Fatty Liver and Risk of Head and Neck Cancer in Type 2 Diabetes Mellitus: A Nationwide Cohort Study

SIMPLE SUMMARY: The incidence of non-alcoholic fatty liver disease (NAFLD) is >2-fold higher in patients with diabetes mellitus (DM). NAFLD is thought to increase the risk of extrahepatic cancer; however, existing data on NAFLD and the risk of head and neck cancer (HNC) are limited. This is the first study to report the associations between NAFLD and HNC in Type 2 DM (T2DM) patients. Using a population-based retrospective cohort study with a total of 1,904,376 subjects with T2DM who received a health checkup during 2009–2012, NAFLD was associated with an increased risk of developing HNC in the oral cavity, pharynx, and larynx, but not in the salivary gland. Future investigations which would determine the underlying mechanism and how improvement of NAFLD can reduce the development of HNC are necessary. ABSTRACT: This study is aimed at investigating the association between NAFLD and the risk of HNC separately based on cancer site using a large population-based cohort of patients with T2DM. The data used in this population-based retrospective cohort study were provided by the Korean National Health Insurance Service. The Cox proportional hazards model was used to estimate multivariable adjusted hazard ratios and 95% CIs for the association of the fatty liver index (FLI) and the risk of HNC. During the mean 6.9 years of follow-up, approximately 25.4% of the study cohort had NAFLD, defined as an FLI ≥60. A total of 3543 HNC cases were identified. Overall, patients with a higher FLI had a significantly higher risk of HNC in the oral cavity, pharynx, and larynx compared with patients with an FLI <30. An association was not observed between salivary gland cancer and FLI. There was no association between obesity and HNC. However, obese patients showed a lower risk of cancer for the oral cavity (p = 0.040), pharynx (p = 0.009), and larynx (p < 0.001) than non-obese patients with the same FLI level. Neither obesity nor smoking affected the association between FLI- and HNC-risk in stratified analyses. In T2DM patients, NAFLD was associated with an increased risk of developing HNC in the oral cavity, pharynx, and larynx, but not in the salivary gland.