Gaps in health insurance coverage are increasingly found among families above the poverty level, a new study concludes.

While lack of health insurance continues to be highest among families with incomes under $20,000, uninsured rates for moderate- and middle-income earners and their families are rising, according to findings from the Biennial Health Insurance Survey conducted by the Commonwealth Fund, Washington.

The study found 41% of working-age Americans with incomes between $20,000 and $40,000 a year were uninsured for at least part of the past year, up from 28% in 2001.

Among adults with incomes under $20,000, 53% were uninsured for at least part of the past year.

Of the estimated 48 million adult Americans who were uninsured at any time in the past year, 67% were in families where at least 1 person was working full time, according to the study.

“This combination of eroding health insurance coverage and rapidly rising health care costs raises concerns about the ability of U.S. families to obtain timely medical care, protect their finances from catastrophic health care costs, and save for retirement,” the report concludes.

The study, conducted between August 2005 and January 2006, surveyed 4,350 adults age 19 and older.