Abstract 5319: Comparison of changes in waist circumference and body mass index (BMI) through adulthood and their relationship with advanced colorectal neoplasia
Authors: Gathirua-Mwangi Wambui G. , Monahan Patrick , Song Yiqing , Zollinger Terrell , Stump Timothy , Champion Victoria , Imperiale Thomas 
Published: July 2017

Abstract
Background: Waist circumference (WC) is a stronger predictor of colon cancer risk than body mass index (BMI); however, how well change in either WC or BMI over time predicts the risk of AN remains unclear.
Purpose: To investigate 1) the relationship between change in adiposity measures (BMI and WC) from early adulthood to older age and the risk of advanced colorectal neoplasia (AN) and 2) whether WC change or BMI change is a stronger predictor of risk of AN.
Methods: The sample included 4,500 adults, 50-80 years with no previous colorectal cancer or adenomatous polyps and undergoing first-time screening colonoscopy. Participants reported adiposity measures (height, weight and WC) at early adulthood (age 21) and at time of screening (mean age 57). Changes in BMI were categorized as 1) increase from healthy BMI to overweight or obese, 2) increase from overweight to obese, and 3) stable BMI level at age 21 and time of screening. WC was defined as high-risk for females with a WC ≥35 and males ≥40 inches. Changes for WC were categorized as 1) increase from a low-risk WC to a high-risk WC, and 2) stable-risk WC at age 21 and time of screening. Gender, age, family history, exercise, aspirin use, alcohol, smoking and intake of red meat and vegetables were included in the logistic models.
Results: Being obese both at age 21 and at screening resulted in a significant increased risk of AN (OR=1.87; 95% CI 1.08-3.23) compared to those with a stable-healthy BMI at both time points. Stable overweight BMI at age 21 and at screening (OR=1.54; 95% CI 0.97-2.45) and increased BMI from healthy to overweight or obese and overweight to obese were not associated with AN, as compared to those who had a healthy BMI at both time points. Compared to those with a low-risk WC at both time points, those who had a high-risk WC at age 21 and at time of screening had a two-fold increased risk of AN (OR=2.15; 95% CI 1.35-3.45). Increasing WC from age 21 to time of screening compared to those with low-risk WC was not associated with risk of AN (OR=1.23; 95% CI 0.97-1.57).
When both WC and BMI change were included, WC change (=10.15, 2 DF, p-value=0.0062) but not BMI change (=5.66, 2 DF, p-value=0.34) predicted risk of AN.
Conclusions: Maintaining a high-risk WC or obese BMI is associated with increased risk for AN; however, when BMI is controlled, maintaining a high-risk WC may independently increase the risk for AN. Practitioners should caution adults with high-risk WC and obese BMI values to better control their adiposity.
Citation Format: Wambui G. Gathirua-Mwangi, Patrick Monahan, Yiqing Song, Terrell Zollinger, Timothy Stump, Victoria Champion, Thomas Imperiale. Comparison of changes in waist circumference and body mass index (BMI) through adulthood and their relationship with advanced colorectal neoplasia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5319. doi:10.1158/1538-7445.AM2017-5319