Correlation between Mediterranean diet, bowel function, and isolated posterior vaginal defect: A cross- sectional study

Objective: Isolated posterior prolapse is a unique entity that was previously linked to chronic obstructive defecation. Our objective is to evaluate the relationship of low adherence to a Mediterranean diet (LAMD) with bowel dysfunction and isolated posterior compartment prolapse (IPCP). Methods: This multicenter, cross- sectional study compared the dietary outcomes (validated Mediterranean diet [MD] questionnaire) of women who underwent pelvic organ prolapse (POP) repair surgery between August 2020 and October 2021. Results: Among 204 patients enrolled, 108 (52.9%) patients adhered to the MD and 96 (47.0%) did not. Among the LAMD patients, increased symptoms of constipation ( P = 0.047) and higher body mass index ( P < 0.001) were more prevalent. Surgical repairs of the posterior compartment, combined ( P = 0.033) and isolated ( P = 0.021), were more prevalent in the LAMD group. Prolapse of all compartments except the apical compartment was found to be more prevalent in the LAMD group. Multivariate logistic regression analysis was found to be significant as a protective factor for the primary outcome (IPCP). Conclusion: Low adherence to a Mediterranean diet displays a higher prevalence of posterior vaginal defects, both isolated and combined. Hence, we can conclude that LAMD and subsequent bowel dysfunction are significant contributory factors to the prolapse of the posterior vaginal compartment.

been shown that prolapse of the anterior compartment is the most common type, being two times more prevalent than posterior prolapse and three times more prevalent than apical prolapse. 9 It has been determined that posterior wall prolapse has a different prevalence among different countries, with a significantly higher prevalence (48.2%) in Ireland than in other Western countries, such as the United States of America (38.4%) and Germany (33.2%). 10 The reasons behind this remain unclear in the current literature; however, these associations seem to be linked [11][12][13] and are increasingly studied worldwide, as global diets are evolving. The traditional Mediterranean diet, characterized, in particular, by a high consumption of vegetables and olive oil and moderate consumption of protein, is inversely associated with obesity risk or weight gain [14][15][16] and is well known to improve bowel function. 17 We therefore aimed to determine whether there is an association between low adherence to a Mediterranean diet (LAMD) and impaired bowel function as a potential contributing factor to isolated posterior compartment prolapse (IPCP).

| MATERIAL S AND ME THODS
This multicenter, cross-sectional study assessed the correlation between the Mediterranean diet, bowel function and isolated posterior prolapse. Participants' data were collected from two tertiary hospital centers in Ireland and Israel. All patients between August 2020 and October 2021 who underwent a surgical pelvic floor repair were recruited.

| Data collection
Data were retrieved from the Urogynecology Department of Cork Maternity Hospital (Ireland) and Meir Medical Center (Israel). Both are tertiary university-affiliated hospitals. Demographics, and preoperative and operative findings were obtained from electronic medical records. The following variables were collected from electronic medical records: age, country of origin, current smoking, parity, body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters), mode of delivery, previous surgical records, incontinence type prior to the surgery, and type of operation.
The simplified POP-Q scale, 18 which ranges from 1 (no prolapse) to 4 (complete procidentia), was used for the POP assessment.
All patients were followed up during the postoperative examination meeting with the validated Mediterranean diet adherence questionnaire 19 and the Patient Assessment of Constipation Symptom Questionnaire (PAC-SYM). 11 Patients were asked to refer their answers to the questionnaires to the past 12 months.
The Mediterranean diet adherence questionnaire (Supplement 1) is composed of 14 questions that assess the dietary pattern associated with the Mediterranean diet (MD). This diet is characterized by the daily consumption of olive oil, whole grains, fruits, and vegetables, weekly consumption of legumes, nuts, fish, and wine in moderation, and a moderate intake of lean fresh meat and dairy products. 20 A sum total of 5 or below refers to lower adherence to the MD. 21,22 The PAC-SYM (Supplement 2) assesses the symptoms of constipation as experienced by the patient over time. The PAC-SYM consists of 12 items in three subscales: stool symptoms (hardness of stool, size of stool, straining, inability to pass stool), rectal symptoms (burning, pain, bleeding, incomplete bowel movement), and abdominal symptoms (discomfort, pain, bloating, cramps). Item values are scored from 0 to 4, with 4 indicating the worst symptom severity. 11 Impaired bowel function was defined as a score of 0.35 or greater (corresponding to moderate symptom severity). 23 The primary outcome measure was to assess whether LAMD is a risk factor for IPCP. Secondary outcome measures included the relation of bowel function (defined from the questionnaire) to the type of diet and other risk factors for poste's rior compartment prolapse.

| Ethics approval
The study was approved by the Institutional Ethics Committee (project number MMC-21-0232 in September 2019). Institutional review board approval was obtained for all institutions participating in the study. All patients gave informed consent for their participation in this study.

| Statistical analysis
Nominal data were described as numbers and percentages.
Continuous variables with normal distribution were presented as mean ± and standard deviation (SD) or median and range whereas those without normal distribution were presented as median and interquartile range (IQR). Quantitative data were analyzed using the χ 2 or Fisher exact test. Continuous variables were compared between groups using t-test or Mann-Whitney non-parametric test, as appropriate. A P-value < 0.05 was considered statistically significant. Relative risk (RR) was calculated using the Fisher exact probability statistic, the maximum-likelihood ratio χ 2 , or Pearson χ 2 .
Multivariable logistic regression and adjusted odds ratios (aOR) were calculated to examine the correlation between diet to other factors.
Data were analyzed using SPSS version 26 (IBM Corp).

