Income Dynamics and Incident Esophageal Cancer: A Retrospective Cohort Study

BACKGROUND: Although socioeconomic status is a recognized risk factor for esophageal cancer (EC), most studies have examined socioeconomic status at a single time point. We investigated the association between income dynamics and incident EC. METHODS: We analyzed 3,361,091 Korean adults aged 30-65 years who underwent health screening in 2012. Income dynamics from 2008 to 2012, derived from National Health Insurance premium data, were characterized as i) income variability (year-to-year percentage change standard deviations), ii) cumulative years in the lowest or highest income group, and iii) directional income change. Incident EC was identified using ICD-10 codes from 2013 to 2022. RESULTS: During follow-up of 9.3 years, 1,943 EC cases occurred. Compared to the highest income group, the lowest income group (Medical Aid + quartile 1) had a higher EC risk (adjusted hazard ratios [aHR]Q4 vs. MA+Q1 1.22; 95% confidence interval [CI], 1.07-1.38; p for trend <0.001). Greater income variability (aHRQ4 vs. Q1 1.21; 95% CI, 1.06-1.37; p for trend=0.003), longer cumulative low-income duration (aHR5 vs.0 years 1.21; 95% CI, 1.03-1.42; p for trend=0.001), and a decline from high- to low-income status (aHR 1.39; 95% CI, 1.05-1.83) were also associated with increased risk. Sustained high-income status was inversely associated with EC risk (aHR5 vs.0 years 0.83; 95% CI 0.73-0.93; p for trend=0.002). CONCLUSIONS: Higher income variability, persistently low income, and income decline over the 5-year income assessment period were independently associated with increased EC risk. IMPACT: Incorporating income trajectories may help EC risk stratification and preventive strategies.