Excerpt: In addition to the 45 million uninsured adults in the United States, at least another 16 million adults were underinsured in 2003, meaning they did not have enough financial protection to cover their health care expenses, finds a study in Health Affairs. An estimated total of 61 million adults, or 35 percent of individuals, ages 19 to 64, had either no insurance, sporadic coverage, or insurance coverage that exposed them to catastrophic medical costs during 2003.