Nonalcoholic Fatty Liver Disease and Renal Function Impairment: A Cross‐Sectional Population‐Based Study on Its Relationship From 1999 to 2016

There is growing evidence that links nonalcoholic fatty liver disease (NAFLD) with impairment of renal function. As such, we aimed to demonstrate the trend of NAFLD, NAFLD with renal insufficiency (RI), disease awareness, and mortality over time. Patient data were extracted from the National Health and Nutrition Examination Survey (NHANES) 1999‐2016. A total of 14,255 adult study participants without competing liver disease or heavy drinking and with complete laboratory data were included. NAFLD was defined using the U.S. Fatty Liver Index (USFLI) and RI was defined using the Chronic Kidney Disease Epidemiology Collaboration equation and urine albumin:creatinine ratio. Death data were obtained from the National Death Index (up to December 31, 2015). Prevalence of NAFLD in participants was 31.2% (95% confidence interval [CI], 30.01‐32.46); of these participants, 22.05% (95% CI, 20.34‐23.85) had RI. From 1999 to 2016, prevalence of both NAFLD without RI (P = 0.048) and NAFLD‐RI (P = 0.006) increased significantly. Among those with NAFLD‐RI, awareness of kidney disease was 8.56% (95% CI, 6.69‐10.89), while awareness of liver disease among all NAFLD was 4.49% (95% CI, 3.17‐6.33). Among those with NAFLD, mortality incidence per 1,000 person years was highest among those with severe RI in all‐cause mortality (104.4; 95% CI, 83.65‐130.39) and other residual causes of mortality (mean, 50.88; 95% CI, 37.02‐69.93). Conclusion: Prevalence of NAFLD and NAFLD‐RI has increased over the past 2 decades in the United States. Low kidney disease and liver disease awareness are major public health issues as those with NAFLD‐RI have significantly higher mortality than those with only NAFLD.