Breast cancer risk factors in Iranian women: a systematic review and meta-analysis of matched case–control studies

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Abstract
Background: Identifying breast cancer risk factors is a critical component of preventative strategies for this disease. This study aims to identify modifiable and non-modifiable risk factors of breast cancer in Iranian women. Methods: We used international databases (PubMed/Medline, Scopus, Web of Knowledge, and Embase) and national databases (SID, Magiran, and ISC) to retrieve relevant studies until November 13, 2022. The odds ratio (OR) with a 95% confidence interval using the random-effect model was used to estimate the pooled effect. The publication bias was assessed by the Egger and Begg test. A sensitivity analysis was conducted to evaluate the effect of each included study on the final measurement. Results: Of the 30,351 retrieved articles, 24 matched case–control records were included with 12,460 participants (5675 newly diagnosed cases of breast cancer and 6785 control). This meta-analysis showed that of the known modifiable risk factors for breast cancer, obesity (vs normal weight) had the highest risk (OR = 2.17, 95% CI 1.47 to 3.21; I2 = 85.7) followed by age at marriage (25–29 vs < 18 years old) (OR = 2.00, 95% CI 1.53 to 2.61; I2 = 0), second-hand smoking (OR = 1.86, 95% CI 1.58 to 2.19; I2 = 0), smoking (OR = 1.83, 95% CI 1.41 to 2.38; I2 = 18.9), abortion history (OR = 1.44, 95% CI 1.02 to 2.05; I2 = 66.3), oral contraceptive use (OR = 1.35, 95% CI 1.11 to 1.63; I2 = 74.1), age at marriage (18–24 vs < 18 years old) (OR: 1.22, 95% CI 1.02 to 1.47; I2 = 0). Of non-modifiable risk factors, history of radiation exposure (OR = 3.48, 95% CI 2.17 to 5.59; I2 = 0), family history of breast cancer (OR = 2.47, 95% CI 1.83 to 3.33; I2 = 73), and age at menarche (12–13 vs ≥ 14 years old) (OR = 1.67, 95% CI 1.31–2.13; I2 = 25.4) significantly increased the risk of breast cancer. Conclusions: Since most risk factors related to breast cancer incidence are modifiable, promoting healthy lifestyles can play an influential role in preventing breast cancer. In women with younger menarche age, a family history of breast cancer, or a history of radiation exposure, screening at short intervals is recommended.

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