The prevalence of colorectal adenomas in Maori and New Zealand Europeans parallels colorectal cancer rates.

Background: New Zealand (NZ) has a high incidence of colorectal cancer (CRC). Maori have a documented incidence that is approximately half that found in NZ Europeans, possibly the result of under-reporting.
Aim: To determine and compare the prevalence of colorectal adenomas in Maori and NZ European patients.
Methods: Colonoscopy records from the Middlemore Colonoscopy Audit Database between 1 July 2001 and 31 December 2005 were reviewed. Studies performed for indications associated with an increased risk of colorectal polyps were excluded from the analysis. Patient demographics, including self-identified ethnicity, and number and location of colonic polyps were recorded. All polyp histology was reviewed.
Results: Data was analysed from 2842 colonoscopies--2523 were NZ Europeans (mean age 67 yrs) and 319 were Maori patients (mean age 60.6 yrs). To adjust for age, a comparison of data between 40 and 59 years was undertaken. In 643 (81.2%) NZ Europeans, polyps were identified in 213 (33.1%). In the 149 (18.8%) Maori patients, polyps were identified in 35 (23.5%) p=0.029. The comparative rates of adenomas in NZ Europeans and Maori were 16.7% and 8.7% respectively (p=0.019; 8% difference, CI=2.3-13.9%).
Conclusion: The prevalence of colorectal adenomas in Maori is approximately half that found in NZ Europeans. This mirrors the reported difference in CRC incidence between these groups and lends support to this being a real finding and not a bias in the manner in which the data has been collected.