Of the people who develop Alzheimer's disease before the age of 60 but do not yet display any memory problems, more than half may be misdiagnosed with other kinds of brain disease, a new Spanish study suggests.

Among people in the study who had early-onset Alzheimer's disease but whose symptoms did not include a failing memory, 53 percent were incorrectly diagnosed when they first saw a doctor, the researchers in Barcelona said. And 47 percent were still incorrectly diagnosed at the time of their death.

The study was based on 40 patients who, in autopsies, were shown to have had Alzheimer's disease. In the cases of those whose Alzheimer's went unrecognized, the doctors commonly diagnosed other types of dementia .

"People who develop early-onset Alzheimer's disease often experience these atypical symptoms rather than memory problems, which can make getting an accurate diagnosis difficult," study researcher Dr. Albert Lladó, of the Hospital Clinic of Barcelona and that city's August Pi i Sunyer Institute of Biomedical Investigation (known by the Spanish acronym IDIBAPS), said in a statement.

The 40 Alzheimer's patients were from the Neurological Tissue Bank-University of Barcelona-Hospital Clínic-IDIBAPS. Of them, 15 had initial symptoms such as behavioral, visual or language problems but displayed no memory problems . And in eight of those 15 cases, their doctors did not initially recognize that they had Alzheimer's.

Researchers reviewed information about the age at which the symptoms began and family history, and found that about one-third of the people with early-onset Alzheimer's disease didn't have memory problems at the early stages of the disease.

There is no specific, surefire test for Alzheimer's disease today. Diagnosis of the disease is based on symptoms and results from various tests, and overall it is accurate 90 percent of the time. However, Alzheimer's disease can be diagnosed with 100 percent certainty only after death, when examination of the brain is able to reveal the amyloid plaques that are characteristic of the disease.

The new study appears in the May 17 edition of the journal Neurology.

Pass it on: Alzheimer's disease in its early stages may not always manifest as memory problems.

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