FLD is a common clinical pathologic syndrome that manifests from hepatic steatosis and excessive fat accumulation induced by a variety of factors. Despite the increase in alcohol sales in China, the intake of alcohol in public institutions has been significantly reduced by government policies. However, NAFLD is still prevalent and is strongly associated with metabolic disorders. Not surprisingly, FLD has been frequently reported in patients with type 2 diabetes mellitus (T2DM) and obesity, accounting for 40–80% and 30–90%, respectively. Thus it is necessary to track FLD progress as it may develop to steatohepatitis, fatty liver cirrhosis, and associated virus hepatocellular carcinoma. Although liver biopsy is the gold standard for the diagnosis of FLD, abdomen ultrasonography is still a general approach to screen FLD especially in adult populations. The prevalence of NAFLD has increased globally and recently became the predominant cause of chronic liver disease around the world. The epidemiology and demographic characteristics vary worldwide . The incidence rate of FLD, diagnosed by ultrasonography, was reported to be more than 46% in developed countries [7, 22, 23] and 39.5% in developing countries [4, 24], and it is still on the rise.
In the current study in Fangshan Branch of the Beijing Nuclear Industry Hospital, the prevalence of FLD was 43.5%, which was higher than the results reported by another survey study in Beijing . However, only 19 to 60-year-old subjects were employed in the research and 17.9% of patients below 40-year-old were diagnosed with FLD (16.1% is the standard). The prevalence increased with age, which was dramatically higher than previously estimated values in other Chinese cities [25, 26]. Overall, the age group with the highest FLD prevalence was the over 50-year-old group , at which age the adiponectin levels in women also generally decreased. According to the results shown in Table 1, there was a negative correlation between FLD prevalence and adiponectin levels, which could explain the lower incidence of FLD in women over 50-year-old as at this age they undergo menopause and as a result have lower estrogen and higher androgen levels. As a whole, the prevalence of FLD, overweight and obove, prehypertension (hypertension) and hyperlipidemia was relatively high in the total population (Table 2). Actually, age comes with experience and higher responsibility in the working environment. Intense competition for title assessment and promotion and the prolonged working hours in this institute has resulted in the personnel to decrease physical activity time, leading to the prevalence of overweight and obesity and hypertension, which are risk factors for developing FLD with diabetes [3, 11, 20, 24]. The westernized diet, irregular diet, reduced physical exercise, hypertension and diabetes are major determinants of FLD among Chinese scientific researchers. The incidence of overweight and obesity, hypertension and diabetes was considerably high in the 1105 participants diagnosed with FLD. As seen in the Table 2, the prevalence of the other biochemical markers was consistent with that of disease markers, and both resembled that of hyperlipidemia and FLD.
Previous reports have indicated that males have more risk to develop FLD than females after the age of 50 . However, alcohol-related FLD (AFLD) in males is more prominent than in females under excessive alcohol consumption. In this research, AFLD and NAFLD were not separately investigated. The rate of rise of the levels of biochemical markers for MetS in males exceeded that of females, with the exception of AST. The prevalence of FLD was 50% in males and 34.6% in females, which was relatively higher than what has been reported in a previous Chinese study . The results of gender distribution of prevalence and categorization in the 1105 participants with FLD (Table 3), were in agreement with the findings of a Japanese study . Besides, males usually consume high fat diet and as a consequence store fat in their abdomen, whereas females that look after their weight tend to utilize fat in the subcutaneous tissue by weight loss plans such as physical exercise. The reason why the prevalence of overweight and obove was still high remains uncertain. The differential fat accumulation in males and females may be a consequence of their different lipid metabolism pathways. The comparative values and distribution of different genders are listed in Table 3. Briefly, our study, along with previously published findings, highlights the importance of prevention and screening of FLD in specific age populations. It has been reported that a high protein and hypocaloric diet are associated with improved lipid profile, glucose homeostasis and liver enzymes function in NAFLD, independent to BMI decrease or body fat mass reduction . However, our results showed statistically significant differences in all disease markers and two of the biochemical markers (hyperlipidemia and ALT rise) between the age groups in the FLD group. As shown in Table 4, the prevalence of prehypertension and ALT rise decreased by aging, and this rise was surprisingly higher in the 19 to 29 year-old group than in the other three groups. On the other hand, although the prevalence of other markers increased with age, there were no significant differences between the age groups.
In the current study most FLDs were diagnosed in participants without any clinical symptoms. Over 50% of cases with FLD had mildly increased contents of biochemical markers, most of which were also accompanied by a rise in cholesterol, triglyceride, LDL cholesterol, GGT, AST levels. There were significant differences in hyperlipidemia, mixed type hyperlipidemia, hypertriglyceridemia, GGT, AST and AST between the FLD and non-FLD group (Table 5). These alterations were found to be associated with certain disease markers. However, in this cohort study analysis of risk factors contributing to the prevalence of FLD was not performed. These results suggest that FLD, with NAFLD being the most common type, may be correlated with those disorders. Additionally, age and gender are basic risk factors as they play important roles in the development of NAFLD . Multiple Logistic analysis was carried out to identify risk factors for the analysis of the prevalence of FLD. The vital risk factors determined in this study were: age, overweight and obesity, prediabetes, diabetes, mixed type hyperlipidemia, hypertriglyceridemia and ALT (Table 6). However, our study included a single-site population and diagnosis of FLD was based on ordinary physical examination, which may limit the application of the identified markers for screening larger populations. Therefore, further studies with higher number of participants from various institutes of scientific research, including more demographic and biochemical data, are required in the future.
Recently, FLD has also been attributed to NAFLD, which is characterized by a heightened systemic pro-inflammatory state. NAFLD accelerates the risks of arteriosclerosis and other cardiovascular diseases or associated events . However, the previously reported correlation relationship between total cholesterol levels and cancer risk  is controversial because in the current study we found that FLD prevalence was associated with other risk factors (e.g., gender, age, overweight and obesity, hypertension, diabetes and MetS), and NAFLD was closely related to the incidence of cardiovascular disease, a clear risk factor for hyperlipidemia . The incidence and mortality rates of cardiovascular diseases were the highest amongst chronic diseases worldwide . The most common causes of death by NAFLD are atherosclerotic cardiovascular diseases and hepatic cirrhosis , hence it is important to regularly screen for FLD to prevent development of disease. The screening and prevention of obesity and hypertension are also of great importance, as they are risk factors of cardiovascular diseases and their prevalence was 39.1% and 7.9%, respectively, in the FLD group. Therefore, more attention should be paid to systemic diseases of the cardiovascular, urinary, digestive and respiratory system during physical examination, instead of the incidence of overweight and obove, diabetes, hypertension and dyslipidemia.