Critical Perspectives on Racial and Ethnic Differences in Health in Late Life (2004) / Chapter Skim
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4 Ethnic Differences in Dementia and Alzheimer’s Disease
4 Ethnic Differences in Dementia and Alzheimer’s Disease
Pages 95-142
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From page 95... ...
. The studies reviewed in this chapter examine ethnic differences in rates of broad categories such as "cognitive impairment" or "dementia" as well as specific neurodegenerative diseases such as Alzheimer's disease and vascular dementia.
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From page 96... ...
, or more sensitive and extensive neuropsychological test batteries incorporating individual measures such as Logical Memory from the Weschler Memory Scale. To meet clinical criteria for dementia, cognitive impairment must be of sufficient severity to interfere with activities of daily living.
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From page 97... ...
Most U.S.-based studies have focused on comparing rates of dementia or AD among African Americans and Hispanics to rates among whites. These studies found higher rates of cognitive impairment, dementia, and AD among ethnic minorities than among whites (Folstein, Bassett, Anthony, Romanoski, and Nestadt, 1991; George, Landerman, Blazer, and Anthony, 1991; Gurland et al., 1998; Haerer, Anderson, and Schoenberg, 1987; Perkins et al., 1997; Prineas et al., 1995; Schoenberg, Anderson, and Haerer, 1985; Still, Jackson, Brandes, Abramson, and Macera, 1990; Teresi, Albert, Holmes, and Mayeux, 1999)
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From page 98... ...
The role of immigration and changes in environmental risk factors was examined in several epidemiological studies of elders with Japanese ancestry. The age-standardized prevalence of dementia (using Diagnostic and Statistical Manual of Mental Disorders -- Third Edition [DSM-III]
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From page 99... ...
South America The racial, ethnic, cultural, and socioeconomic diversity found within South America provides an excellent opportunity to evaluate biological and environmental risk factors for cognitive impairment and Alzheimer's among elders; however, more work must be carried out in this area to equal the epidemiological information available in other regions. A study of dementia in Chile (Quiroga et al., 1999)
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From page 100... ...
Soon after these reports, Hendrie and his colleagues from the Indiana University School of Medicine and the University of Ibadan, Nigeria began investigating the epidemiology of dementia among community-dwelling African Americans living in Indianapolis and Yoruba living in Ibadan. This study hoped to take advantage of the fact that African Americans are predominantly of the lineage of West African blacks but reside in quite different environments than Nigerians, and are therefore likely to have different exposures to possible environmental risk factors.
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From page 101... ...
. This changing pattern of dementia diagnosis could reflect changes in diagnostic accuracy, a decrease in VAD prevalence due to better control over cardiovascular risk factors, or an increase in AD prevalence due to Westernization of risk factors such as a diet rich in fat and cholesterol.
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From page 102... ...
; however, there were no ethnic differences in survival. A 5-point rating scale of cognitive and daily functioning and a short cognitive screening test that did not involve reading or writing were administered to 1,399 residents of Ashkelon, Israel, who were 75 and older (Korczyn, Kahana, and Galper, 1991)
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From page 103... ...
Autopsy Confirmation of AD Pathology Neuropathological confirmation of the presence and severity of AD pathology among patients diagnosed with AD is the only way to confirm ethnic discrepancies in AD prevalence and incidence. However, African Americans and other ethnic minorities are less likely to consent to autopsy (Amaducci, Baldereschi, Doody, Chandra, and Gaines, 1997; Bonner, Darkwa, and Gorelick, 2000; Fillenbaum et al., 1996; Ganguli et al., 1991; Harrell, Callaway, and Powers, 1993)
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From page 104... ...
One study using MRI and Single Photon Emission Computed Tomography showed no major ethnic differences in degree of white-matter hyperintensities, ventricle-to-brain ratio, and uptake among 3,301 nondemented community-dwelling elders without a history of stroke or transient ischemic attack (Longstreth et al., 2000)
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From page 105... ...
