Intestinal polyps in American negroes and Nigerian africans.

Forty Africans from Nigeria and 89 American negroes with colorectal polyps were analysed by age, sex and type of polyp. The Nigerians were much the younger group (mostly under 20 years of age, whereas most of the American negroes were over 50) and far fewer of their polyps were truly neoplastic (7.5% compared with 87% of the Americans). These differences may be partly due to the American negro population being older than the Nigerian, and partly to environmental factors like those previously postulated to account for the difference in colon cancer incidence between these populations.