Introduction
Interdisciplinary efforts over several decades have provided intriguing information regarding the factors that contribute to racial differences in health status and outcomes. Even with this information on hand, challenges remain regarding improved characterization of these various biological and environmental factors. Advances in genomic studies have provided some of the valuable tools and data needed to move forward in the direction of defining the biologic factors underlying racial differences in disease disposition.
Relationships Between Race, Ethnicity, and Health
Environmental and genetic interactions influence human health and survival. Part of the environment are social factors that can be influenced or defined by the various biological characteristics that determine a person’s response to these environmental factors. It is widely accepted that Black populations from a number of ethnic groups in the U.S. tend to have a higher percentage of individuals that suffer stroke when compared to White populations. For example, Howard et al. found that socioeconomic status may account, in part, for the finding of excess stroke in black males in the U.S. (1). The social and medical science arenas have recognized the role that racism or discrimination plays in the stress levels that can then influence cardiovascular health.
Other diseases with incidences that differ by race include higher rates in whites for skin melanoma and cystic fibrosis (2,3). However, Asians with cystic fibrosis of similar severity as whites have worse outcomes, possibly due to cultural factors and specific cystic fibrosis genotypes (4). These examples highlight the interplay between genetic factors and the socio-cultural environment.
Using the current definitions of race and ethnicity, some genetic factors have been found that contribute to higher incidences of some diseases. Sickle-cell anemia, which has a higher incidence in people of African descent, is caused by a mutation in the hemoglobin-beta gene on chromosome 11. As mentioned previously, cystic fibrosis has a higher incidence in Whites and is caused by mutations in the gene for the cystic fibrosis transmembrane conductance regulator protein.
Racial Disparities in Healthcare
A major contributor to racial differences in disease predisposition is the existence of racial disparities in healthcare. Disparities in healthcare access, for example, result from social constructs attached to biologic factors that define phenotypic racial and ethnic differences. Stark differences in the availability to and options for healthcare in general often lead to poorer survival rates and health status in underrepresented racial groups (5).
Belief systems (whether political, religious, or social in nature) held by both patients and healthcare providers can significantly affect healthcare delivery. There are still major gaps in the knowledge base of many healthcare providers regarding cultural attributes of the diverse patient population. The resultant lack of cultural competence is a factor that remains an area requiring improvement to affect successful healthcare delivery.
Genomic Data and Discovery of Predisposing Factors in Disease Development
Emerging data from genomic studies are uncovering information that is contributing to a better understanding of how individuals’ genomes determine disease predisposition. Haiman et al. observed that a prostate cancer susceptibility locus at 17q21 is more specific to an African population (6). This is thought to contribute to the higher risk of prostate cancer in African descent men.
The Human Genome Diversity Project collects biological samples from different populations of ethnic groups globally with the objective to build a database of human genetic diversity. The results of the project have the potential to contribute to medical research focused on the differences in disease susceptibility or resistance across ethnic groups. However, there are controversies in regard to the potential for incorrect interpretation or misuse of the data, the application of the data to increase racial disparities in healthcare, and to deny human rights.
The various genomic studies such as those previously mention have yielded record volumes of data due to the advent of next-generation sequencing (NGS). This massively parallel sequencing technology has changed the face of medical research. It is used to study common and rare variants associated with diseases such as cancer. This has already been demonstrated with the use of NGS to identify mutations and other genomic factors that contribute to the onset of prostate cancer development (7). This information can potentially be used to determine if there are differences in these genomic sequences across ethnic groups.
Conclusions
Understanding the complex interaction between genetics and environment is benefiting from the newer genomic approaches such as NGS genome-wide association studies. Data is already available that suggests the genomic characteristics and mechanisms that may underlie the observed differences in disease predisposition across racial and ethnic groups. The data can also be harnessed for disease risk prediction, early diagnosis, and the development of effective personalized medical interventions with the goal to eliminate health disparities and overcome the factors leading to disease predisposition.
References
- Howard G, Russell GB, Anderson R, Evans GW, Morgan T, Howard VJ, Burke GL. Role of social class in excess black stroke mortality. Stroke. 1995 Oct;26(10):1759-63.
- U.S. Cancer Statistics Working Group. United States Cancer Statistics: 1999–2013 Incidence and Mortality Web-based Report. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention and National Cancer Institute; 2016. Available at: www.cdc.gov/uscs.
- Kosorok MR, Wei WH, Farrell PM. The incidence of cystic fibrosis. Stat Med.1996 Mar 15;15(5):449-62.
- McCormick J, Ogston SA, Sims EJ, Mehta A. Asians with cystic fibrosis in the UK have worse disease outcomes than clinic matched white homozygous delta F508controls. J Cyst Fibros. 2005 Mar;4(1):53-8.
- Yancy CW. Disparate care for acute myocardial infarction: moving beyond description and targeting interventions. Circulation. 2014 Aug 19;130(8):632-3. doi: 10.1161/CIRCULATIONAHA.114.011482.
- Haiman CA, et al. Genome-wide association study of prostate cancer in men of African ancestry identifies a susceptibility locus at 17q21. Nature Genet. 2011; 43:570–573.
- Berger MF, et al. The genomic complexity of primary human prostate cancer. Nature. 2011; 470:214–220.
About the Author:
Dr. Stacy Matthews Branch is a biomedical consultant, medical writer, and veterinary medical doctor. She owns Djehuty Biomed Consulting and has published research articles and book chapters in the areas of molecular, developmental, reproductive, forensic, and clinical toxicology. Dr. Matthews Branch received her DVM from Tuskegee University and her PhD from North Carolina State University.
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