Urinary incontinence is the involuntary leakage of urine that negatively impacts one’s quality of life and occurs in a variety of forms. The involuntary flow of urine caused by effort such as coughing or sneezing is known as stress urinary incontinence (SUI). Urge urinary incontinence (UUI) on the other hand is the uncontrolled loss of urine that occurs simultaneous with or immediately after urgency. Mixed urine incontinence (MUI) affects women when they experience both stress and urge sensations [1].

MUI affects one out of every three women and involves both physical effort, which raises the intra-abdominal pressure, and urinary urgency [2]. Compared to pure UUI or SUI, MUI is more common in older females and has a bigger impact on a woman’s quality of life [3].

Damage to the muscles, nerves and connective tissue of the pelvic floor causes the symptoms of SUI. Important factors for continence include urethral support, vesical neck function, and urethral muscle function [4].

A woman’s level of SUI is very subjective and unique to each individual. Women who experience only light urine leakage during vigorous activity such as sport or after sneezing, laughing, coughing, or lifting are deemed to have moderate incontinence. Larger amounts of urine loss associated with low-impact activities such as standing, walking or leaning down are classified as moderate to severe SUI [5].

UUI is the uncontrolled loss of urine that occurs when there is a sense of urgency. If there is no underlying urinary tract infection or other evident pathology, UUI is considered to be part of a larger symptom complex known as overactive bladder syndrome. This is characterized by urine leakage and is frequently accompanied by nocturia, with or without UUI [6].

Urinary incontinence is sometimes linked to recurrent urinary tract infection, which is a curable cause of the condition. SUI and UUI are both associated with a higher body mass index and older age. Women with incontinent mothers or sisters are also more likely to experience SUI and MUI [7].

Supportive structures for the bladder neck and urethra are required to maintain urethral closure pressure. The levator ani (LA) muscle creates a powerful shelf that remains stable during the high forces generated by coughing or sneezing. SUI can be triggered by disruption of this shelf through weakening of the LA. The main etiological causes for LA muscle weakening are ageing and childbirth damage [8].

The first line of conservative care for women with MUI includes weight-reduction, behavior modification, pelvic floor muscle training, reduction of fluid intake, and caffeine restriction [9].

Pulsed electromagnetic field therapy (PEMF) conveys pulsed electromagnetic energy through two steel surgical probes applied to the skin. It is used to treat many musculoskeletal abnormalities [10].

PEMF affects numerous physiological mechanisms, improves circulation and increases the permeability of cell membranes. It shows good results for wound healing, the alleviation of muscle soreness, and in reducing the loss in range of motion after exercise. PEMF also has positive effects on muscle strength, muscle temperature, blood flow and oxygenation [11].

Urinary incontinence adversely affects the psychological and social wellbeing of females. Whereas surgical intervention for incontinence can lead to numerous complications, magnetic field therapy is considered to be a non-invasive technique for stimulating the nervous system [12]. So far, however, there are no published reports on the impact of PEMF treatment for MUI. The aim of the present study was therefore to assess the effectiveness and safety of PEMF for the treatment of such cases.

This study was carried out on 40 parous women aged between 40 to 55 years and with a BMI ranging from 24 to 32 Kg/m${}^2$. They were referred with either mild or moderate SUI symptoms associated with urgency. The women were diagnosed by a physician as having MUI, the current International Continence Society guidelines define MUI as a complaint of the involuntary loss of urine during exertion, sneezing, or coughing, as well as leakage associated with urgency, the diagnosis of MUI by a physician based on clinical history, this includes onset and timing of stress and urge symptoms, history of any urinary tract infections or sexually transmitted diseases, an obstetric history, bowel function, a frequency-volume diary, physical examination findings, pelvic examination should include evaluation of urethral mobility, pelvic organ prolapse, and urogenital atrophy, patients were selected from the outpatient clinic of the gynecological department of kafr elshiekh hospital, Egypt. This study was approved by the ethics committee of the Faculty of Physical Therapy, KFS El Sheikh University (No.: P.T./WH/7/2021/11).

