A report issued by the trustees who monitor the government's two main forms of help for the elderly shows that Medicare has become more fragile and is at risk of imminent fiscal collapse. Starting eight years from now, the report says, the health insurance program will be unable to pay all its hospital bills. The trust fund that pays for hospital care under Medicare is now predicted to run out of money in 2017, two years earlier than forecast a year ago. That fund does not involve the parts of Medicare that cover doctor's visits or coverage for prescription drugs.