Can losing the sense of smell be used as an early warning sign that a person will develop Parkinson’s disease? That’s one of the questions Kim Good is trying to answer in her lab at Dalhousie University.
Professor Kim Good, with the Dalhousie University departments of psychiatry and psychology and neurosciences, is conducting a study examining the connection between a poor sense of smell and Parkinson's disease. (ERIC WYNN / Local XPress)
Can losing the sense of smell be used as an early warning sign that a person will develop Parkinson’s disease?
That’s one of the questions Kim Good is trying to answer in her lab at Dalhousie University.
“Parkinson’s is a disease of the motor system. So people start to have a tremor or they’re having trouble eating or chewing. They go to see their doctor and the doctor says, ‘Oh, you have Parkinson’s disease,’ ” Good, a clinical neuroscientists, said Friday.
“It usually comes as a big surprise to people. The thing is, with Parkinson’s disease there’s lots of data that suggests the disease actually starts a lot earlier than when these motor symptoms start.”
There might be a clue, however, in an area of the brain that controls the sense of smell.
“It’s been known for quite some time that people who have Parkinson’s disease, almost all of them have very, very poor sense of smell,” Good said. “The problem is your sense of smell tends to deteriorate after the age of 65.”
There are lots of reasons people could lose their sense of smell.
“If somebody was punched in the face when they were 20 that could account for an olfactory deficit at the age of 60,” Good said.
Plus, there are other disorders associated with losing the sense of smell, including Alzheimer’s disease, which means doctors can’t use that as sure-fire proof that someone has Parkinson’s.
“So we have used (the sense of smell) and a very specific type of brain scanning technique in order to try to identify changes in the brain that happen in patients with Parkinson’s disease in the earliest stages, with the hopes that if we get a protocol sorted, that we might be able to screen people who are at risk and be able to determine prior to when these motor symptoms start, whether or not they are destined to develop Parkinson’s disease,” said Good, an associate professor in Dal’s departments of psychiatry and psychology and neurosciences.
She’s running a study that aims to test people’s sense of smell using scratch and sniff cards.
Some of subjects are more likely to develop Parkinson’s “because they have a first-degree relative who has Parkinson’s disease,” she said. “So either their mother, their father, sister or brother.”
That pre-disposition isn’t a requirement for the study, she said.
“That’s the group that we think will be the most interesting because they have about a five per cent chance of developing Parkinson’s.”
Good is hoping to recruit 1,200 people between the ages of 40 and 70 for the study, which starts with taking the scratch and sniff test at home and mailing the results back to her lab. The test involves answering multiple-choice questions identifying 40 different smells.
The 10 per cent who score the best and the 10 per cent who do the worst at identifying odours are brought in for further testing.
“We’re only choosing those people we call super smellers — so the people who are really, really good smellers — and those who are at the poorest or the lowest level of performance. And we ask them to come in for MRI scanning.”
The scans will look at the area that connects participants’ noses to their brains.
That’s where a protein called alpha-synuclein is deposited in people with Parkinson’s, Good said.
“It’s not really known what this protein does. But it messes up how the brain basically connects different brain regions together. And early on in the disorder, it’s thought that this pathway between the nose and the brain is affected. So that’s really what we’re looking at. We’re looking to see whether or not the connections are, not scrambled so much, but there are fewer connections between the nose and the brain compared to what should be there in similarly aged people that don’t have Parkinson’s.”
So far, Good’s recruited about 500 people for the study. To learn more about participating in the research, go to predictparkinsons.com.
The study will also look at people’s sleep history and problems with constipation, which can also be clues that Parkinson’s might be in their future.
“There’s this triad of problems that people tend to have,” Good said.
In terms of sleep history, she’s looking for people who have rapid eye movement, or REM, behaviour disorder.
“They have problems with their sleeping patterns in that, when they’re dreaming, they tend to act out their dreams,” Good said.
“In healthy people who have normal dreams you have this paralysis that comes over you in REM sleep — that’s your dream sleep — and in people with REM behaviour disorder that paralysis no longer keeps them from acting out their dreams. So they may thrash around in bed, they may punch their partner, they may do all sorts of things. And the reason why this group is so interesting is, depending on how long you follow these people forward, they are extraordinarily likely to eventually develop Parkinson’s.”
She hopes to follow the test subjects for a decade to identify who develop Parkinson’s.
“The aim of our study is to basically get a number of biomarkers sorted so that people who may be at risk of developing Parkinson’s disease can get, maybe not diagnosed early, but at least have the information prior to any kind of motor symptoms that start.”
Currently, there are no disease-modifying drugs for people with Parkinson’s.
“But that doesn’t mean that there aren’t going to be,” Good said.
If they’re invented, in order to test them we’ll need a way to identify people who are pre-destined to develop Parkinson’s, she said.
“We’re kind of putting the cart before the horse, but at the same time, if these drugs do come into testing or on the market, then we’ll be able to identify people who might benefit from them.”
About one per cent of the population develops Parkinson’s, she said.
“Of course, as the population is aging, the number of people who have the disorder is going to increase,” Good said.The usual age of onset is between 50 and 60, she said.“So it’s a little bit earlier than Alzheimer's,” Good said.
“It kind of comes on without people really realizing because sense of smell deficits are not something that you tend to be aware of. Typically what we have is partners saying to us, ‘Yes, for about about 10 years now my partner’s had to put lots of condiments on their food. That may be the first indicator that something is not quite right.”Individuals might want prepare if they learn Parkinson’s is in their future, she said.
“Maybe people don’t want to know, but you can make lots of decisions, you can change your lifestyle around if you know that there is the possibility that you might not be as mobile in the next five to 10 years, or 10 to 15,” Good said.
“And who knows? There may be a treatment coming right down the pipeline we don’t know about yet.”
https://www.localxpress.ca/local-news/study-sniffing-out-parkinsons-disease-607450
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