A Cohort Study on Smoking Prevalence and Cancer Incidence: A County-Level Analysis (2011-2015) Restricted; Files Only
Brooks, Sheree (Spring 2025)
Abstract
Introduction: Smoking is one of the leading causes of cancer and continues to contribute to millions of cases of morbidity and mortality worldwide each year. Despite ongoing efforts to raise awareness and reduce smoking-related cancers, tobacco products generate billions in annual revenue and disproportionately impact minority populations. Understanding population-level smoking patterns across diverse demographics is essential for addressing disparities in current incidence rates of bladder, colorectal, and kidney cancers.
Purpose: The aim of this study was to investigate the association between smoking prevalence and incidence rates of bladder, colorectal and kidney cancers at the county level.
Method: Data were obtained from the Environmental Protection Agency (EPA) and included adults over the age of 50 from 943 counties across 19 states. The dataset covered county-level smoking prevalence and cancer incidence from 2011 to 2015. In this retrospective cohort study, smoking prevalence, the primary exposure variable, was categorized into two quartiles. Incidence rates of bladder, colorectal, and kidney cancers were the primary outcomes. Statistical analyses were performed (adjusting for various covariates), with significance levels set at p < 0.05, and results reported as incidence rate ratios with 95% confidence limits.
Results: Univariable analysis indicated higher incidence rates of bladder, colorectal and kidney cancers in counties with higher smoking prevalence. The strongest associations were observed for bladder (IRR = 1.57) and colorectal (IRR = 1.51) cancers. Multivariable analyses confirmed elevated risks for bladder (IRR = 1.27, 95% Cl: 1.21-1.33), colorectal
(IRR = 1.17, 95% Cl: 1.13-1.21) and kidney (IRR=1.20, 95% Cl: 1.11-1.30) cancers after adjusting for covariates.
Conclusion: This study provides compelling evidence that smoking prevalence at the county level is significantly associated with increased incidence rates of bladder, colorectal, and kidney cancers in the United States. Counties with higher smoking prevalence (>50%) consistently exhibited elevated cancer incidence across all three types, supporting the hypothesis that smoking remains a major contributor to cancer burden at the population level.
Table of Contents
Table of Contents
Chapter I: Introduction…………………………………….1
Chapter II: Literature Review…………………….....……5
Chapter II: Methodology ………………….………….….17
Chapter IV: Results………………………….…..…………21
Chapter V: Implications, Limitation & Conclusion...28
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