Background: The USPSTF recommends beginning colorectal cancer screening at age 50. A recent study showed prevalence of colorectal adenomas among individuals aged 40-49 was similar to that among those aged 50-59.
Aim: To assess the prevalence of colorectal neoplasia, detected during colonoscopy, by age among average-risk patients.
Methods: Nine-hundred and ninety-four colonoscopies were analyzed (247 ages 40-49, 747 ages 50-59). We included consecutive patients of ages 40-59 undergoing their first colonoscopy. Colonoscopies that did not reach the cecum and patients at increased risk of colorectal cancer were excluded. The primary endpoint was the prevalence of colorectal neoplasia by age. Secondary endpoints included the prevalence of colorectal neoplasia by gender, ethnicity, and BMI.
Results: The prevalence of colorectal neoplasia was 12.1% in patients aged 40-49 and 22.6% in those aged 50-59. Compared with individuals aged 40-49 there was a significantly greater prevalence of adenomas (chi-squared = 12.72, P = 0.0004) and of advanced adenomas or cancer (chi-squared = 5.73, P = 0.01) in individuals aged 50-59. After adjusting for gender, race, and BMI the effect of age remained significant (OR 0.5, 95% CI 0.33-0.76). Higher BMI was associated with increased risk of colorectal neoplasia (OR 1.03, 95% CI 1.00-1.06). The number that had to be screened to detect one advanced lesion in the 40-49 age group was 49 compared with 20 in those aged 50-59.
Conclusion: Individuals aged 40-49 have a lower but measurable risk of colorectal neoplasia compared with those aged 50-59. Although there may be population subgroups for which screening below the age of 50 may be indicated, our results do not support lowering the age threshold for colonoscopy in the general population.