page_title: Race and health
section_title: Evolutionary factors
hierarchical_section_title: Race and health / Genetic factors / Evolutionary factors
caption_attribution_description: English: Malaria-endemic countries western hemisphere
context_page_description: Race and health refers to how being identified with a specific race influences health. Race is a complex concept that changes across chronological eras and that depends on both self-identification and social recognition. In the study of race and health, scientists organize people in racial categories depending on different factors such as: phenotype, ancestry, social identity, genetic makeup and lived experience. “Race” and ethnicity often remain undifferentiated in health research.
  Differences in health status, health outcomes, life expectancy, and many other indicators of health in different racial and ethnic groups are well documented. Some individuals in certain racial groups receive less care, have less access to resources, and live shorter lives in general. Epidemiological data indicates that racial groups are unequally affected by diseases, in terms or morbidity and mortality. These health differences between racial groups create racial health disparities.
  Health disparities are defined as “preventable differences in the burden of disease, injury, violence, or opportunities to achieve optimal health that are experienced by socially disadvantaged populations”.
context_section_description: Genes may be under strong selection in response to local diseases. For example, people who are duffy negative tend to have higher resistance to malaria. Most Africans are duffy negative and most non-Africans are duffy positive. A number of genetic diseases more prevalent in malaria-afflicted areas may provide some genetic resistance to malaria including sickle cell disease, thalassaemias, glucose-6-phosphate dehydrogenase, and possibly others.
  Many theories about the origin of the cystic fibrosis have suggested that it provides a heterozygote advantage by giving resistance to diseases earlier common in Europe.
  In earlier research, a common theory was the "common disease-common variant" model. It argues that for common illnesses, the genetic contribution comes from the additive or multiplicative effects of gene variants that each one is common in the population. Each such gene variant is argued to cause only a small risk of disease and no single variant is enough to cause the disease. An individual must have many of these common gene variants in order for the risk of disease to be substantial.
  More recent research indicates that the "common disease-rare variant" may be a better explanation for many common diseases. In this model, rare but higher-risk gene variants cause common diseases. This model may be relevant for diseases that reduces fertility. In contrast, for common genes associated with common disease to persist they must either have little effect during the reproductive period of life (like Alzheimer's disease) or provide some advantage in the original environment (like genes causing autoimmune diseases also providing resistance against infections). In either case varying frequencies of genes variants in different populations may be an explanation for health disparities. Genetic variants associated with Alzheimer's disease, deep venous thrombosis, Crohn disease, and type 2 diabetes appear to adhere to "common disease-common variant" model.
caption: Malaria-endemic countries western hemisphere
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