Vaginal disorders, including vulvovaginal candidiasis (VVC), bacterial vaginosis (BV), and genitourinary syndrome of menopause (GSM), are highly prevalent conditions that significantly affect women's quality of life and sexual health. These disorders are associated with inflammatory changes, vaginal dysbiosis, and symptoms such as pruritus, abnormal vaginal discharge, dryness, and dyspareunia. In this context, photobiomodulation has emerged as a noninvasive therapeutic approach with anti-inflammatory and tissue-repair properties. This study is a randomized clinical trial designed to compare the therapeutic response to blue LED photobiomodulation (401 ± 5 nm) delivered through home-based and outpatient treatment protocols. A total of 150 women aged 18 to 75 years with a diagnosis of GSM, BV, or VVC will be enrolled and randomly assigned to one of two treatment groups. Clinical and laboratory assessments will be performed before and after treatment. Participants will also complete the Female Sexual Function Index (FSFI) and the 36-Item Short Form Health Survey (SF-36). Outcomes will include the evaluation of gynecological signs and symptoms, sexual function, quality of life, treatment adherence, and adverse events. The anticipated risks are minimal and primarily related to potential discomfort during gynecological examinations and possible embarrassment associated with discussing sensitive health information. The study is expected to demonstrate that photobiomodulation may improve clinical and functional outcomes, representing a safe, non-hormonal therapeutic alternative for the management of vaginal disorders.

INTRODUCTION Vaginal dysfunctions represent a frequent problem in clinical practice, with high prevalence and a significant impact on women's quality of life and sexual health. Among the most common conditions are vulvovaginal candidiasis (VVC), bacterial vaginosis (BV), and genitourinary syndrome of menopause (GSM). It is estimated that approximately 75% of women will experience at least one episode of VVC during their lifetime, with 5% to 8% progressing to recurrent forms. BV affects approximately 23% to 29% of women of reproductive age, whereas GSM may affect up to 50% of postmenopausal women.

These conditions share alterations in vaginal homeostasis, including microbiome dysbiosis, local inflammation, and impairment of epithelial integrity, factors that are directly associated with the presence of symptoms such as vaginal discharge, pruritus, odor, vaginal dryness, and dyspareunia. Such manifestations have a substantial impact on sexual function, contributing to pain during sexual intercourse, reduced sexual desire, and impairment of interpersonal relationships. This impact is even more pronounced among women undergoing cancer treatment, particularly in cases of hormone-dependent neoplasms, in which the use of hormonal therapies is contraindicated. In these patients, GSM tends to be more severe and more difficult to manage, reinforcing the need for non-hormonal therapeutic alternatives.

In this context, photobiomodulation has been investigated as an innovative therapeutic approach capable of acting on multiple mechanisms involved in vaginal dysfunctions. Evidence demonstrates that this therapy promotes modulation of the inflammatory response, increased mitochondrial activity, stimulation of angiogenesis and collagen synthesis, in addition to immunomodulatory effects. Recent studies have reported clinical benefits of photobiomodulation in vulvovaginal conditions, including improvements in tissue trophism and associated symptoms.

Fungal and bacterial infections, such as vulvovaginal candidiasis and bacterial vaginosis, have shown increasing recurrence rates, making clinical management more complex and frequently associated with limited resolution of the clinical condition. Evidence suggests that photobiomodulation may act as an adjuvant therapy, contributing to the modulation of the local inflammatory response and the improvement of tissue conditions. In GSM, photobiomodulation has demonstrated the potential to improve vascularization, epithelial thickness, and vaginal elasticity, representing a particularly relevant alternative for women with contraindications to hormone therapy, such as those in the post-cancer treatment setting.

Despite these promising findings, gaps remain regarding the standardization of therapeutic protocols and the comparison between different modalities of photobiomodulation delivery, particularly between home-based and outpatient protocols. In light of this scenario, the present study aims to compare the therapeutic response to photobiomodulation administered through home-based and outpatient protocols in the treatment of genitourinary syndrome of menopause, bacterial vaginosis, and vulvovaginal candidiasis.

