Energy balance, risk of breast cancer, and prognosis after breast cancer: Investigating the complex roles of diet and physical activity.

摘要

Introduction: Breast cancer is a major cause of morbidity and mortality. Modifiable health behaviors, such as diet and physical activity, may be important for breast cancer prevention and survival, and are also key factors in regulating energy balance. The complex relationships between diet, physical activity, obesity, breast cancer risk reduction, and prognosis are understudied.;Methods: The three studies of this dissertation utilize detailed diet and physical activity questionnaires to estimate exposure to these potentially beneficial behaviors. Study I is a prospective cohort study of postmenopausal women without cancer that examines occupational and household activity, transportation activity, and sedentary behavior in relation to breast cancer risk. Study II is a prospective cohort study of survivors of early-stage breast cancer that tests whether postdiagnosis diet quality---alone and combined with recreational physical activity---is related to risk of death and breast-cancer-related events. Study III is a cross-sectional analysis among a cohort of breast cancer survivors that investigates the relationship between postdiagnosis diet quality, biomarkers of chronic inflammation, and adipokines.;Results: Study I: Postmenopausal women who routinely engaged in heavy lifting/carrying versus mostly sitting, as part of occupational/household activity, had a reduced risk of invasive breast cancer. Among these women, walking/biking to work for 6+ years versus 1 year was associated with a suggestive reduced risk of invasive breast cancer. Study II: Breast cancer survivors with better quality postdiagnosis diets had a reduced risk of death from any cause. Physically active survivors consuming better quality diets had a substantially reduced risk of death and of breast cancer-related events compared with inactive survivors with poor quality diets. Study III: Breast cancer survivors with better quality postdiagnosis diets had lower concentrations of C-reactive protein, a biomarker of chronic inflammation, and this relationship was pronounced among inactive survivors.;Conclusions: This dissertation provides evidence that routine occupational/household and transportation-associated activity may be related to lower risk of invasive breast cancer. Women diagnosed with breast cancer may benefit from adopting better quality postdiagnosis diets and active lifestyles. A better quality postdiagnosis diet may affect prognosis by reducing chronic inflammation, particularly among inactive survivors.