Fecal incontinence (FI) is defined as the uncontrolled passage of solid or liquid stool and affects approximately 14.4% of adults.1 Studies have shown that there are racial and ethnic differences in the clinical rates of FI. For example, several studies from the United States have shown that white adults are more likely to have FI than blacks.2,3 Additionally, another study suggested that Hispanics are more likely to have FI, and Asians are less likely, than either whites or blacks.1 It remains unclear why ethnicity affects rates of FI.

FI can result from numerous etiologies.4,5 Patients being evaluated for FI often undergo anorectal manometry (ARM) testing which has been shown to have good diagnostic accuracy.6,7 Measurements for ARM in healthy volunteers are known to vary based on several factors including age, gender, and parity.8

Additionally, studies suggest that there may be ethnic differences in normal-value measurements of healthy subjects between Western and Asian populations.9 For example, in a study of healthy Korean volunteers, women had lower anal resting and squeeze pressures than were reported in a Western population.10

As there are known ethnic differences in clinical FI rates and possible ethnic differences in healthy-value ARM measurements, this suggests that there may be ethnic differences in ARM measurements in patients with FI. As no studies have previously evaluated this, we sought to evaluate this by comparing the ARM parameters between 3 distinct ethnic groups from our diverse population with FI—Arab Israelis (AI), immigrants from the former Soviet Union (SU), and Jewish Israelis (JI).

Study Design

A retrospective study was performed using data from 2 tertiary medical centers (Shamir Medical Center and Nazareth Hospital EMMS), each of which serves a diverse, multi-ethnic population. The study was approved by the Ethics Committee (ASF-0159-21).

High-resolution anorectal manometry (HR-ARM) reports were reviewed for all patients referred for evaluation of FI between January 2014 and May 2021. Patients were referred by gastroenterologists, colorectal surgeons, gynecologists, or primary care physicians. Demographic data including age, gender, ethnicity, and parity were recorded. Additionally, data on smoking status, diabetes, and body mass index (BMI) was obtained by telephone interview with the subjects. Obesity was defined as a BMI > 30.

All subjects were included in the study if FI was the main indication on their referral for ARM. This was the definition of FI used in the study as no further data on the quality and severity of their FI was available. No specific prior medical or surgical history was used as exclusion criteria. Subjects under the age of 18 were excluded. If a subject underwent multiple studies during the study period, only the first (index) study was included. Studies in which the ARM data was not interpretable were excluded.

High-resolution Anorectal Manometry Protocol and Interpretation via the London Classification

At each center, HR-ARM was performed using the same system (ManoScanAR, Medtronic, Minneapolis, MN, USA). HR-ARM studies were performed according to the standard protocol,8 and the results were recorded. A study of healthy subjects from the Mayo Clinic using the same HR-ARM system was chosen to use for its normal values.11 The HR-ARM values from our study subjects were compared to these normal values according to gender. Any value outside of the 10-90% normal range was considered abnormal. The normal values used in this study can be found in Supplementary Table. Using these values and the London classification definition, dyssynergia was defined as a failure of coordinated anal relaxation during push (< 20% relaxation of the anal sphincter).8

These findings were then interpreted according to the London classification,8 with the following exceptions. As the balloon expulsion test was not regularly performed at our institutions, it was not included. For measurements of anal tone, a 20-second measurement was used for the mean maximum pressure as was used by Oblizajek et al,11 as opposed to a 60-second measurement recommended by the London classification. Also for anal squeeze pressures, three 20-second measurements were recorded and the greatest value was used,11 as opposed to the 5-second measurements recommended by the London classification.8 Finally, the length of the high pressure zone, which may impact FI, was included in this study even though it is not part of the London classification. Any study in which no abnormalities were identified in any of the 4 areas of the London classification was considered a “normal exam.”

Ethnic Groups of Subjects

The HR-ARM variables were compared between subjects from 3 different ethnic groups. Data on residents’ ethnicity, religion, and country of birth are collected by the government and available via the medical centers’ electronic records.