HYPOTHESIS Photobiomodulation administered through a home-based protocol demonstrates clinical effectiveness comparable to that of photobiomodulation administered through an outpatient protocol in the treatment of genitourinary syndrome of menopause, bacterial vaginosis, and vulvovaginal candidiasis.

PRIMARY OBJECTIVE To compare the proportion of participants who achieve clinical improvement following LED photobiomodulation delivered through home-based and outpatient protocols for the treatment of genitourinary syndrome of menopause, bacterial vaginosis, and vulvovaginal candidiasis.

SECONDARY OBJECTIVES To evaluate the sexual function of women with genitourinary syndrome of menopause, bacterial vaginosis, or vulvovaginal candidiasis treated with photobiomodulation using the Female Sexual Function Index (FSFI); To assess the quality of life of women with genitourinary syndrome of menopause, bacterial vaginosis, or vulvovaginal candidiasis treated with photobiomodulation using the Short Form Health Survey (SF-36); To assess therapeutic adherence in the home-based and outpatient treatment modalities; To evaluate the occurrence of adverse events related to photobiomodulation. METHODOLOGY A comparative randomized clinical trial will be conducted involving 150 women aged 18 to 75 years with a confirmed diagnosis of genitourinary syndrome of menopause (GSM), bacterial vaginosis (BV), or vulvovaginal candidiasis (VVC), according to the specific clinical and laboratory assessment established for each condition.

Sample size calculation was performed separately for each vaginal dysfunction investigated, considering the clinical, pathophysiological, and therapeutic differences among GSM, BV, and VVC, although all conditions are included within a single randomized clinical trial. A significance level of 5% (α = 0.05), a statistical power of 90% (1-β = 0.90), a two-tailed test, and a 1:1 allocation ratio between the outpatient and home-based groups were adopted. Given the scarcity of previous studies directly comparing photobiomodulation administered in home-based and outpatient settings for the vaginal dysfunctions under investigation, a moderate-to-large effect size (d = 0.7) was assumed. Based on these parameters, the minimum required sample size was estimated at 44 participants for each pathology investigated, comprising 22 participants in each therapeutic group. Considering a potential attrition rate of 10%, the sample size was increased to 50 participants per pathology, resulting in a total sample of 150 participants.

Pregnant women; women using pacemakers; women with a diagnosis or suspicion of active gynecological malignancies; women with neurological or psychiatric disorders; women presenting cognitive impairment that compromises understanding of the study instructions; and, in cases of BV and VVC, women who have used antibiotics, antifungal agents, corticosteroids, or vaginal creams within the 30 days preceding study inclusion will be excluded. Participants with suspected or confirmed vulvovaginitis not contemplated in this study will also be excluded.

Participants will be recruited through spontaneous demand and referrals from gynecology services in the city of Salvador, Bahia. The study will be conducted at the Patrícia Lordelo Institute (IPL). All participants will sign the Informed Consent Form prior to undergoing any study-related procedures.

Initially, participants will undergo the collection of sociodemographic and clinical data, including age, educational level, monthly income, marital status, body mass index, presence of comorbidities, medication use, and gynecological history.

Subsequently, a standardized gynecological assessment will be performed in a private setting. In suspected cases of BV and VVC, clinical examination, vaginal pH assessment, fresh wet-mount cytology, and collection of vaginal secretions for laboratory analysis will be performed. Participants with suspected GSM will be clinically evaluated according to the characteristic signs and symptoms of the syndrome. Participants presenting other gynecological conditions incompatible with the diagnostic criteria will be excluded and referred for appropriate treatment.

Following diagnostic confirmation, participants will be randomized to one of two treatment groups: the outpatient group or the home-based group. Randomization will be performed using an electronically generated random numerical sequence through the Random.org platform.