Women with any dysfunction or associated injuries, or with any pathological conditions such as cardiac abnormalities, recurrent urinary tract infections, hypertension or diabetes mellitus, malignancy, cardiac pacemakers, TB, epileptics or hysterectomy were excluded from the study.

Following an orientation session describing the aim of the study and explanation of the treatment protocol, randomization was performed using a computer program (Microsoft Excel 2010). None of the participants withdrew from the study after randomization and each female gave written consent before treatment. The randomization procedure was performed through a computer program (Microsoft Excel 2010) that created a random table of numbers in which each number corresponded to the group A or B. After that, participants were allocated according to the corresponding number of their allocation code. A researcher was conducted the drawing procedures without informing participants and evaluators, to determine which was in group A or group B.

Women were randomized into two groups of equal size (n = 20). Group A received PEMF in addition to 12 sessions of pelvic floor muscle training and general advice conducted every other day, while group B received the same program but without PEMF.

The primary outcome measure was the strength of pelvic floor muscles as measured by perineometer. The secondary outcome measure was the severity of urinary incontinence as measured by the ISSI before and after 12 sessions of treatment.

To avoid a type II error, preliminary power analysis [power (1-$\alpha$ error P) = 0.90, $\alpha$ = 0.05, effect size = 1.05405] determined that a sample size of 40 (two groups of 20 subjects each) was appropriate for this study. The effect size was calculated according to an earlier pilot study on 12 subjects (6 in each group) that used perineometer measurement as a primary outcome. The power analysis was performed by G*Power 3.1.9.2 software (Heinrich-Heine-Universität Düsseldorf in Germany) using t-test family and the statistical test difference between two independent means (two groups).

Statistical analysis was performed using SPSS for windows, version 26 (SPSS, Inc., Chicago, IL, USA). Prior to final analysis, the data were screened for normality assumption and the incidence of extreme scores. This was done as a prerequisite to parametric calculations on the analysis of difference. Descriptive analysis using histograms with a normal distribution curve and normality testing using the Shapiro-Wilk test showed the data for age, BMI and perineometer in both groups was not normally distributed. The Mann-Whitney U test and the Wilcoxon Signed Rank Test were therefore used to compare variables of interest in the different test groups (between groups) and measuring periods (within a group), respectively, for each dependent variable.

Comparison of nominal variables between the two groups was done by Chi-square test, with the Alpha level set to 0.05.

The final statistical analysis included 40 patients, with 20 in group A (PEMF treatment) and 20 in group B. At baseline, there were no significant differences between the two groups with regard to age, BMI, level of education, parity or occupation (Table 1).

Mixed incontinence is a critical healthcare issue with important personal, family and economic impacts. Its incidence is likely to increase as the elderly population continues to increase in number. The incidence of mixed incontinence is currently one in three women [2, 16].

SUI is more likely to occur after childbirth, especially if the baby is delivered vaginally. This is because the pelvic floor muscles can expand, weaken, or be injured, causing a lack of bladder/urethral support and bladder leakage [13].

Surgical repair of SUI may not be successful and could lead to complications such as infection and delayed wound healing. PEMF on the other hand is a noninvasive technique that can be used to manage such conditions. Patients do not need to undress for this procedure because the magnetic field goes through clothing. PEMF has previously been investigated for its ability to activate striated urethral sphincters and to cause a short-term decrease in the activity of neurogenic and idiopathic detrusor. Magnetic stimulation has traditionally been used as a single pulse or else in a repetitive manner if there is overheating of the coil [17].

PEMF is a type of electromagnetic field at the lower end of the electromagnetic spectrum that has frequencies ranging from 6 to 500 Hz. It emits non-ionizing radiation that directs a sequence of magnetic pulses through the medium of biological tissue, each causing a tiny electrical signal that encourages cellular healing. The radiation has a non-thermal effect on biological targets [18].

