Providing greater access to health insurance led to a decline in deaths, according to a new study of Massachusetts' health care reform law.

Massachusetts passed comprehensive health care reform in 2006, providing a model for the Affordable Care Act -- dubbed by some as "Obamacare." In the four years after the law took effect in Massachusetts, deaths from all causes dropped nearly 3 percent compared with similar counties in states without health reform, the study found.

Researchers estimate that the Massachusetts law prevented 320 deaths a year. That works out to one life saved for every 830 people who gained insurance.

The study, published in the May 6 issue of the Annals of Internal Medicine also noted a 4.5 percent decline in deaths from preventable and treatable conditions, such as cancer, infections and heart disease.

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Massachusetts differs in many ways from the nation as a whole. But in a larger expansion of coverage, "there is a very real likelihood that you're going to help people live longer," said Dr. Benjamin Sommers, assistant professor of health policy and economics at Harvard School of Public Health and the study's lead author.

Much like Obamacare, the Massachusetts health care reform law expanded Medicaid, subsidized private health plans and created an individual mandate to hold people accountable for getting health coverage. The reforms took effect in 2006 and 2007, several years before President Obama signed the Affordable Care Act into law in 2010.

Using data from the U.S. Centers for Disease Control and Prevention, Sommers and colleagues examined changes in death rates for adults, ages 20 to 64, before and after the state enacted health reform, and compared them with the experience in similar counties in states that had not enacted health reform.

The largest gains in life occurred in counties with high poverty and higher rates of uninsured adults before health care reform.

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Health care reform lowered death rates in Mass., study finds