Racial and Ethnic Differences in the Health of Older Americans (1997) / Chapter Skim
Currently Skimming:
7 Are Genetic Factors Involved in Racial and Ethnic Differences in Late-Life Health?
7 Are Genetic Factors Involved in Racial and Ethnic Differences in Late-Life Health?
Pages 210-232
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 210... ...
First, I briefly discuss two well-understood disease entities of early onset that are almost entirely restricted to blacks and use these diseases as a point of departure for the possible health implications of racial and ethnic differences in allele frequencies with respect to single-locus polymorphisms. (An allele is any one of two or more different genes that may occupy the same position on a specific chromosome.)
|
From page 211... ...
, diseases so uncommon that only medical specialists recognize them. Noting that the sickle cell gene originated in a tropical ecosystem in which malaria, especially Plasmodium falciparum malaria, was a major cause of morbidity and mortality, Allison (1954)
|
From page 212... ...
2. The morbidity and mortality associated with infections with falciparum malaria are less in persons with the sickle cell trait than in persons without the trait.
|
From page 213... ...
By now, population surveys for the frequency of the G-6-PD deficiency are almost as numerous as surveys for the frequency of the sickle cell trait. More than 300 different G-6-PD variants have been identified, and at least 100 of these are relatively common in the males of the populations in which they occur.
|
From page 214... ...
falciparum malaria is epidemic and malaria is making a comeback people with the sickle cell trait or with G-6-PD deficiency trait should at any age level enjoy superior health through a "natural" resistance to the disease. On the other hand, the drug sensitivities of the male with the G-6-PD deficiency persist throughout life and may first become manifest with the increased medication of senior citizens.
|
From page 215... ...
The protection to the individual is not as great as that conferred by heterozygosity for the sickle cell allele, but since these alleles have a higher frequency in West Africa than the sickle cell allele, the protection to the population as a whole appears to be somewhat greater than that afforded by hemoglobin S heterozygosity. Here would seem to be a clear ex
|
From page 216... ...
216 s~ ~ ~ ca ~ o ~ Cq a' Cq a' Cq C)
|
From page 217... ...
217 .~ o o ~ ~ ~CM CM ~oo oo ~ ~ CM ~ ~ ~ CM ~ ~ ~ o ~oo ~ ~ ~ ~ ° ~ _.
|
From page 219... ...
JAMES V NEEL TABLE 7-2 A Companson of Three Ethnic Groups with Respect to the Frequency of Certain HLA Types 219 HLA-A Frequency HLA-B Frequency European African European African Gene Whites Blacks Japanese Gene Whites Blacks Japanese Locus (n = 228)
|
From page 220... ...
Further studies on this association will be as important as further studies on the associations of HLA alleles with disease in blacks, since cross-racial studies of both of these disease associations will reveal much about the specificity of the association. Most of the human genetic polymorphisms have been discovered in white populations, and studies of the comparative frequency of the variant alleles in whites and blacks are often limited.
|
From page 221... ...
Indeed, the possible role of racial and ethnic differences in late-life diseases related to differences in allele frequencies with respect to known polymorphism is still poorly understood. SOME GENETICALLY COMPLEX, ENVIRONMENTALLY INFLUENCED DISORDERS DIFFERING IN FREQUENCY IN BLACKS AND WHITES This section considers the possible role of genetic factors in two diseases that differ in frequency in blacks and whites, namely, diabetes mellitus of the noninsulin-dependent type and essential hypertension, that is, hypertension that is not a consequence of renal or other disease.
|
From page 222... ...
. However, I remind you that the inability to metabolize glucose is a continuously distributed trait.
|
From page 223... ...
Numerous studies on native Africans document the increase in blood pressure that occurs with the transition from a relatively unacculturated rural setting to urban life, with hypertension then apparently as prevalent as in U.S. blacks (reviewed in Kaufman and Barkey, 1993; see especially Scotch, 1963~.
|
From page 224... ...
The genes for susceptibility appear to be relatively common and widespread. This pattern raises the same question as was raised by the frequency of the sickle cell trait.
|
From page 225... ...
The data on ethnic differences in end-stage renal disease from the U.S. Renal Data System are especially striking, the incidence of blacks with end-stage renal disease averaging three to four times higher than for whites, at all age groups (Lopes et al., 1993, 1994~.
|
From page 226... ...
, with particular reference to hypertension. Although the application of the techniques of molecular biology to genetic studies of non-insulin-dependent diabetes mellitus and essential hypertension will undoubtedly result in significant insights into the genetic component of these two diseases over the next several decades, I suspect that really definitive insights into the differences between blacks and whites that I have discussed must await progress in equalizing the epigenetic factors at work on white and black genotypes, or research designs that take advantage of unusual social circumstances.
|
From page 227... ...
Mullan 1994 The APOE locus advances disease progression in late onset familial Alzheimer's disease but is not causative. American Journal of Human Genetics 55(suppl.)
|
From page 228... ...
Greenwood 1991 Common West African HLA antigens are associated with protection from severe malaria. Nature 352:595-600.
|
From page 229... ...
Chartier-Harlin, and the French Alzheimer Collaborative Group 1994 Increase of the Apo E4 allele frequency in a subgroup of early-onset Alzheimer's patients. American Journal of Human Genetics 55(suppl.)
|
From page 230... ...
Singer, and I.C. Wells 1949 Sickle cell anemia, a molecular disease.
|
From page 231... ...
Rao 1994 Cross-trait familial resemblance for body fat and blood pressure: Familial correlations in the Quebec Family Study. American Journal of Human Genetics 55:1019-1029.
|
From page 232... ...
Neel, and J Colaert 1955 Evidence concerning the inadequacy of mutation as an explanation of the frequency of the sickle cell gene in the Belgian Congo.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.