HealthDay News — For cognitively unimpaired older adults, the presence of Alzheimer disease pathology is related to memory impairment according to the Stages of Objective Memory Impairment (SOMI) system, according to a study published online Feb. 23 in Neurology.
Ellen Grober, PhD, from the Albert Einstein College of Medicine in New York City, and colleagues examined neuroimaging correlates of the SOMI system using data from 4,484 cognitively unimpaired participants (mean age, 71.3 years) from the Anti-Amyloid Treatment in Asymptomatic Alzheimer’s (A4) study. All of the participants had amyloid positron emission tomography imaging, and a subset of 1,262 β-amyloid positive (Aβ+) participants had structural magnetic resonance imaging. The Aβ mean cortical standardized uptake value ratio (SUVR) and volumetric measures of hippocampus, parahippocampal gyrus, entorhinal cortex, and inferior temporal cortex were compared between the 5 SOMI stages.
The researchers found that in the entire sample, an analysis of covariance showed that individuals in higher SOMI stages had higher global amyloid SUVR while controlling for age, sex, education, and APOE4. Higher amyloid SUVR was seen in SOMI-4 and SOMI-3 than in SOMI-0 and SOMI-1 subgroups. Smaller hippocampal volume, entorhinal cortex, and inferior temporal lobes were seen at higher SOMI stages, but no difference was seen between parahippocampal gyrus volume according to SOMI stage. SOMI-4, -3, and -2 had smaller hippocampal volumes than SOMI-0 and -1. A significantly smaller entorhinal cortex and smaller inferior temporal lobe were seen for SOMI-4 compared with all other groups.
“These findings suggest that this test can be used to improve our ability to detect cognitive decline in the stage before people are diagnosed with Alzheimer disease,” Grober noted.
Several authors disclosed financial ties to biopharmaceutical companies, including Eli Lilly, which partly funded the A4 study, with in-kind support from Avid and Cogstate.