Home and outpatient electrostimulation in the treatment of urinary incontinence in women: a systematic review

Abstract

Introduction and hypothesis

Urinary incontinence (UI) is defined as any involuntary loss of urine and can be associated with urgency and/or physical exertion. Electrical stimulation (ES) has recently been identified as a proven therapeutic alternative for UI, with few side effects and low cost. This systematic review, registered on the Prospective Register of Systematic Reviews (RD42024528812), investigated whether home-based ES would be as viable as outpatient ES in the treatment of women with UI.

Methods

Study selection was conducted by two independent researchers across the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Embase, Web of Science, Scopus, and PEDro (search conducted on February 25, 2024). We also searched the reference lists of eligible articles. There were no restrictions on date and language. The RoB2 and GRADE tools were used to assess methodological quality and evidence recommendation.

Results

723 articles were found, and four trials were eligible. Very low-quality evidence indicated statistically significant differences in cure rates or improvement of urinary symptoms in women treated with both outpatient and home-based ES. Low-quality evidence recommends home-based ES in maintaining improvement of urinary symptoms, and moderate-quality evidence indicates no severity of symptoms in the home-based group.

Conclusion

Home-based ES is shown to be as effective as outpatient ES in the treatment of UI in women. However, data analysis revealed low-quality evidence regarding the cure or improvement of the women’s conditions.

Introduction

Urinary incontinence (UI), according to the International Continence Society (ICS), is defined as any involuntary loss of urine [1]. This involuntary loss can be associated with urgency and/or physical exertion. Prevalence estimates of UI range from 8.7% worldwide, with 25% to 45% of all women being affected [2], and older women are more likely to be affected [2, 3]. Additionally, UI is associated with negative impacts of quality of life (QoL), depression and anxiety [4].

Behavioral therapy and the use of non-implanted electrical stimulation (ES) devices in the treatment of UI represent minimally invasive therapies without side effects [2, 5,6,7,8]. Various studies show clinical improvement in UI symptoms through ES compared to sham groups or medication therapy [9,10,11]. When combined with pelvic floor muscle training (PFMT), ES also shows benefits, achieving symptom resolution with fewer side effects and less discomfort [12,13,14,15]. Systematic reviews on the effectiveness of ES in women with stress urinary incontinence (SUI) have not differentiated the rout of administration [16,17,18].

Electrostimulation techniques aimed at treating urinary incontinence (UI) include sacral nerve stimulation, which modulates neuromuscular reflex pathways in the pelvic floor, and functional electrical stimulation, which seeks to rehabilitate muscular functionality and improve voluntary control [19]. Both interventions have proven effective in managing UI across various clinical settings. Home-based ES offers additional advantages beyond mere convenience and adaptability, such as the potential to reduce healthcare costs by decreasing the need for frequent clinical visits and optimizing healthcare resource allocation. Furthermore, HE promotes patient autonomy by providing individuals with greater control over their treatment protocols, thereby fostering sustained adherence to long-term treatment strategies [20].

This study aims to address the research gap regarding the rigorous comparison of the effectiveness and cost-effectiveness of outpatient and home-based ES in the treatment of urinary incontinence in women. Despite the clinical benefits of both approaches, there is a lack of systematic investigations analyzing standardized clinical parameters, costs, and their impact on quality of life. Given the growing interest in accessible interventions like HE, which can alleviate pressure on healthcare systems and improve adherence, this study seeks to provide a solid foundation for clinical and policy-making decisions.

Physiotherapeutic treatment with ES for UI in women can be administered in outpatient settings but can also be associated with home-based treatment. Outpatient ES therapy involves a comprehensive treatment program requiring time commitments and travel to clinics and/or hospitals. Home-based ES treatment is usually performed with a portable stimulator equipped with a disposable electrode, which has the potential to be an economical, flexible and convenient alternative, facilitating patient adherence to treatment [21, 22]. However, there is considerable uncertainty regarding the real and potential therapeutic efficacy, cost-effectiveness, and risks of home-based ES treatment of women with UI. Therefore, we aim to answer the following question: in women with urinary incontinence, is home-based ES as viable as outpatient electrical stimulation?

