Award Date

5-1-2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental and Occupational Health

First Committee Member

Francisco Sy

Second Committee Member

Paulo S. Pinheiro

Third Committee Member

Tirth Bhatta

Fourth Committee Member

Brian Labus

Fifth Committee Member

Timothy Bungum

Number of Pages

113

Abstract

Colorectal cancer (CRC) is the third leading cause of cancer incidence and mortality in the United States, with an estimated 140,000 new cases and 51,000 deaths expected in 2018. Like most cancers, the burden of CRC is unequally distributed among population groups. The current dissertation included two studies filling gaps in knowledge about CRC disparities. Study 1 characterized the relationship between educational attainment and CRC mortality by race/ethnicity. Six years of CRC mortality data (2012-2017) from the diverse state of California, with 30,180 deaths were analyzed. Sex-specific mortality rate ratios (MRR) stratified by race/ethnicity as well as by educational level were computed using negative binomial regression models. Among Non-Hispanic White (NHW), Non-Hispanic Black (NHB), Hispanic, and Asian/Pacific Islander (API) men and women, those with only a high school education had between 8%-45% higher CRC mortality than those with at least an Associate’s Degree. Mortality advantages for APIs and Hispanics, typically reported in the literature, were limited to the lower levels of education. At the highest educational level, Filipino men had 17% (MRR:1.17; 95% CI: 1.01-1.37) higher mortality than NHWs. Study 2, using 12,413 CRC cases in Nevada from 2003-2013, calculated five-year cause-specific, age-adjusted, overall survival from CRC, stratified by sex, race/ethnicity, and region of Nevada using the life tables method. Cox Proportional Hazards regression modelling computed determinants of CRC survival. Five-year CRC survival was low: 56.0% (95% CI: 54.6-57.5) among males and 59.5% (95% CI: 58.0-61.1) among females; significantly lower than national 5-year survival. No survival disparities were found between NHW and NHB populations in Nevada. Low survival was driven by populous Southern Nevada: After adjustment for all covariates, Southern Nevadans were at 17% higher risk of death than their counterparts in Northwestern Nevada (HR: 1.17; 95% CI: 1.08-1.27). CRC screening, comparatively low among Nevadans, immigrants, minorities, and people with lower levels of education, is one modifiable factor that has the potential to improve CRC outcomes. Collaboratively, all stakeholders must aggressively approach any opportunities to improve primary prevention of CRC as well as to maximize the CRC survival potential, thus, reducing the number of deaths from this potentially preventable cancer.

Keywords

Colorectal cancer; Disparities; Education; Immigrants; Mortality; Survival

Disciplines

Epidemiology | Public Health

Language

English

Available for download on Friday, May 15, 2020


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