Clinical Epidemiological Features and Risk Factor Weight Remodeling in Gallstone Patients on the Plateau

Objective: To test the hypothesis that body mass index (BMI) replaces sex as the core risk factor for cholecystitis in plateau populations, and to characterize the true risk factor profile of gallstone patients at high altitude. Methods: A single-center retrospective cohort study included 605 elective laparoscopic cholecystectomy patients at Qinghai Red Cross Hospital (2,260 m; 2020-2023), categorized into simple gallstones (n=434) and gallstones with cholecystitis (n=171). Univariate analysis, multivariate logistic regression, nested model comparison, interaction analysis, and sensitivity analyses were performed. All statistics were independently recomputed using Python 3.11 and cross-validated against original statistical deliverables. Results: The original hypothesis was falsified. The cohort had a mean age of 43.7+/-11.8 years, BMI of 24.2+/-3.8 kg/m^2, female-to-male ratio of 2.10:1, and SBP of 117.4+/-15.8 mmHg. Multivariate logistic regression (adjusting for age, BMI categories, sex, SBP, and DBP) showed that SBP was the only significant positive predictor (OR=1.027/mmHg, 95%CI: 1.008-1.047, P=0.005), while BMI overweight (OR=1.038, P=0.856) and obesity (OR=0.645, P=0.137) were non-significant, as was sex (OR=0.814, P=0.322). Age showed a significant negative association (OR=0.978/year, P=0.007), constituting an "age paradox" with younger patients having higher cholecystitis rates (<30 years: 36.8% vs >=60 years: 25.0%; Spearman rho=-0.087, P=0.032), which may reflect selection bias or plateau-specific mechanisms. Nested model comparison showed that adding blood pressure to the classical model (age+BMI+sex, AUC=0.575) significantly improved discrimination (AUC=0.615, DeltaAUC=+0.040, 95%CI: +0.007 to +0.084; LR chi^2=8.19, P=0.017). SBP was non-significant in univariate analysis (OR=1.005, P=0.346) due to a suppression effect: age was a negative confounder, simultaneously increasing SBP and decreasing cholecystitis risk, thereby masking the true SBP effect. Conclusion: The risk weight of cholecystitis is remodeled in the plateau hypoxic environment, but in a direction opposite to the original hypothesis: SBP is the only significant positive predictor (P=0.049 in the SBP-only recommended model), while BMI and sex are non-significant, and age shows an inverse association. Blood pressure management should be integrated into the risk stratification system for plateau cholecystitis. The original hypothesis that BMI replaces sex is explicitly falsified.