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Obesity Increases Prevalence of Colonic Adenomas at Screening Colonoscopy: A Canadian Community-Based 时间:2017-07-17 13:38 来源:未知作者:admin 点击: 次 Abstract:Background and Aims. Obesity is a risk factor for colorectal neoplasia. We examined the influence of obesity and metabolic syndrome (MetS) on prevalence of neoplasia at screening colonoscopy. Methods. We evaluated 2020 subjects undergoing first screening colonoscopy. Body mass index (BMI) was calculated at enrolment. Hyperlipidemia (HL), hypertension (HT), and diabetes mellitus (DM) were identified. Details of colonoscopy, polypectomy, and histology were recorded. Odds for adenomas (A) and advanced adenomas (ADV) in overweight (BMI 25.1–30) and obese (BMI > 30) subjects were assessed by multinomial regression, adjusted for covariates. Analyses included relationships between HL, HT, DM, age, tobacco usage, and neoplasia. Discriminatory power of HT, HL, DM, and BMI for neoplasia was assessed by binary logistic regression. Odds were calculated for neoplasia in each colonic segment related to BMI. Results. A and ADV were commoner in overweight and obese males, obese females, older subjects, and smokers. HL, HT, and DM were associated with increased odds for neoplasia, significantly for A with hypertension. BMI alone predicted neoplasia as well as HT, HL, DM, or combinations thereof. All segments of the colon were affected. Multiple polyps were particularly prevalent in the obese. Conclusions. Obesity and MetS are risk factors for colonic neoplasia in a Canadian population.
1. Background
Colorectal cancer (CRC) is the third most common cancer in Canada and the second and third commonest fatal cancer in men and women, respectively [1]. Several modifiable factors have been suspected to increase susceptibility to CRC. Of these, increased weight and smoking have been strongly implicated [2, 3].
Obesity is increasingly prevalent in Canadians. In 2014, 62% of males and 46% of females were self-reportedly either overweight (BMI 25 to 30 kg/m2) or obese (BMI > 30 mg/kg2) [4]. If CRC risk indeed increases with weight, the burden of CRC in Canada will be substantially augmented as the population becomes heavier. In that case, lifestyle counselling might ameliorate the risk or the overweight population might be targeted for enhanced CRC screening.
CRC evolves via the adenoma-carcinoma sequence. Modifiable factors might influence CRC incidence through an increase in adenoma formation, an increased conversion rate of adenoma to carcinoma, or an amplification of alternate pathways. Studies carried out elsewhere describe an increased prevalence of both nonadvanced and advanced adenomas with increasing BMI [5, 6], suggesting that obesity promotes neoplastic change at an early stage by increasing adenoma formation.
The mechanisms whereby obesity might promote colonic carcinogenesis are complex, involving insulin resistance, hyperinsulinemia, insulin-like growth factor, adipokines, and inflammation [7]. Insulin resistance and hyperinsulinemia are the foundation of the metabolic syndrome (MetS), whose elements include obesity, type II diabetes mellitus (DM), hyperlipidemia (HL), and hypertension (HT). Earlier studies indicate an increased risk for CRC in persons with MetS [8] as well as an incrementally increased risk for CRC and colorectal adenomas with the number of elements of MetS present [9, 10] suggesting that MetS might be included in the list of CRC risk factors. However, others have not found such an association [11].
Risk stratification for CRC assigns subjects to average versus high risk categories. There is controversy about the most cost-effective screening strategy for average-risk individuals. Controlled trials demonstrating the superiority of colonoscopy are in progress. In the meantime, some jurisdictions, including our own, advocate for fecal occult blood testing or flexible sigmoidoscopy as proven entities [12]. Even so, it is agreed that subjects considered at high risk for CRC would be better served by colonoscopy [13]. This would currently apply to those with a significant family history of CRC or a personal history of colonic neoplasia. Other risk factors, including male sex, ethnicity, tobacco usage, and obesity are not considered sufficiently influential to justify primary colonoscopy. Should any of these factors prove to be strongly associated with CRC, affected individuals might be preferentially assigned to colonoscopy.
This study was designed to examine the relationship between BMI and colonic neoplasia in a Canadian population undergoing screening colonoscopy. The secondary objective was to determine which components of MetS are associated with adenoma prevalence.