg’s test (P = 0.062) and Egger’s test (P = 0.034). Supplementary Fig. S1B also shows the trim and fill analysis.

Sensitivity Analysis

The sensitivity analysis showed that the sequential exclusion of each study did not influence the outcomes regarding the effective rate (Supplementary Fig. S2A) and the cure and improvement rate (Supplementary Fig. S2B), and the analyses were robust. For the analysis of PFM strength, excluding the study by Yao et al. [21] significantly changed the results, but not the conclusion of the analysis (Supplementary Fig. S2C).

Discussion

EMG-BF can be regarded as an adjuvant to PFMT to manage SUI or PFD [15, 16]. This meta-analysis aimed to summarize the recent literature comparing the efficacy of PFMT with and without EMG-BF on the cure and improvement rate, PFM strength, urinary incontinence score, and quality of sexual life for the treatment of SUI or PFD. The results showed that EMG-BF + PFMT improved the cure and improvement rate, quality of life using the I-QOL tool, quality of sexual life using the FSFI tool, urinary incontinence using the ICI-Q-SF tool, PFM strength, and urodynamics using Qmax and MUCP.

A Cochrane review published in 2011 suggested that EMG-BF + PFMT benefited women with urinary incontinence, but that further evidence was still needed [16]. Still, this previous meta-analysis was not limited to SUI and included all women with urinary incontinence. Since the different types of urinary incontinence have different pathogenic mechanisms [1,2,3,4,5], the inclusion of all types probably biased the results. The present meta-analysis only included SUI/PFD, which could help refine the results. It showed that EMG-BF + PFMT had benefits over PFMT alone regarding the outcomes of SUI/PFD, concordant with the previous meta-analysis [16], although with different patient populations and different outcomes.

Nevertheless, these benefits of EMG-BF + PFMT are not observed in all included studies. Three studies reported no benefit of EMG-BF + PFMT on the cure and improvement rate [15, 22, 23]. Two of these studies still reported a tendency toward a benefit of EMG-BF + PFMT [22, 23], while Hagen et al. [15] showed no tendency toward a benefit of EMG-BF + PFMT on the cure and improvement rate, quality of life, and urinary incontinence. The reasons why are difficult to determine since no particular characteristics of the study or the patient population differentiate that study from the others. Still, among the 21 included studies, only three were negative, and the publication bias analysis suggested the possible presence of such bias. Hence, additional studies are still necessary to confirm the benefits of EMG-BG + PFMT on SUI.

Nevertheless, the benefits of EMG-BF are not based on any direct effect of EMG-BF on the PFMs, but rather indicate the activity of the PFMs and aim to improve the teaching of the adequate contraction techniques by showing the patients the actual activity of their PFMs in real time. Therefore, it has the indirect effects of motivating them and increasing their adherence to the PFMT. PFMT alone is already known to improve SUI/PFD [24]. Thus, EMG-BF could be an adjunct management method to PFMT. It could also increase the patients’ empowerment toward their condition and increase their sense of control, which could help them manage their symptoms. Indeed, Hagen et al. [15] showed that the self-efficacy of the EMG-BF + PFMT group was higher than in the PFMT group.

This meta-analysis has limitations. First and foremost, heterogeneity was high for nearly all analyses. That is probably due to the use of different diagnostic criteria for SUI and PFD, the use of different protocols and devices for EMG-BF, and different definitions of treatment success. In addition, different tools were used for the assessment of the quality of life, sexual quality of life, and urodynamic indicators, including qualitative and quantitative assessments, severely limiting the meta-analyses for these outcomes because of the lack of direct comparability among the different tools. In addition, different results were observed with different tools for the same outcome (e.g., quality of sexual life), probably because of the questionnaires’ constructs. Third, most of the included studies were from China, which could introduce some bias. It could be that EMG-BF is more popular in China, but this might constitute a bias since the physicians would have more experience with the treatment. Fourth, studies in languages other than English and Chinese were excluded, possibly excluding useful and precious data. Finally, this meta-analysis was not registered.

Conclusions

PFMT combined with EMG-BF achieves better outcomes than PFMT alone in SUI or PFD management. Still, RCTs in different countries are still necessary to confirm the results.