Dietary Patterns and Risk of Colorectal Cancer Among Adults in South West Nigeria: A Hospital-Based Case-Control Study

Colorectal cancer incidence is rising in Nigeria, consistent with the broader trend of increasing diet-related non-communicable diseases accompanying urbanisation and dietary transition. Dietary patterns are modifiable determinants of colorectal cancer risk, yet evidence from sub-Saharan African populations remains sparse. This study examines the association between dietary patterns and colorectal cancer risk at Lagos University Teaching Hospital and University College Hospital Ibadan, South West Nigeria. A hospital-based case-control study enrolled 120 histologically confirmed incident colorectal cancer cases and 240 controls hospitalised for non-malignant conditions, matched by age, sex, and hospital. Habitual dietary intake was assessed using a validated semi-quantitative food frequency questionnaire capturing the two years prior to diagnosis or interview. Major dietary patterns were derived using principal component analysis, and pattern scores were computed for each participant. Conditional logistic regression estimated odds ratios and 95 percent confidence intervals for colorectal cancer risk across tertiles of dietary pattern scores, adjusting for total energy intake, physical activity, alcohol consumption, body mass index, family history of colorectal cancer, and non-steroidal anti-inflammatory drug use. Findings will characterise protective and risk-associated dietary patterns in a Nigerian population and generate hypothesis-generating data to inform diet-cancer research in West Africa. This study fills an important evidence gap in the nutritional epidemiology of colorectal cancer in Nigeria. Keywords: dietary patterns, colorectal cancer, case-control, South West Nigeria, nutritional epidemiology.