I have a running theory that Alzheimer’s is a cro thing, whereas schizos are more thal. Clicking around, I ran into a devious bit of statistical deception.
Another large study, the Duke Established Populations for Epidemiological Studies of the Elderly project, found no differences in frequency of dementia between African Americans and whites. This study described a sample of 4,136 participants (Fillenbaum et al., 1998), 55 percent of whom were African American. The sample was defined using multistage probability sampling with unequal probabilities of selection to sample community-dwelling residents age 65 and older within five adjacent counties, one urban and four rural. However, the way in which the racial groups were defined is unclear. The authors used the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) Neuropsychological Test battery to assess cognitive functioning, and norms correcting for years of education (Unverzagt, Hall, Torke, and Rediger, 1996) were used for the determination of significant cognitive deficit and dementia. The prevalence of dementia among elders above age 67, as determined by clinical consensus, was 7 percent for African Americans and 7.2 percent for whites. There were also no differences in the 3-year incidence of dementia for African Americans (5.8 percent) versus whites (6.2 percent). The authors did not report incidence of dementia subtypes; therefore, it is possible that although the overall rates of dementia were similar among African Americans and whites, the frequencies of AD and vascular dementia may differ within the groups.
That’s the conclusion? Similar rates? There are lies and damned lies.
By correcting for postsecondary education, it is as if the researchers had decided to study only high school graduates. (This is not precisely true, so think of it as a thought experiment which illustrates the statistical idea.) This would exclude a significant number of AARP-eligible whites and a negligible number of blacks.
Remember, this study was in 1998 and deals with elders more than 67 years old, or those born before 1931, at least. Brown v. Board of Education was in 1954. This is not to say that recent black academic achievement is stellar, only that the bias is systematic.
Having compared, apple-to-apple, almost the entire black population with only low-performing whites, the study unjustifiably extrapolated its conclusions to the entire white population. This might have been justified if we believed that Alzheimer’s were due in part to a deficit of education, but that is silly on its face. It’s akin to accusing a comatose man of laziness.
Of course, when it comes to free tax handouts the blinders come off immediately:
The proportion of ethnic minorities among the elderly in the United States is increasing. The U.S. Census Bureau estimates that the proportion of elders who are white and non-Hispanic will decline from 87 percent in 1990 to 67 percent in 2050. As compared to the 1990 Census, the population of Hispanic elders is expected to double in 2010, and will be 11 times greater by 2050. Of the 80.1 million elderly projected for 2050, 8.4 million (10.4 percent) will be black, as compared to 8 percent of elders in 1990. With these changes, ethnic minority populations will bear an increased share of the economic and social burden associated with diseases that predominantly affect the elderly, such as Alzheimer’s disease (AD). This presents the potential for a major public health issue because ethnic minorities may be at higher risk for AD and dementia than non-Hispanic whites.