Prevalence and risk of colorectal adenoma in asymptomatic Koreans aged 40-49 years undergoing screening colonoscopy

Background and Aim: Colorectal cancer screening is recommended for average-risk persons beginning at age 50. However, information about the incidence and risk factors of precursor adenoma in preceding decades is limited. The aim of this study was to determine the prevalence and risk factors of colorectal adenoma in persons aged 40-49 years and to compare the data with those aged 30-39 years and 50-59 years. Methods: A cross-sectional study of 5254 asymptomatic subjects who underwent screening colonoscopy was conducted. Data were stratified by age into three groups: 608 aged 30-39 years, 1930 aged 40-49 years, and 2716 aged 50-59 years. Results: Prevalence of overall adenomas was 10.4% in the 30-39 years age group, 22.2% in the 40-49 years age group, and 32.8% in the 50-59 years age group. Advanced adenoma was found in 0.7% of the 30-39 years age group, 2.7% of the 40-49 years age group, and 4.1% of the 50-59 years age group. In the 40-49 years age group, male sex and current smoking habits showed associations with low-risk adenoma after multiple adjustments. Moreover, male sex (odds ratio [OR] = 1.55, 95% confidence interval [CI]: 1.02-3.23), current smoking (OR = 1.58, 95%CI: 1.06-3.50), and family history of colorectal cancer (OR = 2.54, 95%CI: 1.16-5.56) were independent predictors of advanced adenoma in this age group. Conclusions: Prevalence of adenoma in subjects aged 40-49 years was higher than in previous studies. Male sex and current smoking habits along with a family history of colorectal cancer were associated with advanced adenoma in this age group.