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Scientific Review Identifies Possible Risk Factors for Parkinsonís

Family history is still the best predictor of developing Parkinsonís disease.

An analysis of recent studies has found that among the simple screening tests, family history, history of constipation and smoking are the best predictors of future of Parkinson’s disease (PD).  This study was published on July 10 in the Annals of Neurology.

Epidemiological studies, which investigate associations between behaviors or factors and disease, can provide clues to understanding Parkinson’s.  However, they can be difficult to interpret on their own.   As a result, researchers often undertake meta-analyses, in which they attempt to see whether, across many studies, there is a positive relationship between the factor and the risk of developing PD. 

In the new study, researchers in London and Brazil led by Anette Schrag Ph.D., F.R.C.P., of the University of College, London, looked at over 200 studies carried out between 1966 and 2011. They then isolated the factors that were associated with PD, either positively or negatively, in more than one study for further analysis.  They focused on factors that can be identified during a routine primary care medical visit.


  • The researchers identified 30 risk factors that were described in multiple studies.
  • Of those 30 factors, 19 significantly changed the likelihood of someone developing PD, while 11 did not.
  • The factor that was associated the most to a future diagnosis of PD was a family history of the disease, which increased the relative risk by four times. A family history of any tremor nearly tripled the risk of developing PD.
  • A history of constipation, mood disorders, or exposure to pesticides appeared to nearly double risk of PD as well.
  • A history of smoking cut risk of developing PD in half while coffee consumption or hypertension lowered the risk by nearly 40 percent.


What Does it Mean?

Meta-analyses such as this one occasionally reveal underlying causes of diseases that are not yet recognized.  In this case, the analysis reinforced that family history remains the strongest predictor of whether or not someone will develop PD.

It is important to remember that none of the risks that were assessed in this study are strong predictors of PD by themselves.  If family history is associated with a four fold increase of PD risk, it means that over 90 percent of those with family history of PD will NOT develop the disease. Additionally, we know that only a small percentage of people inherit Parkinson’s because of genetic mutations passed down through the family.

While these findings do not provide a direct explanation for the cause of Parkinson’s, they do provide insights for future research.  Furthermore, a technique known as risk stratification, where risk is calculated based on multiple factors (e.g., a non-smoker with low blood pressure, exposed to pesticides and with a family history of PD) may be more helpful in predicting future risk of PD.

Noyce, A. J., Bestwick, J. P., Silveira-Moriyama, L., Hawkes, C. H., Giovannoni, G., Lees, A. J., & Schrag, A. (2012). Meta-analysis of early non-motor features & risk factors for Parkinson’s disease. Annals of Neurology, n/a¬n/a. doi:10.1002/ana.23687.

Source Date: Aug 13 2012