Methods

Kind of study

This is a systematic literature review conducted according to the guidelines of the Cochrane Collaboration [23] and the Systematic Reviews and Meta-Analyses (PRISMA) [24]. The protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO: CRD42024528812) [25].

Eligibility criteria

Studies were selected based on the following inclusion criteria: 1) randomized controlled trials (RCTs) that included adult women (18 years or older) with stress urinary incontinence (SUI), urgency urinary incontinence (UUI), and/or overactive bladder (OAB) treated with ES, diagnosed based on symptoms and clinical signs or urodynamic tests; 2) studies comparing home-based ES with other outpatient therapeutic forms; 3) no restrictions on publication year or languages.

Non-inclusion criteria

The following non-inclusion criteria were applied: 1) studies involving pregnant women, women with pelvic organ prolapse, other pelvic diseases such as pelvic inflammatory disease, or previous surgical treatment for UI; 2) studies involving participants with neurological and/or psychiatric impairment; 3) studies using implanted or magnetic ES devices.

Search strategy and data extraction

The final search for studies investigating the effects of home-based and outpatient ES in the treatment of female UI was conducted on February 25, 2024, without date or language restrictions, across the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Embase, Web of Science, Scopus, and PEDro. We also searched the reference lists of eligible articles. The PICOS anagram was used to construct the research question: in women with urinary incontinence, is home-based ES as viable as outpatient ES in randomized clinical trials? The inclusion criteria were population: women diagnosed with UI treated with electrotherapy; intervention: application of intracavitary or non-intracavitary ES in a home setting; comparison: any other control interventions conducted in a clinical or hospital setting; outcome: complete resolution or reduction of self-reported or objectively assessed incontinence, and UI-specific quality of life (QoL); study design: RCTs. The keywords and MeSH (Medical Subjective Headings) terms used were “urinary incontinence”, “Transcutaneos Electrical Nerve Stimulation”, “electrostimulation”, and “women”. The terms were combined using Boolean operators and adapted for each database (supplementary material).

Two authors independently and blindly assessed the studies in two stages. In the first stage, titles, abstracts, and duplicates were checked according to the eligibility criteria using the Rayyan QCRI application® (Qatar Computing Research Institute, Doha, Qatar) [26]. In the second stage, selected studies were read in full and evaluated against the stated criteria. At the end of the process, the two authors reached a final decision on the selection of articles. A third reviewer was consulted to resolve disagreements. Information extracted from the selected articles included: author, country, year, sample size, study design, study objective, type of intervention, parameters used, treatment duration, and outcomes.

Risk of bias assessment from scientific evidence

The methodological quality of the selected studies was assessed using the Cochrane risk-of-bias 2 (RoB2) tool, developed for RCTs. The following domains were evaluated: bias arising from the randomization process, deviations from intended interventions, measurement of outcomes, incomplete outcome data, and selection of the reported result, according to low, high and some concerns criteria [27]. Disagreements were discussed between the two investigators in a subsequent stage, and a third reviewer was consulted to resolve any discrepancies.

The certainty of evidence in recommending the use of ES for the treatment of female UI was evaluated using the GRADEpro GDT: GRADEpro Guideline Development Tool® (Software), considering domains such as risk of bias, inconsistency, indirect evidence, imprecision, and publication bias. The quality scores used were high, moderate, low, and very low quality [28].

Results

Characteristics of included studies

A total of 1,218 studies were identified according to the search criteria. The titles and abstracts of 723 articles were selected for preliminary analysis, and eight potentially eligible studies were chosen for full-text review. Four studies were excluded for not meeting the eligibility criteria [29,30,31,32]. Thus, only four clinical trials were evaluated in this systematic review [33,34,35,36]. Figure 1 illustrates the study selection process.

Fig. 1

Study eligibility flow diagram, adapted from the PRISMA checklist

The studies were published between 1998 and 2021, conducted in different countries: Bosnia [33], England [34], China [35], and the United Kingdom [36], totaling 214 participants. All studies compared outpatient and/or hospital-based electrostimulation (ES), versus home-based ES for treating urinary incontinence (UI) in women.