The first group consisted of AI. The second group consisted of immigrants from the former SU, many of whom speak Russian and immigrated to Israel in the 1990’s after the fall of the Soviet Union. Finally, the third group consisted of all other JI. This was likely the most ethnically diverse group as it included subjects of both Ashkenazi (European) and Sephardic (Middle Eastern) heritage, including both immigrants and native-born Israelis. Studies evaluating these specific ethnic groups are found throughout the medical literature, including studies such as this comparing all 3 of these groups to each other.12-14

Statistical Methods

Categorical variables were summarized as frequency and percentage. Age, parity, and BMI were evaluated for normal distribution using histogram and since they were skewed, they were reported as median and interquartile range (IQR). T squared test and Fisher’s exact test were applied to compare categorical variables between the ethnic groups. Kruskal-Wallis test and Mann–Whitney U test were used to compare age and parity between the groups. Multiple logistic regression was used to study the association between ethnicity and the study outcomes while controlling for age, gender, smoking, diabetes, and obesity. In a further analysis, only women were included in the multivariable regression, and age and parity were considered as confounders.

All statistical tests were two-sided and P < 0.05 was considered as statistically significant. SPSS software was used for all statistical analysis (IBM SPSS Statistics for Windows, version 26; 2019; IBM Corp., Armnok, NY, USA).

Overall Study Population

A total of 1022 HR-ARM studies were performed during the study period, of which 479 (46.9%) were performed for the evaluation of FI and included in the study (Figure). No studies were excluded due to uninterpretable data. Demographic data of the study population can be found in Table 1. The median age was 67 years old (IQR, 59-74) with 76% being women. Of the women, 90.4% were parous with a median number of children of 3 (IQR, 2-4).

Table 1 . Demographic Data of the Study Population

Demographic variables	All patients N = 479	Arab Israeli n = 87 (18.2%)	Former Soviet Union n = 76 (15.9%)	Jewish Israeli n = 316 (66.0%)	P-value
Age (yr)	67 (59-74)	64 (53-70)	68 (60.5-74.75)	68 (60-75)	0.014
Age < 50 (yr)	60 (12.5)	16 (18.4)	7 (9.2)	37 (11.7)	0.153
Female gender	364 (76.0)	71 (81.6)	59 (77.6)	234 (74.1)	0.326
Parity amongst females (n = 364)	329 (90.4)	68 (95.8)	43 (72.9)	218 (93.2)	< 0.001
Number of children per woman	3 (2-4)	4 (3-6)	2 (0-3)	3 (2-4)	< 0.001
Current smoker (n = 475)	76 (16.0)	30 (35.7)	4 (5.3)	42 (13.3)	< 0.001
Diabetes (n = 476)	174 (36.6)	47 (55.3)	30 (39.5)	97 (30.8)	< 0.001
Body mass index (n = 454)	26.7 (23.3-30.1)	28.0 (24.3-34.0)	27.9 (24.8-30.9)	26.0 (23.1-29.4)	< 0.001
Obesity (n = 454)	120 (26.4)	36 (43.9)	22 (31.9)	62 (20.5)	< 0.001

Data are presented as median (interquartile range [IQR]) or n (%).

P < 0.05 was considered statistically significant.

Figure 1. Flow chart of the study population. HR-ARM, high-resolution anorectal manometry.

Demographic Differences Between the Ethnic Groups

Of the study population, 87 (18.2%) were AI subjects, 76 (15.9%) were in the SU group, and 316 (66.0%) were JI subjects. These percentages are similar to each groups’ representation within the overall Israeli population.15,16 No significant differences were noted between the groups in terms of gender, but other demographic differences were noted. The median age of the AI group was significantly younger than the other 2 groups, although there was no difference in the percentage of subjects under the age of 50. There were also differences in terms of parity. Less women in the former SU group were parous than the other groups, while the AI group had significantly more children per woman than the other groups. Finally, smoking, diabetes, and obesity were all more prevalent in the AI group.

High-resolution Anorectal Manometry Findings

Over 95% of the study population had abnormalities per the London classification. Details of the HR-ARM findings can be found in Table 2. Disorders of anal tone and contractility were common with nearly one-quarter of subjects having “combined anal hypotension and hypocontractility” and over a third of the population having “anal normotension with anal hypocontractility.” The most common abnormality was “dyssynergia” which was identified in two-thirds of cases. Additionally, nearly two-thirds had either “rectal hyposensation” or “borderline rectal hyposensation,” while “rectal hypersensation” was extremely rare.

