Researchers have uncovered new evidence that Parkinson's disease can run in families, according to a study to be published Thursday of 772 Icelanders who developed the illness after age 50.

Doctors have known for a few years that the form of Parkinson's that strikes earlier in life, as it did with US television star Michael J. Fox, comes from a genetic mutation that makes them prone to the disease.

The new study, published in Thursday's New England Journal of Medicine, suggests that a person's genes contribute to the risk of getting Parkinson's later in life as well. The disease typically appears in older people.

A team led by Dr. Sigurlaug Sveinbjornsdottir of the National University Hospital in Reykjavik found that the risk of Parkinson's was 6.7 times higher if you had a sibling with the disease, 3.2 times greater if you had a parent with Parkinson's, and 2.7 times higher if you had a niece or nephew who was afflicted.

The researchers said the effects of the genetic mutation appear to be subtle, which is why Parkinson's frequently skips generations.

The findings were derived by cross-referencing 772 people who had developed the disease in the previous 50 years with an extensive genealogical database on 610,920 people in Iceland.

The team found no evidence that spouses were more likely to develop Parkinson's. That suggests that environmental factors such as exposure to chemicals later in life do not play a role.

But the researchers left open the possibility that environmental factors shared by family members early in life could be a factor.

"This may indicate a role for some shared environmental factor early in life," they said.

(From ChinaDaily)