A report released by the Centers for Disease Control and Prevention (CDC) on November 9 found that 59.1 million people under age 65 were uninsured for at least part of the preceding 12 months.  The CDC also found that 26 percent of the adult population, or 49.9 million individuals between the ages of 18 and 64, had no medical coverage for at least part of the previous year.  Examining data from National Health Interview Survey (NHIS), the study found a growing number of uninsured Americans, with 59.1 million uninsured during first quarter of 2010, 58.7 million during the first quarter of 2009, and 56.4 million during the first quarter of 2008.

From the report: 

New 2010 estimates show that the number of Americans without health insurance is growing, affecting middle-income Americans as well as those living in poverty. About 50 million adults 18–64 years old had no health insurance for at least some of the past 12 months. People in all income brackets have been affected, not just adults living in poverty, according to a 2009 survey. In the past few years, the number of adults aged 18–64 who went without health insurance for at least part of the past 12 months increased by an average of 1.1 million per year. About half of those additional adults were middle-income. Adults without consistent health insurance are more likely to skip medical care because of cost concerns, which can lead to poorer health, higher long-term health care costs, and early death.

Full Report: Access to Health Care: A record number of adults 18–64 years old are uninsured (PDF | 582 KB)

Centers for Disease Control and Prevention. (2010). Access to health care: a record number of adults 18-64 years old are uninsured.