The number of uninsured adults decreased by more than 3 percentage points in the first quarter of this year, according to a report released Wednesday by the CDC.

In the first 3 months of 2015, the percentage of adults ages 18-64 without insurance stood at 13%, down from 16.3% in 2014, wrote Robin Cohen, PhD, and Michael Martinez, MPH, both from the CDC's National Center for Health Statistics, in Hyattsville, Md. The number of uninsured people of any age also dropped, from 36 million in 2014 to 29 million in 2015.

The number of people getting coverage through the Affordable Care Act's (ACA) state-run and federally-run health insurance exchanges increased, going from 2.5%, or 6.7 million, at the end of 2014 to 3.6%, or 9.7 million, at the beginning of 2015, they found. In particular, there was a large increase in adults covered by exchange plans, from 2.9% of adults ages 18-64 (5.7 million) in 2015 to 4.4% (8.6 million) in the first quarter of 2015.

Data for the report came from the National Health Interview Survey conducted from January through March, 2015, as well as comparable estimates from the same survey in 2015. The 2015 estimates are based on data from slightly more than 26,000 people, the researchers noted. The investigators looked at three types of data: those who were uninsured at the time they were interviewed; those who were uninsured at least part of the year before the interview; and those who were uninsured for more than a year.

The researchers also found:

The percentage of children under age 18 with private coverage increased from 52.6% in 2013 to 56.3% in the first 3 months of 2015, "reversing a 14-year trend of declining rates of private coverage."

In the first 3 months of 2015, 13% of adults ages 18-64 were uninsured, while 18.1% had public coverage and 70.4% had private coverage. The number of uninsured adults dropped by more than 9 percentage points in the last 5 years (from 22.3% to 13.0%).

Among children ages 0-17, 4.6% were uninsured during the first 3 months of 2015, while 40.4% had public coverage and 56.3% had private coverage. "From 1997 through 2010, the percentage of children with private coverage generally decreased and the percentage of children with public coverage generally increased," the investigators wrote. "However, more recently the percentage of children with public coverage has leveled off, and the percentage of children with private coverage has increased from 52.6% in 2013 to 56.3% in the first 3 months of 2015."

In terms of poverty status, 28% of poor adults (defined as those with incomes below the federal poverty level), 23.8% of near-poor adults (those with incomes between 100% and 200% of the poverty level), and 7.5% of not-poor adults (those with incomes of 200% of the poverty level or greater) lacked health insurance during early 2015. "There was a decrease in the percentage of uninsured adults from 2010 through the first 3 months of 2015 among all three poverty groups; however, the greatest decreases in the uninsured rate since 2013 were among adults who were poor or near-poor," the researchers noted.

Medicaid expansion also appeared to have an effect on uninsured rates; in states that expanded their Medicaid programs under the ACA, the percentage of uninsured dropped from 18.4% in 2013 to 10.6% in the first 3 months of 2015, while in states that didn't expand the program, the percentage dropped from 22.7% to 16.8% during the same period.

Among the ethnic groups studied, uninsured rates were highest among Hispanic adults, with 28.3% uninsured during the first quarter of 2015. They were followed by blacks, at 15.6%, whites, at 8.7%, and Asians, at 7.2%, the report found.