Understanding the Rising Incidence of Early-Onset Colorectal Cancer: Life-Course Determinants and Opportunities for Primary Prevention
Simple Summary Colorectal cancer diagnosed before age 50 is becoming more common in many countries, although the reasons remain uncertain. This review examined 75 publications on lifestyle, metabolic, clinical, medication-related, and social factors associated with early-onset disease. The clearest associations involved excess body weight and poor metabolic health. Physical inactivity, smoking, alcohol consumption, and dietary patterns showed less consistent associations, while inflammatory bowel disease emerged as a clinical risk condition. Evidence on medications and social conditions was limited. Many of these factors influence colorectal cancer at older ages; their relevance to earlier-onset disease may depend on when exposure begins, its duration, and how exposures interact over time. The findings support prevention throughout the life course with healthier food and activity environments, tobacco control, reduced harmful alcohol use, and better metabolic health. However, observational evidence does not establish that any single factor causes early-onset colorectal cancer or should independently determine screening eligibility.