Fatty liver disease has the highest prevalence rate among liver diseases not only worldwide but also in South Korea. According to a recent study conducted in South Korea, the prevalence rate of fatty liver disease diagnosed using ultrasonography was 30%, accounting for 69.7% of liver disease cases . Similarly, the morbidity rate of fatty liver disease in this study was 32.3%. The worldwide prevalence rate of NAFLD varies between studies . In the United States, one-third have been diagnosed with NAFLD, and in the UK, it is reported as 29 cases per 100,000 person-years, which is clearly on a globally increasing trend [17, 18].
Because it is a standard commonly used in the diagnosis of NAFLD, the weekly alcohol consumption among patients diagnosed with NAFLD ranges from to 0-140 g for men and 0–70 g for women[14, 15]. In this study, we defined nondrinkers as individuals who consumed < 140 g per week, according to the standard proposed by Choi et al. . In addition, while the total drinking quantity was measured through the questionnaire, 350 mL of beer, 120 mL of wine, 25 mL of brandy, or 50 mL of soju was considered to contain 10 g of alcohol by surveying the type of alcohol and the number of bottles consumed.
There was no difference between the NAFLD and AFLD groups for each of the indicators of cardiovascular risk factors. Importantly, however, these indicators differed between the two groups and the healthy group. This conclusion suggests that the risk factors are more related to the presence or absence of fatty liver, regardless of the cause of the occurrence of fatty liver. Systolic blood pressure, diastolic blood pressure, fasting plasma glucose level, total cholesterol level, and TG level were higher, whereas high-density cholesterol was lower in the NAFLD group than in the healthy group, indicating an increase in cardiovascular risk indicators in the NAFLD group. NAFLD is reportedly accompanied by obesity (30–100%), diabetes (10–75%), or dyslipidemia (20–92%) . In a study on the association between NAFLD and cardiovascular disease, blood pressure, fasting plasma glucose level, total cholesterol level, and TG level were higher in the NAFLD group than in the healthy group. In another study , systolic blood pressure, fasting plasma glucose level, total cholesterol level, and TG level were higher in the NAFLD group than in the healthy group, although sex-related differences in the values were found. The previous results are similar to the results of this study.
Diastolic blood pressure, fasting plasma glucose level, total cholesterol level, TG level, and hsCRP level were all higher in the AFLD group than in the healthy group. That is, except for high-density cholesterol levels, the values of the cardiovascular indicators in the AFLD group, as in the NAFLD group, were higher than those in the healthy group. Studies on the relationship between high-density cholesterol levels and fatty liver disease reported that high-density cholesterol levels were decreased in fatty liver [20, 21], although one study reported a contradictory result . Additionally, other studies reported that low-density cholesterol levels were decreased in NAFLD [23, 24]. In this study, low-density cholesterol levels were higher in the NAFLD group than in the healthy group. Several studies that investigated TG levels reported, as found in this study, that TG increased in both the NAFLD and AFLD groups [20–22, 25]. Although no difference was found in the hsCRP level, a cardiovascular risk indicator, in both the healthy and NAFLD groups, it was lower than that in the AFLD group. Among the many studies that support the association between fatty liver disease and inflammation indicators, one identified that high hsCRP levels were independently associated with fatty liver disease, obesity, and metabolic syndrome , whereas another reported that hsCRP level was a strong predictor of NAFLD .
While the metabolic syndrome rate was higher in the NAFLD and AFLD groups than in the healthy group, no significant difference was observed between the NAFLD and AFLD groups. A previous study reported that the fatty acid content in the liver was increased in patients with metabolic syndrome regardless of age, sex, or BMI , and an association between several metabolic disorders and serious liver diseases was identified [28, 29].
As for the limitations of this study, the study results cannot be generalized because all the patients included in the study were hospitalized at the same health promotion center. Moreover, achieving reliability was difficult because alcohol consumption level, smoking habit, and exercise frequency were surveyed through a self-administered questionnaire. In addition, NAFLD was determined by CT with no histologic confirmation of fatty liver. However, the fact that the AST/ALT ratio in most NAFLD patients was below 1 rationalizes the selection method of patients for the NAFLD group in this study .
This is a comparative study on not only NAFLD, which has been previously studied extensively, but also on AFLD, and patients taking medications for hypertension, diabetes, hyperlipidemia, ischemic heart disease, myocardial infarction, cerebral infarction, and hemorrhage were excluded. Therefore, this study is significant in that it provided a pure association between the cardiovascular risk indicators and the NAFLD or AFLD group.
The values of the cardiovascular risk indicators were significantly higher in the NAFLD and AFLD groups than in the healthy group in this study. Ultimately, considering that the patients in both the NAFLD and AFLD groups have the same cardiovascular disease risks, patients diagnosed with fatty liver disease should be examined for risk factors of cardiovascular diseases and should undergo management and treatment of such diseases. Although this study demonstrated that cardiovascular risk indicators and the severity of fatty liver are not associated, additional studies in this area are necessary.