"The financial and health insecurity that comes from being underinsured is substantial and puts people's health and well-being at risk," said Dr. David Blumenthal, president of The Commonwealth Fund nonpartisan research foundation.
"If health insurance costs continue to be shifted to consumers at the rates we have seen over the past 10 years, the problem will likely grow."
The report, conducted every two years, defines being underinsured as having health coverage throughout the year but having out-of-pocket health costs that are 10 percent or more of household income. That bar is lowered to 5 percent or more of household income for low-income families. Having a deductible that exceeds 5 percent of income also qualifies one as being underinsured.
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"Someone who is underinsured does have health insurance, but with coverage that does not protect against high health costs relative to income," Blumenthal said.
The report noted that the share of people who were underinsured because they had high-deductible health plans has more than tripled from 2003, when it was 2 million people, to 7 million people last year. Though there is sometimes a tendency for people to choose low-premium plans with high deductibles, "that may not tend to be a wise choice in all cases," Blumenthal said.
The research, which was primarily based on a survey of more than 3,000 adults, found that there was no significant change in the total number of people who are underinsured since 2010. But the current underinsured rate, of 23 percent of adults ages 19 to 64, is still sharply higher than the 12 percent of such people who were underinsured in 2003, according to the report.
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Blumenthal noted that while recent years have seen a marked slowdown in the increase in health-care costs, the rate of underinsurance could grow if those costs accelerate.