For participants with GSM, a photobiomodulation protocol involving LED application for 8 minutes, three times per week, totaling 24 sessions, will be used. For participants with BV or VVC, the protocol will consist of 15-minute applications, twice weekly, totaling 8 sessions. Therapeutic parameters will be identical in both the home-based and outpatient groups, differing only with regard to the setting in which the intervention is administered.

In the outpatient group, applications will be performed at the Patrícia Lordelo Institute by a trained healthcare professional. In the home-based group, participants will receive standardized training on device use, safety instructions, and educational materials to perform the treatment at home.

Throughout the treatment period, participants will be monitored to assess therapeutic adherence, clinical progression, and the occurrence of adverse events.

Upon completion of the therapeutic protocol, all participants will undergo clinical and laboratory reassessment. Gynecological signs and symptoms will be re-evaluated, and previously performed laboratory examinations will be repeated, including vaginal pH assessment, fresh wet-mount cytology, and microbiological analysis, when applicable.

Assessments will be conducted at five time points: baseline (before treatment initiation), immediately after completion of the therapeutic protocol, and at 30, 60, and 90 days following treatment completion.

The clinical signs assessed will include hyperemia, edema, leukorrhea, and fissures, classified during gynecological examination as either present or absent. Results will be expressed as the proportion of participants presenting each clinical sign (%).

Symptoms reported by participants will include pruritus, burning sensation, pain, vaginal dryness, and dyspareunia. Each symptom will initially be classified as present or absent. During subsequent assessments, the clinical progression of each symptom will be classified using a three-point ordinal Likert scale categorized as improved, unchanged, or worsened compared with baseline assessment.

For analytical purposes, clinical improvement will be defined as the complete resolution or reduction of at least one sign or symptom present at the initial assessment, without worsening of any other assessed sign or symptom. This variable will be expressed as the proportion of participants demonstrating clinical improvement (%).

Among participants diagnosed with bacterial vaginosis or vulvovaginal candidiasis, follow-up laboratory results will be classified as either presence or absence of the investigated condition according to the previously established diagnostic criteria. Microbiological resolution will be expressed as the proportion of participants without laboratory evidence of infection (%).

Vaginal pH will be measured using an appropriate reagent strip and expressed in pH units.

In addition to clinical aspects, potential effects of the intervention on participants' sexual function will be evaluated using the Female Sexual Function Index (FSFI). The FSFI consists of 19 questions distributed across six domains (desire, arousal, lubrication, orgasm, satisfaction, and pain), with a total score ranging from 2 to 36 points. Scores equal to or lower than 26.55 will be considered indicative of female sexual dysfunction. The unit of measurement will be the total questionnaire score.

Quality of life will also be assessed using the Short Form Health Survey (SF-36), which comprises eight domains related to physical and mental health. Scores range from 0 to 100 points, with higher values indicating better quality of life. The unit of measurement will be the total questionnaire score.

Therapeutic adherence will be calculated as the proportion of sessions effectively completed relative to the total number of sessions prescribed for each participant. The unit of measurement will be expressed as adherence percentage (%).

Adverse events related to photobiomodulation will be monitored throughout the entire follow-up period, from the first treatment session until 90 days after treatment completion. The unit of measurement will be the number of participants experiencing at least one treatment-related adverse event.

PRIMARY OUTCOME Clinical improvement following LED photobiomodulation. Clinical improvement will be assessed by the proportion of participants who demonstrate complete resolution or reduction of at least one vaginal sign or symptom present at the initial assessment, without worsening of any other evaluated sign or symptom.

The clinical signs evaluated will include hyperemia, edema, leukorrhea, and fissures, classified as either present or absent during the gynecological examination. The symptoms evaluated will include pruritus, burning sensation, pain, vaginal dryness, and dyspareunia. The progression of each symptom will be classified using a three-point Likert scale (improved, unchanged, or worsened) relative to the baseline assessment.

