Risk Factors of Proximal and Distal Advanced Colorectal Conventional and Serrated Neoplasia in Adults Younger Than 50 Years of Age.

[INTRODUCTION] Colorectal cancer (CRC) has increased in adults younger than 50 years of age, particularly in the distal colon. Data examining the risk factors of 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 younger than 50 years of age. 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-sided and right-sided advanced conventional neoplasia (≥1 cm; villous or high grade dysplasia), advanced serrated neoplasia (>1 cm or with dysplasia), and having synchronous advanced neoplasia and sessile serrated polyps/lesions.

[RESULTS] We included 14,369 patients, younger than 50 years at colonoscopy. Increased risk of left-sided advanced neoplasia was observed with current smoking (odds ratio [OR] 2.14), male sex (OR 1.66), older age (OR 1.07), and higher body mass index (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% CI for each OR was ＞1.

[DISCUSSION] 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 nonmodifiable predictors. These data can help to inform screening and prevention of CRC in young adults.