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Inflammatory Mechanisms & PD Risk: A Discordant Twin Pairs Case-Control Study

The cause of Parkinson’s disease is unknown. A genetic cause is identified in only a small percentage of cases. We believe that environmental factors play an important role in most cases of PD. While few specific risk factors have been linked definitively, a growing body of research suggests that inflammatory processes may be crucial in the development and progression of PD. We believe that environmental factors that increase inflammation in the brain may increase the risk of PD, while factors that decrease inflammation may decrease the risk of PD.

In order to test this hypothesis, we will continue our ongoing work studying a remarkable group of twins, members of the World War II Veteran Twins Cohort. Originally 16,000 pairs strong, the Twins, now 75-85 years old, have been willing participants in dozens of studies since the 1960s. Our previous work with the twins found that if one twin has PD, the likelihood that their co-twin has PD is the same whether they are identical or fraternal. This strongly suggests that environmental factors are more important than inherited factors (genes).

Because twins are genetically identical or very similar, studying twins is a powerful way to detect environmental factors that might be related to disease. Specifically, if one twin has PD and their co-twin doesn’t, what was different about their environments?

The present study will answer the following questions: Are environmental factors that increase inflammation in the brain more common in the twin with PD? Are environmental factors that decrease inflammation more common in the twin without PD? If our hypothesis is correct, our results will help to explain the cause of PD, and may aid in preventing and slowing its progression.


  • Caroline Tanner, MD, PhD

    San Francisco, CA United States

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