Cancer Risk Among Young Adults With Clinically Diagnosed Fatty Liver Disease: A Nationwide Cohort Study in South Korea.

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing public health concern, particularly among young adults. While MASLD is a well-established risk factor for liver-related complications, growing evidence suggests an association with several extrahepatic cancers. However, data regarding cancer risk among young adults with MASLD remain limited. This study investigates the association between MASLD and cancer risk in young adults in South Korea.

METHODS

A nationwide cohort study was conducted using the Korean National Health Insurance Service database, including individuals aged 20-39 years who underwent health screenings (2004-2007). Clinically diagnosed fatty liver disease was identified using ICD-10 code K76.0, and incident cancers were identified using ICD-10 malignant neoplasm codes recorded in the National Health Insurance Service claims database through 2022. Cox proportional hazards models estimated hazard ratios (HRs) for cancer risk, adjusting for confounders.

RESULTS

Among 4,094,241 participants, 254,897 (6.22%) had clinically diagnosed fatty liver disease. Clinically diagnosed fatty liver disease was significantly associated with increased all-cancer incidence in both men (HR: 1.48, 95% CI 1.45-1.51) and women (HR: 1.23, 95% CI 1.20-1.27). The highest risks were observed for liver cancer (men, HR: 2.39, 95% CI 2.28-2.50, women, HR: 2.88, 95% CI 2.56-3.23), thyroid cancer (men, HR: 1.49, 95% CI 1.43-1.55, women, HR: 1.18, 95% CI 1.13-1.24). BMI-based fatty liver disease (BMI < 25 kg/m2) showed a higher liver cancer risk. Non-drinkers with clinically diagnosed fatty liver disease also had increased cancer risk.

CONCLUSIONS

Clinically diagnosed fatty liver disease in young adults was associated with a higher risk of both hepatic and extrahepatic cancers. Further studies are needed to determine appropriate risk-stratified prevention and surveillance strategies in this population.