New Diagnostic Approach Catches Early Development of Alzheimer’s

Alzheimer disease is the sixth leading cause of death in the United States. One in eight older Americans suffer from Alzheimer's disease. Difficulty in remembering names or recent events is often an early clinical symptom. One of the hallmarks of Alzheimer's disease is the accumulation of amyloid plaques between the nerve cells in the brain.

A latest finding states that excessive amount of beta amyloid or plaques in the brain is associated with Alzheimer's disease may cause steeper memory decline in mentally healthy older people than does having the APOE Ε4 allele, also associated with the disease.

The APOE Ε4 allele is the only consistently identified risk factor for late onset Alzheimer's disease (LOAD). 

"Our results show that plaques may be a more important factor in determining which people are at greater risk for cognitive impairment or other memory diseases such as Alzheimer's disease," said study author Yen Ying Lim, MPsych, with the University of Melbourne in Victoria, Australia. "Unfortunately, testing for the APOE genotype is easier and much less costly than conducting amyloid imaging."

In order to conduct this study the researchers had nearly 141 subjects who were free of any problems in memory and thinking underwent PET brain scans. The average age of the subjects was 76. They were even tested for the APOE gene.

For the following year and a half, the memory and thinking of these subjects was monitored with the set of computer-based cognitive assessments based on playing card games and remembering word lists.

On analyzing these subjects for more than a year the researchers noticed that people who had more brain plaques at the start of the study had up to 20 percent greater decline on the computer based assessments of memory than did those who had fewer brain plaques. In addition to this, carrier of the APOE Ε4 allele also showed greater decline on the memory assessments when compared to those who did not have the allele. Carrying the Ε4 allele did not change the decline in memory related to the plaques.

"Our finding that brain plaque-related memory decline can occur while people still have normal memory and thinking shows that these plaque-related brain changes can be detected and measured while older people are still healthy. This provides an enormous opportunity for understanding the development of early Alzheimer's disease and even a sound basis for the assessment of plaque-targeting therapies," said Lim.

The study was published in the October 16, 2012 print issue of Neurology, the medical journal of the American of Neurology.