Alzheimer’s disease is a neurodegenerative disease which can start a decade before symptoms allow for an easy diagnosis. While genetic factors and other risks can be examined to determine whether or not an individual is at high risk of developing Alzheimer’s, so far there is no good way to conclusively diagnose the disease early.
That may be about to change, however, as researchers in Canada are looking at ways to diagnose Alzheimer’s well before the nerves start decaying and the damage accrues. Specifically, they have investigated whether or not a sniff test can be used to detect Alzheimer’s before its onset.
Early Detection is a Boon
There is no cure for Alzheimer’s disease, not yet. Scientists are trying to discover such a cure, but in the meantime, treatment options are available which can slow down the progression of the disease.
Because Alzheimer’s gets worse over time, when these treatments increase the quality of life of affected individuals, it has a sort of snowball effect. Or rather, it slows down the snowball effect of Alzheimer’s, allowing them to have a better life for a greater length of time.
So, finding it early is helpful. According to Dr. John Breitner, who is the director of the Center for Studies on Prevention of Alzheimer’s Disease, "[I]f we can delay the onset of symptoms by just 5 years, we should be able to reduce the prevalence and severity of these symptoms by more than 50 percent."
The difficulty is in detecting the disease early. Current detection methods include examining the person’s medical history and going over any recent behavioral or personality changes. Tests for cognition and memory are often performed. But these only catch Alzheimer’s once the disease has progressed enough to cause damage.
Before it reaches that point. brain scans can reveal plaque deposits and neurofibrillary tangles which are a sign of the disease. Unfortunately, a brain scan is a complicated and expensive procedure which cannot be performed at the drop of a hat, and so is rarely used to catch Alzheimer’s a decade before it causes trouble.
It is therefore easy to see why a reliable method of early detection would be so helpful to the millions of people who are at risk of developing Alzheimer’s disease.
The Nose Knows
Dr. John Breitner and other researchers from the Centre for Studies on Prevention of Alzheimer’s Disease at the Douglas Mental Health Research Centre of McGill University, in Montreal, Canada, have trodden down the path of finding such an early detection test.
Their idea was to examine the ability of people to identify odors and figure out whether or not that was a good indicator of Alzheimer’s disease before it started causing cognitive decline. It has been known for a while that a loss of the sense of smell is correlated with Alzheimer’s disease.
A sense of smell can trigger a memory, and one of the strongest senses able to be felt while remembering something is sometimes the sense of smell. Even in the brain, the sense of smell and memory are connected, and both parts are affected by the degeneration brought on by Alzheimer’s.
As they are so entwined, Dr. Breitner thought testing for smell could discover the damage before it causes serious issues. He said, “[a] simple smell test may potentially be able to give us information about the progression of the disease that is similar to the much more invasive and expensive tests of the cerebrospinal fluid that are currently being used.”
Plus, it is cheap and easy to figure out whether or not someone has a strong sense of smell. Much less expensive than a brain scan or spinal tap.
Did they find out if this good idea turned out to be practical?
Dr. John Breitner was joined by Marie-Elyse Lafaille-Magnan, BSc, MSc, Judes Poirier, PhD, CQ, Pierre Etienne, MD, Jennifer Tremblay-Mercier, MSc, Joanne Frenette, BSN, MN, and Pedro Rosa-Neto, MD, PhD. The study was published in the Official Journal of the American Academy of Neurology on June 28, 2017.
Two hundred and seventy-four volunteers took part in the study, all of whom had a parent or siblings with Alzheimer’s disease and so were at risk of developing it themselves. The average age was sixty-four years old.
One hundred and one of them provided cerebrospinal fluid. This CSF possibly contains biomarkers for Alzheimer’s, proteins such as beta amyloid and tau which are involved with the plaques and tangles mentioned earlier.
Every participant also underwent the more traditional methods of detecting Alzheimer’s disease, such as the cognitive testing and examination of medical history. The cognitive performance test used was the Repeatable Battery for Assessment of Neuropsychological Status.
The method by which the researchers examined the participant’s ability to detect smells was by using the University of Pennsylvania Smell Identification Test. It is basically a multiple-choice test of forty questions, with scratch-and-sniff odors instead of written questions. It is known as the most reliable and accurate smell identification test available.
Generally, a participant’s ability to identify odors decreased with age. However, even stronger than that was that the fact that the more biomarkers someone had for Alzheimer’s disease, the less they were able to detect and correctly identify odors!
According to Marie-Elyse Lafaille-Magnan, “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.”
It is important to realize that all of these variables, age, Alzheimer’s disease, and the sense of smell, have a complicated relationship. One of the biggest risk factors for Alzheimer’s is advancing age, and everybody’s sense of smell—with or without Alzheimer’s—decreases with age.
So, the authors caution people to not take the loss of smell as gospel that one is developing Alzheimer’s. It could be a result of normal aging. Also, there are other unrelated diseases which can negatively impact a person’s sense of smell.
Or it could be a temporary issue. Several participants had to be turned away because they were congested at the time of testing, for example. A diminished sense of smell does not automatically equate to Alzheimer’s disease.
However, it is a good potential test to see whether or not other tests are required. A brain scan can reveal damage, and a spinal tap can show the biomarkers of Alzheimer’s, but neither of those tests should be performed without caution.
If, however, someone with a family history of Alzheimer’s starts to show signs of losing their sense of smell, confirming that is cheap and can potentially catch the degenerative disease before degeneration hits a bad level.
The sniff test is not a substitute for proper testing, but it can lead people toward proper testing earlier than other methods.
The bottom line
For a long time, loss of your sense of smell was correlated with Alzheimer’s disease. Recently, some scientists showed that the link is very strong. While it is not strong enough to be the sole diagnostic criteria for determining whether or not someone has Alzheimer’s, it is still a viable test to direct someone without other symptoms to other tests, to catch the disease early.
After all, the earlier it is caught, the better it can be treated and the slower the disease will affect the individual. If you are at risk of developing Alzheimer’s, perhaps you should go and have your sense of smell tested.
While you are at it, go out and smell the flowers. It will lighten your day.