Risk Factors for Proximal and Distal Advanced Colorectal Conventional and Serrated Neoplasia in Adults Under Fifty Years of Age

Introduction: Colorectal cancer (CRC) has increased in adults <50, particularly in the distal colon. Data examining the risk factors for advanced colorectal neoplasia in young adults as stratified by anatomic location have important implications for screening and risk modification. Methods: We conducted a cross-sectional analysis of data from New Hampshire Colonoscopy Registry participants <50. We developed an ‘average-risk equivalent’ sample by excluding patients with IBD, genetic syndromes and those with indications predictive of colorectal neoplasia such as anemia or hematochezia. Our outcomes were left and right-sided advanced conventional neoplasia ( > 1cm; villous or high grade dysplasia), advanced serrated neoplasia (>1cm or with dysplasia) and having synchronous advanced neoplasia and sessile serrated polyps/lesions. Results: We included 14,369 patients, <50 years at colonoscopy. Increased risk of left-sided advanced neoplasia was observed with current smoking (OR 2.14), male sex (OR 1.66), older age (OR 1.07), and higher BMI (OR 1.02). Right-sided advanced neoplasia was associated with smoking (OR 1.71), family history of CRC (OR 1.62), older age (OR 1.07), and higher BMI (OR 1.03). Left advanced serrated neoplasia was associated with older age (OR 1.08), and higher BMI (OR 1.05). Left- sided synchronous lesions were associated with smoking (OR 2.33), older age (OR 1.08), and higher BMI (OR 1.04). Right-sided synchronous lesions were associated with family history of CRC (OR 1.67). The lower bound of the 95% confidence interval for each odds ratio was greater than 1. Conclusion: We identified modifiable risk factors including current smoking and higher BMI in young adults with right and left sided colorectal polyps. Older age, male sex and family history were non-modifiable predictors. These data can help to inform screening and prevention of CRC in young adults.