Dynamic income patterns and risk of pancreatic and biliary tract cancers: A nationwide cohort study

This study aimed to evaluate the associations of baseline income, cumulative income exposure, and income volatility with the incidence of pancreatic and biliary tract cancers in a nationwide Korean cohort.

We analyzed 3,361,091 adults aged 30-65 years who underwent the 2012 National Health Insurance Service (NHIS) health screening. Income level was derived from insurance premium data assessed over the five years preceding baseline (2008-2012) and categorized into baseline income quartiles, cumulative exposure to low or high income, and income volatility based on annual percentage changes. Incident pancreatic and biliary tract cancers were identified using diagnostic codes and the copayment reduction registry. Associations were evaluated using Cox proportional hazards models with adjustment for demographic, lifestyle, and clinical covariates, and cumulative incidence was compared using Kaplan-Meier curves.

During a median follow-up of 9.6 years, 14,469 pancreatic cancers and 6,647 biliary tract cancers were newly diagnosed. Lower baseline income was associated with a higher risk of pancreatic and biliary tract cancers, whereas sustained high-income exposure was associated with reduced risk. Cumulative low-income exposure showed a positive linear trend with pancreatic cancer incidence. Income volatility was modestly associated with pancreatic cancer and was positively associated with biliary tract cancer in the fully adjusted model. These associations were generally consistent across subgroups, with a stronger inverse association between prolonged high-income exposure and pancreatic cancer among individuals without diabetes.

Income level and income stability were significantly associated with the incidence of pancreatic and biliary tract cancers. Lower baseline income was associated with higher risk, whereas sustained high-income exposure was protective. Income volatility was associated with increased cancer risk, particularly for biliary tract cancer. These findings highlight the importance of incorporating income dynamics into cancer prevention strategies and addressing socioeconomic instability among vulnerable populations.