A new study in Massachusetts shows that as the number of urgent care and retail clinics in the state climbed during the last dozen years, there’s been a reduction in emergency room use.

The report—released this week by the Massachusetts Health Policy Commission—showed a 30 percent decrease in the use of emergency departments when there are nearby urgent care centers or retail clinics.

The trend is positive for both patients and providers, as reported at MassLive.com. ER visits are about four times more expensive than other ambulatory visits, adding billions of dollars in unnecessary health care costs every year in the United States.

The commission tracked the urgent care growth, from 8 clinics in the state in 2008 to 84 this year. The number of retail clinics grew from 11 to 58 during the same time period.  Nationwide there are around 6,400 urgent care centers in operation.

Alan Ayers, Vice President of Strategic Initiatives at Practice Velocity, noted that the benefits of urgent care centers in Massachusetts arrived very quickly—since the rapid growth in the number of centers there has just been in the past few years.

“Massachusetts has been somewhat late to embrace urgent care,” he said. “The dominant payers in Massachusetts for years would only reimburse urgent care at the same rate as primary care. As a result, despite long wait times to get into primary care and urgent care thriving in neighboring Rhode Island and Connecticut, urgent care wasn’t a viable business model in Massachusetts.”

The diversion of many patients from emergency rooms is important. The report noted 40 percent of ER visits in the last year were for “non-emergency” reasons; 76 percent were for care after normal doctor’s office hours; and 60 percent were because the patient could not get a timely appointment at a physician’s office.

A survey released this month from the Center for Health Information and Analysis found that more than one-fifth of respondents had trouble getting a timely appointment with a doctor. Further, another 21 percent of adults said they skipped medical care due to cost. About 16 percent reported they spent more than $3,000 on medical expenses during the past year, not including health insurance premiums.