Uninsured, near elderly adults with health problems end up with much higher medical costs once they become eligible for Medicare.

Researchers at Harvard University have reported that finding in a report commissioned by the Commonwealth Fund, New York, and is set to appear Thursday in the New England Journal of Medicine.

In 1992, the researchers started looking at 5,158 adults, ages 59 to 64, who were diagnosed with high blood pressure, diabetes, heart disease or stroke. The study period ended in 2004 after the study subjects became eligible for Medicare.

Once the subjects who were uninsured had Medicare coverage, their medical costs were 51% higher than the costs for the other subjects, the researchers report.

The subjects who started out without health insurance also reported 13% more doctor visits and 20% more hospitalizations than those who were insured before they received Medicare coverage, the researchers report.

The researchers note that the gap in costs was not a result of a one-time spike. The gap persisted at least until the subjects were 72, the researchers report.