Abstract
Objective
To examine the association between oxidative balance score and the risks of gallstones and gallbladder surgery in US adults, addressing the lack of reliable oxidative stress–related indicators for gallstone prediction.
Methods
A cross-sectional study was conducted using data from the National Health and Nutrition Examination Survey 2017–2020. Multivariate logistic regression, subgroup analyses, and smoothed curve fitting models were applied to investigate the relationship between oxidative balance scores and gallstone outcomes, adjusting for age, sex, race, and health conditions.
Results
Higher oxidative balance score was significantly associated with lower risks of gallstones and gallbladder surgery. Each 1-unit increase in the oxidative balance score corresponded to a 2.6% reduction in gallstone risk (odds ratio = 0.974; 95% confidence interval: 0.958, 0.990) and a 3.3% reduction in gallbladder surgery risk (odds ratio = 0.967; 95% confidence interval: 0.950, 0.983). Subgroup and dose–response analyses confirmed these consistent, negative associations.
Conclusions
Higher oxidative balance score is independently associated with a reduced prevalence of gallstones and gallbladder surgery. Furthermore, maintaining a higher antioxidant status may play a role in the management of gallstone disease risk.
Keywords
Introduction
Gallstones are among the most common gastrointestinal disorders worldwide, affecting approximately 10%–20% of the population. Their prevalence varies across region and ethnicity, with generally higher rates reported in Europe and the United States than in Asia. 1 Gallstones pose a considerable economic and resource burden on healthcare systems. In the United States alone, over 700,000 cholecystectomies are performed annually, accounting for healthcare costs exceeding US$6.5 billion. When considering the total healthcare expenditures for the prevention and management of gallstone disease, the costs can reach up to US$62 billion annually, placing considerable strain on the healthcare infrastructure. 2 Although most individuals with gallstones remain asymptomatic, the absence of timely intervention can lead to severe complications such as acute pancreatitis, cholangitis, and acute cholecystitis, which can be life-threatening in extreme cases. 3 Several risk factors contribute to the development of gallstones, including pregnancy, obesity, metabolic syndrome, a high-fat diet, and rapid weight loss.4–6 However, effective clinical indicators predicting or preventing the occurrence of gallstones are lacking. Therefore, effective management of gallstone-related complications and associated risk factors for mitigating the increasing health and economic challenges is crucial.
Gallstone formation is closely associated with several factors, including abnormal cholesterol metabolism, changes in bile composition, dysfunctional gallbladder dynamics, and inflammatory responses, with oxidative stress playing a central role in these processes. 7 Oxidative stress arises from the imbalance between the body’s oxidative and antioxidant systems, resulting in an excess of free radicals such as reactive oxygen species (ROS) and reactive nitrogen species (RNS). This imbalance triggers inflammatory responses and results in cellular damage. Certain conditions such as cholestasis and gallbladder dysfunction can increase oxidative stress, which further alters the composition of bile, affecting components such as cholesterol, bile salts, and phospholipids, thereby promoting the formation of gallstones. 8 Furthermore, oxidative stress activates specific signaling pathways, including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf2), which disrupt the balance in the expression of inflammatory factors and antioxidant enzymes. This disruption contributes to cholesterol crystallization and accelerates the overall process of stone formation. 9
The oxidative balance score (OBS) serves as a comprehensive index for evaluating an individual’s oxidative stress status by integrating 16 nutrients and 4 lifestyle factors, which include 15 antioxidants and 5 pro-oxidants. 10 This score provides a quantitative measure of oxidative balance, where a higher OBS signifies elevated antioxidant levels and reduced oxidative stress. Previous studies have established an association between OBS and various health conditions, including non-alcoholic fatty liver disease and kidney stones, indicating that a higher OBS is associated with a lower prevalence of these conditions.11,12 Despite these findings, no studies have evaluated the relationship between OBS and gallstones or the need for gallbladder surgery.
