Plasma α-Tocopherol, γ-Tocopherol and Incident, Sporadic Colorectal Adenoma Risk: A Pooled Case-Control Study Open Access

Tao, Liang (2014)

Permanent URL: https://etd.library.emory.edu/concern/etds/1831ck526?locale=en
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Abstract

Background: Since evidence on an association between tocopherols and colorectal cancer is limited, and mechanistic results from cell and animal models have been inconsistent with those from human studies, we investigated associations of plasma α-tocopherol (α-T) and γ-tocopherol (γ-T) concentrations with risk of incident, sporadic colorectal adenomas in a pooled colonoscopy-based case-control study.

Methods: We used pooled data collected in two previously conducted case-control studies (n = 184 adenoma cases and 250 controls). Multivariable logistic regression was used to estimate the associations of tocopherols with adenoma risk. Stratified analyses and the likelihood ratio test were used to examine effect modification by various risk factors and adenoma characteristics.

Results: No clear patterns of associations between the two tocopherols and incident, sporadic colorectal adenomas were found. Participants in the highest relative to those in the lowest tertile of plasma α-T levels were at an estimated 20% lower risk for adenoma, and those in the highest relative to the lowest tertile of plasma γ-T were at an estimated 24% higher adenoma risk. However, these results were not statistically significant, and there were no dose-response patterns to the associations across the tertiles. In stratified analyses, among those who regularly took NSAIDs, there was a stronger inverse association of α-T with adenomas (OR for those in the highest vs. the lowest tertile = 0.45 (95% CI 0.21, 1.00; Ptrend 0.03). Associations of plasma α-T and γ-T did not substantially differ by other demographic, lifestyle, dietary risk factors or by adenoma characteristics.

Conclusion: The results from this small case-control study suggest that high circulating α-T may be associated with lower, and high circulating γ-T may be associated with higher risk of incident sporadic colorectal adenomas, and support further investigation in a larger, preferably prospective study.

Table of Contents

Table of Contents

Chapter 1. Background................................................................................................................. 1

Chapter 2: Manuscript................................................................................................................. 11

Abstract............................................................................................................................ 11

Introduction...................................................................................................................... 12

Methods............................................................................................................................ 14

Study Population........................................................................................................ 14

Data Collection........................................................................................................... 16

Case-control assignment ............................................................................................. 16

Laboratory methods.................................................................................................... 17

Statistical Analysis...................................................................................................... 17

Results.............................................................................................................................. 19

Discussion.......................................................................................................................... 21

Reference........................................................................................................................... 25

Tables................................................................................................................................ 31

Chapter 3: Summary.................................................................................................................... 36

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