A POPULATION STUDY ON GENDER AND ETHNICITY DIFFERENCES IN GALLBLADDER DISEASE IN BRAZIL

ABSTRACT - BACKGROUND: Gallbladder diseases (GBD) are one of the most common medical conditions requiring surgical intervention, both electively and urgently. It is widely accepted that sex and ethnic characteristics mighty influence both prevalence and outcomes. AIM: This study aimed to evaluate the differences on distributions of gender and ethnicity related to the epidemiology of GBD in the Brazilian public health system. METHODS: DATASUS was used to retrieve patients’ data recorded under the International Code of Diseases (ICD-10) - code K80 from January 2008 to December 2019. The number of admissions, modality of care, number of deaths, and in-hospital mortality rate were analyzed by gender and ethnic groups. RESULTS: Between 2008 and 2019, a total of 2,899,712 patients with cholelithiasis/cholecystitis (K80) were admitted to the hospitals of the Brazilian Unified Health System, of whom only 22.7% were males. Yet, the in-hospital mortality rate was significantly higher in males (15.9 per 1,000 male patients) than females (6.3 per 1,000 female patients) (p<0.05). Moreover, men presented a significantly higher risk of death (RR=2.5; p<0.05) and longer hospital stay (4.4 days vs. 3.3 days; p<0.05) than females. Compared to females, men presented a higher risk of death across all self-declared ethnic groups: whites (RR=2.4; p<0.05), blacks (RR=2.7; p<0.05), browns (RR=2.6; p<0.05), and Brazilian Indians (RR=2.13; p<0.05). CONCLUSION: In the years 2008-2019, women presented the highest prevalence of hospital admissions for GBD in Brazil, and men were associated with worse outcomes, including all ethnic groups.


A QUEDA DA PRESSÃO PORTAL APÓS DESVASCULARIZAÇÃO ESOFAGOGÁSTRICA E ESPLENECTOMIA INFLUENCIA A VARIAÇÃO DO CALIBRE DAS VARIZES E AS TAXAS DE RESSANGRAMENTO NA ESQUISTOSSOMOSE NO SEGUIMENTO EM LONGO PRAZO?
Does the drop in portal pressure after esophagogastric devascularization and splenectomy variation of variceal calibers and the rebleeding rates in schistosomiasis in late follow-up?
Walter de Biase SILVA-NETO 1  The relationship between cholelithiasis/ cholecystitis and lifestyle conditions (e.g., smoking status and alcohol consumption, physical activities routines, comorbidities, drug use, obesity, and food) must be considered important in current situations.

Central message
Gallbladder disease affects about 10% of the general population, in Brazil, accounting for over 185,000 cholecystectomies yearly. In the years 2008-2019, women presented the highest prevalence of hospital admissions, and men were associated with worse outcomes, including all ethnic groups. admission for an inpatient as remaining in hospital for more than 24 h; thus, day-hospital approaches were not included in the analyses. All data were stratified geographically by the patient place of residence. Data were collected based on the International Disease Classification (10th Revision -ICD-10), using the K80 code, recorded on DATASUS as "Cholelithiasis and Cholecystitis," from January 2008 to December 2019. To perform this investigation, we analyzed the following variables: gender, self-reported ethnicity (i.e., white, black, brown, and Brazilian Indians), cases above and below the age of 40, total number of hospital admissions and number of admissions by gender and by ethnicity, emergency and elective interventions, total number of in-hospital deaths and the in-hospital mortality rate, and average length of stay.

RR
Normality of the variables was assessed by the Shapiro-Wilk test and the Q-plot. Homogeneity of the compared groups' variances was assessed using the Levene's Test for Equality of Variances. Descriptive statistics such as mean, standard deviation (SD), median, interquartile range (IQR: Q1-Q3), relative risk (RR), and confidence intervals (CI) were used to describe numbers and proportions of admissions, gender-and ethnic-related risk of deaths, and length of in-hospital stay.
