Self reported non-insulin dependent diabetes, family history, and risk of prevalent colorectal cancer: population based, cross sectional study.

Several studies have shown positive associations between non-insulin dependent diabetes (NIDDM) and incidence of colorectal cancer. This relation, as well as the marked similarity of dietary and lifestyle risk factors for the two conditions, has led investigators to propose that hyperinsulinaemia may be the underlying link between NIDDM and colorectal cancer. It is thought that raised insulin levels, either indirectly or directly, may promote the growth of colorectal tumours. 3 Thus people with an inherited susceptibility to colorectal cancer and who also have NIDDM may be expected to be at even greater risk of colorectal cancer than from either risk factor alone. One measure of inherited susceptibility is family history of disease—an established risk factor for colorectal cancer. 5 We therefore examined the relation between NIDDM, family history and risk of prevalent colorectal cancer among middle aged and older British adults using data from a large population based study.