Later, people in both groups take the test again. Some still test normal for their age; others show signs of cognitive decline or even symptoms of dementia. After following the groups long enough, researchers can calculate how blacks and whites may differ in their risk of dementia.

Neuropsychologist Jennifer Manly, Ph.D., is involved in just such a study with her colleagues at Columbia University: the Washington Heights-Inwood Columbia Aging Project. Since 1992, they have followed a group of older New Yorkers in two racially diverse Manhattan neighborhoods, Washington Heights and Inwood. It turns out the risk of dementia varies in these neighborhoods quite a bit depending on the person’s race or ethnic heritage. Indeed, the African-Americans are 2.3 times more likely to develop Alzheimer’s Disease than their white neighbors.

In studying risk for dementia and diagnosing the disease, it’s critical that the neuropsychological tests work the same among people from diverse backgrounds. If not, then the risks may be exaggerated, or underestimated. Some may be diagnosed inaccurately, or missed altogether.

Manly’s research in Washington Heights and Inwood has revealed that inequalities in “educational experience” — the quality of education the people receive, not merely how many years they spend in classrooms — accounts for some of the difference in scores between African-Americans and other groups. And she thinks she’s found a way to level the testing field: measure the person’s reading level.

“What we’re finding is that reading level, in every racial and ethnic group, and at all levels of education, helps us predict who will experience cognitive decline,” Manly says. “If we don’t take into account someone’s reading level, even though we have their years of education, it doesn’t necessarily reflect their educational experience.”

Cognitive reserve

Tests for diagnosing dementia use total years in school to estimate a person’s “cognitive reserve.” Hypothetically, you end up with greater cognitive reserve by attending more years in school. More educated people, studies suggest, are at lower risk of Alzheimer’s disease and show less mental decline with aging.

Education may impart skills and knowledge that allow people to compensate for declining brain function. Conversely, less-well-educated people tend to develop dementia sooner and decline faster. “People with very little formal education are more vulnerable to the effects of aging and Alzheimer’s pathology on the brain,” Manly explains.

By asking an elderly person how many years she went to school, doctors or Alzheimer’s researchers get an idea of how well the person ought to score on cognitive tests. The less-educated person’s “high score” may be the same as a more-educated person’s “low” score. It’s all relative to education.

Southern schooling

Manly’s research suggests years of education does not level the field between racial and ethnic groups. The reason may be that African-Americans who were schoolchildren in the segregated South were not provided the same quality of education as white children. Black children attended fewer months per year in schools with lower funding, less teacher training, and inferior books.

Testing reading skill might level the playing field, Manly thought, because it reflects formal schooling as well as subsequent self-taught knowledge. The Washington Heights-Inwood Columbia Aging Project provided a way to see the effect of reading level on test scores.

About 1,000 people participated in the reading study. The participants were given a standard reading test to divide them into “high literacy” and “low literacy” groups. The test measures the ability to name letters and pronounce words out of context. It’s essentially a test of one’s ability to process written language.

The team returned to retest for changes in cognitive function every 18 to 24 months. People with low reading levels showed more memory loss over time than people at a higher reading level — just what you would expect to see if reading level reflects cognitive reserve. When reading level is factored in, the disparity in test scores between black and white people in Washington Heights narrows. Literacy also predicted mental decline more strongly than either race or years of education.

“It’s a strong predictor of cognitive decline across racial groups,” Manly says. “In fact, it’s stronger than race itself.”

Diversity and dementia

Culturally appropriate tests will allow researchers to accurately determine differences in risk among groups so prevention efforts can be targeted properly. It may also be useful on the treatment side of things. Right now, people from minority groups are underrepresented in clinical trials of new drugs. Scientists hope future treatment trials will be more diverse.

But if they get their wish, neuropsychological tests will have to be carefully designed to reflect the diverse Alzheimer’s population. That way, the people who suffer from the highest rates of dementia may get the full benefit of early diagnosis, despite past inequities in the schoolroom.

Copyright © 2008 Memory Loss and the Brain

Further Reading

Cognitive decline and literacy among ethnically diverse elders, by Jennifer Manly and others. (Journal of Geriatric Psychology and Neurology, 2005, Vol. 18. pp. 213-217.)

“Racial differences in the progression of cognitive decline in Alzheimer disease,” by Lisa L. Barnes and others. (American Journal of Geriatric Psychology, November 2005, Vol. 13, pp. 1-9.)

“Implementing diagnostic criteria and estimating frequency of mild cognitive impairment in an urban community,” by Jennifer J. Manly and others. (Archives of Neurology, November 2005, Vol. 62, pp. 1739-1746.)

“Potential ethnic modifiers in the assessment and treatment of Alzheimer’s disease: challenges for the future,” by Warachal E. Faison and others. (International Psychogeriatrics, 2007, Vol. 19, pp. 539-558.)

“Cognitive functioning among African American older adults,” By Sheila Black. (African American Research Perspectives, Spring/Summer 2004, Vol. 10, Issue 1, pp. 106-118.)