A new research has confirmed five new genes involved in Parkinson’s Disease (PD), bringing the total to eleven, showing that genetic factors play a greater role in the disease than previously believed.

For the vast majority of people, the cause of Parkinson's is still unknown. But genetic susceptibility combined with lifestyle, environmental factors and ageing are all thought to be involved.

PD is a common neurodegenerative disease, affecting more than 2 percent of people over the age of 75 years. Most individuals develop the disorder in their 60’s and 70’s. The disease occurs when the nerve cells in the brain that make a chemical called dopamine are slowly destroyed. Without dopamine, the nerve cells in that part of the brain cannot properly send messages. This leads to the loss of muscle function.

Changes in certain genes seem to make the nerve cells that die in Parkinson's more vulnerable.

In most cases, Parkinson’s is not directly inherited. However, in a very small number of families (around 5 percent) Parkinson’s does seem to be inherited. In these rare cases, changes in specific genes have been identified which directly cause Parkinson’s.

These genetic changes are found at higher rates in people with Parkinson's compared to people without the condition but do not directly cause Parkinson's.

In the new study, researchers from 6 different countries pooled 5 genome-wide association studies in which more than 5,000 individuals with PD were studied and compared with 12,000 healthy individuals.

Variations in a total of 11 genes were shown in this study to influence genetic susceptibility to Parkinson's. The researchers also found that the more of these variations a person had, the greater their risk of Parkinson's.

The results confirmed the role of the 6 genes previously identified, as well as revealing a further 5 new genes likely to be important in the development of PD.

These data provide an insight into the genetics of Parkinson's disease and the molecular cause of the disease and could provide future targets for therapies, the researchers say. This new research has substantially increased our understanding of these common but low-risk genetic changes.

The researchers plan to study these genes in greater detail to determine how changes in these genes influence the development of PD.

These findings significantly add to the knowledge base of the increasingly complex picture of the molecules that can cause Parkinson's. We hope that by studying them more closely new research avenues will open up, says Professor Nick Wood, who led the UK team at University College London.

The international team of researchers from 6 countries included teams from the UK, US, Germany, Holland, Iceland and France.