Overweight and obesity are associated with colorectal neoplasia in an Australian outpatient population

Colorectal cancer is a major cause of cancer-related deaths within the Australian population. Colonoscopy and polypectomy represent effective forms of prevention. Factors such as diabetes, hypertension and dyslipidaemia have been linked to adenoma development across a range of ethnicities, however there are limited data from the Australian population. This study investigates established and potential risk factors for early colorectal neoplasia in an Australian population. This was a prospective, observational case-control study in subjects aged 20-85 years, referred for outpatient colonoscopy. Clinical, anthropometric, and biochemical variables were collected at baseline. Polyps were classified as conventional adenomas or sessile serrated lesions, and correlated with clinical and biochemical variables. The study included 357 subjects, median age 55 years (IQR: 43.0-64.0), and 52.9% were female. 41.7% had metabolic syndrome. Multiple positive associations were observed in those over 40 years and with a BMI ≥ 25, including any polyp (aOR: 2.26; 95%CI: 1.22-4.18); adenoma (aOR: 2.64; 95%CI: 1.31-5.31); and, non-advanced adenoma (aOR: 2.66; 95%CI: 1.25-5.68). Our study demonstrates that elevated BMI is an independent risk factor for colorectal neoplasia in Australians undergoing colonoscopy. Further efforts should be focused on both diet and weight optimization in the general population given these findings and the recent national statistics indicating that almost two-thirds of the population are either overweight or obese.