Relationships between Socioeconomic Status, Handgrip Strength, and Non-Alcoholic Fatty Liver Disease in Middle-Aged Adults

Although low socioeconomic status (SES) and decreased muscle strength have been found to be associated with the risk factors of non-alcoholic fatty liver disease (NAFLD), including insulin resistance, obesity, and metabolic syndrome, the associations among SES, muscle strength, and NAFLD are still unclear. We aimed to investigate the combined effect of SES and relative handgrip strength (HGS) on the risk of NAFLD in middle-aged adults. Data from 5272 middle-aged adults who participated in the Korea National Health and Nutrition Examination Surveys (KNHANES) from 2014–2018 were analyzed. NAFLD was defined using the hepatic steatosis index (HSI) > 36 and the comprehensive NAFLD score (CNS) ≥ 40 in the absence of other causes of liver disease. SES was based on a self-reported questionnaire. Overall, individuals with low SES (odds ratio (OR) = 1.703, 95% confidence interval (CI): 1.424–2.037, p < 0.001) or low HGS (OR = 12.161, 95% CI: 9.548–15.488, p < 0.001) had a significantly higher risk of NAFLD. The joint association analysis showed that a low SES combined with a low HGS (OR = 2.479, 95% CI: 1.351–4.549, p = 0.003) further significantly increased the risk of NAFLD when adjusted for all the covariates, compared with individuals with a high SES and a high HGS (OR = 1). The current findings suggest that both low SES and low HGS were independently and synergistically associated with an increased risk of NAFLD in middle-aged Korean adults.