"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," study author Yen Ying Lim of the University of Melbourne. "Unfortunately, testing for the APOE genotype is easier and much less costly than conducting amyloid imaging."
The study involved 141 people with an average age of 76 who were free of any problems in memory and thinking, who underwent PET brain scans and were tested for the APOE gene.
Their memory and thinking was then tracked for 18 months, using a set of computer-based cognitive assessments based on playing card games and remembering word lists.
The study, published in the journal Neurology, found after 1 1/2 years, 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.
The study found carriers of the APOE 4 allele also showed greater decline on the memory assessments than those who did not have the allele, but carrying the 4 allele did not change the decline in memory related to the plaques.