title: Non-alcoholic fatty liver disease associated with gallstones in females rather than males: a longitudinal cohort study in Chinese urban population.
abstract: BACKGROUND
  Whether non-alcoholic fatty liver disease (NAFLD) is a risk factor for gallstones remains uncertain. Few longitudinal or cohort studies have been used to identify this relationship. The aim of this study was to confirm the association between NAFLD and gallstones in a longitudinal cohort of urban dwellers in China.
  
  
  METHODS
  To elucidate the association between NAFLD and gallstones, we fitted a generalized estimating equation (GEE) model in a large-scale longitudinal cohort over 6 years, which included 11,200 participants with at least three regular health check-ups.
  
  
  RESULTS
  A total of 498 cases of gallstones occurred during the 6-year follow-up, which resulted in a total incidence density of 12.73 per 1000 person-years (498/39, 135.5 person-years). The GEE analyses confirmed and clarified the association between NAFLD and gallstones (relative risk (RR) = 1.2381, 95% confidence interval (CI) = 1.003-1.528, P = 0.047) after adjusting for other potential confounding factors, especially in females (RR = 1.707, 95% CI = 1.245-2.341, P = 0.001).
  
  
  CONCLUSIONS
  NAFLD is associated with gallstones in an urban Chinese population from the middle to upper socioeconomic strata. Moreover, this association is more strongly apparent in females than in males. Further cohort studies must be conducted to confirm this association in the general population.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Shandong University, PO Box 100, Jinan, 250012, China. liujia250189@163.com.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: Center for Health Management, Provincial Hospital affiliated to Shandong University, Jinan, 250021, China. zxhlhy@163.com.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Lin
authors.affiliation: Health Management Center, Shandong Provincial Qianfoshan Hospital, Jinan, 250014, China. chengqijn@yahoo.com.cn.
authors.forename: Chengqi
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Shandong University, PO Box 100, Jinan, 250012, China. 595630422@qq.com.
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Shandong University, PO Box 100, Jinan, 250012, China. 410450390@qq.com.
authors.forename: Shuo
authors.initials: S
authors.lastname: Wu
authors.affiliation: Center for Health Management, Provincial Hospital affiliated to Shandong University, Jinan, 250021, China. toshiba1222@163.com.
authors.forename: Dongzhi
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Health Management Center, Shandong Provincial Qianfoshan Hospital, Jinan, 250014, China. iamtangfang@126.com.
authors.forename: Fang
authors.initials: F
authors.lastname: Tang
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Shandong University, PO Box 100, Jinan, 250012, China. xuefzh@sdu.edu.cn.
authors.forename: Fuzhong
authors.initials: F
authors.lastname: Xue
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Shandong University, PO Box 100, Jinan, 250012, China. liu-yx@sdu.edu.cn.
authors.forename: Yanxun
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000328:Adult; D044466:Asian People / Q000706:statistics & numerical data*; D002681:China / Q000453:epidemiology; D015897:Comorbidity; D005260:Female; D042882:Gallstones / Q000150:complications / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease / Q000150:complications / Q000453:epidemiology*; D012307:Risk Factors; D012737:Sex Factors; D012923:Social Class; D014505:Urban Population