Dr. David Russell is associate director for clinical research at the Institute for Neurodegenerative Disorders in New Haven, Connecticut Ė one of 24 sites carrying out the Parkinsonís Progression Markers Initiative (PPMI). PPMI recently launched recruitment for a new arm of the study looking at smell loss as a biomarker for Parkinsonís disease (PD). Dr. Russell answered some questions on the basis of the study and what researchers and volunteers hope to accomplish. Hear more from him in the video above of his segment on FoxCT in June, and take the smell survey yourself!
Why are you focusing on smell loss?
Smell loss is a biomarker for PD. Biomarkers are biological features of disease, such as a chemical or molecular change, a brain scan finding or even a behavior. Biomarkers show us a pattern that results from an underlying problem.
Diabetes and blood sugar are a good example: Blood sugar is a biomarker for diabetes, and too high or too low blood sugar may indicate a problem with insulin. High blood sugar may or may not be due to diabetes (maybe you just ate a cookie), but looking for high blood sugar in everyone, and then doing more tests, helps us find the people who do actually have diabetes. Similarly, looking for smell loss among healthy people can lead us to people who may be at elevated risk for PD.
Identifying biomarkers can also help us delve deeper to pinpoint that underlying problem. When we know the problem, we can develop solutions.
How do you know loss of sense of smell is related to PD?
Most people with PD report smell loss or test positive for smell loss very early in their disease, often even before they develop other symptoms. PPMI builds on previous studies that have looked at the connection between smell loss and PD, such as the Parkinsonís Associated Risk Study (PARS). In studies like PARS, healthy volunteers with and without smell loss underwent a specialized scan to look at dopamine levels in the brain. The people who developed PD in the few years after the scan were among those with the lowest smell test scores and low dopamine levels. Thus, smell loss may be an early indicator that one should have more testing to measure PD risk.
Does smell loss therefore mean low dopamine levels and a high chance of developing PD?
No. There are many causes for a loss of the sense of smell, and individuals with smell loss do not necessarily have low dopamine levels. Only approximately 10 percent of individuals with a decreased sense of smell turn out to be at high risk for PD.† Take our smell survey if youíd like to participate in the study, and speak to your physician if you have any concerns about your PD risk. †Actually, since 70 percent of people with smell loss donít know they have it, you should take the survey even if you think you donít have smell loss!
If you know it is a biomarker, why do you need to do more research?
We need to validate and identify the parameters of smell loss as it relates to PD. When we have more data and more biomarkers, then we can go to academic research partners and ask them to identify the underlying problem. We can also approach the pharmaceutical industry and ask them to begin drug development to address that problem. Smell loss may be a precursor to PD development. If we can correct the underlying problem before it progresses to the point of expressing PD symptoms, we should be able to prevent disase. The way I see it, thatís the greatest cure Ė not to treat the disease once you already have it, but to prevent it in the first place.†