This study used data from the National Health and Nutrition Examination Survey (NHANES) conducted between 2017 and 2020, integrating a range of demographic information, lifestyle factors, and disease characteristics to investigate the potential associations between OBS and the occurrence of gallstones as well as the need for gallbladder surgery. The anticipated findings aimed to provide valuable insights into how OBS influences the risk of developing gallstones and undergoing surgical procedures, helping clinicians to more accurately identify high-risk populations and develop tailored prevention and treatment strategies to improve health management for patients affected by gallstones. A preliminary version of this manuscript has been previously published as a preprint on Research Square. 13
Materials and methods
The study was conducted in accordance with the Declaration of Helsinki. NHANES is a comprehensive national survey conducted by the Centers for Disease Control and Prevention (CDC) that has provided valuable insights into the health trends of the US population since the 1960s. By systematically collecting and analyzing data on health, nutrition, disease prevalence, and physical condition, NHANES provides critical information that informs public health policies and programs. Importantly, NHANES ensures that all participants provide a written informed consent form before enrollment in the survey. Additionally, to protect the privacy of individuals, all personal information collected during the survey is strictly anonymized, safeguarding the confidentiality of participants and allowing for the aggregation of data for research purposes. Of the initial 15,560 participants with available gallstone data in NHANES 2017–2020, we excluded individuals based on the following criteria: (a) age <20 years (n = 6328); (b) missing OBS data (n = 3045); (c) lack of data on gallstone prevalence or surgery (n = 14); (d) pregnancy (n = 57); and (e) missing other covariates (n = 781). Consequently, 5335 participants were included in the final analysis. Of these, 2560 were male and 2775 were female. The detailed screening process is presented in Figure S1.
Exposure definition
The OBS was calculated by integrating 16 dietary nutrients and 4 lifestyle factors to quantify an individual’s oxidative stress status.14–16 Dietary nutrient data were obtained from the 24-h dietary recall interviews. To better represent the usual dietary intake of participants, we calculated the average nutrient intake from two days of recall. For the 16 dietary components, which included 14 antioxidants and 2 pro-oxidants (total fat and iron), scores were assigned based on sex-specific tertiles derived from the average of two 24-h dietary recall interviews. Particularly, for antioxidant factors, participants in the lowest (T1), middle (T2), and highest (T3) tertiles were assigned scores of 0, 1, and 2, respectively, whereas for pro-oxidants, the scoring was reversed (T1 = 2, T2 = 1, and T3 = 0). The four lifestyle factors were scored based on established criteria: physical activity was categorized into tertiles of metabolic equivalent (MET) scores (0–2); alcohol consumption was divided into non-drinking (2), moderate drinking (1), and heavy drinking (0); smoking status was assessed via serum cotinine levels, with scores of 0–2 assigned accordingly; and body mass index (BMI) was stratified into three categories with lower BMI receiving higher scores (0–2). The total OBS was obtained by summing all component scores, where a higher total score indicated a greater antioxidant capacity and lower oxidative stress (Table S1).
Outcomes definition
Patients with gallstones were defined as those who responded “yes” to the NHANES multiple choice question (MCQ) questionnaire, “Has a doctor or other health professional ever told you that you have gallstones?” Patients who had undergone gallbladder surgery were identified by answering “yes” to the question, “Have you had gallbladder surgery?”
Covariates
To minimize the influence of confounding factors, we included relevant covariates in our analysis. The covariates included age, sex, race, educational level, marital status, poverty-to-income ratio (PIR), stroke, lung disease, heart disease, hypertension, diabetes mellitus, alanine aminotransferase (ALT), alkaline phosphatase (ALP), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), and total energy intake. Race was categorized as Mexican American, non-Hispanic Black, non-Hispanic White, other Hispanic, and other ethnic groups. Educational level was categorized as less than high school, high school graduate, and more than high school education. Marital status was categorized into three groups: married or cohabiting; divorced, separated, or widowed; and never married. PIR was categorized into low-income (<1.3), middle-income (1.3–3.5), and high-income (≥3.5) groups. Stroke diagnosis was based on patient self-report. Participants were categorized as having heart disease if they were diagnosed with any of the following conditions: congestive heart failure, coronary artery disease, myocardial infarction, or angina pectoris. Participants were categorized as having lung disease if they had been diagnosed with any of the following conditions: asthma, chronic obstructive pulmonary disease, or emphysema. Hypertension was defined as meeting any of the following criteria: (a) diagnosed by a physician; (b) having a mean systolic blood pressure ≥130 mmHg or a mean diastolic blood pressure ≥80 mmHg; and (c) receiving antihypertensive medication. Diabetes was defined as (a) a physician-confirmed diagnosis; (b) glycated hemoglobin (HbA1c) ≥6.5%; and (c) management with diabetes medication or insulin. Energy intake was derived from the mean of two 24-h dietary recall interviews from NHANES.
