Background: Breast cancer is the most common cancer among women in North Africa, yet subtype-specific and modifiable determinants remain insufficiently characterized. Morocco is undergoing rapid transitions in reproductive behaviours and lifestyle, including reduced parity and breastfeeding, dietary changes, and increasing overweight and obesity, but their contribution to breast cancer risk remains unclear.
Objectives: To investigate reproductive, anthropometric, lifestyle, and environmental factors associated with breast cancer among Moroccan women in the Determinants of Breast Cancer in Morocco (EDSMAR) study.
Methods: EDSMAR is a population-based, individually matched case–control study conducted in Rabat and Fez by Moroccan cancer centres in partnership with the International Agency for Research on Cancer (IARC) and funded by the Lalla Salma Foundation for the Prevention and Treatment of Cancer. Incident, histologically confirmed breast cancer cases were recruited within one month of diagnosis and before initiation of systemic treatment. Controls were selected from the same neighbourhoods and individually matched to cases by age (±5 years). Data were collected using standardized face-to-face questionnaires and anthropometric measurements. Information included socio-demographic characteristics; reproductive history; breastfeeding; medical history; family history of breast cancer; hormonal factors; screening practices; radiation-related history; lifestyle factors; and environmental exposures, notably insecticide exposure. Anthropometric measurements included weight, height (BMI), and waist and hip circumferences. Univariate analyses were performed using chi-square or Fisher’s exact tests and ANOVA when appropriate. Multivariable conditional logistic regression models included variables with p<0.20 in univariate analyses, and results are presented as adjusted odds ratios (ORs) with 95% confidence intervals (CI).
Results: The analysis included 497 cases and 497 matched controls (mean age: 49.8 years). In univariate analyses, breastfeeding and higher parity were inversely associated with breast cancer, while insecticide exposure, higher BMI, central adiposity, sedentary behaviour, thoracic irradiation, and prior mammography were more frequent among cases.
In multivariable analysis, insecticide exposure remained independently associated with increased breast cancer risk (OR=1.59; 95% CI: 1.08–2.33). Sedentary behaviour was also associated with higher risk (OR=5.56; 95% CI: 1.26–24.53). Compared with women with 0–1 pregnancy, those with 2–3 full-term pregnancies had a significantly reduced risk (OR=0.43; 95% CI: 0.21–0.87). A strong association was observed for prior mammography (OR=8.61; 95% CI: 5.69–13.02), which should be interpreted cautiously due to potential reverse causation or detection bias.
Conclusions: In this large Moroccan case–control study, reproductive factors, sedentary behaviour, and environmental insecticide exposure were independently associated with breast cancer risk. These findings highlight the importance of modifiable lifestyle and environmental