Memory problems are a frequent complaint among the elderly. The most important underlying issue for patients and physicians alike is to identify a link between memory loss and Alzheimer's disease. Cognitive decline often occurs gradually over a period of years before the diagnostic criteria for Alzheimer's disease are met. Previous studies have suggested that memory loss often precedes dementia, but the cognitive states of the subjects have never been differentiated. Geerlings and colleagues investigated whether memory complaints in elderly patients with normal, borderline-impaired or impaired cognitive function precede Alzheimer's disease.
Patients between 65 and 84 years of age selected from 30 general practice offices in Amsterdam were eligible for the study. Trained laypersons assessed memory complaints in the participants' homes with the question, “Do you have any complaints about your memory?” Participants' educational level and rating on a depression scale were also recorded. Responses were coded and categorized using four mental status tests, including the Mini-Mental State examination. Cognitive function was classified as normal (Mini-Mental State scores of 26 to 30) or borderline and impaired (scores of 25 or less). The follow-up period for all participants classified as either normal or borderline impaired was three years after the initial assessment. Those who scored 23 or less on the Mini-Mental State examination or had low scores on a memory test were evaluated further to rule out other causes of dementia. Alzheimer's disease was diagnosed by a physician based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria.
A total of 3,778 noninstitutionalized elderly persons took part in the study. Of these, 267 underwent further evaluation, and 77 were diagnosed with Alzheimer's disease. The latter group had a mean Mini-Mental State score of 16.7 and a mean decline in score of 9.5 over the study period. A total of 408 persons (10.8 percent) complained of memory impairment. These persons, on average, were better educated and had a higher incidence of depression. Alzheimer's disease was three times more likely to develop in persons with normal cognition who complained of memory loss than in those who reported no memory loss or those with borderline or impaired cognition. However, many of these persons were lost to follow-up; therefore, the true incidence may be underestimated.
The authors conclude that memory loss preceded Alzheimer's disease in elderly persons with normal cognition. The screening question used in this study appears to identify these persons, as they may be aware of cognitive decline before mental status examinations are able to detect such a decline.