Obesity as a risk factor for early-onset colorectal cancer: Evidence from a nationally representative database.

BACKGROUND

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths worldwide with an alarming rise in early-onset CRC (eoCRC) over the past several decades. Unlike late-onset CRC, the drivers behind eoCRC remain less clear. While certain risk factors such as obesity and smoking have demonstrated a relatively strong association with eoCRC in the literature, some studies have challenged these associations, emphasizing the need for additional studies.

AIM: To investigate the impact of various risk factors on eoCRC with a special focus on obesity.

METHODS

This cross-sectional study used de-identified data from the National Health and Nutrition Examination Survey (1999-2023), including 30321 United States adults aged 18 to 49 years. Participants with missing key variables were excluded. Standardized protocols were used to collect demographic, lifestyle, anthropometric [body mass index (BMI), body roundness index (BRI), waist circumference (WC)], and self-reported CRC data. Logistic regression and propensity score matching assessed associations between obesity-related parameters and eoCRC. Statistical analyses were performed in R and Stata, with P < 0.05 defined as significant.

RESULTS

Of 30321 participants, 48 received a diagnosis of eoCRC. Patients with eoCRC were older (mean age 39.96 years vs 34.36 years; P < 0.001) and had higher WC and BRI. None of the eoCRC patients were heavy drinkers (P = 0.006). Unadjusted models demonstrated significant associations of eoCRC with BRI quartiles, as well as BMI-defined obesity, WC, and smoking. In unadjusted models, BRI remained the strongest independent predictor; those in the highest BRI quartiles had over 10-fold greater odds of eoCRC. In fully adjusted models, BRI remained significant, but BMI- and waist-based obesity were not.

CONCLUSION

BRI is a stronger predictor of eoCRC risk compared to other obesity indices and is a superior tool for identifying young individuals at higher risk of CRC.