A closer look at the genetic roots of Alzheimer's disease
A genetic factor associated with late-onset Alzheimer’s disease is apolipoprotein E, or ApoE. People inherit one form of the ApoE gene from each parent. Those who inherit the e4 form of the ApoE gene from one parent have an increased risk of developing Alzheimer’s. Those who inherit it from both parents have an even higher risk. The relationship between ApoE-e4 and Alzheimer’s has been studied in populations across the U.S. and around the world. A widely cited meta-analysis of 5,930 people with Alzheimer’s and 8,607 without the disease showed that whites who inherited the e4 form from one parent had a 3.2 times greater risk of developing Alzheimer’s than whites who did not. Hispanics who inherited the e4 form from one parent had a 2.2 times greater risk of developing Alzheimer’s than Hispanics who did not. The risk of Alzheimer’s disease was 14.9 times higher for whites who inherited the e4 form of the ApoE gene from both parents and 5.7 times higher for blacks who inherited it from both parents. On the other hand, blacks who inherited the e4 form from one parent and Hispanics who inherited it from both parents did not have increased risks.
What are health disparities?
Sex, sexual identity, age, disability, socioeconomic status, geographic location, race and ethnicity all influence health (1). If a health outcome is seen to a greater or lesser extent in certain populations, there is a disparity. Biological, genetic, environmental and cultural factors and access to medical care all play a role. Compelling evidence indicates race and ethnicity correlate with increasing health disparities between U.S. subpopulations.
Heart disease is the leading cause of death for people of most races and ethnicities. For American Indians, Alaska Natives, Asians and Pacific Islanders, it is second only to cancer. Heart disease death rates are more than 40 percent higher for blacks than for whites (2). Blacks who receive drug-coated stents have more than double the rate of clotting compared with those of other races despite taking anti-clotting medications (3).
The risk of being diagnosed with diabetes is 77 percent higher among non-Hispanic blacks, 66 percent higher among Hispanics and 18 percent higher among Asian-Americans compared with non-Hispanic white adults. Interestingly, Mexican-Americans show a blunted response to insulin (4), which may be one of the causes. Furthermore, Hispanics are almost twice as likely to die from diabetes as are non-Hispanic whites (5, 6). The diabetes rate for American Indians and Alaska Natives is more than twice that for whites.
Blacks, Hispanics and American Indians are at high risk for developing kidney failure. This risk is due in part to high rates of diabetes and high blood pressure in these communities. Blacks make up about 13 percent of the U.S. population, but they account for 32 percent of kidney failure cases. Since 2000, the number of Hispanics with kidney failure has increased by more than 70 percent (7). American Indians also are disproportionately affected. Compared with whites, they are 1.8 times more likely to be diagnosed with it.
INFANT BIRTH WEIGHTS AND DEATH RATES
Whereas the rate of low-birth-weight infants is generally lower for Hispanics than for whites, Puerto Ricans have a low-birth-weight rate that is 50 percent higher than the rate for whites. American Indians and Alaska Natives have an infant death rate almost double that for whites.
The death rate for all cancers is 30 percent higher for blacks than for whites; for prostate cancer, for example, the death rate for blacks is more than double that for whites. Black women have a higher death rate from breast cancer despite having a mammography screening rate nearly on par with that of white women (8). Of the cities where black women were more likely to die of breast cancer, that disparity ranged from a 24 percent higher risk of death in New York to more than twice the risk of death in Memphis between 2005 and 2007. Other cities with racial disparities included Los Angeles; Chicago; Houston; Philadelphia; San Diego; Dallas; Jacksonville, Miss.; Columbus, Ohio; Milwaukee; Boston; and Denver. Meanwhile, there was no difference in black and white women’s chances of dying from breast cancer in Phoenix; San Antonio; San Jose, Calif.; Detroit; San Francisco; Austin, Texas; Baltimore; Fort Worth, Texas; Charlotte, N.C.; El Paso, Texas; and Seattle (9).
Older blacks in America are about two times more likely than older whites to have Alzheimer’s disease and other forms of dementia (see sidebar). Older Hispanics are 1.5 times more likely than older whites to have these conditions (10). High blood pressure and diabetes, both risk factors for Alzheimer’s and dementia, are more common in older blacks and Hispanics than in older whites and probably account for some of the differences.
While scientific advances have increased longevity and improved quality of life for Americans, racial and ethnic minorities have not experienced these gains equally. Advancing scientific knowledge and technology can improve patient-centered research in the areas of prevention, screening, diagnostics and treatment, and it can strengthen existing information systems to improve the quality of health, public health and biomedical research. It makes a big difference when breast cancer is diagnosed early; when a patient having a heart attack is given the correct treatment quickly; when medications are correctly administered; and when doctors listen to their patients and their families, show them respect and answer their questions in a culturally and linguistically skilled manner.
To better reach out to all the different ethnic groups, it pays for the medical community to develop cultural and linguistic skills. Strategies include expanding the use of interpreters, improving the quality of patient-provider interactions in clinical settings, improving cultural-competence education and training for health-care professionals, and increasing racial and ethnic diversity in the health-care work force.
It is necessary to educate physicians about pervasive racial and ethnic health disparities and to assist them in developing strategies to deliver quality care to underserved populations. In addition, we must foster the training of scientists with the best biochemical and molecular technologies to investigate the causes of many the diseases prevalent among minorities.
- 1. Mollon, L. Journal of Health Care for the Poor and Underserved 23, 1 – 6 (2012).
- 2. Ulmer, C., et al. National Healthcare Quality and Disparities Reports, Institute of Medicine: 1 – 159 (2010).
- 3.Collins, S.D., et al. Circulation 122, 1085 – 1090 (2010).
- 4. Lorenzo, C., Hazuda, H. and Haffner. J. Clin. Endocrinol. Metab. 97, 793 – 799 (2012).
- 5. The National Institute of Diabetes and Digestive and Kidney Diseases, National Diabetes Statistics (2011).
- 6. Trends in Nutrient Intakes and Chronic Health Conditions Among Mexican-American Adults, a 25-year Profile: United States 1982 – 2006. National Health Statistics Reports #50 (2012).
- 7. Flack., J.M., et al. Cardiovascular Disease, Chronic Kidney Disease, and Ethnic Minorities: A Triple Threat. National Kidney Foundation (2010).
- 8. Breast Cancer Rates by Race and Ethnicity. Centers for Disease Control and Prevention (2010).
- 9. Whitman, S. et al. Cancer Epidemiology 36, 147 – 151 (2012).
- 10. Alzheimer’s Disease Facts and Figures 2010, Alzheimer’s Association.
Frank Talamantes (email@example.com) is a professor emeritus at the University of California, Santa Cruz.