Long-Term Dietary Patterns and Breast Cancer Risk Among Nigerian Women: A Multi-Centre Case-Control Study

Breast cancer is the most common female malignancy in Nigeria, and while hormonal, reproductive, and genetic risk factors have received research attention, the contribution of long-term dietary patterns to breast cancer risk in Nigerian women remains empirically underdeveloped. This study examines the association between habitual dietary patterns and breast cancer risk in a multi-centre hospital-based case-control study conducted across three geopolitical zones. Study sites include the University College Hospital, Ibadan (South West), Federal Medical Centre, Owerri (South East), and Aminu Kano Teaching Hospital (North West). Three hundred and sixty histologically confirmed incident invasive breast cancer cases and 720 hospital controls were enrolled. Habitual dietary intake over the three to five years preceding diagnosis was assessed using a study-validated semi-quantitative food frequency questionnaire developed with culture-specific food lists derived from formative research in each zone. Major dietary patterns were identified using reduced rank regression using established breast cancer-relevant nutritional biomarkers as response variables, including serum oestradiol, insulin-like growth factor 1, adiponectin, and high-sensitivity C-reactive protein. Unconditional logistic regression with restricted cubic splines modelled dose-response relationships between dietary pattern scores and breast cancer risk, adjusting for age, menopausal status, body mass index, physical activity, breastfeeding history, parity, oral contraceptive use, and family history. Findings will generate the first multi-site dietary epidemiology evidence on breast cancer risk in Nigerian women, contributing to the development of culturally grounded dietary cancer prevention recommendations. Keywords: breast cancer, dietary patterns, case-control, Nigeria, reduced rank regression.