Adenoma detection and advanced neoplasia prevalence in average-risk adults aged 40 to 49 years: a systematic review...

The prevalence of adenomas and advanced neoplasia (AN) in average-risk adults younger than 50 years remains incompletely characterized. We performed a systematic review and meta-analysis to estimate adenoma detection rate (ADR) and AN prevalence in average-risk individuals aged 40 to 49 years.

PubMed (MEDLINE), Web of Science, and Scopus were searched from January 1, 2010, to August 8, 2025. Epidemiologic studies reporting outcomes for individuals aged 40 to 44 and/or 45 to 49 years were included; studies reporting only an aggregated "<50 years" category were excluded. Quantitative pooling was restricted to average-risk and screening-equivalent populations, excluding cohorts enriched for high-risk symptoms or family history. Random-effects meta-analyses were performed with prespecified sensitivity analyses.

Nineteen studies including 7.2 million colonoscopies met the inclusion criteria for qualitative synthesis and 16 for quantitative meta-analysis. Pooled ADR increased from 13.4% (95% CI, 7.4-20.9; I² = 99.8%) at ages 40 to 44 to 18.4% (95% CI, 12.8-24.8; I² = 99.6%) at ages 45 to 49. Pooled AN increased from 3.3% (95% CI, 2.3-4.6; I² = 97.5%) to 4.5% (95% CI, 3.5-5.7; I² = 97.4%). In several cohorts, AN prevalence in individuals aged 45 to 49 years was comparable to that observed in early-50s comparator groups. Sensitivity and exploratory analyses yielded consistent estimates.

Average-risk adults aged 45 to 49 years demonstrated a clinically meaningful burden of adenomas and AN, exceeding that of 40- to 44-year-olds and approaching early-50s comparator groups in several cohorts. These findings provide colonoscopy-based evidence relevant to ongoing discussions regarding the optimal age for colorectal cancer screening initiation.