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

Objectives: 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). Study design: 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. Methods: 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). Results: 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. Conclusion: 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.