Genetic admixture and gallbladder disease in Mexican Americans.

Gallbladder disease is a common source of morbidity in the Mexican American population. Genetic heritage has been proposed as a possible contributor, but evidence for this is limited. Because gallbladder disease has been associated with Native American heritage, genetic admixture may serve as a useful proxy for genetic susceptibility to the disease in epidemiologic studies. The objective of our study was to examine the possibility that gallbladder disease is associated with greater Native American admixture in Mexican Americans. This study used data from the Hispanic Health and Nutrition Examination Survey and was based on 1,145 Mexican Americans who underwent gallbladder ultrasonography and provided usable phenotypic information. We used the GM and KM immunoglobulin antigen system to generate estimates of admixture proportions and compared these for individuals with and without gallbladder disease. Overall, the proportionate genetic contributions from European, Native American, and African ancestries in our sample were 0.575, 0.390, and 0.035, respectively. Admixture proportions did not differ between cases and noncases: Estimates of Native American admixture for the two groups were 0.359 and 0.396, respectively, but confidence intervals for estimates overlapped. This study found no evidence for the hypothesis that greater Native American admixture proportion is associated with higher prevalence of gallbladder disease in Mexican Americans. Reasons for the finding that Native American admixture proportions did not differ between cases and noncases are discussed. Improving our understanding of the measurement, use, and limitations of genetic admixture may increase its usefulness as an epidemiologic tool as well as its potential for contributing to our understanding of disease distributions across populations.