Competition between doctors' offices, urgent care centers and retail medical clinics that cater to wealthy elites often leads to an increase in the number of antibiotic prescriptions written per person, finds a new analysis.

The number of physicians per capita and the number of clinics are significant drivers of antibiotic prescription rate, they found, with the highest per capita rates of antibiotic prescriptions found in the southeastern U.S. and along the West and East coasts. The team's comparative analysis of data for the years 2000 and 2010 were collected from the U.S. Census Bureau and the IMS Health Xponent database, which tracks prescriptions dispensed at the ZIP code level. Notably high rates were found in Manhattan, southern Miami and Encino.

The data showed that the presence of retail medical clinics, like those found in chain drug and "super" stores, and of urgent care centers increases the prescribing rate, but the effect was different in wealthy versus poor areas.

In wealthy areas, the presence of clinics correlated to an increase in the prescribing rate of physicians. However, while the presence of retail or urgent care clinics in poorer areas increased access to health care, it did not generate competition among providers that resulted in higher prescribing behavior by physicians' offices.

The findings, according to the research team, add to the growing body of evidence indicating that social and economic factors are contributing to the overuse of antibiotics in the United States. The Centers for Disease Control and Prevention reports that such overuse is a major factor in the spread of antibiotic resistance and a worldwide health threat resulting in 23,000 deaths a year in the U.S. alone. The researchers say their results also suggest that in wealthy areas, residents may be more able and likely to shop for a health care provider willing to write a prescription than is the case in poorer areas.

 "The increase in the number of antibiotic prescriptions written in wealthy areas appears to be driven primarily by increased competition among doctors' offices, retail medical clinics and other health care providers as they seek to keep patients satisfied with medical care and customer service," says lead study author Eili Klein, Ph.D., an assistant professor of emergency medicine in the Johns Hopkins University School of Medicine. "We were surprised to find in this study that there is a really strong suggestion in the data that physicians are competing with other physicians, and they are doing that through the mechanism of prescribing antibiotics."

"It speaks to the fact that health care is a business," he adds. "But it also underscores that there is a lot of pressure on doctors to prescribe antibiotics -- even when they aren't 100 percent certain they are necessary."

One of those pressures, Klein says, is the time available to spend with each patient. There are reliable estimates, he notes, that it takes a doctor five minutes to see a patient who isn't feeling well and write a prescription for an antibiotic, but it takes 15 minutes to explain to the patient why they don't need one. Pphysicians' offices also face pressure from patients shopping around for care or from retail medical clinics that may offer a prescription if a physician office doesn't.

"These are all real pressures contributing to a public health crisis driven by the overuse of antibiotics," says Klein, who has published other studies looking at how social and economic interactions and trends are contributing to antibiotic resistance.

Klein cautioned that the new study did not seek to determine any possible link between antibiotic resistance rates and high prescribing rates in specific ZIP codes marked by such behavior, reliable ZIP code-specific data on antibiotic resistance are not available.

 Published in the Journal of Antimicrobial Chemotherapy. Other authors contributing to the study include Michael Makowsky and Erez Hatna of the Johns Hopkins Department of Emergency Medicine; Megan Orlando and Ramanan Laxminarayan of Princeton University; and Nikolay P. Braykov of the Center for Disease Dynamics, Economics and Policy.