Fisher's exact test and chi-square test with Yates' continuity correction were used to compare proportions between two groups. Depending on the normal or non-normal distribution of the variables, a Mann-Whitney U test and a Student's t-test for independent samples were also used when appropriate to compare differences between groups. To assess the data variance along time, percentage variation was calculated between the years applying the following formula: [(next year − previous year)/previous year] ×100, in order to identify the stability, increase, or decrease of the numbers. Adjusted r² values were obtained using linear regression to evaluate the variance of trends, considering a p<0.05 result as significant.
Data management and the statistical analysis were conducted using the Microsoft Office Excel 2019 software (Microsoft, Redmond, WA, USA), the BioEstat software (Instituto de Desenvolvimento Sustentável Mamirauá, version 5.3), and the R software (RStudio, Inc. -R Foundation for Statistical Computing, version 4.0.3), a free from charge software for data analysis.
Approval of the Ethics Committee in Research is considered dispensable, since secondary data were obtained from the public domain and online database, without individual identification of patients.

INTRODUCTION
Gallbladder disease (GBD) is one of the most common gastrointestinal disorders and the leading causes of hospital admissions and surgery worldwide, responsible for over 700,000 cholecystectomies per year in the United States 4,19,25 . Global prevalence varies from 3% to 47%, with an estimated risk of 7.9% in men and 16.6% in women 4,25,29 . In Brazil, GBD affects about 10% of the general population, being accountable for over 185,000 cholecystectomies yearly 6,9 . The term GBD refers to a diverse spectrum of conditions affecting the biliary tract, which is frequently associated with the presence of gallstones (cholelithiasis) 19,29 . Ultrasound study of the gallbladder is considered the gold-standard method to diagnose GBD 19,21 .
In Western countries, the disease is mainly caused by cholesterol stone formation (>85%), and approximately 95% of cases of cholecystitis are the result of obstructive lithogenesis 4,13 . Pathogenesis of gallstone disease is considered multifactorial and results from a complex interaction between genetic, hormonal, physiological, behavioral, and environmental factors 10,27,29 . Several authors have demonstrated the relationship between GBD and metabolic disorders such as obesity, hypertriglyceridemia and type 2 diabetes, family history, physical inactivity, tobacco and alcohol consumptions, age (directly proportional), gender (female > male), animal fat-rich diets, rapid weight loss, and drugs 10,19,24,29 . About one in five stones carriers will develop clinical manifestations, and the potential risk for the progression to symptomatic disease is briefly explained by the "4F" rule: Fatty, Forty, Fertile, and Female 10,24,25 .
There is a strong and well-established direct association between body mass index (BMI) and the incidence of the disease, in which a high BMI poses an up to 7-fold increased risk for cholelithiasis 21 . Age is also a major risk for GBD, achieving relatively high rates in individuals over 40 years of age, possibly as a result of cumulative stone formation 21 . Moreover, ethnic differences seem to influence the variation of prevalence, which previous studies have suggested that the greatest risks occur among Amerindians and that the black skin population presents the lowest prevalence of GBD 11,13 . Nevertheless, associative studies between ethnicity and gallstone diseases in Brazil are scarce.
Therefore, given the prevalence of GBD, the scarcity of reports in the literature comparing ethnicity and sex-related outcomes and, since epidemiological data are indispensable for diagnostic, therapeutic, and public policies strategies, this study aimed to assess the ethnic distribution and gender disparities in the GBD among patients attending public hospitals in the Brazilian Unified Health System (Sistema Único de Saúde -SUS).