Table 2 . Anorectal Manometry Results According to the London Classification

London classification diagnoses	All patients N = 479	Arab Israeli n = 87 (18.2%)	Former Soviet Union n = 76 (15.9%)	Jewish Israeli n = 316 (66.0%)	P-value
Disorders of rectoanal inhibitory reflex
Rectoanal areflexia	54 (11.3)	6 (6.9)	7 (9.2)	41 (13.0)	0.247
Disorders of anal tone and contractility
Max resting pressure	62.6 ± 28.1	52.2 ± 24.7	65.1 ± 29.4	64.9 ± 28.0
Max squeeze pressure	127.2 ± 65.0	82.2 ± 43.7	146.6 ± 65.3	134.8 ± 64.6
Combined anal hypotension and hypocontractility	113 (23.6)	38 (43.7)	15 (19.7)	60 (19.0)	< 0.001
Anal hypotension with normal contractility	36 (7.5)	0 (0.0)	9 (11.8)	27 (8.5)	0.007
Anal normotension with hypocontractility	174 (36.3)	37 (42.5)	20 (26.3)	117 (37.0)	0.090
Disorders of rectoanal coordination (n = 357)
Dyssynergia	238 (66.7)	45 (54.9)	37 (66.7)	156 (69.6)	0.036
Poor propulsion	12 (3.4)	5 (6.1)	2 (3.9)	5 (2.2)	0.353
Poor propulsion and dyssynergia	22 (6.2)	4 (4.9)	2 (3.9)	16 (7.1)	0.628
Disorders of rectal sensation
Rectal hyposensation	197 (41.1)	39 (44.8)	36 (47.4)	122 (38.6)	0.276
Borderline rectal hyposensation	118 (24.6)	17 (19.5)	20 (26.3)	81 (25.6)	0.485
Either rectal hyposensation or borderline hyposensation	315 (65.8)	56 (64.4)	56 (73.7)	203 (64.4)	0.288
Rectal hypersensation	2 (0.4)	0 (0.0)	0 (0.0)	2 (0.6)	-
Overall London classification
Normal exam per London classification	22 (4.6)	1 (1.1)	1 (1.3)	20 (6.3)	0.048
High pressure zone
High pressure zone length	2.54 ± 0.82	2.41 ± 0.76	2.49 ± 0.96	2.59 ± 0.80
Short high pressure zone	208 (43.4)	45 (51.7)	35 (46.1)	128 (40.5)	0.157

Data are presented as n (%) or mean ± SD.

P < 0.05 was considered statistically significant.

Ethnic Differences in High-resolution Anorectal Manometry Findings

Several differences were noted in HR-ARM findings between the 3 ethnic groups. Significant differences were noted in the rates of “anal hypotension with normal contractility,” “combined anal hypotension with anal hypocontractility,” and “dyssynergia.” Due to this, there was also a significant difference in the percentage of those with a normal examination. However, no significant differences were noted in terms of the other diagnoses.

Logistic Regression Analyses

Multivariable logistic regression analyses were performed adjusting for age and gender (Table 3). These analyses showed that significant differences still persisted between the ethnic groups. Compared to the other 2 groups, the AI group was several times more likely to have “combined anal hypotension and hypocontractibility.” Also, the AI group was less likely to have “dyssynergia” compared to the JI group.

Table 3 . Multivariate Logistic Regression Analysis Adjusting for Age and Gender

Outcome	Arab Israel compared to Jewish Israeli	Former Soviet Union compared to Jewish Israeli	Former Soviet Union compared to Arab Israeli
Combined anal hypotension and hypocontractility	3.759 (2.213-6.385)	1.033 (0.546-1.954)	0.275 (0.133-0.567)
	P < 0.001	P = 0.920	P < 0.001
Anal hypotension with normal contractility	-	1.393 (0.617-3.143)	-
	P = 0.996	P = 0.425	P = 0.996
Dyssynergia	0.575 (0.339-0.976)	1.168 (0.589-2.319)	1.817 (0.891-3.147)
	P = 0.040	P = 0.658	P = 0.103

Data are presented as adjusted odds ratio (95% confidence interval).