These include statistical limitations, discrepancies in cognitive test performance, differential genetic factors, differences in prevalence of nongenetic medical risk factors, and differences in the social meaning and reaction to cognitive decline. Certainly, differential exposure to environmental risk factors may also help to explain ethnic group differences in frequency of AD; however, little work has been published addressing ethnic differences in these exposures.
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From page 106... ...
For example, if educational level is cut at 9 years, residual confounding will occur if the mean for African Americans below the cutpoint is 6 years and the mean for whites below the cutpoint is 8 years. The use of aggregated SES measures can also inflate group effects; one simulation demonstrated that when SES was estimated for each ethnicity by using average income for that group, the effect of race as a predictor of outcome was inflated 38 percent as compared to a model where SES was estimated using individual values (Geronimus, Bound, and Neidert, 1996)
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From page 107... ...
When the concept of race is deconstructed into more meaningful variables (Kaufman and Cooper, 2001; Manly and Jacobs, 2001) , the underlying reasons for racial or ethnic differences in rates of AD may be determined more definitively.
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From page 108... ...
Lack of such validation may account for the fact that, based on neuropsychological test performance, ethnic minorities are judged to be cognitively impaired more often than non-Hispanic whites. This section will review studies within and outside the United States that have compared the cognitive test performance of different ethnic groups, and describe constructs that might allow for more sophisticated investigations of ethnic differences in the future.
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From page 109... ...
compared neuropsychological test performance between 69 African-American and 64 non-Hispanic white nondemented, community-dwelling elders, all of whom had less than 10 years of formal education. Although education accounted for a significant amount of variance in nearly every measure that was administered, race was an independent predictor of performance on WAIS-R Vocabulary and Block Design subtests, as well as Wechsler Memory Scale-Revised (WMS-R)
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From page 110... ...
For example, there were no significant ethnic differences among a small number of African Americans (n = 11) and whites (n = 32)
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From page 111... ...
. Although it is common for investigators to use covariance, matching procedures, or education-corrected norms in order to "equate" ethnic groups on years of education before interpreting neuropsychological test performance, as discussed earlier, these techniques ignore ethnic discrepancies in quality of education.
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From page 112... ...
Despite the clear improvement in specificity that is provided by adjusting cognitive test scores for differences in educational experience across ethnic groups, some researchers caution against controlling for educational variables in studies of dementia because low education may itself be a risk factor for disease. The logic behind this argument will be discussed in the section on the nongenetic risk factor of cognitive reserve.
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. Few studies have examined the relationship of cognitive test performance to within-group ethnic or cultural factors independent of those associated with SES.
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. The role of stereotype threat in neuropsychological test performance of African Americans and Hispanics has not been investigated to date.
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Development of Cross-Cultural Cognitive Tests A number of measures have been adapted for use in different cultures and for multiple languages, and proven to be useful in distinguishing de
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These measures may be suitable for direct comparison between cultures, while for the rest of the battery, the use of norms may allow groups to be compared. However, further research is needed to determine the sensitivity and specificity of the Cross-Cultural Neuropsychological Battery to detect subtle cognitive impairment and early AD among ethnically diverse elders.
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From page 117... ...
The MMSE, Clinical Dementia Rating Scale, Global Deterioration Scale, and Functional Assessment Staging proved able to discriminate participants with AD from controls and were all equally sensitive to disease severity. Mungas and colleagues also report the successful development of a neuropsychological test battery for English and Spanish speakers (Gonzalez, Mungas, Reed, Marshall, and Haan, 2001; Mungas, 1996; Mungas et al., 1996; Mungas, Reed, Marshall, and Gonzalez, 2000)
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From page 118... ...
These investigators found no ethnic differences in frequency of the 4 allele (Ashkenazi Jewish = 30 percent; African American = 29 percent; Hispanic = 28 percent; and non-Hispanic non-Jewish white = 33 percent) or the 2 allele.
