A study analyzing the medical data of more than 133,000 people shows that those with diabetes and a medical history of non-alcoholic fatty liver disease have a significantly higher risk of cardiovascular disease and mortality.
Recent data suggest that non-alcoholic fatty liver disease (NAFLD) is the most common type of liver disease affecting people in the United States. NAFLD is defined by a range of conditions determined by excess fat accumulating in the liver.
Liver disease is also associated with a high risk of developing cardiovascular disease (CVD) and brings an elevated risk of mortality. At the same time, studies have shown that there is a strong association between NAFLD and type 2 diabetes. Often, when the two conditions coexist, they augment the probability of developing other complications.
However, although diabetes and NAFLD so commonly occur together, and although NAFLD is associated with a risk of CVD and death, no studies so far have conclusively shown that people with both NAFLD and diabetes are also more exposed to CVD and mortality.
But now, Prof. Sarah Wild, from the University of Edinburgh, and Prof. Christopher Byrne, from the University of Southampton - both in the United Kingdom - have analyzed data from hospital records to confirm this risk in people with NAFLD and diabetes.
They have recently presented their findings at the European Association for the Study of Diabetes Annual Meeting, held in Lisbon, Portugal.
Higher CVD incidence, doubled death risk
To test for a higher risk of mortality and CVD in people with both diabetes and NAFLD, the researchers looked at the data of individuals diagnosed with diabetes while also targeting a "clinically significant" history of NAFLD. Clinically significant was defined as at least one hospital admission on the basis of NAFLD-associated symptoms.
The researchers looked at the records of people in Scotland who had been diagnosed with type 2 diabetes between 2004 and 2013. All the people were between 40 and 89 years old at the time of diagnosis.
In all, Profs. Wild and Byrne analyzed the data of 133,312 people diagnosed with diabetes. Of these, 1,998 had also been admitted to hospital due to NAFLD over an average follow-up period of 4.7 years.
The team noted that people who already had NAFLD at the point of their diabetes diagnosis had a specific risk pattern profile: they were younger, more of them were women, they were more likely to smoke, and they had a higher body mass index (BMI).
These risk factors, the researchers suggest, may play an important role across the medical conditions with which these people were diagnosed.
It was found that, for people with diabetes, NAFLD was linked to an approximately 62 percent higher incidence rate for serious cardiovascular events, such as strokes or recurrent cardiovascular disease.
This increase was not significantly associated with any of the confounding variables that the team tested for.
The researchers also found that NAFLD in people with type 2 diabetes was associated with a 40 percent higher risk of CVD-related mortality. The risk of all-cause death was also doubled, and there was a 41-fold increase in death due to cancer of the liver, or hepatocellular carcinoma.
'Prevention is preferable, but difficult'
Profs. Wild and Byrne told Medical News Today that, while this study cannot confirm that any of the associations are of a causal nature, the various biological mechanisms at play do appear to indicate a causal relationship.
"This research alone cannot attribute causality," they explained, "however there is accumulating evidence to support a causal relationship."
"For example," they added, "with NAFLD there is increased risk of atherogenic dyslipidemia [condition wherein triglyceride levels are high, and some cholesterol levels abnormal], increased pro-inflammatory cytokines that increase liver and vascular inflammation, and increased production of factors involved in the renin angiotensin system [hormonal system regulating arterial blood pressure] that contribute to hypertension."
Profs. Wilde and Byrne told us that they hoped that their findings would allow for better preventive care, targeting risk factors for NAFLD and diabetes. At the same time, they emphasized that better treatments focusing on the coexistence of these two conditions are a must.
"Prevention of both diabetes and liver disease by increased adoption of healthy lifestyles is the preferred approach, but very difficult to implement. As a consequence, there is an important role for developing safe and effective treatments."
They also explained to MNT that further research should seek to investigate whether or not other liver diseases also raise the risk for CVD and mortality in people diagnosed with diabetes.
"It is important to test whether other liver diseases are also associated with these outcomes in people with type 2 diabetes," they said.