P < 0.05 was considered statistically significant.

A more robust model was then constructed adjusting for age, gender, smoking, diabetes, and obesity (Table 4). Even controlling for these variables, the AI group remained several times more likely to have “combined anal hypotension and hypocontractibility” than the other groups, although “dyssynergia” became non-significant.

Table 4 . Multivariate Logistic Regression Analysis Adjusting for Age, Gender, Smoking, Diabetes, and Obesity

Outcome	Arab Israel compared to Jewish Israeli	Former Soviet Union compared to Jewish Israeli	Former Soviet Union compared to Arab Israeli
Combined anal hypotension and hypocontractility	5.114 (2.753-9.498)	1.137 (0.582-2.223)	0.222 (0.100-0.496)
	P < 0.001	P = 0.707	P < 0.001
Anal hypotension with normal contractility	-	1.453 (0.580-3.640)	-
	P = 0.997	P = 0.425	P = 0.997
Dyssynergia	0.689 (0.373-1.271)	1.547 (0.701-3.415)	2.247 (0.924-5.464)
	P = 0.233	P = 0.280	P = 0.074

Data are presented as adjusted odds ratio (95% confidence interval).

P < 0.05 was considered statistically significant.

Finally, additional multivariate analyses were performed on the subgroup of women adjusting for the impact of age and parity (Table 5). These analyses showed that the AI group remained several times more likely to have “combined anal hypotension and hypocontractibility” compared to the other groups despite controlling for parity.

Table 5 . Multivariate Logistic Regression Analysis of Women Adjusting for Age and Parity

Outcome	Arab Israel compared to Jewish Israeli	Former Soviet Union compared to Jewish Israeli	Former Soviet Union compared to Arab Israeli
Combined anal hypotension and hypocontractility	2.740 (1.467-5.116)	1.077 (0.508-2.283)	0.393 (0.156-0.989)
	P = 0.002	P = 0.846	P = 0.047
Anal hypotension with normal contractility	-	1.136 (0.453-2.848)	-
	P = 0.997	P = 0.786	P = 0.997
Dyssynergia	0.563 (0.298-1.066)	1.187 (0.535-2.633)	2.105 (0.803-5.525)
	P = 0.078	P = 0.674	P = 0.130

Data are presented as adjusted odds ratio (95% confidence interval).

P < 0.05 was considered statistically significant.

This is the first study to evaluate and show differences in HR-ARM findings in patients with FI based on ethnicity. As such, this study adds to the literature on ethnic differences in patients with FI.

Studies showing racial or ethnic differences in FI rates mainly come from the diverse population of the United States. The largest such study included over 71 000 participants involved in the National Gastrointestinal Survey.1 This study, including both men and women, found significant differences in FI rates based on ethnicity and race. White individuals were more likely to have ever experienced FI compared to black or Asian individuals. Additionally, Hispanic participants were even more likely to report FI than white participants. The authors hypothesized that differing rates of pelvic organ prolapse and pelvic organ dysfunction may account for these differences in prevalence. Another study also showed increased rates of FI amongst both white women and men as compared to blacks.17

A study from Alabama also showed that black women were less likely to report FI than white women, but showed no difference amongst men.2 Many studies on FI are conducted just amongst women, and this finding that black women have lower rates of FI than white women has been repeatedly shown.3,18-20 One study also showed that American Indian/Native Alaskan women had lower rates of FI than white women.19 Data on Hispanic women has been more variable with the largest study showing a higher rate of FI compared to white women,1 but other studies showing either no difference19 or a lower prevalence compared to white women,21,22 with potential reporting bias being proposed as the reason for this discrepancy.1,22

While these studies evaluated clinical rates of FI between races and ethnicities, there is a lack of studies evaluating ethnic differences in HR-ARM. HR-ARM is an important diagnostic technique as it can objectively assess anorectal sensorimotor function, obtaining measurements that describe voluntary and involuntary control of the anal canal, rectoanal coordination, and rectal sensation.8 Studies of healthy volunteers, in which normal values for HR-ARM are obtained, tend to come from mostly homogenous populations, therefore limiting the ability to compare between races and ethnicities. For example, studies from Western populations tend to come from heavily Caucasian populations,11,23 while studies from Asian exclusively contain Asian subjects.10 The authors of a study evaluating normal values in a Korean population noted differences in their values as compared to a study of Western volunteers, and they hypothesized that differences in physical stature and physique between ethnic groups may contribute to these differences in HR-ARM measurements.10 However, this suggestion was debated by others, with multiple other factors, including differences in HR-ARM technique, being suggested as the actual cause.24 Regardless, the lack of studies from diverse, multiethnic populations in which these groups can be compared head-to-head remains one of the limitations of our knowledge of HR-ARM values at this time.

