Parkinson's disease is more common in the U.S. than previously thought. A new study out today says Parkinson's strikes nearly 90-thousand Americans each year. That's 30-thousand more than previously estimated. States with higher rates of older Americans saw more cases of Parkinson's, but so did some "Rust Belt" states that have a history of heavy manufacturing. Parkinson's is a degenerative disease that can cause tremors and stiffness.