Regional, seasonal variation in US antibiotic use highlights persisting issue

By Sarah Guy, medwireNews Reporter

US study results reveal "substantial" quarterly and regional variation in outpatient antibiotic use among older adults, indicating the possible need for targeted programs to reduce unnecessary prescriptions.

The highest antibiotic use was in the South of the country, reports the research team, while the lowest was in the West. The winter months (January through March) accounted for the highest prescription rates of the calendar year.

"Not only can overuse lead to unnecessary spending for prescription drugs, but also it can increase the risk for adverse effects and population-level antimicrobial resistance," explain Yuting Zhang (University of Pittsburg, Pennsylvania) and co-investigators in the Archives of Internal Medicine.

They add that older patients may be more susceptible to adverse drug reactions because of an increased comorbidity burden, therefore identifying variations in prescription can help target policy efforts to these specific areas.

The team evaluated antibiotic use per person per year for a 5% random sample of Medicare beneficiaries aged 65 years and above registered with the insurance system between January 2007 and December 2009. Analysis included the proportion of patients using an antibiotic, the mean number of antibiotic prescriptions filled, and total gross spending on antibiotics.

All data were adjusted for patient demographics, insurance status, and clinical characteristics to avoid possible confounding.

Rates of patients taking antibiotics were a significant 4.0 percentage points higher in the South than in the West - the highest and lowest regions of antibiotic use respectively, at 21.4% versus 17.4%.

The researchers also identified significant seasonal differences in antibiotic use, which was lowest in the quarter July, August, and September, at 16.9%, compared with 20.9% in the quarter January, February, and March.

Zhang and colleagues adjusted results for regional variation in three specific conditions; bacterial pneumonia (which should almost always be treated with antibiotics), acute nasopharyngitis (which should typically not receive antibiotics), and other acute respiratory tract infections (for which antibiotics are often unnecessary). However, the association remained.

In an accompanying editorial, Ralph Gonzales (University of California, San Francisco) and colleagues suggest that Zhang et al's study results raise the question of why the problem of overprescribing persists in the USA - more than 15 years since it became a national priority.

The editorialists believe that the persistence is a "failure to translate national public health priorities and evidence into local practice and policies," and call for "better ways to address the significance of the problem."

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