All participants were clinically assessed before and after interventions using the following methods: Pad Test [37] to quantify urine loss, a three-day diary (DM) [38], and urodynamic studies to evaluate bladder filling and emptying phases [39]. Validated instruments such as the Overactive Bladder Q-quality of Life Short-Form Questionnaire (OAB-q SF) [40] and the International Consultation on Incontinence Questionnaire Short Form (ICIQ-SF) were also used to assess symptom discomfort and quality of life (QoL) specific to UI patients. Additionally, two studies [36, 37] employed perineometry and electrophysiological examination to investigate the function of pelvic floor muscles (PFMs). Studies were divided into subgroups based on the therapy studied: two investigated percutaneous vs. transcutaneous ES and two investigated intravaginal ES. Table 1 summarizes the information extracted from the included studies.

Table 1 Description of randomized clinical trials included in the systematic review

Percutaneous vs. transcutaneous electrical stimulation

Two randomized trials [34, 35] treating women with Overactive Bladder (OAB) with a total of 84 participants were included. These studies compared outpatient percutaneous tibial nerve stimulation (PTNS) versus home-based transcutaneous tibial nerve stimulation (TTNS).

Zonić-Imamović et al. [33] used symptoms frequency and QoL as outcome measures. They reported significant improvement from baseline in both groups. For the TTNS home treatment symptom score (daily) (p < 0.0001) and QoL (p < 0.0001). the PTNS clinical (weekly) group showed significant reduction in all bladder symptoms and QoL (p < 0.0001 and p < 0.0001, respectively). Intergroup analysis showed significant reduction favoring the PTNS group (p < 0.0001). The authors suggested that the use of acupuncture needles placed at the acupoint SP6 may have favored the PTNS group and should be discussed.

Martin-Garcia and Crampton [34] studied symptoms frequency, symptom severity and QoL as outcome measures. They reported that urinary frequency, urgency episodes, and UUI episodes did not significantly change from baseline to six months in both groups. Similarly, OAB-q symptom severity scores and QoL remained stable in both groups at all study points, suggesting that bilateral home-based TTNS application could be an effective and well-tolerated treatment for maintaining OAB symptoms in women benefiting from an initial course of PTNS.

Intravaginal electrical stimulation

Two trials [35, 36] were included to treat stress urinary incontinence (SUI) with a total of 128 participants. Both studies used home-based intravaginal ES versus clinical or hospital ES, with different parameters and therapy durations. Only one study [36] included a control group with pelvic floor muscle exercises (PFME) alone. Most patients in the studies had homogeneity in basic characteristics, except for the study by Knight, 1998 [36], which showed baseline differences between groups. The most common outcome measures were the pad-test to quantify urine loss, perineometry, and electrophysiological exams to assess the strength of the pelvic floor muscles (PFM).

Sun Zhijing et al. [35] demonstrated significant results at six and nine months of follow-up after treatment. At six months, the average decrease in urine loss in the control and intervention groups was (75% ± 24%) and (98% ± 3%), respectively (p < 0.01). This result was maintained at nine months in the control and intervention groups (75% ± 24%) and (99% ± 3%), respectively (p < 0.01). For subjective UI results, the ICIQ-SF scores at six months for the intervention and control groups were (2,1 ± 2,4) and (6,8 ± 3,2), respectively (p < 0.01), with significant reduction at nine months for the intervention and control groups (1,8 ± 1,7) and (6,5 ± 2,9), respectively (p < 0.01). The improvement in the intervention group was substantial. Comparing the two groups, the difference was statistically significant (p < 0.01).

Data from Knight, 1998 [36], found insufficient evidence to differentiate between ES plus PFME versus PFME alone in terms of cure or objective improvement. There were no statistically significant differences in outcome measures such as cure or improvement of urinary symptoms and pad-test among the three groups. However, the highest percentage of subjects cured or improved subjectively (80%) and by pad-test (80%) were in the maximum stimulation group, 35 Hz (n = 20). Participants who received low-intensity stimulation for SUI at home had a lower improvement rate than the clinical treatment or control group.