Statistical analysis
The reporting of this study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. 17 Continuous variables were reported as mean ± SD, and categorical variables were reported as percentages. Statistical significance was assessed using the t-test and chi-square test. OBS was divided into four quartile groups, with Q1 as the reference group. A multivariate logistic regression analysis was conducted to examine the association between OBS and the prevalence of gallstones, prevalence of gallbladder surgery, and age at first gallbladder surgery. Model 1 was unadjusted. Model 2 was adjusted for age, sex, and race. Model 3 was additionally adjusted for age; sex; race; educational level; marital status; PIR; history of stroke, lung disease, heart disease, hypertension, and diabetes mellitus; liver function indicators (ALT, ALP, AST, and GGT); and total energy intake. Results were expressed as odds ratios (OR) with 95% confidence intervals (95% CI). The robustness of the results was assessed via subgroup analyses, and the dose–response relationship between OBS and gallbladder surgery was assessed using smoothed curve fitting. To account for the complex, multistage cluster survey design of NHANES, all statistical analyses were performed using appropriate sample weights, strata, and primary sampling units (PSUs). Particularly, for the combined 2017–2020 cycles, we used the specialized weights (WTMECPRP), cluster variables (SDMVPSU), and strata variables (SDMVSTRA) to ensure that the findings are representative of the noninstitutionalized US civilian population. All results were expressed as weighted ORs with 95% CIs. To further evaluate the robustness of our findings, two sensitivity analyses were conducted: (a) an unweighted analysis was performed for comparison with the primary survey-weighted model and (b) multiple imputation was employed to account for missing values among covariates (n = 781) to minimize potential selection bias. All statistical analyses were conducted using R software (version 4.4.1, http://www.R-project.org) and EmpowerStats software (versions 2.0 and 4.2, http://www.empowerstats.com). A p-value of <0.05 was considered statistically significant.
Results
Participant characteristics
This study included 5335 participants aged ≥20 years. As shown in Table 1, the mean age of the participants was 50.843 ± 17.122 years, and 47.985% of the participants were male. A total of 586 participants were diagnosed with gallstones and 603 underwent gallbladder surgery. The mean value of OBS was 21.093 ± 7.280. Compared with the participants in the lower OBS group, those in the highest OBS group had higher ALT and AST levels, lower ALP and GGT levels, and higher total energy intake. They were more likely to be Mexican American, have an educational level more than high school, and have a high PIR. Additionally, they were less likely to have comorbidities such as stroke, lung disease, heart disease, hypertension, diabetes, gallstones, or gallbladder surgery.
Characteristics of the study cohort.
Continuous variables were presented as mean ± SD, whereas categorical variables were expressed as percentages. The statistical significance was assessed using the t-test for continuous data and the chi-square test for categorical data.
PIR: poverty-to-income ratio; ALT: alanine aminotransferase; ALP: alkaline phosphatase; AST: aspartate aminotransferase; GGT: gamma-glutamyl transferase.
