Ronstadt: I can't sing due to Parkinson'sSinger Linda Ronstadt, who revealed last month that she is suffering from Parkinson's disease, says the degenerative nervous-system disorder is so painful, "I can't sing at all." In an interview on Rachael Ray's cooking and talk show, People magazine reports, the multiple Grammy-winner, 67, laments that, "Things that require a lot of coordination with your hands, like brushing your teeth or washing your hair . . . It's hard to ask other people to do things for me. I feel like a big demanding baby."