PET links accelerating memory decline to APOE ε4 allele

According to a recent study published in JAMA Neurology, memory decline and the potential to develop Alzheimer's disease may increasingly accelerate with age in certain individuals. 

Specifically, the study analyzed the relationship between increasing age, the presence of the β-amyloid (Aβ) amino acid, the apolipoprotein E (APOE) ε4 allele and memory decline in older adults.

"The extent to which increasing age, Aβ, and ε4 are associated with memory decline remains unclear, and the age at which memory decline begins for Aβ-positive ε4 carriers and noncarriers has not been determined," said Yen Ying Lim, PhD, from the Florey Institute of Neuroscience and Mental Health at the University of Melbourne in Australia.

Researchers analyzed a group of 447 healthy older adults 60 years or older enrolled in the year-long Australian Imaging, Biomarkers and Lifestyle (AIBL) study. Of the 447 participants, 203 were men and 244 were women. According to study methods, all participants underwent Aβ imaging using positron emission tomography (PET) and genotyping for APOEɛ4 for more than 72 months of follow-up (at 18-month intervals). 

The study results included the following:

• The same number of female participants were observed in each Aβ-ɛ4 group (24 of 51 Aβ-positive ε4 noncarriers, 35 of 64 Aβ-negative ε4 carriers, 40 of 72 Aβ-positive ε4 carriers and 145 of 260 Aβ-negative ε4 noncarriers).
• Adults with Aβ findings were four years older than those negative for Aβ. 
• Memory decline "diverged significantly" from Aβ-negative ɛ4 noncarriers at an earlier age in Aβ-positive ɛ4 carriers (64.5 years) than in Aβ-positive ɛ4 noncarriers (76.5 years).
• The memory performance of Aβ-negative ɛ4 carriers did not differ from Aβ-negative ɛ4 noncarriers.

"Results of this study indicate that increasing age may further exacerbate these effects [of memory decline]," Lim et al. concluded. "The estimates provided may be used to determine the risk of memory decline associated with Aβ and ε4 at each age."