One in four U.S. families struggled to pay medical bills in 2012, and 1 in 10 said they had costs they couldn’t pay at all, according to a government survey.

The survey released today from the National Center for Health Statistics at the U.S. Centers for Disease Control and Prevention also found the lack of health insurance increased the burden of medical debt.

Major provisions of the 2010 Patient Protection and Affordable Care Act take effect this year as the Obama administration seeks to extend health-care coverage to most of the nation’s 48 million uninsured. The law may help lessen some of the financial burdens of medical care, said Karen Pollitz, a fellow at the Kaiser Family Foundation and lead author of a separate study on medical debt published Jan. 7.

“Unpaid medical bills is the number one reason why families declare personal bankruptcy,” Pollitz said in a telephone interview. “It causes people to lose equity in their homes, to endanger their retirement and their kid’s college education. It will destroy a family financially.”

Besides bringing coverage to the previously uninsured, the Affordable Care Act requires that health plans remove annual dollar limits on covered benefits, meaning patients will no longer face huge bills after reaching their coverage limit.

Health coverage alone can’t prevent medical debt. Among families in which all members were insured, 21 percent had difficulty paying medical bills, the survey found.

The Affordable Care Act marks the largest U.S. expansion of medical insurance in more than 40 years. The law created government-run insurance exchanges where Americans can buy private health plans with the help of federal tax credits. It also expanded eligibility in some state-run Medicaid programs for the poor.

The Kaiser Family Foundation study found that 70 percent of people reporting problems with medical debt were already insured. Cost-sharing was the leading contributor to the debt, as typical out-of-pocket costs were higher for health bills than the amount of cash most households had available.

Insurers, trying to lower premiums on the government-run exchanges, have raised co-pays and deductibles to compensate. Deductibles for some policies can reach $6,350 for a single person and $12,700 per family, according to a November survey by HealthPocket Inc. of seven states, including California and Ohio.

“There will continue to be millions of people in health plans with deductibles in excess of what they have on hand,” Pollitz said.