Levodopa motor complications in Parkinson's disease.

Parkinson's disease (PD) is an age-related neurodegenerative disorder with an average onset age of 60 years. In the United States, approximately one million persons suffer from PD, and there are 60,000 newly diagnosed cases every year. The estimated cost of PD to society is $27 billion per year. Based on United States Census Bureau projections, it is estimated that the frequency of PD will increase fourfold by the year 2040, making it an even larger burden on patients, their families and society.