Date on Master's Thesis/Doctoral Dissertation

8-2024

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Epidemiology and Population Health

Degree Program

Public Health Sciences with a specialization in Epidemiology, PhD

Committee Chair

Dupre, Natalie

Committee Member

Baumgartner, Rick

Committee Member

Boone, Stephanie

Committee Member

Ellis, Tyler

Committee Member

Ruther, Matthew

Author's Keywords

colorectal cancer; hotspot; greenness

Abstract

Background: Across Kentucky, county-level geographic disparities in colorectal cancer (CRC) incidence and outcomes exist. Given the heterogeneity of lifestyle, socioeconomic (SES), and environmental factors within a county, more granular approaches should be used to identify local areas with a high CRC burden and identify the area-level factors that may contribute to geographic disparities. Studies reported that living in greener areas is associated with beneficial health outcomes, including lower mortality. Despite growing evidence that natural vegetation (greenness) exposure is associated with increased physical activity and obesity, two well-known CRC risk factors, epidemiological studies investigating the association of residential greenness exposure with CRC incidence and CRC mortality are sparse.

Methods: Using the Kentucky Cancer Registry 1995-2018 CRC case listing, I identified census-tract level hotspots of high CRC incidence, CRC mortality, and EOCRC incidence rates using a Getis-Ord Gi* statistic. Using logistic regression, I identified neighborhood-level characteristics associated with the identified CRC outcome hotspots. Additionally, an individual-level analysis utilized stratified multivariable logistic regression models to estimate the association of residential greenness in relation to residing in a CRC incidence hotspot among urban-dwelling and rural-dwelling CRC cases independent of individual and neighborhood CRC risk factors. Cox proportional hazards models were used to examine the association between residential greenness at diagnosis and CRC-specific mortality. Results: I identified 116 CRC incidence hotspots, 101 CRC mortality hotspots, and 81 EOCRC incidence hotspots. CRC incidence and CRC mortality hotspots were predominately urban, while EOCRC hotspots were predominately rural census tracts. All CRC outcome hotspots were associated with low SES markers. I observed that CRC cases living in census tracts with higher greenness exposure had lower odds of residing in a CRC hotspot, independent of individual-level risk factors and neighborhood characteristics. Residential greenness was not associated with colorectal cancer-specific death among Kentucky cases after adjustment. Conclusion: This research suggests that in addition to area-level SES and health behavior factors, residential greenness may be a contextual factor that contributes to certain areas having higher colorectal cancer rates, particularly in urban areas. Due to limited literature pertaining to residential greenness and CRC incidence and mortality, these relationships should be investigated further.

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