New tests for early detection of Alzheimer's disease: your eyes and nose may provide information about what is happening in your brain.
"There is a pressing need for easier, less invasive diagnostic tests that will identify the risk of Alzheimer's much earlier in the disease process," says Michael Tai-Ju Lin, MD, associate professor of neurology at Weill Cornell Medical College.
The sooner the disease is detected, the quicker treatment and management can begin, which can help both the individual and their caregivers, especially women. A recent report found women comprise 65 percent of dementia caregivers.
But there may be good news on the horizon. Several recent studies, reported at the 2014 Alzheimer's Association International Conference (AAIC), suggest there are ways to quicker diagnosis during the early stages of AD--not in your brain, but through your nose and eyes.
The nose knows
In one AAIC study, Harvard University researchers examined the link between sense of smell, memory performance, and loss of brain cell function in 215 normal, elderly individuals. They used the 40-item University of Pennsylvania Smell Identification Test (UPSIT) and various cognitive tests. They also measured the size of the en torh i nal cortex and hip-pocampus--two brain regions involved with memory.
The results found that participants with a weaker ability to identify smells and a decreased memory also had a smaller hippocampus and a thinner entorhinal cortex. The sense of smell-AD connection appears to be linked to the first cranial nerve, which is often the initial brain area affected in cognitive decline.
Another related study applied the UPS IT to more than 1,000 healthy elderly adults with an average age of 80. The researchers found that those who scored lowest on the UPSIT had a higher risk of dementia and AD. In fact, for each point lower a person scored on the test, his or her risk for AD increased by about 10 percent.
Looking for beta-amyloid plaque
Beta-amyloid plaque build-up in the brain is a distinctive characteristic among AD patients. The traditional way to measure it is with a brain scan, but the experience can be stressful and expensive for patients. However, one study from the AAIC showed that the telltale sign can be identified by using a simple, noninvasive eye test. Researchers had study participants drink a supplement that contained curcumin, the main substance in the spice turmeric. Curcumin binds to beta-amyloid plaques, and it has fluorescent properties that enable the plaques to be imaged in the retina. The participants then underwent a technique called retinal amyloid imaging (RAI), as well as brain PET imaging.
Preliminary results found that high plaque levels detected with the RAI correlated 100 percent with plaque levels found with the brain scans
The scientists also observed an average 3.5 percent increase in retinal plaque over a 12-plus week period, which suggests the test also may be used to monitor ongoing AD therapy. Lead researcher Shaun Frost, MSc, predicted that the test could one day be added to an individuals regular eye checkup.
Another study demonstrated that a fluorescent ligand eye scanning (FLES) system could be used to Find beta-amyloid plaque in the eye's lens.
Researchers studied people with probable AD, including mild cases, and healthy volunteers of similar age. An ointment that binds to beta-amyloid plaque was applied to the inside of the participants' lower eyelids. A day later, the participants underwent eye scanning, which was able to detect plaque by a florescent signature. Based on the scanning results, the researchers were able to distinguish between those with AD and the healthy control group with an 85 to 95 percent accuracy rate.
While these findings still need further exploration, they offer additional hope for future generations of Alzheimer's patients and their families.
"Perhaps the greatest advantages of these studies is they offer speed and accu-racy--factors that are crucial for early diagnosis of AD," says Dr. Lin.
One new test for Alzheimer's disease uses retinal amyloid imaging, in which a scan of the eye's retina can detect the presence of beta-amyloid plagues (see arrows, top right), one of the markers of Alzheimer's disease; until now, these plagues could be detected only in brain tissue.