Cancer in North American Indians: Environment versus heredity

The risk of cancer is significantly lower among the Indians of North America than in the general populations of the United States and Canada. In American Indians (Amerinds), the age-adjusted mortality rate of cancer is only one-half to two-thirds the national overall rate for non-Indians living in the United States. Indian males of British Columbia also reportedly have about half the age-standardized cancer mortality rate recorded for non-Indian populations of that southwestern Canadian Province. Among the Amerind, the relative deficit for malignant neoplasms has been largely confined to males. Native Americans, as compared with Whites, have significantly lower rates for cancer of the lung, breast, and colon, but higher rates for the gallbladder, kidney and cervix. For these six anatomic sites, the cancer mortalities of populations with only partial Indian ancestry, such as the tribes in Oklahoma and the Mexican-Americans (most of whom have some Indian admixture) are generally intermediate between the rates for the US general population and the rates for tribes having predominantly full Indian heritage, (e.g., the Indians in Arizona and New Mexico).