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

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.

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.

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; I(2) = 85.7) followed by age at marriage (25-29 vs < 18 years old) (OR = 2.00, 95% CI 1.53 to 2.61; I(2) = 0), second-hand smoking (OR = 1.86, 95% CI 1.58 to 2.19; I(2) = 0), smoking (OR = 1.83, 95% CI 1.41 to 2.38; I(2) = 18.9), abortion history (OR = 1.44, 95% CI 1.02 to 2.05; I(2) = 66.3), oral contraceptive use (OR = 1.35, 95% CI 1.11 to 1.63; I(2) = 74.1), age at marriage (18-24 vs < 18 years old) (OR: 1.22, 95% CI 1.02 to 1.47; I(2) = 0). Of non-modifiable risk factors, history of radiation exposure (OR = 3.48, 95% CI 2.17 to 5.59; I(2) = 0), family history of breast cancer (OR = 2.47, 95% CI 1.83 to 3.33; I(2) = 73), and age at menarche (12-13 vs ≥ 14 years old) (OR = 1.67, 95% CI 1.31-2.13; I(2) = 25.4) significantly increased the risk of breast cancer.

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.