ATRI’s Dr. Paul Aisen has been credited alongside other prominent researchers in the field of Alzheimer's Therapeutics in a medical paper that investigated comparing the Stages of Objective Memory Impairment (SOMI) system to neuroimaging to determine how accurately the higher stages of SOMI were associated with higher amyloid imaging and a reduced hippocampus, entorhinal cortex, and inferior temporal lobes. The objective is to assess if SOMI should be used to help identify individuals at greater risk of developing Alzheimer’s disease. This paper is possible due to the data provided by the A4 Study made accessible by ATRI.
What Is SOMI?
SOMI is a system that ranks memory impairment from 0 to 4, with no memory impairment at level 0, and significant issues with memory storage at level 4.
- SOMI rankings are determined by the results of the Free and Cued Selective Reminding Test (FCSRT)
- FCSRT is a cuing test in which people are shown multiple cards and asked to identify the items on the cards as belonging to a particular category. After being shown the cards, participants are asked to recall the items (Free Recall). If the participant cannot recall the items, they are presented with the category cues (Cued Recall).
- SOMI looks particularly at the scores of Free Recall and Total Recall (Free Recall + Cued Recall) to determine what level of SOMI an individual would fall at. See the chart below (Tabel 1 SOMI) to see the various rankings and how the SOMI stages correlate to various classes of memory impairment.
Participants and Data
The data for this study came from the Anti-Amyloid Treatment in Asymptomatic Alzheimer's (A4) study
- A total of 4,484 cognitively unimpaired adults were included in this study
- The A4 study is being conducted in the United States, Canada, Australia, and Japan
- Participants eligible were 65 to 85 years of age, assessed to be cognitively normal and living independently, and had a study partner who would be able to provide information on daily life cognitive function on an annual basis
Assessments and Imaging
Participants went through the Free and Cued Selective Reminding Test (FCSRT), to gain scores of both Free Recall and Total Recall (sum of free recall and cued recall) which would determine their SOMI stage.
- Participants underwent amyloid PET imaging at screening, to determine if they were “amyloid-positive” or not. An excess of beta-amyloid buildup is a characteristic of Alzheimer’s disease.
- Only individuals who were amyloid positive received an MRI at the baseline visit, meaning there are only brain measurements available for approximately a quarter of the participants of the study.
Results
In normal older individuals, higher stages of memory impairment assessed with FCSRT were associated with higher amyloid imaging burden and lower volume of specific areas of the brain, namely the hippocampus, entorhinal cortex, and inferior temporal lobes.
- There was no difference between amyloid amounts in SOMI rankings of 0 and 1. These individuals also had the largest hippocampal volume and inferior temporal lobes.
- Individuals in SOMI 3 and 4 had higher levels of amyloid buildup than those in SOMI 0 and 1.
- Those in SOMI-4 also had smaller entorhinal cortexes and inferior temporal lobes.
What Does This Mean?
These findings support the notion that using the SOMI system can improve our ability to detect early and late cognitive decline during the preclinical stages of AD, which may prove advantageous in the design of prevention trials.
- Even in highly selected cognitively normal older adults, the presence of AD pathology is closely related to memory impairment based on SOMI stages. We envision that SOMI could be used for the enrichment of future clinical trials.
- SOMI staging provides a practical system (and cutoffs for classification) that can be used as part of the design of future interventional studies that use FCSRT for cognitive testing.
Learn More
Read the full paper on PubMed to learn about how this study was completed and more specifics about the findings.
