Early warning signs of Alzheimer's show up across cognitive areas years before official diagnosis

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December 20, 2005

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Alzheimer’s warning signs show up years before diagnosis, researchers say

Aug. 9, 2005
Courtesy American Psychological Association
and World Science staff

People who will go on to develop Alzheimer’s disease display warning signs years before their official diagnosis, researchers have found. The signs include a worsened memory for past episodes in their own life.

Unfortunately, most of these warning signs are also characteristic or normal aging, the researchers said. This could make it hard to diagnose the disease earlier, although the problems are worse in those who go on to be diagnosed with it.

The psychologists said they reached the conclusions after combing through 47 Alzheimer’s disease studies from the past 20 years. The findings appear in the July issue of Neuropsychology, a research journal of the American Psychological Association.

The researchers, at the Karolinska Institute in Stockholm, Sweden, crunched data from a decade’s worth of studies. This included records on 1,207 people who were later diagnosed with the disease, and 9,097 controls who stayed healthy.

Scientists are investigating the disease’s pre-diagnosis stages in hopes that it might help them understand how the disease progresses, and help doctors improve treatment by catching at-risk patients earlier.

The researchers said they found pre-diagnosis Alzheimer’s patients had marked deficits in overall cognitive ability, memory for episodes in their own life, speed of perceptions, and executive functioning, a set of processes that includes planning, inhibitory control and flexibility in attention.

The pre-diagnosis patients showed somewhat smaller deficits in verbal ability, visuospatial skill, and attention, the researchers said. However, there was no deficit in their so-called primary memory, the information actively kept in mind for a task.

The authors said the deficits seen in these patients mirror quite closely those seen in normal aging. Still, said lead author Lars Bäckman, these problems are exacerbated in those who will go on to be diagnosed.

“There are no clear qualitative differences in patterns of cognitive impairment between the normal old 75-year old and the preclinical AD [Alzheimer’s disease] counterpart,” he said.

“Rather, we think of the normal elderly person, the preclinical AD person, and the early clinical AD patient as representing three instances on a continuum of cognitive capabilities. This presents an obvious challenge for accurate early diagnosis.”

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