In analyzed studies, the dropout rate was observed only in one study, Knight, 1998 [36], where 13 out of 70 patients did not complete the six-month program (three in the control group, four in the clinical group and six in the home-based group). Six participants did not complete the six to 12-month program (three in the control group and three in the home-based group), with the highest dropout rate in the home-based group. Participants reported that the equipment was intrusive and uncomfortable, requiring significant time. It is worth noting that the study did not specify the usage time of the home-based device, only mentioning that it was used at night with a break during menstruation. Reasons for not completing the clinical treatment, conducted twice a week, included difficulties with public transport, inability to attend due to work and/or family demands.

Adverse events were evaluated in all studies for severity, but no participant reported complaints during or after treatment. Only one study [34] reported three episodes of bleeding and one episode of discomfort at the needle site in the PTNS group.

All studies measured short to long-term follow-up, ranging from three to 12 months. Two studies measured intermediate follow-up, from three to six months [33, 34]. Two of the included studies measured follow-up beyond six months [35, 36].

Regarding the methodological quality of the studies included in this systematic review, it was observed that, in general, the studies presented some risk of bias when analyzed together. In the individual analysis, only one study presented low risk in all domains investigated [34]. In missing outcomes, all studies presented low risk of bias. Figure 2 summarizes the results of the RoB2 tool.

Fig. 2

Representative summary for assessing the risk of bias (RoB2) in selected randomized clinical studies

In the randomization process, two included trials adequately reported randomization and allocation methods [34, 36], resulting in a low risk of selection bias. Two studies reported randomization but did not provide information on allocation concealment procedures [33, 35]. Regarding deviations from intended interventions, blinding of therapists and patients was not possible for the proposed intervention. For missing outcome data, three trials did not report losses during follow-up. Only one trial reported losses exceeding the maximum of 20% [36]. However, missing data were replaced with empirical data according to the intention-to-treat (ITT) principle. In measuring the outcome, registered protocols were available for only one trial, which mentioned blinding of the evaluator [34]. Trials for which protocols could not be found but it was clear that all expected outcomes were included met this criterion [33, 35]. These three cited studies [33,34,35] had a low risk of bias for this criterion, except for the study [36] that provided ITT data for only two outcomes reported as percentages. The certainty of evidence across studies was considered very low to moderate, as described in Table 2.

Table 2 Summary of the GRADE assessment of the evidence on the use of outpatient electrical stimulation associated with home ES in the treatment of urinary incontinence in women

Discussion

Summary of main results

To date, this review represents the first synthesis of available evidence from randomized clinical trials that explore the efficacy of ES performed in an outpatient setting versus at home for treatment of UI in women. This analysis aims to fill a gap in the current literature by systematically gathering and analyzing the results of these studies, providing a comprehensive overview of the available ES treatment approaches for this specific condition.

Only randomized clinical trials, considered the gold standard for evaluating the efficacy of interventions, were included [41, 42]. Most of these studies used a variety of ES techniques, comparison groups, and outcome measurements, resulting in substantial heterogeneity < 50%. These results were not combined; however, they are presented as a narrative synthesis.

The heterogeneity of studies presented in this systematic review can be attributed to several specific factors, such as variations in the parameters used in electrostimulation (ES), differences in patient population characteristics, and the choice of outcome measures. ES parameters, such as frequency, intensity, and session duration, showed significant variations across studies, which may affect the reported treatment efficacy [43]. Additionally, the populations assessed showed significant differences in terms of age, severity of urinary incontinence, and comorbidities, which can influence therapeutic outcomes [20]. The lack of uniformity in the outcome measures used, such as continence rates, quality of life improvements, and treatment adherence, makes direct comparisons between studies difficult.

The studies measured cure or improvement in urinary symptoms and QoL scores, but the mean data and standard deviations (SD) were not available in the text, and the authors did not provide this information upon request [33,34,35]. Therefore, we could not analyze the outcomes cited in the protocol through a meta-analysis.

