Could a simple saliva test detect Alzheimer's?
News Jul 22, 2015
Your spit might just reveal whether you’re a likely candidate for developing Alzheimer’s disease.
That at least is the hope of Canadian researchers whose study suggests that analyzing certain chemical compounds in saliva could provide a cheap, non-invasive way to learn whether the brain has begun to undergo the changes that culminate in loss of memory and cognitive function.
Their study was one of several on the hunt for new biomarkers that were presented at the Alzheimer’s Association International Conference in the District. Other biomarker research looked at the possibility of analyzing brain fluid for the elevated presence of neurogranin, a protein that is found only in the brain and plays an important role in conducting signals between the synapses of nerve cells, or using PET scans to identify inflammation, which can be fatal for brain tissue.
The scientific gathering — which is expected to draw nearly 4,500 researchers from around the world — comes as several developed nations shift toward older populations. More than 5 million people are living with Alzheimer’s in the United States, a number expected to increase to 13.5 million by 2050.
With about 10,000 baby boomers turning 65 every day, Alzheimer’s researchers and their advocates say the United States needs to step up the search for a cure or treatments before the costs to family caregivers and the federal government, through Medicare, begin to soar. A step forward means finding ways to diagnose the disease better, particularly in its early stages before symptoms appear. And it also is likely to involve a multi-pronged approach.
A lot of attention was given to the search for new, reliable biomarkers of Alzheimer’s disease. Because the preclinical stage of Alzheimer’s can last as long as 20 years, scientists are devoting more attention to finding ways that could determine whether a person is at risk well before memory loss or cognitive impairment occurs.
The ability to develop easy screening methods for them could allow doctors to intervene in ways to someday delay or prevent the onset of dementia. It is also key to enhancing pharmaceutical research, as drug companies are especially interested in identifying people at risk and enrolling them in clinical trials to test the efficacy of possible treatments.
In recent years, scientists have reported discoveries on a number of possible biomarkers linked to Alzheimer’s-related changes in the brain. Some might involve nothing more invasive than an eye scan or a skin test. But the test papers have been more hopeful than results.
Shraddha Sapkota, a neuroscience graduate student at the University of Alberta, said her team studied the presence in saliva of metabolites — which are molecular byproducts of metabolism — to see whether they could be a reliable early indicator of metabolism changes in the brain that also signal the early stages of Alzheimer’s disease.
Using liquid chromatography-mass spectrometry to analyze the samples, the researchers distinguished between groups of participants who were aging normally, suffering from mild cognitive impairment, or already diagnosed with Alzheimer’s. Sapkota said her team also found that higher levels of specific metabolites in the saliva also correlated to evidence of declining cognitive abilities.
“So that’s promising. What that does is it tells a physician in a regular doctor’s office that this person should get more testing,” said Maria C. Carrillo, chief science officer at the Alzheimer’s Association.
Other scientists were more cautious. Creighton H. “Tony” Phelps, director of the National Institute on Aging’s Alzheimer’s Disease Centers program, said it would be wonderful if doctors could eventually ask someone to spit in a cup or submit to an oral swab and determine whether the person is at greater risk for dementia. But the research seemed preliminary, he said.
“The idea is good. And I hope someday we’ll be able to do that. But we’ve had very bad luck with these panels of biomarker,” Phelps said.
Marilyn Albert, director of the Division of Cognitive Neuroscience at Johns Hopkins University’s Department of Neurology, presented a briefing whereher team assessed a variety of current diagnostic tools and found that about six measures were particularly useful in predicting which cognitively normal people would develop Alzheimer’s within five years. Among the most useful measures were the Digit Symbol and Paired Associates Immediate Recall tests, which measure memory and cognition; analyzing cerebrospinal fluid for the presence of amyloid beta and tau, which are the two abnormal proteins that distinguish the presence of Alzheimer’s; and MRI scans that assess the volume or thickness, respectively, of the hippocampus and the right entorhinal cortex, which are parts of the brain critical to memory.
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