| Sample size calculation
The sample size was calculated using the Sample Size Calculator (www.clinc alc.com). As reported earlier in the literature, 24 the rate of isolated posterior repair is 7%. We calculated the power analysis based on the assumption that the isolated posterior repair rate in the LAMD group will be compared with the prevalence of a combined posterior repair rate in the general population (21%). 24 The sample size calculation indicated that 95 participants were needed for each arm of the study, using an Alfa of 0.05 and 80% power.

| RE SULTS
Overall, 204 patients were included in this study. A flowchart of patient recruitment and participation is shown in Figure 1 Table 2.
The correlation between the Mediterranean diet and the prolapse stage among the different compartments is summarized in Table 3.

| Multivariable logistic regression
Multivariate logistic regression analysis for the association between isolated posterior compartment repair and MD is presented in Table 4.  The MD was found to be significant as a protective factor for the primary outcome (IPCP). Impaired bowel function and obesity failed to be a risk factor for IPCP.

| DISCUSS ION
The major finding of our study is that there is a direct correlation between LAMD and bowel dysfunction and IPCP. Furthermore, combined posterior compartment prolapse, obesity, and impaired bowel function (PAC-SYM questionnaire) were more prevalent in the LAMD group. Multivariable regression found the MD to be a protective factor for IPCP surgical repair.
The MD is a complex set of eating habits adopted by people living in the Mediterranean region. It includes a high consumption of olive oil and fiber-rich foods, and a low consumption of meat or meat-based products. 25 It has previously been shown that MD is associated with a wide range of benefits for health function 26-28 and subsequently for digestion and bowel function. 29 Mancini et al. 30 show that higher adherence to the MD has been associated with increased stool frequency and moisture. Our study finding is in agree- Abbreviations: aOR, adjusted odds ratio; CI, confidence interval. similar among women (OR 0.69, 95% CI 0.54-0.89) and men (OR 0.68, 95% CI 0.53-0.89). 15 Obesity was significantly higher in the LAMD group evaluated in our study (P = 0.002), although a subanalysis found that only obesity classes II and III were more significant in the LAMD group (P = 0.045 and P = 0.047, respectively).
Although research on the associations between chronic constipation and POP in women has increased in recent years, there has yet to be a conclusive finding as to the direction of this causal relationship.
It is unclear whether chronic constipation and straining predispose an individual to POP 33  The present study found a link between LAMD and impaired bowel function (P = 0.047). Soligo et al. 35 determined that anterior prolapse was less common than posterior prolapse in constipated women. This finding is similar to that of Weber et al., 13 in which women with posterior prolapse had a high degree of bother related to bowel function. However, this is contradictory to the findings of Arya et al., 8 where there was no significant correlation between constipation and the type of prolapse (anterior or posterior) seen in participants.
As previously mentioned, the relationship between a specific diet and posterior compartment prolapse is not well described in the literature. The anatomical changes related to diet type may be biased by the weight of the patient, which might be the cause of the prolapse, or the diet itself, which influenced the weight or the bowel function as a causal relationship to the prolapse. An important finding of the present study is that we did note an association between diet type and the type of prolapse. These results help to support the significant correlations between IPCP and LAMD.
In this multivariable regression model, MD was the only significant protective risk factor for IPCP. Given the significant difference between the groups related to BMI, the association of LAMD with a higher incidence of posterior prolapse/prolapse repair is likely a reflection of the pure relationship between the two and not a confounding effect of the known factor such as obesity, as this was insignificant in this model. Although low bowel function and obesity were not significant risk factors for IPCP, this finding is probably related to the small cohort size. It is known that there is a causative relationship among diet, bowel function, and posterior compartment prolapse, as previously described. 8,12,13,34

| Strengths and limitations
The strengths of this study are that it is the first to compare MD with the type of prolapse and correlate it to bowel function. In addition, it was powered to answer the research question. This study was performed at two academic institutions from two areas with differing dietary habits. This wide range of population strengthens the comparisons between the study groups.
This study is not without limitations. We only included patients who underwent a surgical procedure, excluding many others who managed their prolapse by conservative means or did not consent to surgery. Additionally, it is difficult to assess the duration of the patients' diet and how this may have influenced the prolapse compartment from this data. In addition, it is important to note that other variables are probably connected to defecation disorders, such as physical and sports activities, 37 and their possible problems with the spine. However, as both demographic groups were equally distributed, we believe that diet plays a stronger part in the formation of posterior compartment disorder due to its continuous impact on bowel function.

| CON CLUS IONS
Given the increasing prevalence of isolated posterior prolapse in the LAMD group, the data here help to advance our understanding of POP with the MD. In addition, understanding the correlations between impaired bowel function and LAMD will allow healthcare providers around the world to provide better assistance to individuals in preventing POP, especially in the context of IPCP. writing-review and editing. All authors approve the final version of the manuscript and its submission to journal.

FU N D I N G I N FO R M ATI O N
This study did not receive any funding.

CO N FLI C T O F I NTE R E S T S TATE M E NT
The authors have no conflicts of interest.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.