Background

MS is one of the main neurological disorders associated with neuron demyelination and axonal loss [1]. This pathology is the primary cause of progressive neurological disability in young adults [2]. Genetic alterations and environmental factors have synergistic roles in MS development [3]. The prevalence of MS is estimated at 28,000,000 individuals by 2020 [4], which is more common in women than men [1]. Mostly, the incidence of MS appears in the age of 20–30 [5]. FSD is defined as dyspareunia, lack of sexual desire, disturbance in arousal, and the absence of orgasm [6].

Sexual function is often impaired following the presence of neurological disorders such as MS [2]. FSD is a widespread sexual problem with the prevalence of 25.8–67%, globally [7].

Sexual dysfunction is a problem that can happen during any phase of the sexual response cycle. This cycle traditionally includes excitement, plateau, orgasm, and resolution [3,4,5,6,7,8]. This dysfunction generally is classified into four categories: lack of sexual desire or interest in sex, inability to become physically aroused or excited during sexual activity, delay or absence of orgasm, and pain during intercourse [3,4,5,6,7,8].

There are a number of causes of sexual dysfunction. Physical causes include urological infections or cancer, diabetes, cardiovascular disease, high blood pressure, high cholesterol, hormonal imbalances, alcoholism, and neurological disorders, and psychological causes include depression, stress, anxiety self-esteem or body image issues, and the effects of past sexual trauma, such as rape, molestation, or a negative sexual experience [3,4,5,6,7,8].

Patients with MS have different complications such as depression, anxiety, and sexual irregularities [1]. Among these, SD is one of the most common [8], affecting more than 74% of women with MS [9]. This complication can also lead to various social problems, such as marriage [10].

Some studies revealed that the SD could also have a more significant impact on individuals’ morals and quality of life. However, while 83% of women with MS have the tendency to talk about the disease, 63–94% of which deny visiting doctor [2]. Frequent sexual changes reported by women with MS included partial or total loss of libido, vaginal dryness, lack of vaginal stimulation, decreased status of orgasm, and the presence of unpleasant feelings in the genital system [5].

The exact causes of SD in MS patients are unclear; however, it is estimated that various interfering physical, psychological, and social factors caused by MS can eventually lead to the occurrence of SD [11]. Also, several studies revealed that the SD is associated with the neural lesions in the central nervous system (CNS) responsible for sexual behaviors. Some symptoms related to MS, including urinary and digestive problems, fatigue, neurological disorders, and spasticity, can also indirectly affect the sexual activity in MS patients [12, 13].

According to the high rate of MS incidence, especially in females, along with the crucial role of SD in women, the authors of this systematic review and meta-analysis study aimed to investigate the global prevalence of SD in women with MS. We believe that the findings of this present study can guide the legislators of the field of health sciences to manage the MS patients.

Methods

Initial systematic searching was conducted in July 2022 using PubMed, Web of Science, Scopus, ScienceDirect, and Embase databases. For systematic searching, the main keywords of “Female Sexual Dysfunction,” “FSD,” “Multiple Sclerosis,” and “MS” were also hired. For the preservation of comprehensive searching protocol, no time restriction was considered, and to increase the number of collected articles, the citations of the included papers along with final screening using Google Scholar search engine were also hired. All gathered data were transferred to the Information Management Software (EndNote, v. × 8).

Inclusion and exclusion criteria

English studies reporting the prevalence of SD in women with MS and English investigations with available full texts or sufficient data for meta-analysis (such as sample size and MS prevalence) were included in this systematic review and meta-analysis. Besides, other assessments such as case reports and case series, reviews, and the studies with insufficient data or provided in non-English languages were totally excluded.

Study selection

Investigations were included in this study based on the PRISMA guideline. First, duplicated studies were removed and then followed by primary screening according to the titles and abstracts. In this stage, the irrelevant papers were excluded based on the inclusion and exclusion criteria. Full texts were prepared and evaluated, and other non-eligible papers were also removed from the investigation. To avoid potential bias during the assessments, all the abovementioned stages were conducted by two researchers independently. Also, following detection of inconsistency among the findings, the third author (corresponding author) was responsible for disagreement management.

Quality evaluation of the included papers

The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) as an observational-associated checklist was hired to evaluate the quality of articles. Different parts of the manuscript (title, abstract, introduction, methods, results, and discussion) were assessed by the STROBE checklist using 32 different items of title, problem statement, study objectives, type of study, statistical population, sampling method, determination of appropriate sample size, variables and procedures definition, data collection tools, statistical analysis methods, and findings. The STROBE scoring ≥ 16 was considered good and moderate methodological quality papers, and articles < 16 were poor and excluded from the study.

Data extraction

Two authors conducted this procedure based on a pre-designed checklist including first author’s name, publication year, study location, sample size, age group of women, SD prevalence in women with MS, and study tools.

Statistical analysis

Following data extraction, the CMA software (Comprehensive Meta-Analysis, v.2) was used for data analysis. The heterogeneity of the studies was assessed through the I2 test, and the Egger test and the Funnel plot were used to check the publication bias at a significance level of 0.05.

Results

In this systematic review and meta-analysis, the global prevalence of SD in women with MS was assessed. Following systematic and manual searching, 292 and 10 papers were selected, respectively. Using Information Management Software (EndNote × 8), 96 duplicated articles were detected and removed. Following title and abstract assessment, 139 irrelevant articles were excluded in the screening stage. Through the deep investigation of full texts, 36 papers and other poor studies were ignored, and finally, 14 investigations were included for meta-analysis assessment (Fig. 1) (Table 1).

