Low scores on a simple memory test may be able to detect the cognitive decline that precedes Alzheimer's disease without resorting to expensive or invasive medical procedures. The corresponding research was conducted by the American Academy of Neurology and published in their journal Neurology.
The study consisted of 4484 individuals of an average age of 71, with no recorded history of cognitive or memory impairment. The participants were shown items with a relevant prompt, such as grapes with the prompt "fruit". They were then tested by remembering the items, using the prompt for those they could not remember.
After the study, test scores were divided into four categories, or "stages". Stages 0, 1 and 2 were marked by difficulty recalling the items without prompts, and precede the more serious symptoms of dementia by five to eight years. Stages 3 and 4 included participants who were unable to remember all of the items even with prompts. Participants in these stages were expected to develop dementia within one to three years.
Participants also underwent brain scans to measure the volume of different brain areas, as well as levels of beta-amyloid plaque that indicate the development of Alzheimer's disease. Rates of beta-amyloid positivity - the build-up of amyloid proteins -were 30% at Stage 0, 31% at Stage 1, 35% at Stage 2, 40% at Stage 3, and 44% at stage 4, indicating that those who struggle the most with memory are prone to having higher levels of beta-amyloid.
They were also found to have lower volume in the hippocampus, entorhinal cortex, and inferior temporal lobes; all areas associated with Alzheimer's pathology. Overall, "half had no memory impairment; the other half had retrieval deficits, storage limitations or both".
From their results, the researchers concluded that the presence of Alzheimer’s pathology is closely related to lower scores on the memory test.
Their study also enabled them to distinguish between difficulty in retrieving and storing memories. While the former is indicative of impaired recall that occurs before dementia diagnosis, the latter is indicative of memory storage problems that occur in the later stages of pre-dementia.
The researchers say their findings could be used to choose who to enroll in clinical trials investigating cognitive decline, to inform clinical trial design, and improve diagnostics.
They, however, note some limitations to their findings. Their participants lacked diversity; all were highly educated, so the findings may not be representative of wider trends in the general population. The researchers are thus hoping to conduct further research using more diverse samples.
Sources: Neurology, ScienceDaily
