Tag Archives: test

Saliva Test for Alzheimer’s Disease Shows Encouraging Results

A small study suggests that saliva tests for amyloid-beta could be a useful method for diagnosing Alzheimer’s disease.

As we discussed in last week’s article, Alzheimer’s disease is notoriously difficult to diagnose, particularly in its early stages. Some estimates suggest that up to half of all Alzheimer’s diagnoses are incorrect. Currently-available tests for Alzheimer’s are often expensive and invasive, and in many cases they still can’t offer a completely accurate diagnosis.

In a recent study published in BMC Neurology, researchers investigated whether saliva could be used to detect the hallmarks of Alzheimer’s disease. The test quantifies levels of amyloid-beta, a toxic protein that accumulates in the brains of Alzheimer’s disease patients. Since detecting amyloid-beta inside the brain can be difficult, its levels in the saliva could be a useful proxy to aid in diagnosis.

The study included 15 patients with mild to moderate Alzheimer’s disease and 8 patients with normal cognition. The researchers collected saliva samples and used a highly sensitive protein test called an ELISA to quantify how much amyloid-beta each sample contained. They found that the saliva of Alzheimer’s patients contained more than twice as much amyloid-beta than that of the healthy patients.

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This figure from the paper shows that Alzheimer’s disease patients (represented as diamonds) all had higher salivary amyloid-beta levels than the normal patients (represented as squares). This relationship held true regardless of the patients’ age.

The results of this study suggest that the levels of amyloid-beta in the saliva could be a cheap and easy method for improving the accuracy of Alzheimer’s disease diagnoses. Since the current diagnostic methods require a spinal tap or blood sample, a saliva test could help encourage people to get tested for Alzheimer’s, considering an estimated 3-10% of individuals have a phobia of needles.

Due to the small sample size, this study needs to be repeated and expanded before we can draw broader conclusions. However, the preliminary results are encouraging and help to corroborate previous studies that have shown similar accuracy for these saliva tests. Perhaps in the future, diagnosing Alzheimer’s disease will be as simple as spitting into a tube.

 

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Cleveland Clinic Website Offers Free Brain Health Checkup

While browsing the web recently, I stumbled onto a fantastic resource that I wanted to share with you all. About a year ago, the Cleveland Clinic Lou Ruvo Center for Brain Health launched a new site called HealthyBrains. The website is centered around the six pillars of brain health: physical exercise, food/nutrition, medical health, sleep/relaxation, mental fitness, and social interaction. The goal of the site is to allow everyday people to take their brain health into their own hands. There are so many simple ways to incorporate small lifestyle changes that can dramatically reduce your risk of Alzheimer’s and other neurocognitive disorders.

One of my favorite parts about the site is the Brain Health Checkup, a free quiz that takes around 20 minutes to complete. It asks you a variety of questions about your lifestyle and medical history to calculate a Brain Health Index (BHI), a score between 0 and 100. The higher the score, the better your odds of minimizing your dementia risk based on the latest scientific research. After receiving your score, you can read personalized tips on how to improve your BHI. Your information is saved so that you can retake the checkup later and see how your brain health has improved. You can also take a memory test and see how your brain stacks up against others.

This is such an easy way to learn how to improve your brain health. I highly recommend that you check it out, no matter your age. Click here to visit the site!

 

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A New Approach to Predicting Risk of Alzheimer’s Disease

Background

An individual’s risk for Alzheimer’s disease is affected by a variety of genetic and environmental factors. While the causes of early-onset Alzheimer’s are well understood, the genetic factors underlying late-onset Alzheimer’s disease (LOAD), which makes up 95% of total cases, are less clear. The APOE4 allele is considered the major risk factor for this form of Alzheimer’s, as it can increase your risk by 2-3 times if you have one copy of the allele or up to 15 times if you have two copies. APOE4 does not guarantee that an individual will develop LOAD, and researchers have been searching for other genes that may be involved. (For more background see The Genetics of Alzheimer’s Disease).

Genome-wide association studies, which systematically analyze the 0.1% of DNA sequence that varies between individuals, have linked at least 21 other genes to an increased risk of LOAD. Individually, each of these genes has only a small influence in comparison to APOE4, often increasing one’s risk by only a few percentage points. However, when many of these small genetic risk factors are combined, they can greatly affect an individual’s chances of developing LOAD.

Overall, studies suggest that approximately 33% of an individual’s risk for developing LOAD is attributable to genetics, with the rest being due to lifestyle choices and environmental factors. Of this, APOE and the 21 already-identified genes account for less than 25% of the genetic risk, suggesting that the majority of genetic risk factors for Alzheimer’s disease remain unknown.

New Results

In a recent study published in the journal Neurology, a group of researchers from the Alzheimer’s Disease Neuroimaging Initiative searched for other genes, outside of the 21 already identified, that could also act as slight risk factors for Alzheimer’s. They used data collected from the International Genomics of Alzheimer’s Project to compute polygenetic risk scores, or PGRS, for both young and elderly adults who did not have dementia. Each person’s PGRS was calculated using his or her unique combination of small genetic risk factors (including many that were not statistically significant in genome-wide association studies) in order to estimate the genetic risk for LOAD. The researchers then analyzed whether PGRS were associated with biological markers of preclinical Alzheimer’s disease.

In elderly subjects who did not have dementia, high PGRS was associated with poorer memory, smaller volume of the hippocampus (the part of the brain that helps us form new memories), and increased levels of toxic beta-amyloid in the brain. High PGRS in these individuals also correlated with an increased rate of cognitive decline and a greater probability of later being diagnosed with Alzheimer’s disease. The researchers also computed PGRS for younger subjects under the age of 35. They found that a high PGRS was associated with reduced hippocampal volume, similarly to the older subjects.

Together, these results suggest that more genes besides the currently-identified 21 may need to be considered when evaluating an individual’s risk for LOAD. The researchers plan to repeat this study using a larger sample size to verify the results. Future studies also will track younger subjects to see if PGRS can predict their risk for Alzheimer’s as they age, and compare these results to less comprehensive systems of genetic prediction. The hope is that by refining PGRS, we may one day be able to develop better genetic tests for young people that yield more accurate predictions of future Alzheimer’s risk.

 

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