Date

April 2010

Document Type

Thesis

Degree Name

M.P.H.

Department

Dept. of Public Health and Preventive Medicine

Institution

Oregon Health & Science University

Abstract

With the rapid increase of obesity and cancer in the United States, it is imperative for scientists to understand how these two entities may be related to possibly increase risk of cancer. Incidence of type 2 diabetes and of prostate cancer have been increasing over the past 8 years, suggesting a possible shared mechanism of risk or association between the two. Previous epidemiological studies found that those with type 2 diabetes have a decreased risk of prostate cancer, while other epidemiological studies show that those with a history of type 2 diabetes may have a increased risk of other cancers such as lung and colorectal cancer. However, many of these studies have not evaluated an association between type 2 diabetes and fasting glucose and insulin levels and incident prostate cancer as the outcome in a large, prospective fashion and therefore, require further investigation. In addition, previous studies have not examined prediabetes as determined by fasting glucose and insulin levels in a prospective fashion and the relationship between these factors and prostate cancer risk. Analyzing these exposures (fasting glucose, insulin, and type 2 diabetes) is crucial to determining risk factors for and the biological mechanisms behind the onset of prostate cancer. We determined the relative risk estimates for the relationships between baseline fasting glucose and insulin levels and type 2 diabetes with incident prostate cancer in 5,995 men in the Osteoporotic Fractures in Men Study (MrOS) over 8 years of follow up. Compared to men with normal fasting glucose levels and no history of diabetes, we found no increased risk for incident prostate cancer in men with impaired fasting glucose levels (HR = 1.18; 95% CI 0.94, 1.50). Men with higher fasting insulin level had an increased risk of prostate cancer (HR = 1.52; 95% CI 1.09, 2.13) compared to those with lower fasting insulin level, but men with type 2 diabetes had a decreased risk of prostate cancer (HR = 0.56; 95% CI 0.37 - 0.85). The finding of increased prostate cancer risk in men with higher fasting insulin levels fits with current biologic models linking enhanced insulin signaling with development of prostate cancer. Finding that older men with type 2 diabetes are at a decreased risk of prostate cancer compared to those without diabetes suggests that other biological factors involved in glucose metabolism and obesity also play important roles in the relationship between obesity and prostate cancer.

Identifier

doi:10.6083/M4WM1BCJ

School

School of Medicine

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