While fewer Americans said they couldn't afford to pay for medical expenses in 2012, there are still millions who still have a have a hard time paying medical bills and costs for treatments, medication and nursing homes, among other cares.

The latest report from the Centers for Disease Control and Prevention (CDC) found that 20.3 percent of people below the age of 65, or one in five, couldn't pay medical bills in the first half of 2012. The figure is a slight improvement from 21.7 percent in 2011.

Most Americans between the 2011 and 2012 who had the toughest time were persons from families who are uninsured, have public coverage, or families with children.

"Females were more likely than males to have been in a family having problems paying medical bills in both halves of 2011," the authors write. "However, in the first 6 months of 2012, there was no significant difference between females and males who were in a family having problems paying medical bills."

The data was collected by statisticians for the CDC's National Center for Health Statistics survey. Despite the slight drop, more than 54 million Americans are having trouble keeping up with payments.

In the survey, households were asked whether they experienced problems paying or were unable to pay any medical bills in the past 12 months.

Among households that answered yes, 36 percent were uninsured, 25 percent had public coverage, and 14 percent had private insurance.

These figures are expected to change once the Affordable Care Act rolls out measures and incentives to cover all Americans in 2014.

The households who had the toughtest time were more likely to have children ages 17 or below rather than adults only.

Source: Cohen RA, Kirzinger WK, and Gindi RM. Problems paying medical bills: early release of estimates from the National Health Interview Survey, January 2011-June 2012. CDC. 2013.