The study data, published online Thursday in The American Journal of Medicine, likely understate the full scope of the problem because the data were collected before the current economic crisis. In 2007, medical problems contributed to 62.1 percent of all bankruptcies. Between 2001 and 2007, the proportion of all bankruptcies attributable to medical problems rose by about 50 percent.

“The U.S. health care financing system is broken, and not only for the poor and uninsured,” the study authors wrote. “Middle-class families frequently collapse under the strain of a health care system that treats physical wounds, but often inflicts fiscal ones.”

The data on medical bankruptcy, compiled by researchers at Harvard Law School, Harvard Medical School and Ohio University, is based on a survey of 2,314 randomly selected bankruptcy filers during early 2007.