Non-alcoholic fatty liver disease with obesity as an independent predictor for incident gastric and colorectal cancer: a population-based longitudinal study

BACKGROUND: Colorectal cancer is known to be an extrahepatic complication of non-alcoholic fatty liver disease (NAFLD). However, the interaction of NAFLD with obesity for incident colorectal cancer has not been clarified yet. Moreover, the effect of NAFLD and obesity for incident gastric cancer has not been clarified yet. Thus, we investigated whether NAFLD with or without obesity would be a risk factor for incident gastric cancer as well as colorectal cancer. METHODS: The study period was set from 2003 to 2016. NAFLD was diagnosed by abdominal ultrasonography using standardised criteria. We applied the Cox proportional hazards model to investigate the effect of NAFLD with or without obesity at baseline on incident gastric cancer as well as colorectal cancer. Age, sex, lifestyle factors including smoking states, alcohol consumption and exercise, and diabetes were used as covariates. RESULTS: During the study period, 27 944 individuals (16 454 men and 11 490 women) were registered in the NAfld in Gifu Area, Longitudinal Analysis study. During the mean (SD) observational period of 2357 (1458) days, incident gastric cancers were diagnosed in 48 individuals (incident rate 0.48 per 1000 person-years) and incident colorectal cancers were diagnosed in 52 individuals (incident rate 0.51 per 1000 person-years). The adjusted HR of NAFLD with obesity for incident gastric cancer was 3.58 (95% CI 1.73 to 7.38, p=0.001) and that for incident colorectal cancer was 2.96 (95% CI 1.73 to 7.38, p=0.003). CONCLUSION: NAFLD with obesity was a risk factor for both incident gastric cancer and colorectal cancer in apparently healthy Japanese individuals.