The historically higher prevalence rates for community-dwelling African Americans than for Whites may be partially attributable to the measurement of disease prevalence and incidence. For example, historically, lower institutionalization rates among African Americans in the past left more people with dementia in the community, whereas comparable Whites were in nursing homes (Froehlich et al., 2001). The institutionalization rate of people with dementia would affect estimated prevalence rates because most studies are of the community-based population.
The effects of education on cognitive test results, and cultural biases in reporting of cognitive impairment are likely to substantially affect prevalence estimates. The number of years of education may not be equivalent between racial/ethnic groups because of disparities in school quality, particularly in older cohorts. Therefore, even prevalence studies that control for education may not be able to adequately control for differences in educational quality (Glymour & Manley, 2008).
Cognitive testing instruments--including the most widely used instrument, the MMSE--perform differently among individuals of different educational levels and racial/ethnic groups (Teresi et al., 2002). Instrument bias can result from lower literacy and education, lack of test-taking experience and stress related to test-taking, varying degrees of acculturation, and language issues such as poor translation. In addition, greater variability in scores for African Americans on standard cognitive tests makes it difficult to establish cutpoints for abnormal results (Froehlich et al., 2001).
Minorities seeking care are often more impaired at the time of their diagnosis, which suggests that they may be accessing services later in the disease process (Cooper et al., 2010). In addition, many community physicians are reluctant to diagnose Alzheimer's disease for reasons such as inadequate reimbursement for evaluation and management, lack of time to provide appropriate follow-up care, lack of knowledge of when and to whom to refer, lack of information about diagnostic criteria, cultural resistance, and belief that there is no treatment. Anecdotally, this reluctance is more prevalent in minority communities (National Institute on Aging, 2010). Moreover, there is some evidence that caregivers of Black elders with cognitive impairment report less cognitive decline in the care receiver than do their White peers, despite no significant differences in impairment, suggesting that Black caregivers may perceive changes in cognition differently (Rovner et al., 2012).
The issues of cultural framework, perception, and understanding of disability are important when interpreting scales that include items with different cultural connotations. Diagnosis is clearly problematic when physicians and patients do not speak the same language or do not share the same cultural perspective. Moreover, some diagnostic instruments contain items that may carry substantial cultural implications that vary by group. For example, a hangman's noose, one of the items on the Boston Naming Test, may have very different implications for elderly African American and White respondents (Jett, 2006).