Geographic variation in outpatient antibiotic prescribing among older adults

Abstract

Background: Consequences of antibiotic overuse are substantial, especially among older adults, who are more susceptible to adverse reactions. Findings about variation in antibiotic prescribing can target policy efforts to focused areas; however, little is known about these patterns among older adults.

Methods: Using Medicare Part D data from January 1, 2007, through December 31, 2009 (comprising 1.0-1.1 million patients per year), we examined geographic variation in antibiotic use among older adults in 306 Dartmouth Atlas of Health Care hospital referral regions, 50 states and the District of Columbia, and 4 national regions (South, West, Midwest, and Northeast). In addition, we examined the quarterly change in antibiotic use across the 4 regions. Differences in patient demographics, insurance status, and clinical characteristics were adjusted for across regions.

Results: Substantial geographic and quarterly variation in outpatient antibiotic prescribing existed across regions after adjusting for population characteristics. This variation could not be explained by differences in the prevalences of the underlying conditions. For example, the ratios of the 75th percentile to the 25th percentile of adjusted annual antibiotic spending were 1.31 across states and 1.32 across regions. The highest antibiotic use was in the South, where 21.4% of patients per quarter used an antibiotic, whereas the lowest antibiotic use was in the West, where 17.4% of patients per quarter used an antibiotic (P < .01). Regardless of region, the rate of antibiotic use was highest in the first quarter (20.9% in January through March) and was lowest in the third quarter (16.9% in July through September) (P < .01).

Conclusions: Areas with high rates of antibiotic use may benefit from targeted programs to reduce unnecessary prescription. Quality improvement programs can set attainable targets using the low-prescribing areas as a reference, particularly targeting older adults.

Figure 1. Proportion of Patients Using Any Antibiotic, By Region and Quarter

Each of four regions includes the following states: Northeast: CT, ME, MA, NH, NJ, NY, PA, RI, VT; Midwest: IL, IN, IA, KS, MI, MN, MO, NE, ND, OH, SD, WI; South: AL, AR, DE, DC, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV; West: AK, AZ, CA, CO, HI, ID, MT, NV, NM, OR, UT, WA, WY.

Figure 1. Proportion of Patients Using Any Antibiotic, By Region and Quarter

Each of four regions includes the following states: Northeast: CT, ME, MA, NH, NJ, NY, PA, RI, VT; Midwest: IL, IN, IA, KS, MI, MN, MO, NE, ND, OH, SD, WI; South: AL, AR, DE, DC, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV; West: AK, AZ, CA, CO, HI, ID, MT, NV, NM, OR, UT, WA, WY.

Figure 1. Proportion of Patients Using Any Antibiotic, By Region and Quarter

Each of four regions includes the following states: Northeast: CT, ME, MA, NH, NJ, NY, PA, RI, VT; Midwest: IL, IN, IA, KS, MI, MN, MO, NE, ND, OH, SD, WI; South: AL, AR, DE, DC, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV; West: AK, AZ, CA, CO, HI, ID, MT, NV, NM, OR, UT, WA, WY.

Figure 2. Prevalence Rates of Three Conditions by Region and Quarter

Panel A. Bacterial pneumonia Panel B. Acute nasopharyngitis (common cold) and nonspecific upper respiratory infections Panel C. Other acute respiratory infections Notes: Bacterial pneumonia was defined as ICD-9 codes: 481, 482, 483, 485, 486, which should almost always require antibiotics; acute nasopharyngitis (common cold) and nonspecific upper respiratory infections were defined as ICD-9 codes: 460, 465, for which antibiotics typically should not be used; other acute respiratory infections were defined as ICD-9 codes: 461, 473, 462, 463, 466, 490, including sinusitis (ICD-9 461, 473), pharyngitis and tonsillitis (ICD-9 462, 463), and bronchitis (ICD-9 466, 490). The sample in this figure excludes patients enrolled in MA-PD plans, since no medical claims information is available for these patients. Each of four regions includes the following states: Northeast: CT, ME, MA, NH, NJ, NY, PA, RI, VT; Midwest: IL, IN, IA, KS, MI, MN, MO, NE, ND, OH, SD, WI; South: AL, AR, DE, DC, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV; West: AK, AZ, CA, CO, HI, ID, MT, NV, NM, OR, UT, WA, WY.

Figure 2. Prevalence Rates of Three Conditions by Region and Quarter

Panel A. Bacterial pneumonia Panel B. Acute nasopharyngitis (common cold) and nonspecific upper respiratory infections Panel C. Other acute respiratory infections Notes: Bacterial pneumonia was defined as ICD-9 codes: 481, 482, 483, 485, 486, which should almost always require antibiotics; acute nasopharyngitis (common cold) and nonspecific upper respiratory infections were defined as ICD-9 codes: 460, 465, for which antibiotics typically should not be used; other acute respiratory infections were defined as ICD-9 codes: 461, 473, 462, 463, 466, 490, including sinusitis (ICD-9 461, 473), pharyngitis and tonsillitis (ICD-9 462, 463), and bronchitis (ICD-9 466, 490). The sample in this figure excludes patients enrolled in MA-PD plans, since no medical claims information is available for these patients. Each of four regions includes the following states: Northeast: CT, ME, MA, NH, NJ, NY, PA, RI, VT; Midwest: IL, IN, IA, KS, MI, MN, MO, NE, ND, OH, SD, WI; South: AL, AR, DE, DC, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV; West: AK, AZ, CA, CO, HI, ID, MT, NV, NM, OR, UT, WA, WY.

Figure 3. Quintiles of Adjusted Annual Antibiotic Spending and Counts According to State in 2009

Panel A. Variation in Adjusted Annual Antibiotic Spending Panel B. Variation in Adjusted Annual Counts

Figure 4. Quintiles of Adjusted Annual Antibiotic Spending and Counts According to Hospital-Referral Region in 2009

Panel A. Variation in Adjusted Annual Antibiotic Spending Panel B. Variation in Adjusted Annual Counts