Researchers have just identified an early indicator of Alzheimer’s disease that could help with earlier diagnosis and open the door for noninvasive ways of tracking the progress of the disease in patients.
Today, diagnostic tests are largely based on memory. Unfortunately, by the time you start showing signs of memory loss, you may have already had the disease for decades. But scientists at McGill University have just revealed that the loss of smell could be an early indication of the disease.
For their study, researchers observed 300 people at risk of Alzheimer’s disease because they had one or more parents who suffered from it. The participants were given multiple-choice scratch and sniff tests and were asked to identify smells ranging from bubble gum to gasoline. One hundred of the volunteers also allowed themselves to be tested via lumbar puncture for proteins related to Alzheimer’s disease in their spinal fluid.
The researchers observed that those who had the most difficulty identifying smells in the scratch and sniff tests had the most significant biological indications of Alzheimer’s disease.
“This is the first time that anyone has been able to show clearly that the loss of the ability to identify smells is correlated with biological markers indicating the advance of the disease,” said Marie-Elyse Lafaille-Magnan, first author of the study, in a statement. “For more than 30 years, scientists have been exploring the connection between memory loss and the difficulty that patients may have in identifying different odors. This makes sense because it’s known that the olfactory bulb (involved with the sense of smell) and the entorhinal cortex (involved with memory and naming of odors) are among the first brain structures first to be affected by the disease.”
In the future, the smell test could be used to track the disease before other symptoms appear—and potentially reduce symptoms once they begin.
“If we can delay the onset of symptoms by just five years, we should be able to reduce the prevalence and severity of these symptoms by more than 50 percent,” Dr. John Breitner, the director of the Centre for Studies on Prevention of Alzheimer’s Disease at McGill University, said.
Of course, we cannot use the smell alone to diagnose the disease, as the symptom can be indicative of other medical conditions as well.