The primary outcome data, as well as the evidence for symptom quantification, indicate that home-based ES is likely as effective as outpatient ES in treating women with UI. Very low-quality evidence from three included studies pointed to statistically significant differences in cure rates or improvement of urinary symptoms in both groups. The results of symptom quantification, such as urine loss in the pad test and the number of pads used, showed statistical significance, but the quality of the evidence is low. Conversely, low-quality evidence from two included studies recommends home-based ES in maintaining the improvement of urinary symptoms. Additionally, moderate-quality evidence from only one of the included studies indicates that there was no severity of symptoms in the home-based group.

Three studies measured QoL, and very low-quality evidence suggests improvements in QoL. The low quality of the identified evidence indicates that no conclusions can be drawn about the cure or improvement of women from the cited results.

Overall completeness and applicability of evidence

The trials included in this review were conducted in Bosnia, England, China and the United Kingdom, with female participants aged between 18 and 69 years, treated for UI with ES at home and/or in an outpatient setting. All four trials reported that patients received instructions on how to use the equipment at home; however, only two trials provided information about the care providers such as specialist doctors and physiotherapists [35, 36]. Therefore, we cannot generalize the results of this review to different healthcare settings. Regarding our assessment of clinical relevance, most of the included trials provided a clear description of the patients, outcomes and interventions used. However, only three of the included trials found statistically significant results for the cure and/or reduction of urinary symptoms, and only one reported a clinically important effect on the severity of symptoms.

Quality of evidence

One of the most critical steps in conducting a systematic review is the assessment of the risk of bias, which determines the methodological quality of the studies [42]. In this review, the most affected items were the appropriate randomization. In two trials [33, 35], there was no information about the allocation concealment. Similarly, the blinding of participants and caregivers was not adequately addressed. Regarding the outcome assessor, only one trial [34] mentioned the implementation of blinding. Additionally, only this study detailed the process of selecting outcomes and registering the research protocol, highlighting a significant gap in the other studies in terms of bias control and methodological rigor. Furthermore, the lack of details about the methods in most trials meant that when compiling the GRADE evidence profile, we had to downgrade the level of evidence due to unclear risk of bias. We also downgraded the classification of studies due to their small sample sizes (ranging from 24 to 68 participants). Finally, only four studies could be included in this review, compromising the quality of the provided evidence. Therefore, our results cannot be considered robust.

Possible biases in the review process

The main limitation of this review is the low number of trials and the small sample size per comparison, outcome, and follow-up period, which prevented us from performing sensitivity analyses. Additionally, many of the included trials inadequately reported their methods and/or data, making it difficult to assess the extent of potential biases and fully utilize the relevant trial data. Another limitation is the potential for publication bias in the included trials. In this review, it was not possible to assess publication bias using funnel plots because only a few studies were included. Lastly, we did not include conference abstracts and theses. Since unpublished studies are more likely to report negative results, it is possible that the conclusions of the review are overly optimistic.

Agreements and disagreements with other studies or reviews

There was no consistency among the trials in terms of types and parameters of ES. Although ES is recommended by guidelines, there seems to be no consensus on the “best” parameters for treating UI in women. The ICS concluded that ES can be effective in treating UI but warned that there was insufficient evidence to draw any additional conclusions [3].

In the treatment of UUI, low-frequency electrical current is recommended, as ES stimulates the pudendal nerve, which can inhibit the detrusor muscle and reduce involuntary contractions [44]. Studies using Transcutaneous Electrical Nerve Stimulation (TENS) at the S2-S4 level encourage the use of low frequency between 10 and 20 Hz, a pulse width between 250–1000 µs, sensory level, session duration varying from 20 min to 6 h per day, and the number of sessions ranging from 12 to 50 sessions [17, 44]. Previous study protocols have demonstrated that the best frequency for detrusor inhibition is 10 Hz [45,46,47]. This is consistent with the two studies [33, 34] included in this review for OAB, which obtained significant results both in the outpatient group with percutaneous ES and at home with transcutaneous ES.

