Background & Aims: The colorectal adenoma is the precursor lesion in virtually all colorectal cancers. Occurrence of colorectal adenomas has been studied in older adults but analysis in younger adults is lacking. Methods: The prevalence by age, sex, race, and location, and the number of colorectal adenomas detected was investigated using epidemiologic necropsy in 3558 persons ages 20 to 89 autopsied from 1985 to 2004 at the Johns Hopkins Hospital. Results were standardized to the general population. Younger adults 20 to 49 years old were compared with older adults 50 to 89 years old. Results: The prevalence of colorectal adenomas in younger adults increased from 1.72% to 3.59% from the third to the fifth decade of life and then sharply increased after age 50. In younger adults, adenomas were more prevalent in men than in women (risk ratio, 1.09; 95% confidence interval, 1.07-1.11) and in whites than in blacks (risk ratio, 1.28; 95% confidence interval, 1.26-1.31). Overall, both younger and older adults had predominately left-sided adenomas, but blacks in both age groups had more right-sided adenomas. Occurrence of 2 or more adenomas in younger adults and 5 or more in older adults was greater than 2 SDs from the mean. Conclusions: Colorectal adenomas infrequently occur in younger adults and are more prevalent in the left colon. Irrespective of age, blacks have more right-sided adenomas, suggesting the need for screening the entire colorectum. Two or more adenomas in younger adults and 5 or more in older adults represents polyp burden outside the normal expectation.
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