Literature Review

Subjective Memory Complaints May Signal Increased Risk of Dementia



People without dementia who begin reporting memory problems may be more likely to develop dementia later, even if they have no clinical signs of the disease, according to research published in the October 7 issue of Neurology.

“What’s notable about our study is the time it took for this transition to dementia or clinical impairment to occur—about 12 years for dementia and nine years for clinical impairment—after the memory complaints began,” said Richard J. Kryscio, PhD, Chair of Biostatistics at the University of Kentucky in Lexington and lead author of the research. “These findings suggest that there may be a window for intervention before a diagnosable problem shows up.”

For the study, 531 people free of dementia with an average age of 73 were asked yearly if they noticed any changes in their memory. The participants also were given annual memory and thinking tests for an average of 10 years. The investigators examined the brains of 243 participants who died for evidence of Alzheimer’s disease.

Approximately 56% of the participants reported changes in their memory at an average age of 82. People who reported memory complaints were nearly three times more likely to develop memory and thinking problems than were people without memory complaints. About one in six participants developed dementia during the study, and 80% of those participants reported memory changes before developing dementia.

On average, mild cognitive impairment occurred 9.2 years after memory complaints were reported. Participants with subjective memory complaints and an APOE ε4 allele had double the odds of impairment, compared with people with memory complaints alone. Patients with subjective memory complaints who smoked transitioned to mild cognitive impairment more quickly, and women with subjective memory complaints who had undergone hormone replacement transitioned to dementia more slowly. Among participants who died without a diagnosed clinical impairment, subjective memory complaints were associated with elevated neuritic amyloid plaques in the neocortex and medial temporal lobe.

“Our study adds strong evidence to the idea that memory complaints are common among older adults and are sometimes indicators of future memory and thinking problems. Doctors should not minimize these complaints and should take them seriously,” said Dr. Kryscio. “However, memory complaints are not a cause for immediate alarm, since impairment could be many years away. And, unfortunately, we do not yet have preventive therapies for Alzheimer’s disease and other illnesses that cause memory problems.”

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