If current trends in obesity and diabetes continue, at least
520 million people will be living with non-alcoholic fatty liver disease (NAFLD) in
western Europe, China, Japan and the United States by 2030, according to
modelling by the Center for Disease Analysis published in the Journal of Hepatology. The number of people with decompensated cirrhosis as a result of the most advanced form of NAFLD will more than double in each country.
NAFLD occurs when fat
accumulates in the liver due to metabolic disorders including type 2 diabetes.
NAFLD occurs most frequently in people who are obese.
Liver fat accumulation causes no symptoms in most people but
eventually it may become severe enough to cause inflammation and liver damage
(non-alcoholic steatohepatitis, or NASH). In a minority of people with NASH,
liver damage will progress to end-stage liver disease (decompensated cirrhosis)
or liver cancer (hepatocellular carcinoma). The risk of progressive liver
disease is higher in older people, obese people or people with type 2 diabetes.
- decompensated cirrhosis
The later stage of
cirrhosis, during which the liver cannot perform some vital functions and
complications occur. See also ‘cirrhosis’ and ‘compensated cirrhosis’.
A meta-analysis published in 2016 estimated the prevalence
of NAFLD at around 24% in Western countries, but the long-term impact of this
high prevalence on the development of NASH and future mortality from liver
disease, as well as the demand for liver transplants, is unknown.
The Center for Disease Analysis and liver experts in the
United States, China, Japan, the United Kingdom and the four largest countries
in western Europe (France, Germany, Italy and Spain) compiled national
estimates of the prevalence of obesity and type 2 diabetes in 2016 to serve as
the basis for modelling future trends.
The model also incorporated previous estimates of NAFLD
prevalence if available. In the United States, the 2016 prevalence among
over-15s was estimated at 30%, in the United Kingdom, France and Germany
prevalence was estimated at 25% of over-15s and in China and Japan, prevalence
was estimated at 20%.
After adjusting for the prevalence of obesity and type 2
diabetes, the researchers estimated that between 2 and 5% of people with NAFLD
had NASH in 2016, with the highest prevalence in the United States and the
lowest prevalence in China.
By 2030, the model estimates that the prevalence of NAFLD
will have risen in all countries, with the biggest numerical growth in China
owing to population growth (61 million new cases). The prevalence of NASH will
also rise, by almost half in all countries and cases of advanced NASH will
make up a rising proportion of all NAFLD and NASH cases, as the population
ages and the prevalence of type 2 diabetes rises.
By 2030, the countries with the highest proportion of
advanced NASH cases (stage F3 fibrosis or cirrhosis of the liver or stiffening
and scarring of the liver) are projected to be Spain (29% of all NASH cases),
with Italy, Germany and the United Kingdom not far behind.
NASH will greatly increase the number of people with
decompensated cirrhosis – who may be in imminent need of a liver transplant and
will be at high risk of death from liver failure – in every country. The number
of people with decompensated cirrhosis due to NASH will rise from approximately
11,580 cases in France in 2016 to 33,180 cases in 2030 (a 187% increase).
In the United States the number of people with NASH and
decompensated cirrhosis will increase by 161% to 376,140 cases. In 2030 alone,
modelling suggests that 105,430 cases of decompensated cirrhosis will occur
because of NASH. This enormous increase in cases of advanced liver disease will
have serious implications for healthcare costs and the demand for liver
transplants, the authors warn.
Deaths due to NASH (including deaths from cardiovascular
disease) will increase most sharply in Italy, France and China, the modelling
finds. Approximately 163,000 people will die as a result of NASH in China in
2030, and 83,000 in the United States.
These projections of disease and deaths could change if the
global burden of obesity is altered by changes in diet, taxes on sugar or
effective treatment, or if medication to reduce liver fat and arrest the
progression of liver damage due to NASH become widely available. However, in an
accompanying editorial, Suzanne Mahady of the Royal Melbourne Hospital and Jacob
George of the Westmead Hospital in Australia note that a burden of disease
study which calculates the health economic costs of NAFLD and NASH will be the
next step in developing health policies to tackle these conditions.