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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Public Health

Year Degree Awarded

Summer 2014

First Advisor

Susan E. Hankinson

Second Advisor

Katherine W. Reeves

Third Advisor

Jing Qian

Fourth Advisor

Kathleen F. Arcaro

Subject Categories

Epidemiology

Abstract

Over the course of a lifetime, one in eight women will develop breast cancer. To date, 30-40% of breast cancer cases can be attributed to established risk factors, which supports the need for identification of additional modifiable risk factors. Therefore, we conducted three epidemiologic studies to examine the associations between nutritional, hormonal, and psychological risk factors and breast cancer risk.

In our first study, we examined the relationship between urinary melatonin levels and the risk of breast cancer in a nested-case control study within the Nurses’ Health Study II. While limited in some respects, experimental and epidemiologic evidence support the potential relationship between melatonin as a protective factor against breast cancer risk. In this updated analysis of our previously published results with longer follow-up time and a greater sample size, adding cases that occurred more distant from urine collection, we did not observe a significant association between urinary melatonin levels and breast cancer risk.

In our second study, we investigated the associations between dairy consumption (overall and by specific dairy products) and circulating hormone levels in the Nurses’ Health Study. In this study, we observed a significant positive association between low-fat dairy intake and plasma levels of IGF-I that persisted after adjustment for IGFBP-3, and a significant decrease in SHBG; however, no significant associations emerged between dairy intake and prolactin or sex steroid hormone levels.

In our third study, we examined the associations between depressive symptoms, antidepressant (AD) use, and breast cancer risk in the Women’s Health Initiative Observational Study. Depressive symptoms and AD use were associated with a significant increased risk of total breast cancer; however, no association was observed with invasive breast cancer. Depressive symptoms and AD use were each associated with a non-significant increased risk of in situ breast cancer. However, this association appeared due largely to a positive association with in situ breast cancer that was based, at least in part, on increased mammographic screening among exposed women.

In summary, these studies add to the growing literature of potentially modifiable risk factors and their relationships with breast cancer risk.

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