Are my kids going to get PD?

Posting for Dr. Hackney this month is Dr. J. Lucas McKay, Ph.D., M.S.C.R., an Assistant Professor in Biomedical Engineering at Emory / Georgia Tech. Dr. McKay’s research interests include the effects of PD pathophysiology on balance, gait, and fall risk. He is also interested in PD epidemiology (who gets it and why) and in how results from the basic science of Parkinson’s disease (often from rodents and monkeys) can be best translated to clinical interventions in people with PD.

Hello everyone – I’d like to begin by thanking everyone at PD Gladiators for being such a great resource for people with Parkinson’s disease in the Atlanta area.

My formal background is primarily in engineering, and the majority of my work is focused on trying to “reverse-engineer” how Parkinson’s disease affects balance and walking, in order to identify new treatment targets.

That material is pretty technical (although it’s coming out now1), so I thought that I might use this forum to discuss a little bit about the question I receive most often when talking about PD with the people who are affected by it, which is: “are my Madeleine E. Hackney, PhD The Exercise Files blogkids going to get PD?”

The short answer is that there is good evidence that for most (but not all) people with PD, it is not hereditary. If you are diagnosed with PD and you happen to be of Arab or Ashkenazi Jewish descent, the odds that your PD is heritable are increased2 – however, overall only about 1 in 10 PD cases are associated with a family history of parkinsonism.3

The most convincing evidence that I have found for this was a 1999 study of over 19,000 white male twins enrolled in the National Academy of Sciences/National Research Council World War II Veteran Twins Registry.4 In this fairly large sample, there was no evidence that pairs of twins being identical increased the likelihood that they would be “concordant,” (e.g., either both twins got PD or both twins didn’t) rather than “discordant” (e.g., only one of the twins got PD). What this means is that genetic factors did not have a strong impact on the development of PD – because if they did, the identical twin pairs would be expected to be much more likely to be “concordant” than the fraternal twin pairs. (Note that if the PD developed earlier than age 50, there did appear to be some effect.)

So if it’s not genetic, what causes PD? Unfortunately, we do not know yet – this is why most cases are referred to as “idiopathic,” or “with no known cause.” However, there are some known environmental causes of PD. Some agents, including welding chemicals,5 and herbicides and insecticides,6,7 including Agent Orange8 have been linked to increased risk of PD, or to earlier PD onset. (By the way, if you or someone you know with Parkinson’s disease was exposed to Agent Orange, call the VA! They or their descendants might be eligible for benefits.)

Although the amount we do not know about the causes of PD may be frustrating, we are making progress that may lead to better treatments, or even to a cure. It was recently revealed (in mice, at least) that the population of microorganisms in the gut play a very important role in the development of PD motor symptoms. This might be a powerful place to intervene even if we do not know the root cause. In a study in the journal Cell,9,10 the authors showed that in a special strain of mice that were bred to eventually become parkinsonian, motor symptoms could be altered by changing the microenvironment of the gut. The implication of this is that altering the gut microenvironment in people may let us reduce the way PD manifests, even after the exposure to whatever agent causes it has already taken place. (A way to think of this is that you can stop malaria by “draining the swamp” where the mosquitoes live – even if you don’t know how malaria works.)

Thanks all – it has been a pleasure to share some of the recent PD work I find interesting with you. And I hope you’ll keep exercising! The animal work says it’s even good for the 1 in 10 cases of genetic PD.11

References: CLICK HERE to view complete references to published research cited above.

Dr. Madeleine E. Hackney, Ph.D, is a Research Health Scientist at the Atlanta VA Center for Visual and Neurocognitive Rehabilitation and an Assistant professor of Medicine in the division of General Medicine and Geriatrics at the Emory School of Medicine. She holds a Ph.D. in Movement Science from Washington University and a BFA in Dance from NYU, Tisch School of the Arts and has also been an American Council on Exercise certified personal trainer since 2000. Dr. Hackney’s extensive research interests include inquiry into challenging exercise programs–traditional exercise, Tai Chi and partnered tango classes–designed to improve physical function and quality of life in people with PD, older adults and those with serious mental illness. In 2014, she co-founded MDT Education Solutions, which has trained dozens of fitness and allied health professionals how to develop and lead safe, evidence-based exercise programs for people with PD at all stages of the disease, including almost all instructors in the PD Gladiators Metro Atlanta Fitness Network (including the YMCA of Metro Atlanta). She is currently the Research Advisor to PD Gladiators.

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