Synergistic association between underweight and type 2 diabetes on the development of laryngeal cancer: a national population-based retrospective cohort study.

BACKGROUND: Although cigarette smoking is the most significant risk factor for laryngeal cancer, other risk factors might also be associated with the development of laryngeal cancer. We investigated whether underweight and type 2 diabetes are associated with laryngeal cancer in a Korean population. METHODS: A total of 9,957,059 participants (≥20 years) without prior history of cancer who underwent a National Health Insurance Service health checkup in 2009 were followed up until December 31, 2018. Newly diagnosed laryngeal cancer was identified using claim data, and underweight was defined as body mass index (BMI) < 18.5 kg/m2. A Cox proportional-hazards models with multivariable adjustment were used to estimate hazard ratios (HRs) and corresponding 95% confidence intervals (95% CIs). RESULTS: During the median follow-up period of 8.3 years, 3504 cases of laryngeal cancer occurred. Underweight was associated with increased risk of laryngeal cancer after adjusting for potential confounders (HR: 1.43, 95% CI: 1.22-1.69) compared to those who were not underweight. Underweight and type 2 diabetes were synergistically associated with higher risk of laryngeal cancer (HR: 2.33, 95% CI: 1.54-3.51), compared to those without either condition. This relationship was stronger in those with an age < 65 years (HR: 3.33, 95% CI: 1.88-5.87) and alcohol consumption (HR: 2.72, 95% CI: 1.64-4.53). CONCLUSIONS: These results suggest that underweight may be a significant risk factor for laryngeal cancer and that underweight and type 2 diabetes might synergistically increase the risk of laryngeal cancer.