Cancer survivors often have trouble sleeping, but yoga seems to help 29 (UPI) -- Cancer survivors often have problems getting a good night's sleep, sometimes for years due to chemotherapy drugs, or other problems, a U.S. researcher says. Karen Mustian of the University of Rochester Medical Center in New York said some cancer patients might have trouble sleeping because of a worsening sleep problem they had even before their cancer diagnosis. Mustian analyzed data involving survivors with sleep problems who did yoga for 75 minutes twice a week for a month. The study, published in the Journal of Clinical Oncology, found cancer survivors who took up a form of gentle yoga slept better. "While they showed greater improvements in their overall rating of their sleep, they really showed improvements in feeling less tired during the day and napping less," Mustian said in a statement.