Science Fair Project Encyclopedia
Race in biomedicine
Several questions are being considered:
- When should race be taken into account when studying humans?
- What definition of race is appropriate for biomedical research?
- Do the biological differences between races justify the use of racial categories in research?
- Can genetic assignment to population groups be used in lieu of self-identified race?
- What are the ethical implications of using race in research?
The primary impetus for considering race in biomedical research is the possibility of improving the prevention and treatment of diseases. Many previous studies have observed that disease susceptibility and environmental responses vary by race. Thus, some researchers believe that race may be an informative category for biomedical research. Others fear that the use of racial categories in research may cause social harm.
Disease association studies
Race is associated with differential disease susceptibility and environmental responses. Many highly penetrant Mendelian diseases that are caused by mutations in a single gene are known to be found at higher frequencies in certain races. The HbS allele that causes haemochromatosis is found at higher frequencies in sub-Saharan Africans and Southern Europeans. Similarly, the ΔF508 allele of CFTR that causes cystic fibrosis is found in higher frequencies in Northern Europeans. It is believed that many of these mutations first occurred in the population that is most affected.
Race has also been found to be associated with susceptibility to complex, multifactorial and multigenic diseases. The incidence and death rate of prostate and breast cancers are significantly higher in African-Americans than European-Americans. Higher proportions of individual African ancestry is associated with increased susceptibility to both obesity and abnormal levels of insulin secretion. Likewise, Hispanic, American Indian, African American, Pacific Island, and South Asian ancestry is considered a risk factor for diabetes. Also, the incidence of heart disease and high blood pressure is higher in African-Americans than European-Americans.
The common disease-common variant (often abbreviated CD-CV) hypothesis predicts common disease causing alleles will be found in all populations. An often cited example is an allele of apolipoprotein E, APOE ε4, which is associated in a dose-dependent manner with susceptibility to Alzheimer's disease. This allele is found in Africans, Asians and Europeans. However, many disease causing alleles are found to have different (technically called epistatic) effects in different populations. For example, the increased risk of Alzheimer's disease that is associated with the APOE ε4 allele is 5-fold higher in individuals with Asian rather than African ancestry.
Polymorphisms in the regulatory region of the CCR5 gene affect the rate of progression to AIDS and death in HIV infected patients. While some CCR5 haplotypes are beneficial in multiple populations, other haplotypes have population-specific effects. For example, the HHE haplotype of CCR5 is associated with delayed disease progression in European-Americans, but accelerated disease progression in African-Americans. Similarly, alleles of the CARD15 (also called NOD2) gene are associated with Crohn's disease, an inflammatory bowel disorder, in European-Americans. However, none of these or any other alleles of CARD15 have been associated with Crohn's disease in African-Americans or Asians.
|Disease||High-risk groups||Low-risk groups||Reference(s)|
|Obesity||African women, Native Americans South Asians, Pacific Islanders, Aboriginal Australians||Europeans||McKeigue, et al. (1991); Hodge & Zimmet (1994)|
|Non-insulin dependent diabetes||South Asians, West Africans, Peninsular Arabs, Pacific Islanders and Native Americans||Europeans||Songer & Zimmet (1995); Martinez (1993)|
|Hypertension||African Americans, West Africans||Europeans||Douglas et al. (1996); Gaines & Burke (1995)|
|Coronary heart disease||South Asians||West African men||McKeigue, et al. (1989); Zoratti (1998)|
|End-stage renal disease||Native Americans and African populations||Europeans||Ferguson & Morrissey (1993)|
|Dementia||Europeans||African Americans, Hispanic Americans||Hargrave, et al. (2000)|
|Systemic lupus erythematosus||West Africans, Native Americans||Europeans||Molokhia & McKeigue (2000)|
|Skin cancer||Europeans||Boni, et al. (2002)|
|Lung cancer||Africans||European Americans, Chinese, Japanese||Schwartz & Swanson (1997); Shimizu, et al. (1985)|
|Prostate cancer||Africans and African Americans||Hoffman, et al. (2001)|
|Multiple sclerosis||Europeans||Chinese, Japanese, African Americans, Turkmens, Uzbeks, Native Siberians, New Zealand Maoris||Rosati (2001)|
|Osteoporosis||European Americans||African Americans||Bohannon (1999)|
Concept of race
- main article: race.
In biomedical research conducted in the U.S., the 2000 US census definition of race is often applied. This grouping recognizes five races: black or African American, white, Asian, native Hawaiian or other Pacific Islander, and American Indian or Alaska native. However, this definition is inconsistently applied across the range of studies that address race as a medical factor, making assessment of the utility of racial categorization in medicine more difficult.
From the perspective of genetics, human population structure is the result of patterns of mating. Historically, the greatest influence on mating patterns is geography. Genetic research has shown that the greatest genetic differentiation among humans corresponds with continental groupings. To the extent that racial labels correspond to continental groups, some argue that they are informative for biomedical research. Migration between continents in the last two centuries, with consequent racial admixture has caused some to question the significance of this notion of race to medicine.
In multiracial societies such as that of the United States, racial groups also differ by social and cultural correlates such as economic status and access to healthcare. These factors are believed to explain some of the differential health care outcomes among races. An open area of investigation is whether racial differences persist in studies where social and cultural correlates are taken into account.
Genetic differences among races
The existence of genetic differences among races is well accepted. In general, genetic clusters exist that correspond tightly to the census definition of race and to self-identified ancestry. One large exception to this correspondence is that South, Central, and West Asians (e.g. Asian Indians) cluster with Europeans and are separate from East Asians. The association between race and genetics also breaks down for groups, such as Hispanics, that exhibit a pattern of geographical stratification of ancestry. The biomedical relevance of genetic differences among races is a matter of debate. Some researchers argue that the available evidence supports the notion that some of the genetic differences between races have biomedical significance, and thus should be studied.
An alternative view argues that the underlying genetic-cluster categories can be used in lieu of racial labels for biomedical purposes. Proponents of this view argue that by directly examining the genotype, the problem of using racial labels can be avoided. Moreover, they argue that genotyping is more reliable than using self-identified race as a proxy for ancestry. Some fear that the use of racial labels in biomedical research runs the risk of unintentionally exasperating health disparities.
Proponents of using race in biomedical research argue that ignoring race will be detrimental to the health of minority groups. They argue that disease risk factors differ substantially between racial groups, that relying only on genotypical classes ignores non-genetic racial factors that impact health, and, furthermore, that minorities would be poorly represented in clinical trials if race were ignored.
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