INDIANAPOLIS - Nearly one in four older African Americans in Indianapolis have measurable cognitive problems, according to an Indiana University School of Medicine study published in the Nov. 13 issue of the journal Neurology.
The study is the first population-based study of cognitive impairment in the United States. It suggests that the condition may affect a significant proportion of older people. Researchers looked at cognitive difficulties that had not progressed to the point of Alzheimer disease or dementia. Cognition is defined as the process of thinking, learning and remembering.
The study showed that prevalence increased with age, finding that 38 percent of people age 85 and older had some degree of cognitive impairment short of dementia. The findings appear to be consistent with the few studies done to date in other countries.
Researchers interviewed 2,212 African Americans age 65 and older living in the Indianapolis community and 106 people age 65 and older living in nursing homes in the Indianapolis area. They found that 23 percent had cognitive impairment that did not reach the level of dementia. Of those, 25 percent developed Alzheimer disease or other dementia within 18 months.
"Occasionally forgetting where your glasses are doesn't mean you have cognitive impairment," according to study author Frederick Unverzagt, Ph.D., clinical assistant professor of psychiatry at the IU School of Medicine.
"Many people of all ages feel their memory is not what it should be, and that's not necessarily a cause for concern," Dr. Unverzagt said. "Our own judgment of our memory is generally not very accurate. When a relative or someone else notices significant changed, that is an important sign that your should be seeking medical attention."
Dr. Unverzagt was assisted with the research project by Hugh Hendrie, MB ChB, professor of psychiatry at IU School of Medicine and research scientist at the Regenstrief Institute for Health Care in Indianapolis, and colleagues at the University of Ibadan in Nigeria. The work is part of a 10-year study of African Americans living in Indianapolis and Nigeria, which is supported by grants from the National Institute on Aging and the Alzheimer's Association.
A total of 457 of the study participants (351 in the community and 106 in nursing homes) received full clinical assessments and a diagnosis. In a number of cases, the researchers conducted interviews with spouses or close relatives or sources who could describe a participant's symptoms and the progression of symptoms of memory loss, language disturbance, decline in judgment and reasoning, and personality change. After the baseline assessment, the clinically assessed participants were followed for up to 48 months from the start of the study.
Applying the findings from the clinically assessed group to the larger community sample, Dr. Unverzagt and colleagues estimated that 23.4 percent of the community-dwelling participants and 19.2 percent of the nursing home residents were classified as Cognitive Impairment No Dementia (CIND). The prevalence of cognitive impairment increased significantly with age, with rates increasing by about 10 percent for every 10 years of age after age 65. CIND was almost five times more common in the community than dementia (23.4 percent CIND to 4.8 percent dementia for people 65 and older).
In addition, the scientists found 26 percent of those characterized with CIND at the start of the study went on to become demented only 18 months later. Twenty-four percent of participants who were initially diagnosed with CIND appeared normal after 18 months.
The factors that influence whether CIND will progress to dementia or return to normal have yet to be determined. It is unclear whether the prevalence of cognitive impairment short of dementia in the Indianapolis group is higher or lower than other population groups. The new analysis is the first reported in the U.S. and one of only a few worldwide that have examined the prevalence of cognitive impairment short of dementia.
In the research so far, findings of prevalence in large epidemiological surveys have ranged from 10.7 percent in Italy to 26.6 percent in Finland. The variation in findings can be explained by differences in study methodology, including diagnostic criteria, although it is difficult to compare findings directly. However, Dr. Unverzagt says all the studies completed so far suggest that mind cognitive impairment may be common.
The Indianapolis data were approached from a second perspective, figuring the proportion of people in different age groups who were cognitively normal instead of impaired. Incorporating information about the prevalence of dementia from earlier studies of the Indianapolis group, the team added together the prevalence of CIND and dementia and then looked at the proportion remaining, classified as normal. From that perspective, only 45 percent of people age 84 and older were found to be cognitively normal, compared with 79 percent of people ages 65 through 74.
Journal
Neurology