Fundamental causes of colorectal cancer mortality: the implications of informational diffusion

Abstract

Context: Colorectal cancer is a major cause of mortality in the United States, with 52,857 deaths estimated in 2012. To explore further the social inequalities in colorectal cancer mortality, we used fundamental cause theory to consider the role of societal diffusion of information and socioeconomic status.

Methods: We used the number of deaths from colorectal cancer in U.S. counties between 1968 and 2008. Through geographical mapping, we examined disparities in colorectal cancer mortality as a function of socioeconomic status and the rate of diffusion of information. In addition to providing year-specific trends in colorectal cancer mortality rates, we analyzed these data using negative binomial regression.

Findings: The impact of socioeconomic status (SES) on colorectal cancer mortality is substantial, and its protective impact increases over time. Equally important is the impact of informational diffusion on colorectal cancer mortality over time. However, while the impact of SES remains significant when concurrently considering the role of diffusion of information, the propensity for faster diffusion moderates its effect on colorectal cancer mortality.

Conclusions: The faster diffusion of information reduces both colorectal cancer mortality and inequalities in colorectal cancer mortality, although it was not sufficient to eliminate SES inequalities. These findings have important long-term implications for policymakers looking to reduce social inequalities in colorectal cancer mortality and other, related, preventable diseases.

FIGURE 1

Geographic Distribution of Main Independent Variables: (A) County-Level Gradations in Distribution of SES in 2000 and (B) State-Level Gradations in Propensity for Diffusion Before 1965. Source: Data are from the authors' calculations for SES from data by the U.S. Census Bureau's Decennial Census; and diffusion from Walker 1969.

FIGURE 2

Trends in Average Yearly Age-, Race-, and Sex-Adjusted Colorectal Cancer Mortality Rates, Separated into Tertiles of High, Middle, and Low Socioeconomic Status at the County Level, 1968–2008. Source: Data are from the NCHS compressed mortality file, 1968–2008.

FIGURE 3

Trends in Age-, Race-, and Sex-Adjusted Colorectal Cancer Mortality Rates, Separated into Tertiles of Fast, Medium, and Slow Diffusion at the State Level, 1968–2008. Source: Data are from the NCHS compressed mortality file, 1968–2008.

FIGURE 4

The Modified Impact of SES (MRRs) Estimated from Table 1, Assuming Three Different State-Level Diffusion Speeds, 1971–2008. Note: This figure uses estimates from model 3 in table 1 to show the relative impact of higher SES scores in three scenarios: higher propensity for faster diffusion, compared with average diffusion and a propensity for slow diffusion. Significance is achieved at the 1981–1985 year group. The relative impact of a one standard deviation (1 SD) higher SES in counties with average diffusion, compared with states of 1 SD higher SES with diffusion 1 SD above average and diffusion 1 SD below average, with 95% confidence intervals (shown using bars). Source: Data are from the NCHS compressed mortality file, 1968–2008.