Impact of overweight and obesity on the risk of hepatocellular carcinoma: a prospective cohort study in 14.3 million Koreans.

Background: Whether obesity and being overweight, defined by body mass index (BMI), increase hepatocellular carcinoma (HCC) has been less apparent in Asian populations.

Methods: Overall, 14,265,822 Korean adults who underwent routine health examinations during 2003-2006 were followed up for HCC. Multivariable-adjusted hazard ratios (HRs) associated with BMI were calculated.

Results: During 13.7 years (mean) of follow-up, 47,308 individuals developed HCC. HRs of HCC associated with BMIs of 25.0-26.4, 26.5-27.9, 28.0-29.4, 29.5-30.9 and ≥31 kg/m² compared to those for 23.5-24.9 kg/m² were 1.05, 1.20, 1.39, 1.59 and 2.13, respectively. For BMI < 25 kg/m², linear associations were not apparent. For BMI ≥ 25 kg/m, the HR per 5 kg/m increase in BMI was 1.60 (total), 1.60 (men), and 1.59 (women). The corresponding HRs were 1.56, 1.61 and 1.60 for individuals aged <45, 45-64 and ≥65 years, respectively. Further adjustment for alanine transaminase (ALT) levels substantially reduced the HRs for high BMI, especially in men and younger adults.

Conclusions: Overweight and obesity clearly increase HCC risk in Koreans. ALT levels are a mediator of the impact of obesity, but it may not accurately predict high BMI-induced liver damage that can potentially progress to HCC, especially in women and older adults.