Transit Friction as an Independent Predictor of Head and Neck Cancer Mortality

Introduction: Time toxicity is a hypothesized driver of head and neck cancer (HNC) mortality. However, it is unclear if transit barriers persist as independent risk factors. We aimed to quantify the independent mortality of county-level transit friction (defined as the population proportion with public transit commutes 60 minutes or longer).

Methods: This cross-sectional study integrated NCI SEER mortality data with 2022 American Community Survey profiles. A cohort of 751 United States counties was analyzed, stratified by Census region: Northeast (n=124), Midwest (n=168), South (n=339), and West (n=120). The primary outcome was age-adjusted HNC mortality rate per 100,000 person-years. A multivariate linear regression model evaluated the interaction between transit friction and geography, adjusted for population density, educational attainment, insurance status, median income, veteran status, and disability prevalence.

Results: The final model demonstrated robust explanatory power (Adjusted R-squared = 0.484, p < .001). Significant independent predictors of mortality included disability prevalence (Beta = 0.059, p < .001) and southern geography (Beta = 0.306, p = .002). Conversely, population density (Beta = -0.384, p < .001), educational attainment (Beta = -0.022, p < .001), and veteran status (Beta = -0.037, p = .001) were protective. Even after adjusting for these factors, transit friction remained a significant driver of mortality through geographic interaction. The transit-related mortality penalty was most aggressive in the West (Beta = 0.084, p < .001), where infrastructural delays functioned as a structural determinant of survival regardless of household income (p = .59) or insurance status (p = .89).

Conclusions: Nearly half of the geographic variance in HNC mortality is explained by the intersection of biological frailty and transit friction. The finding that veteran status is protective suggests that integrated care coordination and assisted transportation may be the primary levers for achieving health equity in HNC.