Alzheimer’s: a group of experts proposed a new definition of the disease

Written by Sandeep Nehra

A group of international experts, led by the French Bruno Dubois, proposes a new definition of Alzheimer’s disease that overcomes the concept of dementia and integrates a biological signature of the disease.

“We dusted the definition of the disease, which typically was” anatomo-clinical, “he told AFP Professor Dubois (Hospital Pitie-Salpetriere, Paris). That is to say that the diagnosis was “suspected” the lifetime of the patient in the advanced dementia, and already “confirmed” after death by brain biopsy.

This new approach, online Monday by the journal Lancet Neurology, is based on new diagnostic criteria presented in 2007 by the same group of experts. It would define Alzheimer’s disease “in nearly 100% of cases,” according to Professor Dubois.

In 2007, “we had lifted the lid,” said Professor Dubois. It is now “going through the process”, in “clarifying things” with a new lexicon.

“It incorporates the fact that we have a biological signature of life for the patient that the diagnosis is clinical-biological,” he said.

“Alzheimer’s disease can now be defined clinically in vivo through a combination of well-defined symptoms (the hippocampal amnesic syndrome type) and the biological signature,” said the neurologist.

The hippocampal amnesic syndrome type results in a disorder of episodic memory, the inability for the brain to burn information on its hard drive.

The signature includes several biological markers: the demonstration by MRI of a structural change in a brain region associated with the disease (hippocampus) the highlighting of lumbar puncture by an abnormality in the cerebrospinal fluid ( decrease in amyloid peptide and increasing the concentration of tau); highlighting functional imaging of a reduced metabolism in certain brain regions.

The panel also defines a “state pre-clinical Alzheimer’s disease“, people who have positive biomarkers, but no symptoms.

The main advantage of this new definition, “said Professor Dubois is that” it will allow to propose the inclusion criteria of patients for trials of new drugs.”

In an editorial also available online by The Lancet Neurology, Lon Schneider (University of Southern California Keck School, Los Angeles), acknowledges his interest in selecting patients for clinical trials, but remains more reserved about using biomarkers as diagnostic criteria.

The number of patients with Alzheimer’s and related dementias is expected to double in 20 years worldwide, 35.6 million today to 65.7 million in 2030, according to a recent report by the Association Alzheimer’s Disease International.

The disease is in fact strongly linked to aging, the risk of developing it doubles every 5 years from 65 and reaching 50% at the age of 85.

Professor Dubois leads to the Pitie-Salpetriere Institute of memory and Alzheimer’s disease (Im2a) which opened its doors in late September.

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