@article {817, title = {Population structure, admixture, and aging-related phenotypes in African American adults: the Cardiovascular Health Study.}, journal = {Am J Hum Genet}, volume = {76}, year = {2005}, month = {2005 Mar}, pages = {463-77}, abstract = {

U.S. populations are genetically admixed, but surprisingly little empirical data exists documenting the impact of such heterogeneity on type I and type II error in genetic-association studies of unrelated individuals. By applying several complementary analytical techniques, we characterize genetic background heterogeneity among 810 self-identified African American subjects sampled as part of a multisite cohort study of cardiovascular disease in older adults. On the basis of the typing of 24 ancestry-informative biallelic single-nucleotide-polymorphism markers, there was evidence of substantial population substructure and admixture. We used an allele-sharing-based clustering algorithm to infer evidence for four genetically distinct subpopulations. Using multivariable regression models, we demonstrate the complex interplay of genetic and socioeconomic factors on quantitative phenotypes related to cardiovascular disease and aging. Blood glucose level correlated with individual African ancestry, whereas body mass index was associated more strongly with genetic similarity. Blood pressure, HDL cholesterol level, C-reactive protein level, and carotid wall thickness were not associated with genetic background. Blood pressure and HDL cholesterol level varied by geographic site, whereas C-reactive protein level differed by occupation. Both ancestry and genetic similarity predicted the number and quality of years lived during follow-up, but socioeconomic factors largely accounted for these associations. When the 24 genetic markers were tested individually, there were an excess number of marker-trait associations, most of which were attenuated by adjustment for genetic ancestry. We conclude that the genetic demography underlying older individuals who self identify as African American is complex, and that controlling for both genetic admixture and socioeconomic characteristics will be required in assessing genetic associations with chronic-disease-related traits in African Americans. Complementary methods that identify discrete subgroups on the basis of genetic similarity may help to further characterize the complex biodemographic structure of human populations.

}, keywords = {African Americans, Aged, Aging, Algorithms, Cardiovascular Diseases, Cohort Studies, Female, Genetics, Population, Genotype, Humans, Male, Models, Genetic, Phenotype, Polymorphism, Single Nucleotide, Quantitative Trait Loci, Risk Factors, Socioeconomic Factors}, issn = {0002-9297}, doi = {10.1086/428654}, author = {Reiner, Alexander P and Ziv, Elad and Lind, Denise L and Nievergelt, Caroline M and Schork, Nicholas J and Cummings, Steven R and Phong, Angie and Burchard, Esteban Gonz{\'a}lez and Harris, Tamara B and Psaty, Bruce M and Kwok, Pui-Yan} } @article {927, title = {African ancestry, socioeconomic status, and kidney function in elderly African Americans: a genetic admixture analysis.}, journal = {J Am Soc Nephrol}, volume = {17}, year = {2006}, month = {2006 Dec}, pages = {3491-6}, abstract = {

Kidney disease is a major public health problem in the United States that affects African Americans disproportionately. The relative contribution of environmental and genetic factors to the increased burden of kidney disease among African Americans is unknown. The associations of genetic African ancestry and socioeconomic status with kidney function were studied cross-sectionally and longitudinally among 736 community-dwelling African Americans who were aged >65 yr and participating in the Cardiovascular Health Study. Genetic African ancestry was determined by genotyping 24 biallelic ancestry-informative markers and combining this information statistically to generate an estimate of ancestry for each individual. Kidney function was evaluated by cystatin C and estimated GFR (eGFR) using the Modification of Diet in Renal Disease equation. Longitudinal changes in serum creatinine and eGFR were estimated using baseline and follow-up values. In cross-sectional analyses, there was no association between genetic African ancestry and either measure of kidney function (P = 0.36 for cystatin C and 0.68 for eGFR). African ancestry was not associated with change in serum creatinine > or =0.05 mg/dl per yr (odds ratio [OR] 0.94; 95\% confidence interval [CI] 0.83 to 1.06) or with change in eGFR > or =3 ml/min per 1.73 m(2) per yr (OR 1.02; 95\% CI 0.92 to 1.13). In contrast, self reported African-American race was strongly associated with increased risk for kidney disease progression compared with white individuals for change in creatinine (OR 1.77; 95\% CI 1.33 to 2.36) and for change in eGFR (OR 3.21; 95\% CI 2.54 to 4.06). Among self-identified African Americans, low income (< US dollars 8000/yr) was strongly associated with prevalent kidney dysfunction by cystatin C >1.29 g/dl (adjusted OR 2.7; 95\% CI 1.0 to 7.5) or by eGFR <60 ml/min per 1.73 m(2) (adjusted OR 3.2; 95\% CI 1.1 to 9.4) compared with those with incomes >US dollars 35,000/yr. Alleles that are known to be present more frequently in the African ancestral group were not associated with kidney dysfunction or kidney disease progression. Rather, kidney dysfunction in elderly African Americans seems more attributable to differences in environmental and social factors.

