The analysis by the Centers for Disease Control and Prevention comes as Democratic senators wrestle to pass their version of health reform legislation before the end of the year to help make good on President Barack Obama's top domestic goal of overhauling the nation's $2.5 trillion healthcare system.
Much of the focus so far has been on how to expand access to health insurance in a nation where coverage is closely tied to employment but 10 percent of the work force in unemployed. More than 45 million people are uninsured.
While the CDC's findings largely backed that figure, they also found 58.4 million lacked coverage at some point in the year prior to the survey, while 31.9 million -- or nearly 11 percent -- did not have insurance for more than a year.
Two-thirds of those who did not have coverage for at least part of the time were unemployed working-age adults. Those most likely to lack health coverage were Hispanics, men and young adults ages 18 to 24, the CDC found.
The CDC's National Center for Health Statistics analyzed data on 32,694 people who responded from January through June 2009 as part of an ongoing survey.
At a time when much of the debate on the Senate bill has focused on its inclusion of a government-run "public option" insurance plan, the CDC found 20 percent of children and adults age 64 or younger are already covered by government health programs. Democrats plan to strip the public option before the full Senate votes.
The Medicaid program helps cover many of the poor, including children. Youth can also get care under the Children Health Insurance Program, which was extended by lawmakers earlier this year. Younger people with disabilities could also be covered under Medicare, which covers those age 65 or older.