Antibiotic Use in Cold and Flu Season and Prescribing Quality: A Retrospective Cohort Study

Abstract

Background: Excessive antibiotic use in cold and flu season is costly and contributes to antibiotic resistance. The study objective was to develop an index of excessive antibiotic use in cold and flu season and determine its correlation with other indicators of prescribing quality.

Methods and findings: We included Medicare beneficiaries in the 40% random sample denominator file continuously enrolled in fee-for-service benefits for 2010 or 2011 (7,961,201 person-years) and extracted data on prescription fills for oral antibiotics that treat respiratory pathogens. We collapsed the data to the state level so they could be merged with monthly flu activity data from the Centers for Disease Control and Prevention. Linear regression, adjusted for state-specific mean antibiotic use and demographic characteristics, was used to estimate how antibiotic prescribing responded to state-specific flu activity. Flu-activity associated antibiotic use varied substantially across states-lowest in Vermont and Connecticut, highest in Mississippi and Florida. There was a robust positive correlation between flu-activity associated prescribing and use of medications that often cause adverse events in the elderly (0.755; P<0.001), whereas there was a strong negative correlation with beta-blocker use after a myocardial infarction (-0.413; P=0.003).

Conclusions: Adjusted flu-activity associated antibiotic use was positively correlated with prescribing high-risk medications to the elderly and negatively correlated with beta-blocker use after myocardial infarction. These findings suggest that excessive antibiotic use reflects low-quality prescribing. They imply that practice and policy solutions should go beyond narrow, antibiotic specific, approaches to encourage evidence-based prescribing for the elderly Medicare population.

Figure 1. Geographic Variation in Adjusted Flu-Predicted Antibiotic Use per 100 Medicare Part D Beneficiaries

Notes: Deciles of predicted, adjusted flu-associated antibiotic use per 100 Medicare beneficiaries are represented in varying colors. Predicted values are obtained following linear regression that controls for mean antibiotic use by state (using state fixed effects) and time-varying demographic characteristics including the percent of beneficiaries that are in certain age categories, percent on a low-income subsidy, percent male, percent minority and percent with chronic pulmonary disease/tobacco use. The red states are those with greater antibiotic prescribing responsiveness to flu activity and the blue states are those with less responsiveness. The value for each state is provided in Appendix Table 1.

Figure 2. High Risk Medications and Flu-adjusted Antibiotic Use

Notes: The adjusted flu-associated index of respiratory antibiotic is positively correlated to an independent measure of inappropriate prescribing: the fraction of the eligible Medicare population receiving one or more high-risk drugs as defined by the HEDIS high-risk drug list (Dartmouth Atlas, 2013).

Figure 3. Beta-Blocker and Flu-adjusted Responsive Antibiotic Use

Notes: The adjusted flu-associated index of respiratory antibiotic is negatively correlated to an independent measure of appropriate prescribing: the fraction of the of the eligible Medicare population receiving a beta-blocker within six months of a myocardial infarction (Dartmouth Atlas, 2013).