Nonalcoholic Fatty Liver Disease: Prevalence, Influence on Age and Sex, and Relationship with Metabolic Syndrome and Insulin Resistance

Abstract

Nonalcoholic fatty liver disease (NAFLD) is a common condition comprising a wide spectrum of liver damage strongly associated with type 2 diabetes, obesity, and hyperlipidemia. The pathogenesis of fatty liver is multifactorial, and it has been suggested that the presence of insulin resistance (IR) is an essential requirement for the accumulation of hepatocellular fat. Although NAFLD may affect people of any age, in general, increasing age is associated with increasing prevalence. The aim of this study was to determine the prevalence of fatty liver and its influence on age and sex; and to assess the association of different degrees of fatty liver to IR and metabolic syndrome. The study was performed in 8350 alcohol- and virus-negative individuals who underwent routine physical check-up at the health evaluation centre of Mackay Memorial Hospital, from February 2004 to May 2009. They underwent clinical examination, anthropometry, biochemical tests including serum fasting insulin, and routine liver ultrasonography. Steatosis was graded as absent, mild, moderate, or severe. The overall prevalence of fatty liver was 34.40% with the prevalence of fatty liver being significantly higher in males than in females (22.34 vs. 12.06%, p = 0.015). A progressive increase in the means of a homeostasis model assessment of IR (HOMA-IR), body mass index, systolic blood pressure, plasma triglyceride, alanine aminotransferase, low-density lipoprotein-cholesterol and glucose level and decrease in high-density lipoprotein-cholesterol ( p < 0.001 and p < 0.05) was observed from the group without steatosis to the groups with mild, moderate, and severe steatosis. Severe steatosis was associated with the clustering of risk factors for metabolic syndrome. Individuals with metabolic syndrome and a more pronounced HOMA-IR had a higher prevalence of moderate to severe steatosis ( p < 0.001 and p < 0.05) compared to those with HOMA-IR below the median. Fatty liver can be considered as the hepatic consequence of metabolic syndrome, specifically IR. There is a high prevalence of metabolic syndrome and fatty liver among the elderly population. Metabolic disorders are closely related to fatty liver; moreover, fatty liver appears to be a good predictor for the clustering of risk factors for metabolic syndrome.