A new study has shown that there is a variation in the use of antibiotic pills among the older adults across the U.S., a worrisome trend because overuse of antibiotics leads to resistance to these drugs, increased exposure to side effects and increased healthcare cost.

The study was based on the data of about 1 million people each year who were on Medicare between the years 2007 and 2009. Data was collected from 50 states and the District of Columbia plus four geographical regions (east, west, north and south). Researchers also studied the variation in antibiotic prescription according to seasonal changes in the four regions.

The Southern regions had the highest incidences of antibiotic use with 21.4 percent per quarter compared to 14 percent per quarter in the West.

"Overall, areas with high rates of antibiotic use may benefit from more targeted programs to reduce unnecessary antibiotic use. Although antibiotic use in the regions with lower use does not necessarily represent the clinically appropriate use given that overuse of antibiotics is common, quality improvement programs set attainable targets using the low-prescribing areas (i.e. the states in the West) as a reference," note the authors.

There was also a trend of over-prescribing of broad-spectrum antibiotics like quinolones and macrolides in the South, Reuters Health reported. Resistance to these antibiotics leads to particularly complicated cases of infections.

Researchers also found that in all the regions, antibiotic use was highest in the first quarter of the year (January to March) and lowest in the third quarter (July to September). "Although older adults may have higher risk for adverse outcomes from infection, they may also be at particularly high risk for adverse outcomes from antibiotic use. Therefore, it might be necessary to target some quality improvement initiatives toward this age group," researchers said.

Previous research on antibiotic utilization among various healthcare plans in the U.S. had shown that there is a wide variation in antibiotic prescription, with some healthcare plans utilizing 70 percent more antibiotics per person than other plans. This study had also found that the over-prescribing of antibiotics has led to a greater antibiotic-resistance in the southern states than other parts of the country.

"We need to find better ways to compel individuals and organizations to address the significance of the problem of antibiotic overuse and to increase the readiness for change and quality improvement of ambulatory practices in the United States," write Ralph Gonzales and colleagues from the University of California, San Francisco, in a linked commentary

The study was published in the Archives of Internal Medicine.