A fundamental cause approach to the study of disparities in lung cancer and pancreatic cancer mortality in the United States

This study examines how associations between socioeconomic status (SES) and lung and pancreatic cancer mortality have changed over time in the U.S. The fundamental cause hypothesis predicts as diseases become more preventable due to innovation in medical knowledge or technology, individuals with greater access to resources will disproportionately benefit, triggering the formation or worsening of health disparities along social cleavages. We examine socioeconomic disparities in mortality due to lung cancer, a disease that became increasingly preventable with the development and dissemination of knowledge of the causal link between smoking cigarettes and lung cancer, and compare it to that of pancreatic cancer, a disease for which there have been no major prevention or treatment innovations. County-level disease-specific mortality rates for those ≥45 years, adjusted for sex, race, and age during 1968-2009 are derived from death certificate and population data from the National Center for Health Statistics. SES is measured using five county-level variables from four decennial censuses, interpolating values for intercensal years. Negative binomial regression was used to model mortality. Results suggest the impact of SES on lung cancer mortality increases 0.5% per year during this period. Although lung cancer mortality rates are initially higher in higher SES counties, by 1980 persons in lower SES counties are at greater risk and by 2009 the difference in mortality between counties with SES one SD above compared to one SD below average was 33 people per 100,000. In contrast, we find a small but significant reverse SES gradient in pancreatic cancer mortality that does not change over time. These data support the fundamental cause hypothesis: social conditions influencing access to resources more greatly impact mortality when preventative knowledge exists. Public health interventions and policies should facilitate more equitable distribution of new health-enhancing knowledge and faster uptake and utilization among lower SES groups.