If left untreated, NAFLD can develop into fulminant cirrhosis and hepatocellular carcinoma. The consequences are similar to those of conventional alcoholic liver disease. Recent studies now indicate that NAFLD can also affect the function of other organs. In particular, the cardiovascular system is in focus. There is initial evidence that NAFLD may increase the risk of developing heart failure. However, it is unclear how high this risk is and whether the severity of fatty liver disease correlates with the level of heart failure risk. A team led by Alessandro Mantovani from the University of Verona in Italy has therefore investigated the link between NAFLD and heart failure in a meta-analysis.
The researchers analysed 11 cohort studies with a total of 11 million study participants from different regions of the world (Europe, USA, South Korea), of whom about three million had NAFLD. The mean age of the participants was 55 years, half of them were female and the mean body mass index (BMI) was 26.4 kg/m2. The diagnosis of NAFLD was made on the basis of laboratory parameters (elevated gamma-GT), the "Fatty Liver Index", a CT scan or liver histology. The mean observation period of the studies was 10 years. During this period, about 98,000 subjects were diagnosed with heart failure.
The presence of NAFLD was associated with a 50% increased risk of developing heart failure. The increased risk was independent of age, sex, obesity, diabetes and other typical cardiovascular risk factors. The diagnosis of NAFLD also did not play a significant role. Only CT-based diagnostics failed to find a correlation with the occurrence of heart failure. However, this could be due to the fact that the CTs studied only included a small proportion of the liver, as they were originally cardio-CTs. The research team was also able to confirm the association in subgroup analyses (study location, length of follow-up, method of heart failure diagnosis).
They also found evidence that the risk of developing heart failure increases with the progression of NAFLD. Unfortunately, they could not statistically prove this due to insufficient data. But other studies with smaller numbers of cases have already found a positive association. For example, a Swedish study showed a twofold increased risk of developing heart failure in non-alcoholic liver fibrosis (moderate form) and an almost threefold increased risk of developing heart failure in non-alcoholic liver cirrhosis (severe form).
In summary, this study shows that NAFLD is a multi-organ disease that can affect not only the liver but also other organs such as the heart. The authors write that NAFLD promotes cardiac remodelling, which can lead to hypertrophy, cardiac arrhythmias and ultimately heart failure. The underlying mechanisms of this hepato-cardiac axis are still unclear. It also remains unclear why the authors did not include studies in which NAFLD was diagnosed using ultrasound. This method is accurate, simple and inexpensive - but the research team did not comment on this.
Nevertheless, the results are relevant in clinical practice. They show that non-alcoholic steatosis hepatis should not be dismissed as an "incidental finding". Rather, those affected should be actively made aware of fatty liver and the associated cardiovascular risk. Future studies would then only have to show that a reduction in fatty liver disease can also reduce the risk of heart failure.