METHODS
This population-based, retrospective, and longitudinal study, carried out with secondary data from a government database, evaluated the ethnic influences and gender discrepancies as specific risk factors in hospital morbidity and mortality for GBD in Brazil. The Unified Health System Department of Informatics (Departamento de Informática do Sistema Único de Saúde -DATASUS) is a public online data platform, managed by the Ministry of Health, along with the state and municipal health secretariats (available for online access at http://datasus.saude. gov.br/). Data on morbidity were collected through the Hospital Information Systems (Sistema de Informação Hospitalares em Morbidade Hospitalar -SIH) from DATASUS, which gathers most of the information regarding the numbers of hospitalizations and hospital admission authorization forms (Autorização de Internação Hospitalar -AIH), length of stay, list of diseases, and patient outcomes. DATASUS platform defines hospital ORIGINAL ARTICLE 2/8 average of 1,176 (SD=58.8) deaths per year, whereas 10,447 (42.6%) fatalities were related to men, with an average of 871 (SD=52.7) deaths per year. Female-to-male death proportion was 1.35:1 (p<0.05). Overall in-hospital mortality rate was 8.5 deaths per 1,000 patients, and the in-hospital mortality rate of male (15.9 obits per 1,000 patients) was significantly higher than the rate of females (6.3 obits per 1,000 female patients) (p<0.05). Moreover, males presented a significantly higher risk of death compared to females (RR=2.5, 95%CI 2.4-2.6; p<0.05).
As for the modalities of care (Table 2) (Table 2). Male in-hospital mortality rate in elective treatment (4.0 deaths per 1,000 elective male admission) was significantly higher than the rate of females (1.3 deaths per 1,000 elective female admission) (p<0.05).
In the group of patients admitted on an emergency basis, the total number of hospitalizations was 1,272,333 cases (71.64% females and 28.36% males).  (Table 3). Ages over 40 years were also associated with a longer in-hospital stay (7.1 days vs. 4.5 days; p<0.05). Men presented a significantly longer average length of stay compared to women for cases under 40 years of age (6.1 days vs. 3.6 days; p<0.05) and over 40 years of age (7.8 days vs. 6.4 days; p<0.05).
Data regarding deaths (n=24,557) showed that most of the fatalities was counted in patients above the age of 40 (93.8%), with a mean of 3,545.1 (SD=106.13) deaths per year, significantly higher than the annual mean observed in patients under the age of 40 (mean=232.9; SD=12.02) (p<0.05). Age over 40 and hospitalization for GBD predicted an overall higher risk of death (RR=8.3, 95%CI 7.8-8.7; p<0.05), and the same result was also observed for both males (RR=4.5, 95%CI 4.2-4.9; p<0.05) and females (RR=10.1, 95%CI 9.4-10.8; p<0.05), compared to males and females under the age of 40 ( The ethnicity data and proportions broken down by gender are shown in Table 5. Self-declared black men and black women presented the highest risk of death compared to non-self-declared black respective gender (RR=1.2, 95%CI 1.1 -1.4, p<0.05 and RR=1.16, 95%CI 1.0-1.2, p<0.05, respectively). As previously observed, self-declared brown ethnicity was also identified as a protective factor among brown men (RR=0.92, 95%CI 0.8-0.96; p<0.05) and brown women (RR=0.8, 95%CI 0.7-0.8; p<0.05). No association was observed among the selfdeclared Brazilian Indians for both males (p=0.18) and females (p=0.37). Table 6 shows that males presented a significantly higher risk of deaths in all ethnic groups.

DISCUSSION
Cholelithiasis is the presence of one or more stones in the gallbladder and its complications, such as cholecystitis, pancreatitis, cholangitis, and even gallbladder cancer, represent an important public health problem worldwide 16,19 . Despite this, only a few Brazilian population-based studies on the prevalence and epidemiological implications of GBDs have been published. GBD constitutes a major concern for the Unified Health System and accounts for over 240,000 hospital admissions every year in Brazil. This study aimed to evaluate gender and ethnic influences associated with cholelithiasis/cholecystitis in order to obtain knowledge on patient outcomes amidst the Brazilian population.
