Influence of the interaction between abdominal obesity and hypertriglyceridemia on the development of nonalcoholic fatty liver disease

Objective To investigate whether abdominal obesity and hypertriglyceridemia have a synergistic effect on the development of nonalcoholic fatty liver disease( NAFLD). Methods A prospective cohort study was conducted. Physical examination data were collected from 70 776 on-the-job or retired employees of Kailuan Group who underwent physical examination from July 2006 to June 2007,and the development of NAFLD was observed during the follow-up every two years. The subjects were divided into four groups according to the waist-to-height ratio and triglyceride( TG) level,and the person-year incidence rate was calculated. A one-way analysis of variance was used for comparison of normally distributed continuous data between groups,and the Kruskal-Wallis H test was used for comparison of non-normally distributed continuous data between groups; the chi-square test was used for comparison of categorical data between groups.The life-table method was used to calculate the cumulative incidence rate of NAFLD in each group,and the log-rank test was used for comparison between groups. With the non-abdominal obesity and non-hypertriglyceridemia group as the control group,the Cox proportional hazards model was used to analyze the risk of NAFLD and related 95% confidence interval( CI) for each group,and the influence of the interaction between abdominal obesity and hypertriglyceridemia on the development of NAFLD was further analyzed. Results During the mean follow-up time of 5. 03 ± 1. 67 years in this study,a total of 15 684 cases of NAFLD were observed,with a 6-year cumulative incidence rate of 25. 44% and a person-time incidence rate of 44. 03/1000 person-years. The log-rank test showed a significant difference in cumulative incidence rate between groups( χ2= 2479. 40,P < 0. 001). With the non-abdominal obesity and non-hypertriglyceridemia group as the control group,after adjustment for related confounding factors,the abdominal obesity-hypertriglyceridemia group had a hazard ratio( HR) of 2. 50( 95% CI: 2. 38-2. 62) for the development of NAFLD,which was significantly higher than the HR of 1. 99( 95%CI: 1. 92-2. 07) in the abdominal obesity and non-hypertriglyceridemia group and the HR of 1. 71( 95% CI: 1. 59-1. 84) in the non-abdominal obesity and hypertriglyceridemia group. After adjustment for the same confounding factors,the interaction analysis showed multiplicative interaction between abdominal obesity and hypertriglyceridemia( P < 0. 001),and co-existence of abdominal obesity and hypertriglyceridemia had a relative excess risk of 0. 77( 95% CI: 0. 68-0. 86),an attributable proportion of 30. 83%,and an interaction index of 2. 06( 95% CI: 1. 90-2. 24). Conclusion Abdominal obesity and hypertriglyceridemia have a synergistic effect on the development of NAFLD.