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Special Communication |

Genetic Influences on Health:  Does Race Matter?

Mike Bamshad, MD
JAMA. 2005;294(8):937-946. doi:10.1001/jama.294.8.937.
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Race is frequently used by clinicians and biomedical researchers to make inferences about an individual’s ancestry and to predict whether an individual carries specific genetic risk factors that influence health. The extent to which race is useful for making such predictions depends on how well race corresponds with genetic inferences of ancestry, how frequently common diseases in different racial groups are influenced by the same vs different gene variants, and whether such variants have the same effects in different racial groups. New studies of human genetic variation show that while genetic ancestry is highly correlated with geographic ancestry, its correlation with race is modest. Therefore, while data on the correspondence of race, ancestry, and health-related traits are still limited, particularly in minority populations, geographic ancestry and explicit genetic information are alternatives to race that appear to be more accurate predictors of genetic risk factors that influence health. Making accurate ancestry inferences is crucial because common diseases and drug responses are sometimes influenced by gene variants that vary in frequency or differ altogether among racial groups. Thus, operationalizing alternatives to race for clinicians will be an important step toward providing more personalized health care.

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Figure 1. Hypothetical Relationship Between Genetic Risk, Ancestry, and Race
Graphic Jump Location

Distributions of the reduction in blood pressure observed in African Americans and European Americans after treatment with an angiotensin-converting enzyme (ACE) inhibitor. One hypothetical explanation for the mean difference in treatment response is that a genetic risk variant predictive of a positive response to treatment is more common in European Americans (individuals to the right of the dotted line) than in African Americans. Note, however, that some African Americans also have the genetic risk variant and that many African Americans and European Americans who do not have the genetic risk variant have a similar response to treatment (ie, overlap between distributions). In this case, race might not be considered a good predictor of genetic risk or response to treatment. Based on original concept by Seghal.9

Figure 2. Inference of Individual Ancestry Proportions From Genetic Data
Graphic Jump Location

(A) A network depicting the genetic relatedness among individuals (circles) with self-identified ancestry from Africa (20), Asia (19), and Europe (20) genotyped for 250 coding single nucleotide polymorphisms (SNPs) for which the less common allele has a frequency of at least 10% (Bamshad et al32). The length of each branch (black lines) is proportional to genetic distance between individuals and populations. Distinguishing individuals by race (shaded areas) obscures this variation in ancestry. The distance between any 2 circles of the same color (solid lines) is large and reflects high within-population variance, whereas the distance between clusters (dotted lines) is small and reflects low between-population variance. Individuals with a higher proportion of ancestry from more than one population (individual 2) are connected directly to the branches between clusters. (B) The genetic distance between individuals is reflected by the sum of the branch lengths between individuals. The genetic distance between individuals from different populations, such as individuals 1 and 3, is slightly greater than the genetic distance between individuals within the same population, such as individuals 1 and 2. Thus, despite the high within-population variance, individuals from different populations are, on average, more different from one another than individuals from the same population. (C) Inferred ancestry proportions for individuals (circles) used in panel A genotyped for 500 coding SNPs with a minor allele frequency of at least 10%. The distance of each circle to an apex is proportional to the degree of ancestry in African Americans, Asian Americans, or European Americans. The degree to which the circles are clustered within a population reflects the degree of admixture and structure within a population. The circles representing African Americans are less tightly clustered because the proportion of ancestry among individuals is more varied than in Asian Americans and European Americans. Distinguishing individuals by race (shaded areas) obscures this variation in ancestry. Data source for panels B and C, Bamshad et al.32

Figure 3. Distribution of Common Single Nucleotide Polymorphisms (SNPs) Present in Only One Population vs Common in Only One Population Among Hispanics, African Americans, Asian Americans, and European Americans
Graphic Jump Location

Comparison of common SNPs identified by resequencing 3873 genes in 17 Hispanics, 20 African Americans, 19 Asian Americans, and 20 European Americans. (A) The proportion of SNPs that are common (ie, ≥10%) in at least one population but found in both populations is high overall but varies from 72% to 96%. A modest proportion of common SNPs that are common in at least one population are absent in the other population. For example, only 4% of SNPs common in European Americans or Hispanics are not present in both populations, whereas 28% of SNPs common in African Americans or Asian Americans are not present in both populations. (B) The proportion of common SNPs common in both populations compared with SNPs common in only each population compared. Overall, only a modest proportion (44%-72%) of SNPs common in one population are common in both populations. A substantial proportion of common SNPs in African Americans are common only in African Americans. Data source: Genaissance Pharmaceuticals Inc, New Haven, Conn, unpublished data, August 2005.

Figure 4. Comparison of Polymorphism Frequencies Among Hispanics, African Americans, Asian Americans, and European Americans
Graphic Jump Location

Comparison of the frequencies of single nucleotide polymorphisms (SNPs) shared among 17 Hispanics, 20 African Americans, 19 Asian Americans, and 20 European Americans in whom 3873 genes were resequenced. The less frequent SNP in the combined population was designated as the minor SNP, and the frequency of the minor SNP was calculated in each population for the 63 012 SNPs analyzed. Single nucleotide polymorphisms with significant differences (z>1.65, P<.05) between populations that are common in both populations are shown as blue data points. Single nucleotide polymorphisms with significant differences in frequency (z>1.65, P<.05) between populations that are common in only one population are shown as red dark and pale data points. Black data points represent SNPs that are common and that do not differ significantly in frequency between populations. A Spearman rank correlation coefficient between the minor allele frequencies of each SNP were estimated for each population pairwise comparison. Data source: Genaissance Pharmaceuticals Inc, New Haven, Conn, unpublished data, August 2005.

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