Ethnic Variation as a Key to the Biology of Human Disease

Although it is well established that all humans are members of the same species, obvious physical differences exist among human populations (such as differences in hair color and texture, skin color, facial features, and stature). Some less apparent, but clinically more important, ethnic differences also exist. For example, the prevalence of obesity and type 2 diabetes is greater among Native Americans and Hispanic persons in the United States than in the general U.S. population, and hypertension is more common among black persons in the United States. Ethnic differences in the prevalence of complex diseases are probably related to both environmental and genetic differences. Observations of physiologic variation or differences in the prevalence of disease among ethnic groups can be important keys to understanding the causes of complex genetic diseases.

Two studies in this issue address ethnic differences in disease-related traits. Woo and colleagues [1] tested the hypothesis that Chinese persons may not have some of the detrimental effects of cigarette smoking on the coronary and peripheral vascular systems, in part because of greater protection against loss of endothelial function. Wall and associates [2] investigated the effect of a common aldehyde dehydrogenase gene variant that is specific to Asian persons on the rate of blood alcohol and acetaldehyde metabolism. These physiologic features invite questions about the nature of racial or ethnic differences in relation to the prevalence of disease or disease-related traits. Is race a biologically tenable concept? What is the extent of genetic differentiation in human populations? How has our understanding of the medical importance of ethnic differences been affected by the concept of race? Is it appropriate to consider ethnicity as a factor in treatment decisions?

Endothelium-dependent dilatation is much reduced in persons who are exposed to vascular disease risk factors, such as cigarette smoking [3], type 1 …