A new state report finds health insurance coverage grew significantly in rural Minnesota during the early years of the federal health law.

Overall, the uninsured rate among residents under age 65 declined significantly between 2011 and 2015 in both rural and urban areas, landing in both segments at just 5 percent, according to the study released Monday by the Minnesota Department of Health.

While it was unclear statistically whether the magnitude of decline was greater in rural or urban areas, certain subgroups in rural parts of the state clearly saw more benefit than their counterparts in urban areas, said Mark Schoenbaum, director of the office of rural health and primary care at the health department.

In 2015, rural children no longer had significantly higher uninsured rates than their urban counterparts, the report found. Rural areas also saw significant reductions in coverage disparities across racial groups compared to urban areas.

The study can't prove what caused changes, but Schoenbaum pointed to expanded reach under the Affordable Care Act (ACA) of state public health insurance programs for lower-income residents.

"Rural Minnesota has always had greater participation in Minnesota­Care especially, and in Medical Assistance," Schoenbaum said, referring to the state's largest public insurance programs. "That participation has remained higher than in urban areas, and has increased since Medicaid expansion [under the ACA] began."

The health department on Monday released three reports looking at the effects of the ACA on rural Minnesota. The health law expanded access to coverage via Medicaid — called Medical Assistance in Minnesota — and provided subsidies for people buying individual policies through the new MNsure exchange.

Before and after health law changes, rural Minnesota had a greater share of its population enrolled in MinnesotaCare and Medical Assistance, the health department says. By early 2016, more than one in four rural Minnesotans were enrolled in the programs, compared with one in five in urban areas.

Overall, the uninsured rate in rural areas was 12 percent during 2011 and 10 percent in urban areas. Since the rate in both areas measured 5 percent in 2015, the numbers suggest a bigger drop in rural areas than urban areas.

But such a conclusion is uncertain because the 2-percentage-point difference between the rural and urban rates in 2011 isn't considered statistically significant, which means it could have occurred by chance.

"Because of the small sample size, it's more of a pointer," Schoenbaum said, "than a classic indicator of significance."

Some problems with health care costs persist. In 2015, 23 percent of respondents in rural areas said they experienced financial burdens from medical bills — a bigger share than in urban areas.

Twitter: @chrissnowbeck