As a result of our investigation, we identified that female gender, self-declared white ethnicity, age over 40, and elective treatment are important risk factors in the overall in-hospital prevalence of GBDs nationwide. Brazilian women were accountable for over 2 million (77.3%) hospital admissions in the years 2008-2019, with more than 150,000 hospitalized women every year and a total of 57.1% (12,398)  Several authors have concluded that women have higher risk of gallstone formation than do men 10,13,21,[24][25][26] . The observed gender-related discrepancies in GBD prevalence may be due to the effects of endogenous estrogen, which, in turn, may reflect on the secretion and biosynthesis of hepatic cholesterol 25 . Previous studies have suggested that the interaction of 17β-estradiol with the nuclear estrogen receptor (ESR1) leads to a cholesterol hypersecretion into bile 21,28,29 . Estrogen also enhances the activity of hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase, which induces biliary cholesterol hypersecretion 21,25 . Based on this, the estrogen increases biliary cholesterol secretion leading to cholesterol hypersaturation of bile, which favors lithogenesis 25,29 . Exogenous estrogen also seems to contribute to gallstone formation, since hormone replacement therapy and oral contraceptives containing estrogen are associated with a high incidence of GBD 19 . Although gallstones are rare in children, the female gender appears to be a risk characteristic even for pediatric symptomatic GBD, as seen in a retrospective cross-sectional study in the United States, with 404 patients aged between 0.6 and 18 years, in which 73% were girls 17 . Besides sex hormones, the number of gestations also impacts the incidence of the disease. Pregnancy causes a decrease in the gallbladder motility during the third trimester favoring the formation of stones and, since there is a cumulative effect, the risk is increased in multiparous females 19,21 .
Although women represented the largest number of cases in our study, men presented higher chances of worse outcomes. Some studies help to understand these observations based on the biochemical composition of gallstones and differences between sexes. The composition of stones might influence patient prognosis since cholesterol gallstones have less chance  M  F  M  F  M  F  M  F  M  F  M  F  M  F  M  F  2008  18,323 59,231  1,100  4,173  8,705  34,436  191  529  330  441  19  32  124  154  4  3  2009  18,986 59,341  1,245  4,529  10,745 39,915  114  382  357  471  37  38  171  271  2  3  2010  19,169 61,758  1,283  4,797  12,212 45,936  96  349  329  474  31  32  218  235  1  0  2011  19,787 62,665  1,229  4,703  12,556 48,697  62  183  365  449  24  37  181  298  1  0  2012  19,403 62,029  1,271  4,448  12,960 49,429  34  189  311  418  26  30  185  261  0  0  2013  20,419 65,044  1,249  4,886  14,505 56,740  71  266  336  473  21  28  203  309  0  4  2014  22,107 70,581  1,386  5,285  16,384 63,263  70  227  361  459  23  37  234  328  0  2  2015  22,100 68,807  1,367  5,131  17,415 64,826  73  214  332  434  42  37  248  343  0  1  2016  22,647 70,205  1,597  5,691  18,480 67,909  79  219  369  432  20  45  267  414  2  3  2017  23,519 71,770  1,838  6,684  20,405 73,584  94  343  344  430  26  48  270  366  1  1  2018 25   of bacterial colonization and, hence, less risk of progressing to sepsis 5,8,14,30 . A study 8 from Italy evaluated the composition of the stones from 960 patients who underwent surgery for GBD and reported that only 13.5% of patients with cholesterol stones had positive blood cultures, worth mentioning that most non-cholesterol stones have been demonstrated to harbor bacteria 14,30 . Women, especially between the menarche and menopause, are more likely to develop gallstones and tend to have a higher percentage of cholesterol in their composition, when compared to men. In a New Zealand study by Stringer, the analysis of specimens from 107 patients revealed that 60% of stones from female carriers had more than 70% of cholesterol in their composition, whereas the mean fraction of cholesterol in the composition of the stones from male patients was only 37.5% 5 , which might represent a protective factor to women. Our results associated men to a higher overall in-hospital mortality rate (15.88 vs. 6.29 by 1,000 patients; p<0.05) and a higher risk of death by GBD (RR=2.5; p<0.05) compared to women, and similar