What further research might this biomarker test ignite?
Currently, it tests for the marker through spinal fluid, and that is an invasive test. So, there’s work toward trying to optimize a different reliable way to test for the biomarker (e.g., through blood or saliva).
The other thing about this marker is that it is either positive or negative. You can’t use it to predict when someone will develop Parkinson’s disease or how quickly it will progress. So that’s something that’s still needed: a marker that can predict those things as well as allow us to monitor response to treatment.
What makes the PPMI biorepository stand out?
One of the most revolutionary things about PPMI is that it is an open data source. Information is open to any researcher to download. This includes biological and genetics data, as well as imaging data such as MRI and DaTscan (dopamine transporter scan). There are also many questionnaires and the neurologists’ interpretations of the patients’ symptoms.
Additionally, if there are researchers who have an important scientific idea anywhere in the world, they can submit a proposal to PPMI and actually obtain biologic samples (e.g., spinal fluid, blood samples) on which to do experiments. These samples were used for the important αSyn-SAA discovery.
The PPMI repository was started in 2010, correct?
Yes, and that’s the other thing that’s revolutionary about this study. It’s over the long term, so this is a rich dataset of a large group of people who have Parkinson’s, people at risk for Parkinson’s, and of healthy controls who have been monitored over time to see how the disease changes. The other important thing is that it is enrolling people with early Parkinson’s disease who are not yet on medications. Sometimes the medications can change some of the biologic markers we might see or change something on the MRI. So it’s important to evaluate participants before medication begins.
One of the study areas the PPMI focuses on is sleep, and you have done both sleep-related and exercise-related PD research. What is it about sleep and this disease?
For one thing, REM sleep behavior disorder (when people physically act out vivid dreams with sound and sudden, often violent, movements) is very well established as a prodromal feature of Parkinson’s disease, so it happens before the motor symptoms emerge.
That’s exciting to know because you can detect people much earlier who are at risk for Parkinson’s disease and potentially intervene to hopefully slow the progression before onset of other Parkinson’s symptoms. While we don’t have preventive medication yet, there’s good evidence that exercise might slow progression.
Parkinson’s patients also have a lot of what we call sleep fragmentation, where they just wake up more frequently than other older adults would. That might be related to the motor symptoms. When patients with Parkinson’s disease become slow moving and stiff, it’s harder to roll over in bed naturally, so they might have to get handrails or have their bed partner help them roll over. So that leads to more awakenings.
They also might have autonomic problems that make them have to use the bathroom more often at night. And they can also have actual neurodegeneration of areas of the brainstem that can lead to changes in sleep. So people with Parkinson’s often have less amounts of REM sleep and less amounts of the deep slow-wave sleep, and that can lead to problems as well.
One exciting thing that we found in our study is that exercise not only helped people sleep better, but it also actually increased their slow-wave sleep, which is important for cognition.
Another thing the PPMI website does is ask people to undergo scratch-and-sniff smell tests, which anyone can have sent to them in the mail. Why is that?
The early pathology of Parkinson’s disease involves the nerve important for sense of smell. So, many years before developing the motor symptoms of Parkinson’s, people at risk will often lose their sense of smell. Doing that smell test can help increase the likelihood of finding someone who’s at risk.
Michael J. Fox was diagnosed at 29; that’s unusually young, correct?
Yes, Parkinson’s is considered to be a disorder of aging. So the older you get, the more at risk you are. The average age in the first PPMI cohort was about 62. However, there are people who get diagnosed in their 20s.
What else would you like to add?
I think there are many ways that people can help move science forward, but participating in research studies is one of the main ways. Participation in research is important and can change outcomes for patients living with these conditions.
Note: This Q&A was edited for length and clarity.