Parkinson's disease is a degenerative disorder of the central nervous system that often impairs motor skills and speech. 

Heart valves are one-way valves that keep blood flowing in the right direction through the heart. If people have problems with their heart valves then blood may not move the way it should.

The drugs used for the treatment of Parkinson's disease include pergolide, marketed as Permax, and cabergoline, sold as Dostinex, reported the online edition of health magazine WebMD.

Two studies published in the Jan 4 issue of the New England Journal of Medicine involved more than 11,000 patients prescribed anti-Parkinson's drugs from Britain registered in a nationwide database.

The studies compared treatment histories among Parkinson's disease patients who did and did not develop heart valve disease.

The rate of heart valve disease was seven times higher among pergolide-treated patients and five times higher among patients being treated with cabergoline.

"We showed that treatment with either pergolide or cabergoline for more than six months was strongly associated with an increase in valve-related heart disease," researcher Edeltraut Garbe said.