Higher BMI Is Associated with Increased Detection of Adenomatous Polyps During Colonoscopy

Abstract

Purpose: Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer death in the United States. Obesity is a growing national concern; one in two Americans is overweight and one in three is obese. Recent data suggests that obesity is an independent risk factor for adenomas as well as for CRC. The purpose of our study is to characterize the relationship between BMI and the detection of colonic adenomas. Methods: Between March and July 2011 we prospectively enrolled 430 patients into the study. Participants completed a questionnaire before colonoscopy, and self-reported height and weight were used to calculate body mass index (BMI). Polyp detection rate (PDR) was calculated during colonoscopy and adenoma detection rate (ADR) was calculated after histologic review of each polyp. Adenomatous polyps included tubular adenoma, tubulovillous adenoma, villous adenoma and serrated sessile adenoma. BMI was categorized into 4 groups: <25 kg/m2, 25-29 kg/m2, 30-34 kg/m2 and ≥35 kg/m2. Pearson's Chi-square or Kendall's tau-b tests were used to identify factors associated with detection of polyps and adenomas. Multiple logistic regression analysis was performed to determine independent predictors for polyp and adenoma detection. Results: The mean age was 60.4 (24-84) and 211 (49.1%) participants were male. The mean BMI was 26.0 (15.4-53.4), including 45.1% below 25 kg/m2, 38.4% from 25-29 kg/m2, 10.5% from 30-34 kg/m2 and 6.0% ≥35 kg/m2. 87.3% of the bowel preps were excellent or good (total Ottawa score 4 or less). The overall PDR was 57.4% and the ADR was 44%. 35.5% of all adenomas were in the right colon (cecum and ascending colon). In a univariate analysis, age, gender and BMI were all significantly associated with PDR (p=0.001 for all). BMI was significantly associated with adenoma detection in the entire colon (p=0.003) and in the right colon only (p=0.009). After adjusting for age, gender, history of colonoscopy, type of bowel prep, quality of bowel prep (Ottawa score), race, BMI, and comorbidities, BMI remained independently associated with adenoma detection in the entire colon (p=0.032) and in the right colon (p=0.045). In a subset analysis, participants with BMI 30-34 mg/m2 had an odds ratio for adenoma detection in the right colon of 3.03 compared to participants with a BMI <25 kg/m2 (95% CI 1.33-6.90, p=0.008). Conclusion: Higher BMI was independently associated with detection of more adenomatous polyps in both the entire colon and in the right colon after multiple adjustments, including for age, gender, race, and quality of bowel preparation. This finding underscores the importance of aggressive colorectal cancer screening as the population of the United States becomes increasingly overweight and obese.