Non-alcoholic fatty liver disease (NAFLD) refers to a wide spectrum of liver
injuries, ranging from simple steatosis to non-alcoholic steatohepatitis (NASH),
advanced fibrosis and cirrhosis. NAFLD is associated with insulin resistance, type 2
diabetes mellitus, obesity, hypertriglyceridemia and hypertension; thus, it is regarded as
a hepatic component of the metabolic syndrome, and an independent risk factor for
cardiovascular disease.
NAFLD and NASH are common causes of chronic liver disease and elevated liver
enzymes. Their worldwide prevalence continues to increase with the growing obesity
epidemic. Understanding the epidemiology of these pathologies is essential for
developing treatment and prevention strategies. The prevalence of NAFLD and NASH
in the general population has been assessed with a variety of diagnostic means, such as
liver biopsy, non-invasive radiological and ultrasonic techniques, elevated liver
enzymes and combinations of clinical variables. Because liver biopsy is not appropriate
for population studies, only on the basis of autopsy studies it has been suggested that 3-
5% of individuals in the general population might have NASH, and 20-30% of people
in industrialized countries have NAFLD. The prevalence of NAFLD increases with
age, it is highest in males between 40-65 years and is higher in Hispanics and lower in
African-Americans.
Ultrasound is the non-invasive method most commonly used to assess NAFLD, having
a sensitivity of approximately 85% and a specificity of 94% for the detection of
moderated fatty liver. Magnetic resonance imaging (MRI) has also been used to
perform population studies, but it is less portable and more expensive than US. Among
surrogate markers Fatty Liver Index (FLI) has gained much attention.
Several studies have shown that NASH is a risk factor for liver fibrosis. At the same
time, most cases of fatty liver and even fibrosis can regress, particularly due to life
style modification and weight loss. Based on the well-established strong association of
the NAFLD with the metabolic syndrome and the epidemic of obesity, the prevalence
of NASH is expected to increase in the next decade, leading to cirrhosis and even HCC.
There is a need to perform larger, longitudinal studies that assess the long-term natural history of NAFLD with validated non-invasive biomarkers and by integrating
morbidity and mortality data.
Keywords: Epidemiology, Natural history, Non-alcoholic fatty liver disease,
Non-alcoholic steatohepatitis, Prevalence, Risk factors.