Unit of measurement: proportion of participants with clinical improvement (%). Assessment time points: baseline, immediately after completion of treatment, and at 30, 60, and 90 days following completion of the therapeutic protocol.

SECONDARY OUTCOMES

1. Improvement in gynecological clinical signs To assess the presence of hyperemia, edema, leukorrhea, and fissures through a standardized gynecological examination.

   Unit of measurement: proportion of participants presenting each clinical sign (%).

   Assessment time points: baseline, immediately after completion of treatment, and at 30, 60, and 90 days following completion of the therapeutic protocol.

2. Progression of gynecological symptoms To assess the progression of symptoms including pruritus, burning sensation, pain, vaginal dryness, and dyspareunia.

   Unit of measurement: three-point Likert scale (improved, unchanged, or worsened).

   Assessment time points: baseline, immediately after completion of treatment, and at 30, 60, and 90 days following completion of the therapeutic protocol.

3. Microbiological resolution Among participants diagnosed with bacterial vaginosis or vulvovaginal candidiasis, the absence of the condition will be evaluated through the previously established follow-up laboratory examinations.

   Unit of measurement: proportion of participants without laboratory evidence of infection (%).

   Assessment time points: immediately after completion of treatment and at 30, 60, and 90 days following completion of the therapeutic protocol.

4. Vaginal pH To assess changes in vaginal pH throughout the follow-up period. Unit of measurement: pH units. Assessment time points: baseline, immediately after completion of treatment, and at 30, 60, and 90 days following completion of the therapeutic protocol.

5. Sexual function To assess sexual function using the Female Sexual Function Index (FSFI), which consists of 19 questions distributed across six domains.

   Unit of measurement: total FSFI score (2-36 points). Scores ≤26.55 will be considered indicative of female sexual dysfunction.

   Assessment time points: baseline, immediately after completion of treatment, and at 30, 60, and 90 days following completion of the therapeutic protocol.

6. Quality of life To assess quality of life using the Short Form Health Survey (SF-36). Unit of measurement: total SF-36 score (0-100 points), with higher scores indicating better quality of life.

   Assessment time points: baseline, immediately after completion of treatment, and at 30, 60, and 90 days following completion of the therapeutic protocol.

7. Therapeutic adherence To assess adherence to treatment in the outpatient and home-based modalities. Unit of measurement: percentage of completed sessions relative to the total number of prescribed sessions (%).

   Assessment time points: throughout the entire treatment period.

8. Adverse events To assess the occurrence of adverse events related to photobiomodulation. Unit of measurement: number of participants experiencing at least one treatment-related adverse event.

Assessment time points: from the first treatment session until 90 days after completion of treatment

Inclusion Criteria:

• Women aged 18 to 75 years.
• Clinical and/or laboratory-confirmed diagnosis of Genitourinary Syndrome of - Menopause (GSM), Bacterial Vaginosis (BV), or Vulvovaginal Candidiasis (VVC), according to established diagnostic criteria.
• Ability to understand study procedures and provide written informed consent.
• Willingness to comply with study procedures and follow-up assessments.

Exclusion Criteria:

• Pregnancy.
• Use of a pacemaker or other implanted electronic medical device.
• Active gynecological malignancy or suspicion of gynecological cancer.
• Neurological and/or psychiatric disorders associated with cognitive impairment that may interfere with understanding study procedures.
• Use of antibiotics, antifungal agents, corticosteroids, or vaginal creams within the previous 30 days in participants diagnosed with BV and/or VVC.
• Suspected or confirmed vulvovaginal conditions other than GSM, BV, or VVC.
• Any condition deemed by the investigators to compromise participant safety or interfere with study participation.

Individual participant data (IPD) will not be made publicly available in order to protect participant confidentiality and privacy. Data sharing requests may be considered on a case-by-case basis, subject to ethical approval and applicable regulations.