Subjective memory impairment, or mild deficits in memory that may or may not cause worry for an individual, appear to predict progression to more advanced stages of cognitive impairment and dementia, according to a report in the April issue of Archives of General Psychiatry, one of the JAMA/Archives journals.
Individuals with cognitive test results below normal ranges but who are still able to participate in most regular activities are said to have mild cognitive impairment, according to background information in the article. This condition has been established as a risk factor for Alzheimer's disease and other forms of dementia, with 10 percent to 20 percent progressing from mild cognitive impairment to dementia each year. "The concept of mild cognitive impairment as a predementia manifestation of Alzheimer's disease is substantiated by studies providing biologic evidence for the presence of Alzheimer's disease in patients with mild cognitive impairment," the authors write. "However, Alzheimer's disease-related pathologic changes in the brain evolve several years before the onset of mild cognitive impairment."
Frank Jessen, M.D., University of Bonn, Germany, and colleagues in the German Study on Aging, Cognition and Dementia in Primary Care Patients Study tudied 2,415 adults age 75 or older who did not have cognitive impairment at the beginning of the study. Participants were asked whether they believed their memory was becoming worse and whether or not this caused worry for them (one way for researchers to gauge the severity of memory impairments). They were then followed up one and a half and three years later and tested for mild cognitive impairment and dementia.
Individuals who had memory impairment with concern at the beginning of the study were at the highest risk for conversion to any dementia, or Alzheimer's disease-related dementia, at either follow-up. "Subjective memory impairment without worry was independently associated with increased risk for dementia," the authors write. "This risk was roughly doubled by the presence of subjective memory impairment-related worry."
In addition, having memory impairment at the beginning of the study and mild cognitive impairment at the first follow-up increased the risk for conversion to any dementia or dementia related to Alzheimer's disease at the second follow-up; these individuals had the greatest risk for developing dementia.
"Not all subjects with subsequent dementia will experience or report subjective memory impairment at the pre-mild cognitive impairment stage," they conclude. "However, if subjective memory impairment is present in a subject without cognitive impairment as evidenced by neuropsychological test results, it may inform about the risk for dementia and may contribute to individual decisions about diagnostic procedures and interventions to lower the risk factors for Alzheimer's disease based on current knowledge."
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