proportions were also observed among patients below the age of 40 (4.3 vs. 0.9 per 1,000 patients; RR=4.5; p<0.05) and above the age of 40 (19.6 vs. 9.6 per 1,000 patients; RR=2.0; p<0.05). Despite the clearly increased prevalence of GBD in females, the literature shows that males present worse outcomes and seem more likely to be correlated with higher rates of conversion from laparoscopy to an open procedure, longer hospital stay, higher risk of complications in laparoscopic cholecystectomy, and higher risk of death 9,27  The present investigation revealed a remarkable higher risk of death associated with the age over 40 (RR=8.3; p<0.05). Regardless of age, males experienced higher mortality risks, for both men below and above the age of 40 (RR=4.54 and RR=2.0, respectively), compared to women. Further, in the analyses of age groups within the same gender, males and females over 40 years exhibited notably higher risks of deaths compared to the cases under the age of 40 (RR=4.5 and RR=10.1, respectively). Several publications reported that the incidence of stones and GBD increases directly proportional to age, escalating after ages of 40 to become 4-10 times more likely to occur 19,21,28 . The literature shows reduced bile acid biosynthesis as an underlying cause for increased cholesterol saturation in the elderly, which ultimately contribute to gallstone formation and highest risks among people above the fifth decade of life 19 . Sandblom et al. reported similar observations in a Swedish study, which identified a mortality rate two times higher among people between 50 and 70 years of age when compared to the general population and up to seven times higher when compared with individuals above the age of 70 23 12 .
These findings have been confronted by other authors. A retrospective study in Germany with 138 patients presenting with acute cholecystitis (69 males and 69 females) demonstrated no differences in the median length of postoperative in-hospital stay between males and females (6 days in both groups; p=0.27) 3 . In 2019, a 1,645-laparoscopic cholecystectomies patients investigation (540 males and 1,105 females) placed on the state of Paraná (Brazil) also reported no difference in the length of hospital stay between sexes (1.14 days vs. 1.07 days; p=0.206) 9 .
Ethnic background is a well-known non-modifiable risk factor for gallstone diseases 28 . It is important to emphasize that there is no previous nationwide study that statistically compared the prevalence of GBD and relative risks across ethnic groups in Brazil until the present moment. Our data showed that the white group was the most prevalent in the general population (36.6%), with a mean of 88,628 (SD=8,947.7) hospital admissions per year, also observed in both white males (39.2%; mean=21,489, SD=2,571.1 hospitalizations/ year) and white females (35.9%; mean=67,139, SD=6,393.3 hospitalizations/year). A study with 14,238 individuals in the United States, in association with the Third National Health and Nutrition Examination Survey, evidenced that the prevalence of GBD was significantly higher among white non-Hispanic men (8.6%; p<0.001) and women (16.6%; p<0.001) compared to the black non-Hispanic gender groups (5.3% and 13.9%, respectively), and observed a significantly reduced risk of GBD for non-Hispanic blacks men and women (OR=0.58 and OR=0.66, respectively; p<0.001) compared to the whites 11 . Ingraham et al performed an investigation on the risk factors associated with 65,511 cholecystectomies recorded at the American College of Surgeons National Surgical Quality Improvement Program Hospitals database and reported a significantly higher prevalence of GBD among the white group compared to the black group of patients (65.5% vs. 9.4%; p<0.0001) 15 .
Everhart et al., by reviewing the possible reasons for low GBD prevalence found among black people, discussed that U.S. blacks present a lower gallbladder cholesterol saturation index than whites and that African-born blacks may have better gallbladder motor function than European whites 11 . Despite the high prevalence of GBD among the Brazilian self-reported white skin group, our results revealed that the black population presented the highest average mortality rate of 9.8 deaths by 1,000 patients (p<0.05), also higher among black males (19.3 deaths per 1,000 patients) and black females (6.6 deaths per 1,000 patients), compared to the non-black