Obesity and younger versus older onset colorectal cancer in the United States, 1998–2017

The etiology behind the increasing incidence of early onset colorectal cancer (EOCRC) are incompletely elucidated, but could be attributed in part to lifestyle factors. We assessed the association between obesity and colorectal cancer (CRC) in younger versus older adults in the National Health Institute Survey. Multivariable logistic regression defined adjusted odds ratios (AORs) and associated 95% confidence intervals (CIs) for CRC including an age (< vs. ≥50 years) *BMI (< vs. ≥30.0 kg/m²) interaction term. Among 583,511 study participants with a total of 3,173 CRC cases, there was a significant age*BMI interaction term (P=0.02) such that for participants aged 18–49 years, BMI ≥30.0 kg/m² was associated with diagnosis of CRC (34.1% vs. 27.4%, AOR 1.39, 95% CI: 1.00–1.92) but not for participants aged ≥50 (29.6% vs. 31.4%, AOR 0.93, 95% CI: 0.85–1.03). Obese BMI appears to be associated with diagnosis of EOCRC, thus weight control by early adulthood, among other healthy lifestyle behaviors, could serve as potential risk reduction strategies for CRC.