Alzheimer’s is a progressive neurological disease. At its mildest, it can cause a person to experience minor memory loss, while at its most severe, it can leave a person unable to respond to the world around them.
The disease typically affects people over the age of 65 years, and the risk increases as people get older.
Mild cognitive impairment — such as having problems remembering things — can be an early warning sign of Alzheimer’s. However, this is not always the case. Mild cognitive impairment may stay stable over time and be unrelated to Alzheimer’s disease.
Not knowing whether mild cognitive impairment will lead to Alzheimer’s can cause anxiety for those it affects and their family.
Prof. Oskar Hansson — a professor in neurology at Lund University, a consultant at the clinical memory research unit at Skåne University Hospital, Sweden, and a corresponding author of the study — notes that “[m]any people with Alzheimer’s disease currently seek care when they have only developed mild memory impairment, meaning many years before the dementia stage of the disease.”
“It is often difficult for doctors to give the correct diagnosis in people with milder memory impairment, as many different conditions other than Alzheimer’s can be the cause,” he adds.
However, current tests to determine whether mild cognitive impairment is likely to lead to Alzheimer’s come with issues.
Cerebrospinal fluid, which doctors take from a person’s spine through a lumbar puncture, can reflect the brain’s metabolism and pathology. Therefore, it can enable clinicians to identify Alzheimer’s disease prior to the onset of severe symptoms.
However, as the scientists behind the present study note, lumbar punctures are invasive, and this may be off-putting for some people.
Alternatively, doctors can use positron emission tomography imaging to identify early forms of Alzheimer’s. However, this procedure is expensive, and the technology to perform the imaging may not be available in all healthcare settings.
As a consequence, the scientists behind the present study wanted to determine whether it was possible to develop a less invasive and expensive way of predicting Alzheimer’s disease in people with mild cognitive impairment.
The scientists began by looking at biomarkers in the blood of 573 people who had mild cognitive impairment but not dementia. Biomarkers are particular biological characteristics that can signal diseases or physiological processes.
In this instance, following previous research that the scientists had conducted, the biomarkers they analyzed were two types of protein: phosphorylated tau (P-tau) and neurofilament light, which were predictive of dementia in their model.
They also tested the ratio of two types of beta-amyloid, but this did not add anything further to the model, as P-tau proved to be a better predictor.
The scientists then reviewed the participants annually for 4 years to assess the clinical progression of their mild cognitive impairment.
The scientists found that analyzing the two blood proteins was as accurate as — and, in some cases, more accurate than — the analysis of cerebrospinal fluid in predicting Alzheimer’s disease.
As with analyses that use cerebrospinal fluid, the analysis of proteins in the blood was also more accurate than a prognosis based on a person’s age, sex, education, and performance in memory tests (the current basic test).
The research opens the door to less costly, more readily available, and noninvasive approaches to identifying early forms of Alzheimer’s. Despite being an improvement on the current basic test, the sensitivity and specificity of the new model mean that it would still wrongly identify 5% of people as having a high risk of progression to dementia and miss 50% of people who do have a high risk of progression.
The researchers say that there is a need to conduct these studies on larger samples to replicate the findings.
“In addition to this initial evaluation, the methods that are currently on offer for diagnosing Alzheimer’s disease are costly and time-consuming methods using [positron emission tomography] cameras and [cerebrospinal fluid] analyses, which are only available in certain specialist healthcare settings.”
– Prof. Oskar Hansson
“Our goal over the last few years has been to find simple methods that can be used in primary care to make an early diagnosis and to begin treatment to relieve symptoms at an earlier stage. This will require more studies, but we have absolutely come one major step closer to our goal,” he notes.
To this end, the researchers have developed an app that, pending further research, they hope clinicians could use to aid the diagnosis of early Alzheimer’s.