According to the review published on the Clinical and Molecular Hepatology [1], metabolic dysfunction-associated steatotic liver disease (MASLD) has been estimated to affect 38% of the adult population worldwide, with its prevalence increasing from 22% to 37% from 1991 to 2019 [2]. The latest guidelines on the management of MASLD, indicate that the incidental finding of steatosis should prompt assessment of the potential aetiology of steatotic liver disease (SLD) and the presence of advanced fibrosis, which is related to the risk of liver-related outcomes [3]. Uncontrolled steatosis can develop further into progressive fibrosis, cirrhosis, and even liver cancer. Thus, by comprehensive understanding the epidemiology of SLD and fibrosis in the general population, we can conduct targeted education and clinical research for precise prevention and control. China has the highest burden of chronic liver disease worldwide [4]. However, there have been few data from epidemiological investigations of SLD and fibrosis in the Chinese general population in recent years. Therefore, epidemiological studies are urgently needed to determine the prevalence of SLD and fibrosis.

We conducted a prospective, community-based survey in Beizhen City, Liaoning Province, China, from June 2023 to February 2024. Participants (age≥18 years) were recruited from 42 villages. A total of 3,113 individuals were included. All participants underwent liver stiffness measurement (LSM) and controlled attenuation parameter (CAP) assessment using FibroScan^® (Echosens, Paris, France). Liver steatosis grades were indicated by median CAP values: ≥248 dB/m for grade ≥S1, ≥268 dB/m for ≥S2, and ≥294 dB/m for S3. Liver fibrosis grades were determined: ≥F1 at LSM ≥6 kPa, ≥F2 at LSM ≥8 kPa, ≥F3 at LSM ≥10 kPa, and F4 at LSM ≥13.5kPa [5]. All participants underwent physical examinations, including height and weight, waist, and blood pressure. In addition, all individuals underwent body composition assessment by Bio-impedance analysis (BIA) using body fat scale (DORD, Germany). Alanine aminotransferase (ALT) was assessed in 1,610 participants (51.72%) in the fasting state (at least 8 hours).

Supplementary Table 1 presents the characteristics of the subjects. The mean age is 59.29 years. The prevalence of ≥S1, ≥S2, and S3 were 49.60%, 31.32%, and 12.66%, respectively. The prevalence of ≥F1, ≥F2, ≥F3, and F4 were 42.37%, 12.79%, 4.17%, and 1.45%, respectively. As steatosis increased, the value of fibrosis gradually increased. Compared to females and younger individuals (age<60 years), the prevalence of fibrosis in males and elderly (age≥60 years) was significantly higher (all P<0.001) (Supplementary Fig. 1A–1D).

Obesity is established as one of primary drivers of cirrhosis and hepatocellular carcinoma [6]. Here, we compared the prevalence of steatosis and fibrosis across different body mass index (BMI) categories and waist. As the grade of steatosis increased, the average of BMI and waist gradually increased. The prevalence of steatosis dramatically increased with higher BMI categories and waist. Notably, individuals with overweight, obesity, and central adiposity showed a higher proportion of fibrosis grades (all P<0.001) (Fig. 1A–1D). In addition, ALT is one of the common indicators of liver function impairment. According to the result, populations with elevated ALT had higher prevalence of steatosis and fibrosis (Supplementary Fig. 1E, 1F).

Body composition analysis better reflects the distribution of fat and muscle in the body. In recent years, body fat rate and skeletal muscle volume are considered to be related to liver steatosis [7]. So we analyzed the body composition across different steatosis and fibrosis levels. The average body fat percentage of patients with different degrees of steatosis (S0, S1, S2, S3) was 29.06%, 31.71%, 32.56%, 34.59%, respectively. As the grade of steatosis increased, basic metabolism, the body and visceral fat percentage, subcutaneous fat percentage of all sites gradually increased. Subcutaneous muscle percentage of body, upper limb, and torso gradually decreased as the grade of steatosis increased (all P<0.001) (Fig. 1G–1I). However, there were no statistical differences in body composition among the different fibrosis groups (Supplementary Fig. 1G–1I).

SLD was once recognized as a major disease in Western countries. In the National Health and Nutrition Examination Survey database study performed by Tang HX and colleagues, the prevalence of steatosis and clinically significant fibrosis in the US population was 35.70% and 6.50%, lower than the 49.60% and 12.79% in the current study [8]. It can be seen that SLD poses a greater threat to the Chinese population. A recent study in China estimated that the prevalence of steatosis and advanced fibrosis was 38.97% and 2.55%, lower than the 49.60% and 4.17% [5]. This may be attributed to the regional factor. Previous study has marked regional differences in the prevalence of SLD and fibrosis. And the prevalence rate varies greatly among the different provinces in China, ranging from 33.74% to 61.04% [9].

In addition, our study conducted the body composition analysis of all surveyed residents. Sarcopenia and SLD have the common pathogenic basis. Through body composition analysis, the body fat and skeletal muscle content can be scientifically assessed. Their values are correlated with the severity of liver steatosis, which may be the main cause of liver steatosis in thin patients. However, the current clinical focus is mainly on BMI and waist circumference, which usually underestimate such obesity. So clinicians should be aware of body fat rate and skeletal muscle mass, especially those with normal BMI and waist circumference.

In conclusion, this population-based study showed that SLD and fibrosis are found in nearly half of the Chinese general adult population. Therefore, there is an urgent need for public health policies to increase the awareness of residents, and actively conduct early screening, while promoting effective interventions to continuously monitor the development of future cirrhosis and hepatocellular carcinoma. More population-based studies are necessary to determine the epidemiology, treatment and risk factors associated with the SLD and associated fibrosis. In the meanwhile, future studies should consider the influence of region on the prevalence of SLD.