The Commonwealth Fund has published their analysis of the impact of medical bills and accumulated medical debt. Here’s their overview of the publication:

Analysis of the 2007 Commonwealth Fund Biennial Health Insurance Survey finds the proportion of working-age Americans who struggled to pay medical bills and accumulated medical debt climbed from 34 percent to 41 percent, or 72 million people, between 2005 and 2007. In addition, 7 million adults age 65 and older had these problems, bringing the total to 79 million adults with medical debt or bill problems. All income groups reported an increase. Families with low or moderate incomes were particularly hard hit, as were adults who had gaps in health coverage or those underinsured. Because of medical bills or accumulated medical debt, an estimated 28 million adults reported they used up all their savings, 21 million incurred large credit card debt, and another 21 million were unable to pay for basic necessities. Sixty-one percent of those with medical debt or bill problems were insured at the time care was provided.

You can find find the full report, charts and graphs on their web site:
Issue Brief (857K) [download]

Chartpack (86K) [download]

Chartpack – PowerPoint (127K) [download]