PEMF was approved for use by the United States Food and Drug Administration in 1998. The pulsed magnetic fields are generated by an electrified coil that induces flow of ions to form eddy currents when the excitable tissue is exposed to a magnetic field with sufficient intensity. Therefore, magnetic stimulation depolarizes the motor nerve to produce an action potential that ultimately triggers muscle contractions [19].

Shamliyan et al. [20] reported that a magnetic field could activate the pudendal nerve and thus stimulate pelvic floor muscles. The stimulation of these muscles can improve urethral closure and thus treat SUI.

Ross et al. [21] reported that PEMF can penetrate deep into tissues and act at the cellular level, inducing changes to cell proliferation and differentiation, DNA synthesis and RNA transcription, protein phosphorylation, microvesicle motility, ATP production, activation of antioxidant enzyme and hormone secretion.

PEMF has proven to be a viable therapeutic option for UUI and/or SUI, as well as for overactive bladder syndrome caused by neurogenic detrusor overactivity. Its non-invasive nature and exceptional safety and tolerability are the main benefits of this treatment. PEMF can also affect local blood flow and other parameters, with nerves thought to be particularly sensitive. Stimulation by PEMF activates the efferent neurons and motor endplates of the pelvic floor muscle, resulting in increased muscular strength and endurance. It may also affect the rate at which the somatic nerve fires, thus impacting the pelvic musculature and sphincter tone [22].

PEMF has been shown to decrease the micturition reflex by inhibiting detrusor activity through multiple pathways. As the afferent branches of limb muscle nerves prevent voiding during fight-or-flight responses and afferent anorectal nerve branches prevent voiding during defecation, increased activity of the urethral sphincter induces relaxation of the detrusor muscle in response to bladder filling. The activity of the sympathetic nervous system also increases in response to bladder filling [23].

Fergany et al. [24] published a preliminary investigation in 1996 that found PEMF might decrease unstable detrusor contractions in women. PEMF could thus be a more acceptable and convenient form of neuromodulation and a more efficient method of electrical stimulation via implanted electrodes.

PEMF therapies can therefore be used to treat the source of dysfunction in a noninvasive, safe, and simple way [25].

The results of the present study agree with those of Bakar et al. [26] who showed that urinary symptoms and incontinence times improved after PEMF therapy. Yamanishi et al. [27] also reported that magnetic stimulation of the pelvic floor twice per week for 5 weeks significantly decreased stress urinary incontinence.

However, the results of the present study do not concur with those of Petra et al. [28] who reported that magnetic innervation therapy did not improve pelvic floor function.

The results of this study also agree with those of Bo et al. [29] and Hay et al. [30] who reported that pelvic floor training is an effective method for the treatment of SUI. In these studies, women were taught to pre-contract their pelvic floor muscles before and during increases in intra-abdominal pressure in order to avoid loss of urine, as well as to perform strengthening exercises. Soni et al. [31] also demonstrated that kegel exercise training increased the strength and endurance of pelvic floor muscles.

PEMF is an effective therapeutic modality for the treatment of women with mixed incontinence. Moreover, it is a painless and non-invasive method. The addition of PEMF to pelvic floor exercises is also recommended for the strengthening of pelvic floor muscles.

EAE and MAM collected the data design the procedure, and LAF wrote the manuscript. All authors shared in editing and editorial comments in the manuscript. All authors read and approved the final manuscript.

This study was approved by the ethics committee of the Faculty of Physical Therapy, KFS El Sheikh University (No.: P.T./WH/7/2021/11).

Authors would like to thank the physician Magdy El Said specialist in obstetrics and Gynecology who referred and diagnosed all cases who participated in the study, and physicians in Kafrelsheikh University Outpatient Clinic of women health.

This research received no external funding.

The authors declare no conflict of interest.