Jalal Poorolajal - MD, PhD, Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran- Modeling of Noncommunicable Diseases Research Center, Hamadan University of Medical Sciences, Hamadan, Iran- Research Center for Health Sc
Fatemeh Heidarimoghis - MSc, Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran
Manoochehr Karami - PhD, Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran- Social Determinants of Health Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
Zahra Cheraghi - PhD, Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran- Modeling of Noncommunicable Diseases Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
Fatemeh Gohari-Ensaf - MSc, Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran
Fatemeh Shahbazi - MSc, Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran

Background: This report provided the effect of ۱۵ preventable factors on the risk of breast cancerincidence.Study design: A systematic review and meta-analysis.Methods: A detailed research was conducted on PubMed, Web of Science, and Scopusdatabases in January ۲۰۲۰. Reference lists were also screened. Prospective cohort studiesaddressing the associations between breast cancer and ۱۵ factors were analyzed. Between-studyheterogeneity was investigated using the χ۲, τ۲, and I۲ statistics. The probability of publication biaswas explored using the Begg and Egger tests and trim-and-fill analysis. Effect sizes were expressedas risk ratios (RRs) with ۹۵% confidence intervals (CIs) using a random-effects model.Results: Based on the results, out of ۱۴۷,۰۸۳ identified studies, ۱۹۷ were eligible, including۱۹,۴۱۳,۷۰۲ participants. The RRs (۹۵% CI) of factors associated with breast cancer were asfollows: cigarette smoking ۱.۰۷ (۱.۰۵, ۱.۰۹); alcohol drinking ۱.۱۰ (۱.۰۷, ۱.۱۲); sufficient physicalactivity ۰.۹۰ (۰.۸۶, ۰.۹۵); overweight/obesity in premenopausal ۰.۹۲ (۰.۸۲, ۱.۰۳) andpostmenopausal ۱.۱۸ (۱.۱۳, ۱.۲۴); nulliparity ۱.۱۶ (۱.۰۳, ۱.۳۱); late pregnancy ۱.۳۷ (۱.۲۵, ۱.۵۰);breastfeeding ۰.۸۷ (۰.۸۱, ۰.۹۳); ever using oral contraceptive ۱.۰۰ (۰.۹۶, ۱.۰۵); ever using estrogen۱.۱۳ (۱.۰۴, ۱.۲۳); ever using progesterone ۱.۰۲ (۰.۸۴, ۱.۲۴); ever using estrogen/progesterone ۱.۶۰(۱.۴۲, ۱.۸۰); ever taking hormone replacement therapy ۱.۲۶ (۱.۲۰, ۱.۳۲); red meat consumption۱.۰۵ (۱.۰۰, ۱.۱۱); fruit/vegetable consumption ۰.۸۷ (۰.۸۳, ۰.۹۰); and history of radiation therapy,based on single study ۱.۳۱ (۰.۸۷, ۱.۹۸).Conclusions: This meta-analysis provided a clear picture of several factors associated with thedevelopment of breast cancer. Moreover, the useful information in this study may be utilized forranking and prioritizing preventable risk factors to implement effective prevention programs.

Breast neoplasms, Risk factors, Behavior, Nutrition, Meta-analysis