Association between long working hours and metabolic dysfunction–associated steatotic liver disease: a nationwide population-based study in Korea

Long working hour is a known risk factor for metabolic diseases. We explored the association between working hours and metabolic dysfunction–associated steatotic liver disease (MASLD). Data on working hours among 22,818 workers (11,999 females) from the Korea National Health and Nutrition Examination Survey (2013–2021) were used for this study. MASLD was defined as a combination of hepatic steatosis combined with one or more of cardiometabolic risk factors (overweight/obesity, prediabetes/diabetes, raised blood pressure, hypertriglyceridemia, low high-density lipoprotein cholesterol). Hepatic steatosis was assessed using the hepatic steatosis index. Logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs). The overall prevalence of MASLD was 30.4% in men and 18.1% in women. Among male workers, 20.2% worked ≥55 h/week, whereas among female workers, 10.1% worked ≥55 h/week. Compared with working 35–40 h/week, working ≥55 h/week was positively associated with overweight/obesity (OR: 1.21; 95% CI: 1.05–1.40), pre–diabetes mellitus (pre-DM)/DM (OR: 1.20; 95% CI: 1.04–1.38), raised blood pressure (OR: 1.17; 95% CI: 1.02–1.35), and presence of any cardiometabolic risk factors (OR: 1.56; 95% CI: 1.21–2.02). The adjusted OR (95% CI) of the association between working hours and MASLD was 1.27 (1.09–1.47) for ≥55 h/week compared with working 35–40 h/week in male workers. In female workers, long working hours were not clearly associated with cardiometabolic risk factors and MASLD. Long working hours are positively associated with MASLD among Korean male workers. Policy interventions are needed to mitigate the adverse metabolic effects of prolonged working hours.