Innovation

Biomarkers In Saliva Test May Predict Onset Of Alzheimer's Disease, Mild Cognitive Impairment

Q-tip for the taking of DNA analysis
A saliva test may determine whether you’re more likely to develop Alzheimer’s disease and mild cognitive impairment within six years. Photo courtesy of Shutterstock

Mild cognitive decline and the more progressive Alzheimer’s disease become increasingly inevitable for some people as they age. But a simple saliva test may help determine whether you’ll develop the disease over the next six years. In a preliminary study presented at the Alzheimer's Association International Conference (AAIC) in Washington, D.C., researchers at the University of Alberta, Edmonton found specific metabolites — molecular byproducts of metabolism — present in saliva could indicate metabolic changes in the brain signifying early stages of Alzheimer’s.

Similar to other diseases, Alzheimer’s can start years to decades before initial symptoms of memory loss emerge. With an estimated 5.2 million Americans suffering from Alzheimer’s in the U.S., doctors are still trying to determine how to identify these patients early enough to employ interventions. Shraddha Sapkota, neuroscience student at the Neuroscience and Mental Health Institute at UAlberta and her research team believe saliva might serve as a diagnostic tool to evaluate the risk of memory loss or cognitive impairment before it occurs.

"Saliva is easily obtained, safe, and affordable, and has promising potential for predicting and tracking cognitive decline, but we're in the very early stages of this work and much more research is needed," Sapkota said in a news release from the Alzheimer's Association.

In an effort to find a cheap and non-invasive way to predict the loss of memory and cognitive function in the brain, Sapkota and her colleagues tested saliva from a small group of participants with and without memory loss. Using data from the Victoria Longitudinal Study — a long-term and large-scale investigation of human aging — saliva samples were collected from 22 people with Alzheimer’s, 25 people with mild cognitive impairment, and 35 people whose mental skills were normal for their age. The saliva samples were analyzed using liquid chromatography-mass spectrometry to determine which substances were prevalent in the saliva of each of the three types of people.

The findings revealed strong correlations between the concentrations of certain substances and a person’s cognitive abilities. The presence of certain metabolites was associated with higher levels of cognitive decline. Specifically, the researchers found that certain substances found in high concentrations among people with Alzheimer’s were not as high in people with mild cognitive decline or healthy brains. Meanwhile, two different substances that correlated to each of the brain conditions, and were associated with worse episodic memory, weren’t found in high concentrations among those with healthy brains.

In comparison to testing for Alzheimer’s biomarkers, such as beta-amyloid and tau, testing saliva is easy, cheap, and noninvasive. However, the findings should be taken with caution because the preliminary study was small and failed to account for variables, such as coexisting illnesses, medications, and tobacco use — all of which can influence what’s found in saliva. This saliva test is in its infancy but may eventually become a breakthrough Alzheimer’s tool.

Along the same lines of research, a recent study published in the journal Neurology found a blood test may predict whether a person will suffer from Alzheimer’s within the next two to three years. The researchers analyzed blood samples from participants aged 70 and over — none of them had symptoms of Alzheimer’s at the beginning of the five-year study. The results showed that a pattern emerged among those with memory loss or Alzheimer’s; 10 types of lipids in the blood changed in similar ways.

Like a saliva test, blood-based biomarkers can be a more accessible, less invasive, and easier option than expensive brain imaging, spinal taps, and spinal fluid extraction. However, with both studies in their early stages, there still isn’t a way to prevent or treat the disease. Doctors believe existing drugs, as well as those currently in development, will be the most promising way to prevent the disease in those at risk.

With new research, scientists will move closer to easily detecting the mentally debilitating disease that affects millions every year.   

Sources: Sapkita S. Alzheimer's Association International Conference (AAIC) 2015 in Washington, D.C.

Jack Jr. CR, Knopman DS, Mielke MM et al. Predicting the risk of mild cognitive impairment in the Mayo Clinic Study of Aging. Neurology. 2015.

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