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Years of education did not account for these ethnic differences in AD incidence, and reclassifying elders who developed only mild disease (Clinical Dementia Rating Scale of 0.5) as normal did not alter the findings.
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. These results did not change after the removal of elders who had cognitive impairment, but were not demented, from the control group.
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· Factors such as head injury or coronary artery disease may modify the biological effect of the 4 allele. Cross-national studies offer great promise in resolving these possibilities because they permit environmental risk factors for AD to be distinguished from genetic causes.
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NONGENETIC RISK FACTORS Stroke Compared to non-Hispanic whites, African Americans have a 2.4-fold and Hispanics a twofold increase in stroke incidence (Sacco et al., 1998)
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From page 123... ...
If cases of strokeassociated dementia are misclassified as cases of AD, risk factors for stroke-associated dementia can appear to predict AD. One study found a relation of diabetes with vascular dementia (defined by criteria established by the California State Alzheimer's Disease Diagnostic and Treatment Centers)
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From page 124... ...
Cognitive Reserve Cognitive reserve is another possible explanation for ethnic differences in rates of dementia and AD. Studies of ethnically diverse samples indicate that lifetime experiences, reflected in years of education or occupational level, may be independent risk factors for incidence of dementia and cognitive impairment (Callahan et al., 1996; Stern, 2002; Stern et al., 1994)
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From page 125... ...
Ethnic groups often have different levels of SES, and these SES variables may reflect either lack of educational or occupational experiences that contribute to cognitive reserve, or risk factors such as poor nutrition, toxic exposures, or poor health care that may diminish cognitive reserve. For example, cognitive decline appears to be faster (Stern, Albert, Tang, and Tsai, 1999; Unverzagt, Hui, Farlow, Hall, and Hendrie, 1998;)
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From page 126... ...
This kind of research is limited among ethnic minorities, however, if the cognitive measure administered did not accurately reflect true cognitive ability due to cultural effects on test performance. Discrepancies in quantity and quality of education, literacy, and the limitations placed on occupational attainment by institutionalized racism may help to explain the increased rates of dementia and AD among ethnic minorities and illiterate individuals.
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From page 127... ...
These can be explained by differences in biological risk factors such as cerebrovascular disease, differential exposure to environmental risk factors, cognitive reserve, or genetic risk factors. Cross-national studies such as the Indianapolis-Ibadan study indicate that ethnic differences in rates of dementia may be a result of a complex gene
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From page 128... ...
Focus on these variables might guide research on cross-cultural differences in cognitive test performance and assist in the development of tests usable across cultures. Differences in quality of educational attainment within and between ethnic groups could be assessed with measures of reading level, and used in research on cognitive reserve.
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From page 129... ...
. Acculturation and performance of Hispanics on selected Halstead-Reitan neuropsychological tests.
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. Halstead-Reitan neuropsychological test performance of black, Hispanic, and white young adult males from poor academic backgrounds.
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From page 131... ...
. The Cross Cultural Neuropsychological Test Battery (CCNB)
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From page 132... ...
. Epidemiology of vascular and Alzheimer's dementia among African Americans in Chi cago, IL: Baseline frequency and comparison of risk factors.
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From page 133... ...
. A cross-ethnic analysis of risk factors for AD in white Hispan ics and white non-Hispanics.
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From page 134... ...
. Evaluation of risk factors for Alzheimer's disease in elderly east Africans.
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From page 135... ...
. Acculturation and neuropsychological test performance in elderly African Americans.
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From page 136... ...
. Cognitive test performance among nondemented elderly African Americans and whites.
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From page 137... ...
. Development of psy chometrically matched English and Spanish language neuropsychological tests for older persons.
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From page 138... ...
. Apolipoprotein E alleles as risk factors in Alzheimer's disease.
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From page 139... ...
. Stereotype threat and the intellectual test performance of African Americans.
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. Effects of age, education and gender on CERAD neuropsychological test performance in an African American sample.
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From page 141... ...
. Neuropsychological test performance in African-American and white patients with Alzheimer's disease.
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