}, keywords = {African Americans, Aged, Creatinine, Cross-Sectional Studies, Cystatin C, Cystatins, Disease Progression, Female, Glomerular Filtration Rate, Humans, Kidney Diseases, Linear Models, Longitudinal Studies, Male, Social Class}, issn = {1046-6673}, doi = {10.1681/ASN.2006050493}, author = {Peralta, Carmen A and Ziv, Elad and Katz, Ronit and Reiner, Alex and Burchard, Esteban Gonz{\'a}lez and Fried, Linda and Kwok, Pui-Yan and Psaty, Bruce and Shlipak, Michael} } @article {1218, title = {Genetic ancestry in lung-function predictions.}, journal = {N Engl J Med}, volume = {363}, year = {2010}, month = {2010 Jul 22}, pages = {321-30}, abstract = {

BACKGROUND: Self-identified race or ethnic group is used to determine normal reference standards in the prediction of pulmonary function. We conducted a study to determine whether the genetically determined percentage of African ancestry is associated with lung function and whether its use could improve predictions of lung function among persons who identified themselves as African American.

METHODS: We assessed the ancestry of 777 participants self-identified as African American in the Coronary Artery Risk Development in Young Adults (CARDIA) study and evaluated the relation between pulmonary function and ancestry by means of linear regression. We performed similar analyses of data for two independent cohorts of subjects identifying themselves as African American: 813 participants in the Health, Aging, and Body Composition (HABC) study and 579 participants in the Cardiovascular Health Study (CHS). We compared the fit of two types of models to lung-function measurements: models based on the covariates used in standard prediction equations and models incorporating ancestry. We also evaluated the effect of the ancestry-based models on the classification of disease severity in two asthma-study populations.

RESULTS: African ancestry was inversely related to forced expiratory volume in 1 second (FEV(1)) and forced vital capacity in the CARDIA cohort. These relations were also seen in the HABC and CHS cohorts. In predicting lung function, the ancestry-based model fit the data better than standard models. Ancestry-based models resulted in the reclassification of asthma severity (based on the percentage of the predicted FEV(1)) in 4 to 5\% of participants.

CONCLUSIONS: Current predictive equations, which rely on self-identified race alone, may misestimate lung function among subjects who identify themselves as African American. Incorporating ancestry into normative equations may improve lung-function estimates and more accurately categorize disease severity. (Funded by the National Institutes of Health and others.)

}, keywords = {Adolescent, Adult, African Americans, Aged, Aged, 80 and over, Female, Forced Expiratory Volume, Genetic Markers, Genotype, Humans, Linear Models, Male, Middle Aged, Oligonucleotide Array Sequence Analysis, Reference Values, Respiratory Function Tests, Vital Capacity, Young Adult}, issn = {1533-4406}, doi = {10.1056/NEJMoa0907897}, author = {Kumar, Rajesh and Seibold, Max A and Aldrich, Melinda C and Williams, L Keoki and Reiner, Alex P and Colangelo, Laura and Galanter, Joshua and Gignoux, Christopher and Hu, Donglei and Sen, Saunak and Choudhry, Shweta and Peterson, Edward L and Rodriguez-Santana, Jose and Rodriguez-Cintron, William and Nalls, Michael A and Leak, Tennille S and O{\textquoteright}Meara, Ellen and Meibohm, Bernd and Kritchevsky, Stephen B and Li, Rongling and Harris, Tamara B and Nickerson, Deborah A and Fornage, Myriam and Enright, Paul and Ziv, Elad and Smith, Lewis J and Liu, Kiang and Burchard, Esteban Gonz{\'a}lez} }