Association of OBS with gallstones and gallbladder surgery
Table 2 presents the results of the multivariate logistic regression analyses between OBS and gallstones as well as gallbladder surgery, with OBS divided into continuous and categorical variables, across multiple models adjusted for different covariates. The results indicate that in the fully adjusted model (Model 3), OBS was significantly and negatively associated with both gallstone prevalence and gallbladder surgery. Each 1-unit increase in OBS was associated with a 2.6% decrease in the odds of gallstone prevalence (OR = 0.974 (0.958, 0.990)) and a 3.3% decrease in the odds of gallbladder surgery (OR = 0.967 (0.950, 0.983)); the negative association with gallstone prevalence and gallbladder surgery was more pronounced in the highest OBS quartile compared with that in the lowest quartile. In the 4th quartile group, each 1-unit increase in OBS was associated with a 43.3% decreased odds of gallstone prevalence (OR = 0.567 (0.406, 0.793)) and 53.5% lower odds of gallbladder surgery (OR = 0.465 (0.330, 0.655)). We further evaluated the association between individual OBS components and gallstone-related outcomes (Table S2). These findings suggest that the protective effect of the total OBS score is driven by the synergistic contribution of these key dietary and lifestyle components.
Association between OBS and gallstones and gallbladder surgery.
Model 1: No covariates were adjusted. Model 2: Age, sex, and race were adjusted. Model 3: Age, sex, race, education level, marital status, poverty-to-income ratio, stroke, lung disease, heart disease, hypertension, diabetes, and liver function indicators (ALT, ALP, AST, and GGT), as well as total energy intake were adjusted. ap < 0.05, bp < 0.01, cp < 0.001.
P < 0.05 is considered statistically significant.
OBS: oxidative balance score; ALT: alanine aminotransferase; ALP: alkaline phosphatase; AST: aspartate aminotransferase; GGT: gamma-glutamyl transferase.
Subgroup analysis
We performed subgroup analyses stratified by age, sex, race, hypertension, and diabetes to determine whether the association between OBS and gallstones as well as gallbladder surgery was consistent across subgroups. As shown in Figure 1, no significant differences in the associations between OBS and gallstones or gallbladder surgery were observed across the subgroups, suggesting that the negative correlation between OBS and the prevalence of gallstones and gallbladder surgery is consistent.
Stratified analysis of the association between OBS and gallstones and gallbladder surgery. This analysis considered factors such as age, sex, race, education level, marital status, PIR, stroke, lung disease, heart disease, hypertension, diabetes, and liver function indicators (ALT, ALP, AST, and GGT), as well as total energy intake. (a) Stratified analysis of the association between OBS and gallstones; (b) stratified analysis of the association between OBS and gallbladder surgery. OBS: oxidative balance score; PIR: poverty-to-income ratio; ALT: alanine aminotransferase; ALP: alkaline phosphatase; AST: aspartate aminotransferase; GGT: gamma-glutamyl transferase.
Smooth curve fitting and threshold effect analysis
We used smoothed curve fitting to evaluate the dose–response relationship between OBS and gallstones as well as gallbladder surgery. As shown in Figure 2, OBS demonstrated a linear negative correlation with gallstone prevalence, whereas a significant nonlinear negative correlation was observed with gallbladder surgery. OBS significantly reduced the risk of gallbladder surgery when OBS values were <9; however, this relationship leveled off when OBS >9 (Table 3).
The dose–response relationship between OBS and gallstones and gallbladder surgery. Adjusted for Age, sex, race, education level, marital status, PIR, stroke, lung disease, heart disease, hypertension, diabetes, and liver function indicators (ALT, ALP, AST, and GGT), as well as total energy intake. (a) OBS and gallstones; (b) OBS and gallbladder surgery. OBS: oxidative balance score; PIR: poverty-to-income ratio; ALT: alanine aminotransferase; ALP: alkaline phosphatase; AST: aspartate aminotransferase; GGT: gamma-glutamyl transferase.
Analysis of threshold effects between OBS and gallbladder surgery.
OR: odds ratio; CI: confidence interval; OBS: oxidative balance score.
Sensitivity analyses
The sensitivity analyses confirmed the stability of our primary results. The negative association between higher OBS and gallstone prevalence remained statistically significant in both the unweighted model and the dataset after multiple imputation of missing covariates (Table S3 and Table S4).
