Extensive cognitive testing has been a key diagnostic tool in AD, refined over many years. Many existing tests were designed to diagnose relatively later stages of the disease—for example, in people who come to the doctor’s office already complaining of memory problems. What is currently lacking are tests that can detect and track the earliest, most subtle stages of the disease and tests that can identify who is at risk of eventually developing the disease.
Research efforts now concentrate on the development of a new generation of cognitive tests that are more sensitive to changes in cognition and more reliably discriminate between normal aging, early stages of AD, and cognitive impairment due to other diseases, such as cerebrovascular disease or Lewy body disease. Progress toward establishing a detailed account of normal neurocognitive aging will importantly inform this effort.
Mild Cognitive Impairment
MCI is often a transitional stage between normal aging and AD. Sensitive, accurate diagnostic tests for MCI are critical to identify people at risk of developing AD and to predict the likely progression of symptoms. There has been considerable variability in assessing how common MCI is in the population and the rate at which people with MCI progress to AD, due in part to the use of different criteria for diagnosing MCI. Researchers at the University of California, Los Angeles Alzheimer’s Disease Center assessed 115 people with amnestic or nonamnestic MCI using a battery of tests for different neuropsychological functions, such as memory, attention, and visuospatial processing, then followed their progress for 16 months. (In amnestic MCI, memory is the dominant problem; in nonamnestic MCI, other cognitive impairments dominate, such as problems with language, visuospatial processing, and attention. People with amnestic MCI are more likely to progress to AD than those with nonamnestic MCI.) In both the amnestic and nonamnestic groups, the percentage of people who had performance deficits differed significantly for different tests. However, the people who were most impaired on memory tests at the beginning of the study were also the most likely to have persistent memory deficits over the long term (Teng et al., 2009).
Mini Mental State Examination
The Mini Mental State Examination (MMSE) was designed in 1975 and remains the most widely used screening test for dementia. The MMSE is not sensitive to mild cognitive changes, nor is it very useful for distinguishing between AD and other forms of dementia. It has remained in use in part because it is simple, quick to administer, and can be used in any doctor’s office. Most clinical trials use MMSE scores to help determine who is eligible to participate. A number of new tests are under development that retain those virtues but provide more sensitive and accurate diagnoses. For example, researchers at Mount Sinai Medical Center in Miami, FL, reported on the Florida Brief Memory Screen, which shows high sensitivity for detection of MCI and takes only 3 to 4 minutes to administer. The test is available in Spanish and English, an important feature, as linguistic issues can compromise test performance (Loewenstein et al., 2009).
Several computer-based tests have also been developed, most of which can be used with a standard personal computer. Most of these tests have to be administered and scored by a clinician, as is also true for pen and paper-based tests like the MMSE. University of Pittsburgh researchers reported on a new computer-based test, Computer Assessment of Mild Cognitive Impairment (CAMCI), that is both self-administered and automatically scored. The researchers reported a good sensitivity for detection of MCI (Saxton et al., 2009).
For additional information related to cognitive testing, see Schneider LS et al. (2009) Characteristics and performance of a modified version of the ADCS-CGIC CIBIC+ for mild cognitive impairment trials. University of Southern California. Supported by NIA, NCRR.
Ethnicity and AD Diagnosis
Several reports have suggested racial and ethnic differences in the prevalence of AD. Studies seeking to explain these differences have found that cultural factors and variations in education quality, for example, can affect performance on standardized cognitive tests.
Another source of diagnostic information, used in conjunction with cognitive tests, is reports from family members and other caregivers about how well a person is functioning in day-to-day life. However, these informant reports, too, may be affected by ethnic and cultural differences. Investigators from Duke University in Durham, NC, found that family member/caregiver reports were less likely to predict cognitive impairment without dementia in African Americans than in whites (Potter et al., 2009). These results are consistent with previous studies suggesting that African Americans are less likely than whites to report cognitive changes in family members.
This difference may reflect different cultural perceptions of “normal” aging. For example, a research team at the University of Michigan and Boston University Alzheimer’s Disease Centers studied a group of 301 people in the Boston area, most of whom had personal experience with AD as a caregiver and/or relative. Significantly more of the African American than white participants believed that memory impairment is an expected part of aging (Connell et al., 2009).
National Institute on Aging
Page last updated Jan 21, 2011