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Understanding Parkinson's as a Disability

By Eddy Ball
May 2009

A photograph of Xuemei Huang, M.D., Ph.D.
Huang, with microphone, shared insights from her work with patients as Sandler, who moderated the seminar, rested on the podium beside her. (Photo courtesy of Steve McCaw)

A photograph of Honglei Chen, M.D..
As an epidemiologist, Chen was careful to distinguish between association and cause. He said that among PD patients in their 80's, men outnumber women two to one. (Photo courtesy of Steve McCaw)

Bradbury followed the questions the audience had for Huang from her front-row seat beside Moore, left, and Chen..
Bradbury followed the questions the audience had for Huang from her front-row seat beside Moore, left, and DAC member Tina Jones, right. (Photo courtesy of Steve McCaw)

A photograph of NIEHS Principal Investigator Dan Morgan, Ph.D., of the Respiratory Toxicology Group, foreground, and NTP Biologist Stan Stasiewicz.
NIEHS Principal Investigator Dan Morgan, Ph.D., of the Respiratory Toxicology Group, foreground, and NTP Biologist Stan Stasiewicz were part of a diverse audience with a variety of scientific and practical interests in learning more about PD. (Photo courtesy of Steve McCaw)

The NIEHS Diversity Council Disability Advocacy Committee (DAC) presented the latest in its series of specialized seminars on health topics April 7. The program, titled "Parkinson's Disease [PD]: Etiology, Clinical and Disability Management," addressed medical, social and personal dimensions of a condition that affects approximately one million Americans at an estimated cost of $27 billion annually.

The seminar was conducted by Honglei Chen, M.D., Ph.D., principal investigator in the NIEHS Epidemiology Branch (EB), along with his guest collaborator Xuemei Huang, M.D., Ph.D. ( Exit NIEHS, of Milton S. Hershey Medical Center at Pennsylvania State University. Chen is currently involved with two large cohort studies of PD patients, and Huang treats PD patients in the Movement Disorders Clinic at the Center.

DAC member Alyce Bradbury opened the program by welcoming the audience, and Dale Sandler, Ph.D., the Branch Chief of the EB, then introduced the speakers. Huang began her segment of the program with an outline of the characteristics of PD used in diagnosis, such as the classic tremor at rest and rigidity of movement. She progressed to possible early signs of the disease, ranging from loss of the sense of smell and curling toes to lack of facial expression, shuffling walk and decreased arm movement when walking.

Huang surveyed the current array of treatment options, which are largely limited to increasing dopamine through drugs such as levadopa to control motor symptoms and addressing such related symptoms as sleep disturbance, depression and sexual dysfunction with adjunctive treatments and medications. She said that with the drugs currently available, physicians can reduce the impact of PD for decades after onset, but that preventive treatment remains elusive and restorative interventions are still in the experimental stage.

Chen explored the epidemiology of PD, outlining well-established and preliminary associations observed between PD and genetic and environmental factors. He explained that monogenic early-onset and familial PD, manifest in five to ten percent of people with the disease, have been linked to nine PARK genes and 15 loci, while the role of genetics remains unclear in late-onset PD.

Late-onset PD, which manifests in middle age or later and accounts for more than 90 percent of disease incidence, Chen explained, is thought to be more closely related to environmental factors. Research thus far has found well-established associations of risk for PD with age and gender and strong protective associations with caffeine consumption and smoking - which he was quick to warn against because of the serious pulmonary and cardiovascular health risks linked to tobacco use.

Pesticide exposure, especially to rotenone and paraquat, and head injury are highly suspected of increasing risk. Chen noted that recent studies have found higher risk with consumption of milk and dairy foods and reduced risk in people with higher levels of uric acid, physical activity and use of non-steroidal anti-inflammatory drugs (NSAIDs).

With so much left to learn about the causes and prevention of PD, Chen looks forward to more in-depth epidemiological research. Huang recommended that people become aware of the early signs of disease to get treatment started as soon as possible and adopt an holistic approach combining medical treatment with social support, a wellness orientation, and physical and speech therapy. As the boomer generation ages, Sandler observed, expanding training of specialists will become more important than ever before.

The seminar concluded with the presentation of tokens of appreciation to Chen and Huang by NIEHS Biologist and DAC Chair Alicia Moore.

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