Massachusetts enacted comprehensive health coverage in 2006, serving as a model for the 2010 Patient Protection and Affordable Care Act known as Obamacare. The state reported about 3 percent fewer deaths in the four years after the overhaul than previously, according to researchers from the Harvard University School of Public Health. The study published in the Annals of Internal Medicine found no similar decline in death rates in other states that hadn't enacted health reform.

The findings showed that increasing health insurance coverage helped saves lives from illnesses that can get better with timely medical care such as cancer, infections and heart disease, said Benjamin Sommers, a lead study author. The decline in mortality was largest in Massachusetts counties with lower incomes and higher uninsured rates before the changes.

"Our results suggest that health insurance matters a lot for people's lives," Sommers, an assistant professor of health policy and economics at Harvard University School of Public Health in Boston, said in a telephone interview. "It makes it easier for them to get the care they need, they feel better about their health and they live longer. The evidence is mounting that giving people health insurance who didn't have it before makes a major difference in their lives."