Discussion
In this cross-sectional study of 5335 US adults from NHANES, higher OBS was significantly associated with a lower prevalence of gallstones and gallbladder surgery. Subgroup analyses and interaction tests suggested that confounding factors did not influence this association. Furthermore, curve fitting analysis corroborated this negative association and suggested that the risk of gallbladder surgery can be decreased as OBS increased up to approximately 9. These findings highlight the importance of maintaining a robust antioxidant status for the prevention of gallstones and gallbladder surgery.
To the best of our knowledge, this is the first study investigating the association of OBS with the prevalence of gallstones and gallbladder surgery. This study highlights the negative association between diet- and lifestyle-induced OBS levels and the prevalence of gallstones and gallbladder surgery, consistent with previous findings on the relationship between oxidative stress and gallstones.18,19 Liu et al. 20 demonstrated that oxidative stress affects the metabolism of cholesterol and bile acids in bile, promoting cholesterol crystallization and resulting in gallstone formation. Pozo et al. 21 suggested that oxidative stress damages gallbladder smooth muscle cells through ROS, thereby reducing gallbladder contractility and impairing gallbladder emptying and ultimately increasing the risk of stone formation. Another animal study revealed that inhibition of superoxide dismutase activity by a stone-promoting diet led to oxidative stress, which activated inflammatory mediators and induced gallbladder inflammation, with the inflammatory milieu further contributing to stone formation and progression. 19
Evidence from previous studies supports the association between dietary components and gallstone formation. Worthington et al. 22 analyzed 24 blood samples from patients with gallstones and found that dietary antioxidants such as vitamin E, β-carotene, vitamin C, and folic acid were lower than in the controls. This finding was supported by Cikim et al., 23 who found significantly lower levels of vitamin B12, zinc, and selenium in the sera of 40 female patients with gallstones than in 40 healthy women. However, no significant differences were observed between the two groups for copper and folate, possibly due to a sampling error. Naumann et al. 24 found that a hydrophobic interaction may exist between bile acids and dietary fiber, which promotes colonic motility and accelerates the metabolism of stone-promoting bile acids such as deoxycholic acid and lithocholic acid. Different types of fats have varying effects on gallstone formation, with saturated fatty acids elevating cholesterol levels and promoting crystal formation, which can develop into gallstones. 25 High-fat diets may also induce the accumulation of ectopic triacylglycerols, slowing gallbladder emptying and promoting stone formation. 26 In contrast, unsaturated fatty acids, particularly polyunsaturated omega-3 fatty acids, may reduce cholesterol saturation in bile and protect gallbladder mesenchymal stromal cells, thereby preventing gallstone formation. 27 Interestingly, Tong et al. 28 demonstrated that calcium, iron, and copper were positively correlated with gallstone formation by promoting inflammatory factor release and increasing ROS levels, whereas magnesium and zinc exhibited antioxidant properties and were negatively correlated with gallstone formation. Another controlled study from China suggested that low calcium was positively associated with gallstone development. 29 This discrepancy may be attributed to the complex mechanisms of metal ions in the body. Calcium plays an important role in cell signaling and regulates many intracellular processes, including apoptosis and oxidative stress. 30 At normal physiological concentrations, calcium helps maintain cellular function and indirectly supports antioxidant defenses; however, high calcium ion concentrations may promote ROS production, exacerbating oxidative stress. 31 The role of copper is more complex; it can act as a cofactor for antioxidants such as superoxide dismutase by reducing oxygen radical production. 32 However, copper can also react with hydrogen peroxide to produce hydroxyl radicals, triggering oxidative damage. 33
In addition to dietary factors, lifestyle is also closely associated with gallstones. Regular physical activity promotes normal gallbladder contraction and emptying, prevents cholestasis, and reduces cholesterol and bile pigment deposition. Results from a large European prospective study involving 25,639 participants showed that high levels of physical activity were associated with a reduced risk of symptomatic gallstones in participants >70 years. Another study from South Korea suggested that vigorous exercise at least 2 days per week may reduce the risk of gallstone formation.34,35 Several studies have suggested that BMI is positively associated with the development of gallstones, and a study from the US suggested that low body weight is an etiologic factor for gallstones.36–38 Gebhard et al. 39 suggest that a very