Fundamental causes of accelerated declines in colorectal cancer mortality: Modeling multiple ways that disadvantage influences mortality risk

Background Improvements in colorectal cancer (CRC) mortality reflect the distribution of effective preventions. Social inequalities often generate unequal diffusion of medical interventions, resulting in disparate outcomes while preventions are being disseminated throughout the population. This study used a novel method to examine whether Race (Black versus White) and SES influenced when rates of CRC mortality started to decline, and how rapidly they did so. Method Mortality counts from 1968-2010 were derived from death certificates of U.S. residents aged 25 + years. Individuals’ race, age, county of residence, and sex were collected from death certificates. County-level SES was measured using the decennial U.S. census. Layered joinpoint regression was used to model CRC mortality trends over time. Acceleration in rates of historical decline were used to indicate preventability within counties. Results Black race was associated with a 4.1-year delay in colonoscopy-attributable declines in CRC mortality and each standard deviation unit change in SES with a 5.7-year delay in such mortality. Following the onset of a decline, colonoscopy-attributable mortality change was slower by 0.5% among Blacks, and 2.0%/standard deviation in SES. Modifying the rapidity of colonoscopy uptake could have averted 12–14,000 and 83–86,000 deaths among Blacks and residents of lower SES counties, respectively. Conclusions Successful interventions do not uniformly benefit the U.S. population. This study highlighted the notable impact that substantial delays in the provision of interventions, and in the relative rapidity of dissemination, and estimated the extent to which there was a preventable loss of life concentrated amongst the most disadvantaged. A more egalitarian delivery of life-saving interventions could drastically reduce mortality by improving effectiveness of interventions while also addressing inequalities in health.