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We examined the proportions of multiple types of breast cancers in the population that were attributable to established risk factors, focusing on behaviors that are modifiable at menopause. We estimated the full and partial population attributable risk percentages (PAR%) by combining the relative risks and the observed prevalence rates of the risk factors of interest. A total of 8,421 cases of invasive breast cancer developed in postmenopausal women (n = 121,700) in the Nurses' Health Study from 1980-2010. We included the following modifiable risk factors in our analyses: weight change since age 18 years, alcohol consumption, physical activity level, breastfeeding, and menopausal hormone therapy use. Additionally, the following nonmodifiable factors were included: age, age at menarche, height, a combination of parity and age at first birth, body mass index at age 18 years, family history of breast cancer, and prior benign breast disease. When we considered all risk factors (and controlled for age), the PAR% for invasive breast cancers was 70.0% (95% confidence interval: 55.0, 80.7). When considering only modifiable factors, we found that changing the risk factor profile to the lowest weight gain, no alcohol consumption, high physical activity level, breastfeeding, and no menopausal hormone therapy use was associated with a PAR% of 34.6% (95% confidence interval: 22.7, 45.4). The PAR% for modifiable factors was higher for estrogen receptor-positive breast cancers (PAR% = 39.7%) than for estrogen receptor-negative breast cancers (PAR% = 27.9%). Risk factors that are modifiable at menopause account for more than one-third of postmenopausal breast cancers; therefore, a substantial proportion of breast cancer in the United States is preventable.

Original publication

DOI

10.1093/aje/kww145

Type

Journal article

Journal

Am J Epidemiol

Publication Date

15/12/2016

Volume

184

Pages

884 - 893

Keywords

PAR%, modifiable factors, postmenopausal breast cancer, Age Factors, Alcohol Drinking, Body Height, Body Mass Index, Breast Feeding, Breast Neoplasms, Estrogen Replacement Therapy, Exercise, Female, Genetic Predisposition to Disease, Global Health, Humans, Incidence, Life Style, Longitudinal Studies, Menarche, Menopause, Postmenopause, Prevalence, Proportional Hazards Models, Protective Factors, Reproductive History, Risk Factors, United States, Weight Gain