Underinsured adults rose by 80 percent in just beyond the last 7 years, from 16 million to 29 million, a new study found.

Underinsured people are defined as those with health insurance all year but also with very high medical expenses relative to their income.

Underinsured people have “holes or limits in their plans which expose them to often unaffordable medical costs,” said Cathy Schoen, the lead author of the study and Senior VP of the Commonwealth Fund.

“Inadequate health insurance puts families’ health and financial security at risk,” said Karen Davis, the fund’s president.

Forty-four percent – 81 million - of U.S. adults were either underinsured or uninsured in 2010, a figure that has increased from 75 million in 2007 and 61 million in 2003, according to the study.

The study says that the 2010 health law supported by President Barack Obama and passed by the majority Democratic Congress could reduce the amount of underinsured by as much as 70 percent, according to the study.

That would bring the levels of uninsured to nearly the same levels as those in 2003.

Underinsured adults reported high rates of access concerns and financial stress. The study found that underinsured people go without needed health care and struggle to pay medical bills or medical debt at rates at times similar to those without health insurance.

Significant numbers of people – 46 percent - don’t fill a prescription, see a doctor when sick, or go without a recommended medical test or treatment.

The rate in similar categories for people with more adequate health insurance was 28 percent.

The study also compared the number of adults who had trouble paying their bills among underinsured (52 percent) and more adequately insured (27 percent.) Fifty-eight percent of uninsured people had trouble paying.