The use of antibiotics among Americans with commercial health insurance has decreased during the past several years, according to a new analysis that nevertheless shows lingering variations for different ages and in different parts of the country.

The study released Thursday provides the latest evidence of how doctors and patients have begun to heed warnings that excessive antibiotic use breeds dangerous drug resistance and ‘‘superbug’’ bacteria. The analysis is based on 173 million insurance claims from people under age 65 with Blue Cross Blue Shield coverage who filled prescriptions between 2010 and 2016.

It is a sequel of sorts to research by the federal Centers for Disease Control and Prevention, which found a smaller decline and comparable age and geographic variations. The CDC reported a 5 percent decrease overall between 2011 and 2014 in antibiotic prescriptions written in outpatient settings such as doctors’ offices, clinics and hospital emergency rooms. The study by the Blue Cross Blue Shield Association found that 9 percent fewer antibiotics prescribed in outpatient settings were filled in 2016, compared with 2010.

Efforts to make sure that doctors and patients rely on antibiotics only when necessary have gained prominence in recent years. A study last year by the CDC and the Pew Charitable Trusts was the first to try to quantify the overuse, concluding that nearly one-third of the antibiotics prescribed in outpatient settings were not needed.

Many of these estimated 47 million unnecessary prescriptions were for colds or other respiratory illnesses that are caused by viruses and do not respond to antibiotics.

The Blue Cross Blue Shield analysis of 31 million commercially insured customers a year found that the steepest decrease in filled prescriptions was for children — a drop of 16 percent, compared with 6 percent for adults. The prescriptions filled for infants fell the most — 22 percent.

As with earlier research, the analysis also found wide geographic differences, with people in the South and Appalachia tending to fill prescriptions at rates significantly greater than those in New England and along the West Coast. The highest rates were in Mississippi, Alabama, and Arkansas. However, between 2010 and 2016, the rates fell in all states except Delaware, Illinois, and Nebraska.

Among types of antibiotics, the decrease was greatest among those that are broad-spectrum — covering a wide range of bacteria and most likely to lead to drug-resistance. Still, the analysis found that about one in five of the filled prescriptions after outpatient visits were for conditions not considered treatable by such antibiotics.

Washington Post