low-calorie diet (520 kcal) may lead to gallstone formation due to poor gallbladder emptying and increased bile cholesterol saturation, highlighting the importance of sensible eating habits and healthy weight management in preventing gallstones. A recent large cohort study showed that cotinine is an independent risk factor for gallstones, and nicotine can regulate bile acid metabolism through the FXR-megalin/cubilin pathway, thereby promoting gallstone nucleation; these findings suggest that smoking may be a key factor in gallstone development.40,41 In contrast to smoking, alcohol consumption may act as a protective factor against gallstone disease. A meta-analysis by Wang et al. 42 found that higher alcohol intake was associated with a significant reduction in the risk of gallstones, with a 12% reduction in risk for each additional 10 grams of alcohol consumed per day. Another cohort study demonstrated that regular alcohol consumption, particularly 5–7 days per week, significantly reduced the risk of gallstones, whereas infrequent consumption (1–2 days per week) did not have a significant effect. 43 Similarly, Kono et al. 44 reported that alcohol consumption significantly reduced the prevalence of gallstones and post-gallbladder surgery status. However, these results should be interpreted with caution, as sample variations between studies may influence the conclusions. Jayanthi et al. 45 demonstrated that alcohol consumption significantly increased the relative risk (RR) of cirrhosis in South Indian vegetarian women with cirrhosis (RR = 7.03, 95% CI 3.26, 15.12). Although moderate alcohol consumption may have a preventive effect on gallstones, the overall health effects of alcohol consumption need to be considered comprehensively.
In the present study, liver function markers such as ALT, AST, and GGT exhibited statistical variations across OBS groups. Although these values generally remained within normal physiological limits, their upward trend in lower OBS quartiles may reflect subclinical hepatic oxidative stress associated with metabolic syndrome. Given that the liver is the primary site of cholesterol synthesis and bile acid metabolism, these findings suggest that a systemic oxidative imbalance may subtly impair hepatic homeostasis, thereby creating a lithogenic environment conducive to gallstone formation.46,47 However, the clinical significance of these statistical variations remains to be fully elucidated. This interpretation should be considered speculative and requires further validation through prospective studies or direct measurements of hepatic oxidative stress markers.
There are some limitations to this study. As a cross-sectional study, our study could only demonstrate an association between OBS and gallstone prevalence and gallbladder surgery rates; however, a causal relationship could not be established. Although relevant covariates were included, some confounding factors may not have been fully accounted for. Moreover, NHANES is based on a US population sample, and gallstone characteristics vary significantly across regions. Due to the lack of detailed clinical data in NHANES, we were unable to differentiate between primary gallstones and secondary gallstones. Because the pathophysiology of secondary gallstones may differ from that of cholesterol gallstones, this limitation could potentially influence the observed associations. Future large-scale, prospective studies are warranted in multiple regions to further explore the correlation between OBS, gallstone prevalence, and gallbladder surgery rates.
Conclusions
A negative correlation was observed between OBS and gallstone prevalence as well as gallbladder surgery rates, which becomes increasingly significant with an increase in OBS levels. There is a significant dose–response relationship between OBS and gallbladder surgery rates, and maintaining an OBS of at least 9 may significantly reduce the risk of gallbladder surgery. Additionally, conducting larger prospective studies will help explore the mechanisms among OBS, gallstones, and gallbladder surgery in greater depth, thereby providing scientific support for the development of more effective preventive and therapeutic approaches.
Supplemental Material
sj-pdf-1-imr-10.1177_03000605261457792 - Supplemental material for Association between oxidative balance score and gallstone risk and gallbladder surgery: A cross-sectional study
Supplemental material, sj-pdf-1-imr-10.1177_03000605261457792 for Association between oxidative balance score and gallstone risk and gallbladder surgery: A cross-sectional study by Shouxin Wei, Sijia Yu and Yunsheng Lan in Journal of International Medical Research
Footnotes
Acknowledgments
Our team sincerely appreciates all the staff and participants whose invaluable contributions have greatly enhanced the NHANES data collection.
Declaration of conflicting interest
The authors declare that there is no conflict of interest.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Supplemental material
Supplemental material for this article is available online.
References
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