Abstract: Objective:To investigate the predictive value of cumulative body mass index (cumBMI) on newonset cholelithiasis.
Methods:The retrospective cohort study was conducted. The data of 31 794 subjects who participated health examination at the Kailuan Hospital, Kailuan Linxi Hospital, Kailuan Zhaogezhuang Hospital, Kailuan Tangjiazhuang Hospital, Kailuan Fan′gezhuang Hospital, Kailuan Lyujiatuo Hospital, Kailuan Jinggezhuang Hospital, Kailuan Linnancang Hospital, Kailuan Qianjiaying Hospital, Kailuan Majiagou Hospital and Kailuan Branch Hospital in 2006, 2008, 2010, 2012 and 2014 were collected. All the subjects were allocated into 4 groups according to squartiles of cumBMI: 7 949 with cumBMI<140.81 kg/m2×year in the Q1 group, 7946 with 140.81 kg/m2×year≤cumBMI<159.69 kg/m2×year in the Q2 group, 7 949 with 159.69 kg/m2×year≤cumBMI<180.49 kg/m2×year in the Q3 group and 7 950 with cumBMI≥180.49 kg/m2×year in the Q4 group. All the subjects received respectively the five health examinations in 2006, 2008, 2010, 2012 and 2014 at the same place. Epidemiological investigation, anthropometric parameters and biochemical indicators were collected. Observation indicators: (1) incidence of cholelithiasis in the 4 groups; (2)risk factors analysis affecting newonset cholelithiasis: sex, age, cumBMI, BMI, drinking, smoking, physical exercise, hypertension, diabetes, Creactive protein (CRP), triglyceride(TG) and total cholesterol (TC). Measurement data with normal distribution were represented as ±s and comparisons among groups were analyzed using the oneway ANOVA. Pairwise comparison and homogeneity of variance were done using the LSD test. Heterogeneity of variance was done using the Dunnett′s T3 test. Measurement data with skewed distribution were described as M (Q) and comparisons among groups were analyzed using the nonparametric test. Count data were analyzed by the chisquare test. The incidence of cholelithiasis in the 4 groups were calculated by the KaplanMeier method and comparisons of incidence were done by the Logrank test. The univariate analysis and multivariate analysis were done using the COX regression model.
Results:(1) Incidence of cholelithiasis in the 4 groups: 31 794 subjects were observed for (2.1±0.4)years, and 236 had newonset cholelithiasis with an incidence of 7.42‰. Incidences of cholelithiasis in the Q1, Q2, Q3 and Q4 groups were respectively 4.03‰, 7.17‰, 7.93‰ and 10.57‰, with a statistically significant difference among the 4 groups (χ2=72.39, P<0.05). (2)Risk factors analysis affecting newonset cholelithiasis: results of univariate analysis showed that sex, age, cumBMI, BMI, hypertension and CRP were independent risk factors affecting newonset cholelithiasis of subjects ［HR =1.61, 1.75, 1.64, 1.36, 1.39, 1.39, 95% confidence interval (CI): 1.23-2.10, 1.49-2.05, 1.45-1.86, 1.21-1.53, 1.07-1.79, 1.18-1.62, P<0.05］. Results of multivariate analysis showed that female, age between 50 years and 60 years, age≥ 60 years, 140.81 kg/m2×year ≤cumBMI <159.69 kg/m2×year, 159.69 kg/m2×year≤cumBMI<180.49 kg/m2×year, cumBMI≥180.49 kg/m2×year were independent risk factors affecting newonset cholelithiasis of subjects (HR=1.59, 1.78, 2.33, 2.04, 2.42, 3.66, 95%CI : 1.21-2.09, 1.31-2.44, 1.63-3.34, 1.29-3.24, 1.47-3.95, 2.15-6.25, P<0.05).
Conclusion:Female, advanced age and increasing cumBMI are independent risk factors affecting newonset cholelithiasis, and the incidence of cholelithiasis rises as cumBMI increases.