Principal Investigator: Caroline Tanner, Parkinson's Institute

Parkinson's disease (PD), a disease of unknown etiology, continues to be a public health concern.  Analyses of data previously collected from members of the NAS-NRC Twin Registry have shown a significant genetic influence clinical PD of early onset (<50 years of age), but not late onset.  Continued studies of genetics of PD have been difficult to mount, however, because the disease occurs so late in life.  The NAS-NRC Twin Registry thus provides a nearly ideal opportunity to study PD, since its members now average 76 years of age.

 The Medical Follow-up Agency operates a registry of World War II white male veteran twins numbering nearly 16,000 pairs, from which many health studies have been mounted.  The Principal Investigator of this study, Dr. Tanner, has been involved in previous investigations of PD in the NAS-NRC Twin Registry.  This continuing investigation will be focused on identifying genetic influences on pre-clinical PD.  Because a previous investigation has already identified twin pairs in which one or more of the twins are a candidate for PD, further investigations of pre-clinical disease can be efficiently conducted.

The long-term goal of this study will attempt to find the cause of Parkinson's disease, with a particular focus on determining the relative contributions of genetics and environment.  Our work to date indicated no difference in concordance between monozygotic and dizygotic twins with Parkinson's disease after age 50, suggesting a minimal contribution of genetics to the cause of Parkinson's disease.  However, this study was only cross-sectional in nature, and a prospective, longitudinal study is now required to confirm (or refute) these findings.

The purpose of the study is to examine the role of genetic and environmental factors in the cause of Parkinson's disease. To accomplish this goal, we will be screening a cohort of twins that are listed in a registry maintained by the National Academy of Sciences Research Council, to see if any cases have Parkinson's disease.  If our screening procedures indicate that a person has Parkinson's disease, we will contact his co-twin to see if he also has the disease.  Data on Parkinson's disease and attendant risk factors will be gathered by telephone screen and follow-up interview by investigators at The Parkinson's Institute.

We will then compare the number of twin pairs that have Parkinson's disease versus the number we would have expected by pure chance, to see if there is a genetic factor involved.  Furthermore, we will also collect information on environmental exposures and family history, to see if there is a connection between any of these factors, and the onset of Parkinson's disease.