The state has selected six organizations to oversee health care for some of the neediest adults in Massachusetts, as it works to streamline coverage for about 110,000 people who qualify for both Medicare and Medicaid.

The program is aimed at saving money and lessening the confusion for doctors and patients caused by the two programs sharing responsibility for bills. Many dually eligible people have complex and costly health needs, including mental illnesses, developmental disabilities, or drug and alcohol addictions.