Diabetes Mellitus Type 2 and Prolonged Exposure to Estrogen as Risk Factors for Development of Breast Cancer in Women of Age 35-70 in Yerevan: A Case-Control Study

Abstract

Objectives: To investigate the associations of diabetes mellitus type 2 and prolonged exposure to estrogen with the risk of breast cancer development in women of age 35-70 residing in Yerevan. Methods: A sample of 368 cases and controls was contacted through telephone interviews. Cases (n=150) were women of age 35-70 residing in Yerevan, registered in National Oncology Center and Armenian-American Wellness Center with confirmed diagnosis of breast cancer within 2002-2008. Controls (n=152) were women of the same age group residing in Yerevan recruited through random digit dialing. The study employed a telephone based, interviewer-administered structured questionnaire for data collection. Results: Multiple logistic regression analyses revealed that diabetes mellitus type 2 increased the odds of developing breast cancer by factor 5.53 (95% CI 1.34-22.81) and that any birth had a protective effect on breast cancer development (adjusted OR=0.36, 95% CI 0.20-0.66). Additionally, each one year delay in age at first pregnancy was positively associated with breast cancer development (adjusted OR=1.13, 95% CI 1.01-1.27). Induced abortions increased odds of developing breast cancer by factor 2.86 (95% CI 1.02-8.04). Age and BMI were confounding factors for association between diabetes type 2 and breast cancer. Family history had no interaction with diabetes type 2 and women reproductive characteristics resulting in prolonged exposure to estrogen as risk factors for breast cancer development. Conclusions: In this project, diabetes mellitus type 2, live births, early age first full-term pregnancy, and induced abortions were independent risk factors for development of breast cancer. The current findings serve as a basis for further investigations of global regional patterns of association between diabetes type 2 and female reproductive characteristics and risk of breast cancer development.