Increased homeostasis model assessment-insulin resistance is a risk factor for colorectal adenoma in Japanese males

Many previous reports have documented a relationship between metabolic syndrome, in terms of insulin resistance, and colorectal cancer. However, the association of insulin resistance with colorectal adenoma has not been investigated in detail. To elucidate the association of metabolic syndrome components and insulin resistance with adenoma, we investigated homeostasis model assessment insulin resistance (HOMA-IR) in individuals with adenoma. A cross-sectional study was conducted involving individuals who underwent scheduled health examinations using total colonoscopy. Restricting the subjects to males, 261 with adenoma and 702 without adenoma were investigated. HOMA-IR was categorized into three groups: normal (< 1.6), intermediate (≥ 1.6 - < 2.5), and insulin resistance (2.5 ≤). Metabolic syndrome was defined by a combination of any three of the following components: central obesity (waist circumference ≥ 90 cm); elevated blood pressure (systolic blood pressure ≥ 130 mmHg and/or diastolic blood pressure 85 mmHg); elevated fasting plasma glucose (≥ 100 mg/dL); reduced high-density lipoprotein-cholesterol (< 40 mg/dL); and elevated triglyceride (≥ 150 mg/dL). Multivariate analysis of HOMA-IR showed that the intermediate and insulin resistance groups had a significantly increased risk for colorectal adenoma, even after adjustment for waist circumference (odds ratio, 1.62 and 2.23; 95% confidence interval, 1.07-2.45 and 1.31-3.79, respectively). Accumulation of any metabolic syndrome components increased the risk of colorectal adenoma (P trend = 0.001). However, none of the components alone demonstrated a significant risk for colorectal adenoma. Our data indicate that an increased level of HOMA-IR is a risk factor for colorectal adenoma in Japanese males.