For intravaginal ES in SUI, some clinical trials suggest using higher frequencies, such as 50 Hz [48, 49]. In the study by Knight [36], they used parameters of 10 Hz with bursts at 35 Hz in the home group in an attempt to maintain the activity of fast-twitch fibers, but the results were not statistically significant, and patient adherence to the treatment was low. In the control group (outpatient), a higher frequency of 35 Hz was used, and clinically significant results were observed. Conversely, Sun Zhijing [35] used a frequency of 30–35 Hz for SUI and obtained statistically significant results in the home group, indicating that regardless of being self-managed or led by professionals in a clinical setting, ES was strongly favored as an effective treatment approach for UI. This shows that the well-founded choice of ideal parameters for each voiding dysfunction will bring positive responses to the proposed treatment, as well as good patient adherence.

In the study by Knight [36], a number of participant dropouts were also observed in the outpatient groups, caused by difficulties related to mobility, cost, time, and urban travel, as outpatient ES treatment involves a schedule of treatment sessions that require time commitments and travel to clinics and/or hospitals. In this regard, home-based ES could overcome these difficulties, corroborating other studies that report that working women particularly find home self-management convenient and flexible, allowing daily activities to proceed normal while seeking improvement in urinary symptoms and QoL [50].

However, at home, there is a risk that the patient may not perform the treatment correctly or in the correct position, due to the absence of a professional physically providing guidance. Nonetheless, Sun Zhijin’s study [35] points out that UI generally occurs when standing or walking, and it would be more reasonable to maintain the postures that typically cause UI during treatment. Thus, patients treated at home with portable nerve and muscle stimulators can overcome the limitations of outpatient treatment spaces and fixed positions, training participants to stimulate and adapt to different postures in real life and establish and restore the self-control awareness of the PFM.

The proactive involvement of therapists or physical therapists is essential for the safe and effective implementation of home-based electrostimulation for urinary incontinence in women. These professionals play a critical role in assessing the patient’s condition, calibrating device parameters, and educating patients on proper usage. They also conduct follow-ups to monitor adherence, adjust treatment based on clinical responses, and prevent complications from improper use. Literature highlights that professional supervision enhances therapeutic outcomes and ensures the success of interventions [20, 43].

Results from RCTs [22, 51] also demonstrated that ES appears to be effective and safe in-home treatment of women with OAB, confirming the great potential that ES has for home use [52, 53]. Other reviews [17, 54] indicate that ES is probably more effective than no active or sham treatment in treating SUI but report inconclusive results due to the very low quality of evidence found to provide reliable results. Therefore, more multidirectional and multicenter, randomized controlled studies on the efficacy of ES for UI are needed.

Final considerations

There is very low to moderate quality evidence suggesting that home-based ES is as effective as outpatient ES for UI in women, with consistent long-term symptom maintenance benefits (12 months). However, there is an urgent need for large, high-quality studies to evaluate outpatient and home-based ES in the treatment of UI women. Improving ES parameters such as frequency, intensity, and session duration is essential for treatment efficacy. Developing standardized protocols for ES across clinical settings will enhance study comparisons and ensure treatment consistency. Future research should involve larger sample sizes and greater statistical power to detect deeper effects and provide more reliable data on the efficacy and safety of home-based and outpatient ES. These approaches are key to advancing the field and providing consistent evidence for clinical practice. Additionally, including an economic evaluation (cost-effectiveness) alongside a clinical trial of outpatient and home-based ES would be useful to guide clinical choices between competing treatment options. Three studies are currently in the classification section awaiting the next update on this review (NCT01940367, NCT05309993, NCT04909047—‘Clinical trial number: not applicable to our study.’), which will contribute to the results of this review in the future.

Implications for clinical practice

The conclusions of this study have relevant implications for clinical practice, particularly in terms of patient selection and treatment recommendations. Electrostimulation (ES) can be an effective therapeutic option for women with urinary incontinence, but the choice of intervention type should be individualized, taking into account the specific characteristics of each patient. It is crucial that clinicians evaluate these factors when recommending ES. Additionally, the evidence shows that treatment adherence can be facilitated by the convenience of home-based ES, which may be especially relevant for women with difficulties accessing regular clinical care. Clinical practice should therefore consider the individual needs of each patient, balancing the effectiveness, safety, and feasibility of the therapy to optimize long-term outcomes and improve quality of life.