body mass index and risk of breast cancer: a systematic review and meta-analysis in iran

Background: various studies in iran on the role of bmi higher than normal (bmi ≥25) on breast cancer have reported different results.objective: the aim of this systematic review and meta-analysis is to estimate the odds ratio of overweightness and obesity as risk factors of breast cancer in studies conducted in iran.evidence acquisition: the following main databases were searched from 2004 to 2014 to find related articles: pubmed, web of science, google scholar, scopus and iranian databases (sid and magiran), breast cancer conferences held in iran, key journals, and the references of the selected articles. keywords were: cancer, tumor, neoplasm, neoplasia, carcinoma, malignancy, malignant, benign. the combination with or and added it to search field with and to words such as iran and breast was used as the search strategy. the observational studies (cohort, case-control, and cross-sectional) in iran that had reported the relation between bmi and breast cancer in persian and english were searched. there were no limitations in terms of age, race, ethnicity, and marital status for women. the exposure was bmi ≥ 25 (overweight and obese) and the outcome was breast cancer with pathological confirmation. two reviewers separately used the strobe checklist for quality assessment, critically appraised papers and extract the data. the overall estimate was the odds ratio.results: of 4396 studies, after evaluation of heterogeneity, 7 case-control studies with a sample size of 33552 were included in the meta-analysis. a significant relation was observed between obesity (or = 1.81, 95% ci = 1.24 - 2.64) and odds of breast cancer. a significant relation was also observed between overweightness and odds of breast cancer (or = 1.46, 95% ci = 1.13 - 1.89).conclusions: meta-analysis results showed a significant relation between obesity and overweight with risk of breast cancer in iranian women. we recommended iranian women to be aware of the effect of weight on breast cancer and encouraged them to decrease their weight via physical activity and diet control.