Early-life anthropometry and colorectal cancer risk in adulthood: Global Cancer Update Programme (CUP Global) systematic literature review and meta-analysis of prospective studies

While adult anthropometric measures are well-studied in relation to colorectal cancer (CRC) risk, the impact of early-life anthropometry remains unclear. We conducted a systematic literature review and meta-analysis examining early-life anthropometry, including birth size, height and adiposity and adult CRC risk. We searched Medline, Embase, Web of Science and CENTRAL. Early-life stages were categorised as at birth, infancy (0 to <2 years), childhood (2 to 9 years), adolescence (10 to 19 years) and young adulthood (18 to 25 years). Random-effects meta-analyses were conducted when ≥3 prospective observational studies provided sufficient information; otherwise, results were descriptively synthesised. We included 37 publications, and evidence was graded by the Global Cancer Update Programme Expert Panel. Higher birthweight (relative risk [RR] per 1000 g: 1.09, 95% confidence interval [CI] 1.01–1.16; 8 studies, 8134 cases) and young adult body mass index (BMI, RR per 5 kg/m ²: 1.12, 95% CI 1.07–1.17; 16 studies, 20,365 cases) were associated with higher CRC risk. Associations for young adult BMI were most pronounced for colon cancer (RR per 5 kg/m ²: 1.15, 95% CI: 1.06–1.24). Descriptive synthesis showed that childhood and adolescent BMI were also associated with higher colon and/or CRC risk. Evidence for all the above associations was graded by the Expert Panel as “strong-probable.” Additionally, there was “limited-suggestive” evidence linking higher birthweight to higher colon cancer risk, taller childhood height to higher CRC risk, early-life adiposity—measured by BMI pictograms—to higher colon and CRC risk and higher young adult BMI to rectal cancer risk. Other exposure-outcome associations were graded as “limited-no conclusion.” Altogether, these results imply that larger body size during early life is associated with higher adult CRC risk.