One study evaluated differences in ARM findings between men and women with FI.25 This study showed that there were differences in the pathophysiology of FI between the sexes. Women were more likely to have structural abnormalities, while men were more likely to have impaired rectal sensation and functional disturbances of evacuation. This difference in pathophysiology can be explained by the differences in anatomy and effect of childbirth between the sexes.

However, in our study, we also found differences in pathophysiology between ethnicities. AI subjects were more likely to suffer from “combined anal hypotension and hypocontractibility” than SU and JI subjects, even after accounting for age, sex, parity, smoking, diabetes, and obesity. This objective finding is much harder to explain. Previous studies on clinical rates of FI hypothesized that differing rates of pelvic organ prolapse and pelvic organ dysfunction may account for differences in FI prevalence.1 At the current time we are unable to effective explain our findings. The AI population is known to have higher rates of diabetes, obesity, and smoking than other populations in Israel,26-28 and all of these are known risk factors for FI.1,20 However, we accounted for these variables in the study, and while all 3 medical conditions were more common in the AI group, they still did not explain the HR-ARM differences between the groups. This study serves as a reminder that FI is a complex process with many different etiologies and contributing factors, and we still do not fully understand all of the factors involved.

We also found a relatively high rate of “rectoanal areflexia” (11.3%). This may be related to low resting anal pressures noted in some cases which can make evaluation for rectoanal inhibitory reflex (RAIR) more difficult, as well as the high prevalence of diabetes which can also affect RAIR.29 No differences were noted between the ethnic groups.

This study has some limitations. Given the nature of the study, we were unable to collect all of the data that we would have wanted. For example, we were able to obtain information on parity and the number of children that each subject had, but we had no data on the method of childbirth or incidence of perineal trauma during delivery. No did we have data on other defecatory disorders such as constipation or diarrhea, prior abdominal or pelvic surgeries, or a history of pelvic organ dysfunction. All subjects were referred for HR-ARM to evaluate FI, but it is possible that some subjects may have had severe urgency or diarrhea and not true FI. We also had no data on the severity or characteristics of the FI, and no standardized incontinence score, such as the Wexner Continence Grading Scale or the St. Marks Incontinence Scare, was used.30,31 The normal values used in this study came from another institution,11 and they used different parameters to obtain these measurements than were recommended by the London classification.8 It is unclear how this may have affected our results. Additionally, no data on the subjects’ treatments or clinical outcomes was available. Finally, while there is data that clinical rates of FI vary by race or ethnicity in other populations, it is not clear what the rate of FI is in the overall Israeli population or if there are any differences in FI rates between the 3 ethnic groups in this study. Despite these limitations, this study benefits from its large number of subjects, diverse population, and use of the London classification.

In conclusion, this study shows that ethnicity impacts HR-ARM findings in patients with FI. AI subjects were more likely to have abnormalities in anal tone and contractility that could not be explained by known confounding variables such as age, sex, parity, smoking, diabetes, and obesity. Future studies on ethnically diverse populations evaluating the clinical relevance of these findings and the complex pathophysiology leading to FI are certainly warranted.

Note: To access the supplementary table mentioned in this article, visit the online version of Journal of Neurogastroenterology and Motility at http://www.jnmjournal.org/, and at https://doi.org/10.5056/jnm21233.

None.

None.

Daniel L Cohen: study concept and design, data acquisition and interpretation, writing the manuscript, and critical review; Amir Mari, Anton Bermont, and Dana Zelnik Yovel: data acquisition and interpretation, and critical review; and Vered Richter and Haim Shirin: study concept and design, and critical review.