Fig. 1
figure 1

The PRISMA flowchart (2009) represents the stages of study screening in this systematic review and meta-analysis

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Table 1 Characteristics of included studies of the prevalence of sexual dysfunction in women with MS
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Primary assessments revealed that all included studies were cross-sectional and mostly conducted in Asia. According to Table 1, the highest prevalence of FSD (82.5%) was related to the study of Lew-Starowicz et al. conducted by SFQ28 and clinimetric scales with the age group > 18 years [22]. Besides, the lowest prevalence (27.9%) of FSD was associated with the study of Bartnik et al. conducted by the FSFI and EDSS questionnaires with a mean age of 32.3 ± 7.22 [17]. Also, the overall prevalence of SD in women MS patients was 62.5% (95% CI 53.9–70.5). In 9 studies, the scales of FSFI and EDSS were used together, and in other remaining papers, these scales were hired individually or along with other questionnaires. Following an assessment of studies with the sample size of 2115 women with MS, the heterogeneity was found I2 = 92.6%; thus, the random effect model was used for meta-analysis. The overall prevalence of SD in women with MS was reported 62.5% (95% CI 53.9–70.5) (Fig. 2). Besides, the results of the Egger test representing the publication bias showed non-significant (p = 0.570) alteration (Fig. 3).

Fig. 2
figure 2

The forest plot represents the overall prevalence of sexual dysfunction in women with MS based on the random effect model

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Fig. 3
figure 3

Funnel plot representing distribution bias of included studies

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In order to investigate the interfering factor affecting the heterogeneity index, a meta-regression test was used for the sample size and year of the study publication. The results showed that by increasing the sample size and year of the study, the overall prevalence of SD was accelerated significantly (p < 0.05) (Figs. 4 and 5).

Fig. 4
figure 4

Metaregression represents the effect of sample size on the overall prevalence of sexual dysfunction in women with MS

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Fig. 5
figure 5

Metaregression represents the effect of the year of the study on the overall prevalence of sexual dysfunction in women

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Discussion

In this systematic review and meta-analysis study, the authors aimed to report the global prevalence of SD in women with MS, which was found 62.5%. Also, the results showed that following increasing the sample size and the year of the study, the overall prevalence of SD in women with MS was accelerated. This finding showed that the FSD prevalence increases over the time.

SD is one of the most common complications of MS with considerable impacts on quality of life. Many studies reported a higher incidence of SD in patients with MS. In fact, MS is one of the most common causes of SD among patients with neurological disorders [26,27,28]. As mentioned previously, the overall prevalence of SD in women with MS was 62.5%. Although there are different findings representing the percentage of SD in MS women, the general results were consistent with this finding that MS patients contain SD complications [29,30,31]. Similar to the results of our study, in some other investigations, the SD was reported as a common complication among women with MS [14, 25, 32,33,34,35]. Other studies reporting the prevalence of SD in MS patients showed that 40–80% of women and 50–90% of men have sexual complaints or concerns [32, 35,36,37]. In the study of Hadjimichail et al. conducted on 107 MS patients, 29.9% of individuals experienced the SD symptoms (40.0% and 23.9% for males and females, respectively), while in the healthy population as the control group, this value was found 12.5% [38]. Probably, this difference can be associated with the small sample size. Konstantinidis et al. reported that 64.5% of Greek women with MS represented SD, along with high rates of depression (57.3%) and anxiety (58.1%) [39]. Also, Tzortzis et al. found this value 34.9% compared to the control group (21.31%) [25]. The results of these studies were consistent with the findings of the present investigation. Following an assessment of other reports, it is believed that women with MS have low living satisfaction levels according to sexual performance disorders [23, 40]. Orasanu et al. found that the severe FSD symptoms were positively correlated with the duration of MS and the high clinical score [41], which were similar to our findings. They also reported a high prevalence of SD (62.5%) in women with MS. In these studies, the alteration in sexual performance of women with MS was reported including decreased libido, vaginal lubrication, and decreased orgasm [26, 42]. A few studies have also investigated the relationship between neural demyelination in lesions and the prevalence of SD in MS patients concluding that the MS lesions were directly associated with SD incidence [12, 13, 43]. In this era, Barak et al. described the relationship between anorgasmia and the lesions in brainstem or corticospinal system in male and female patients with MS [43]. Zivadinov et al. and Zorzon et al. found a considerable relationship between SD and pontine lesions [12, 13]. Another study detected a relationship between right occipital lesions and arousal disorders or left insular lesions and decreased sexual lubrication [44]. Also, a significant relationship was found between MS lesions around the left temporal ventricle and visual communication areas, which can potentially endanger orgasm performance [45]. Besides, chronic diseases such as MS can lead to feelings of hopelessness, guilt, pain, and sexual disorders in patients with MS [46].

Due to the high global prevalence of MS, more updated investigations with a high sample size are needed, as the major limitation in the present study. Also, since the SD can be affected by various factors which were not considered in the included studies, the final results probably contained bias. The inclusion of English-based papers was also another limitation of this meta-analysis. In addition, several papers were excluded due to low quality or low sample size.

Conclusion

According to the results of the present study, the overall prevalence of SD in women with MS was found 62.5%. Thus, the results seem worthwhile for health policymakers to have more consideration of sexual dysfunction in women with MS. Deep attention to the sexual health of MS patients and sexual performance as a research priority is also suggested.