World Cancer Research Fund International: Continuous Update Project—systematic literature review and meta-analysis of observational cohort studies on physical activity, sedentary behavior, adiposity, and weight change and breast cancer risk

Abstract

Purpose The purpose of the present study was to systematically review the complex associations between energy balancerelated factors and breast cancer risk, for which previous evidence has suggested different associations in the life course of women and by hormone receptor (HR) status of the tumor. Methods Relevant publications on adulthood physical activity, sedentary behavior, body mass index (BMI), waist and hip circumferences, waist-to-hip ratio, and weight change and pre-and postmenopausal breast cancer risk were identified in PubMed up to 30 April 2017. Random-effects meta-analyses were conducted to summarize the relative risks across studies. Results One hundred and twenty-six observational cohort studies comprising over 22,900 premenopausal and 103,000 postmenopausal breast cancer cases were meta-analyzed. Higher physical activity was inversely associated with both pre-and postmenopausal breast cancers, whereas increased sitting time was positively associated with postmenopausal breast cancer. Although higher early adult BMI (ages 18-30 years) was inversely associated with pre-and postmenopausal breast cancers, adult weight gain and greater body adiposity increased breast cancer risk in postmenopausal women, and the increased risk was evident for HR+ but not HR− breast cancers, and among never but not current users of postmenopausal hormones. The evidence was less consistent in premenopausal women. There were no associations with adult weight gain, inverse associations with adult BMI (study baseline) and hip circumference, and non-significant associations with waist circumference and waist-to-hip ratio that were reverted to positive associations on average in studies accounting for BMI. No significant associations were observed for HR-defined premenopausal breast cancers. Conclusion Better understanding on the impact of these factors on pre-and postmenopausal breast cancers and their subtypes along the life course is needed.

Adherence to the World Cancer Research Fund/American Institute for Cancer Research Recommendations and the Risk of Breast Cancer

“…Thus far, only very few modifiable risk factors for breast cancer have been recognized, including overweight/obesity, menopausal hormone replacement therapy (HRT), low physical activity and sedentary behavior, with possible differential associations in the life course of women [4,5]. Despite considerable research on the dietary correlates of breast cancer, no consistent evidence exists for specific foods, food groups or nutrients [6], except for the detrimental role of alcohol drinking [7].…”

Body size and composition, physical activity and sedentary time in relation to endogenous hormones in premenopausal and postmenopausal women: Findings from the UK Biobank

“…1,2 Overweight and obesity increase the risk of several cancers, including hormone-related cancers in women, 3 except for premenopausal breast cancer, for which obesity is associated with a lower risk. 4 In contrast, physical activity, one of the most modifiable lifestyle factors, appears to reduce the risk of several cancers, possibly independently of adiposity. [5][6][7] The associations between obesity, physical activity and cancer risk may be explained by a number of biological mechanisms including changes in hormones, metabolism, immune function and inflammation.…”

Binge Drinking and Risk of Breast Cancer: Results from the SUN (‘Seguimiento Universidad de Navarra’) Project

“…The consumption of sugar-sweetened beverages has been associated with breast cancer risk [20]. TV-watching was included in the model as a surrogate of sedentary behavior (also linked to breast cancer risk) [21]. As sensitivity analysis, we repeated our analyses for probable breast cancer cases and we included participants classified as abstainers at the baseline FFQ questionnaire.…”