Abstract and Introduction
Abstract
Previous estimates of the prevalence of nonalcoholic fatty liver disease (NAFLD) in the US population relied on measures of liver enzymes, potentially underestimating the burden of this disease. We used ultrasonography data from 12,454 adults who participated in the Third National Health and Nutrition Examination Survey, conducted in the United States from 1988 to 1994. We defined NAFLD as the presence of hepatic steatosis on ultrasonography in the absence of elevated alcohol consumption. In the US population, the rates of prevalence of hepatic steatosis and NAFLD were 21.4% and 19.0%, respectively, corresponding to estimates of 32.5 (95% confidence interval: 29.9, 35.0) million adults with hepatic steatosis and 28.8 (95% confidence interval: 26.6, 31.2) million adults with NAFLD nationwide. After adjustment for age, income, education, body mass index (weight (kg)/height (m)2), and diabetes status, NAFLD was more common in Mexican Americans (24.1%) compared with non-Hispanic whites (17.8%) and non-Hispanic blacks (13.5%) (P = 0.001) and in men (20.2%) compared with women (15.8%) (P < 0.001). Hepatic steatosis and NAFLD were also independently associated with diabetes, with insulin resistance among people without diabetes, with dyslipidemia, and with obesity. Our results extend previous national estimates of the prevalence of NAFLD in the US population and highlight the burden of this disease. Men, Mexican Americans, and people with diabetes and obesity are the most affected groups.
Introduction
In the United States, the burden of liver-related diseases is important. Over the last 2 decades, liver-related mortality ranked among the top 12 causes of death, and among adults aged 45–54 years, it has been repeatedly listed as the fourth leading cause of death.[1,2] Nonalcoholic fatty liver disease (NAFLD) is thought to be the most common chronic liver disease in the Western world.[3–5] However, US estimates of the prevalence of NAFLD are lacking, and previous nationally representative studies have been limited by the use of surrogate markers of liver disease, namely liver enzymes, with estimates in the range of 3%–23%.[6–9] Studies that have used more sensitive, specific, or direct methods have been limited by small sample size or by the use of convenience samples and report a range in the prevalence of NAFLD (19%–46%).[10,11]
Although the "gold standard" for diagnosing and staging NAFLD is histology, abdominal unltrasonography allows its detection.[4,5] NAFLD was traditionally thought to be a benign condition; however, longitudinal studies have shown that it can progress to nonalcoholic steatohepatitis and fibrosis,[12–14] leading to cirrhosis.[15,16] Also, there is increasing evidence suggesting that NAFLD may play a significant role in the strong association between obesity and the development of liver cancer.[17,18]
Large, population-based estimates of the prevalence of NAFLD as detected by ultrasonography are available for other Western and non-Western countries and show that its prevalence parallels that of obesity.[11] For the United States, there are no representative data regarding the prevalence and epidemiology of this condition. These estimates are key to assessing the magnitude of the disease and planning and projecting the health-care costs and the burden associated with liver disease. The Third National Health and Nutrition Examination Survey (NHANES III) was a large and representative survey of the noninstitutionalized US civilian population; it included gallbladder ultrasonography of all participants aged 20–74 years. Recently, we reevaluated these ultrasonography videotapes to assess the presence of hepatic steatosis.
By using these ultrasonography data, our aims were 1) to estimate the prevalence of any hepatic steatosis and NAFLD in the United States by key sociodemographic characteristics and 2) to examine metabolic, anthropometric, and laboratory correlates of hepatic steatosis and NAFLD.
Am J Epidemiol. 2013;178(1):38-45. © 2013 Oxford University Press
