Variability in Antibiotic Use Across Nursing Homes and the Risk of Antibiotic-Related Adverse Outcomes for Individual Residents.

IMPORTANCE Antibiotics are frequently and often inappropriately prescribed to patients in nursing homes. These antibiotics pose direct risks to recipients and indirect risks to others residing in the home. OBJECTIVE To examine whether living in a nursing home with high antibiotic use is associated with an increased risk of antibiotic-related adverse outcomes for individual residents. DESIGN, SETTING, AND PARTICIPANTS In this longitudinal open-cohort study performed from January 1, 2010, through December 31, 2011, we studied 110,656 older adults residing in 607 nursing homes in Ontario, Canada. EXPOSURES Nursing home-level antibiotic use was defined as use-days per 1000 resident-days, and facilities were classified as high, medium, and low use according to tertile of use. Multivariable logistic regression modeling was performed to assess the effect of nursing home-level antibiotic use on the individual risk of antibiotic-related adverse outcomes. MAIN OUTCOMES AND MEASURES Antibiotic-related harms included Clostridium difficile, diarrhea or gastroenteritis, antibiotic-resistant organisms (which can directly affect recipients and indirectly affect nonrecipients), allergic reactions, and general medication adverse events (which can affect only recipients). RESULTS Antibiotics were provided on 2,783,000 of 50,953,000 resident-days in nursing homes (55 antibiotic-days per 1000 resident-days). Antibiotic use was highly variable across homes, ranging from 20.4 to 192.9 antibiotic-days per 1000 resident-days. Antibiotic-related adverse events were more common (13.3%) in residents of high-use homes than among residents of medium-use (12.4%) or low-use homes (11.4%) (P < .001); this trend persisted even among the residents who did not receive antibiotic treatments. The primary analysis indicated that residence in a high-use nursing home was associated with an increased risk of a resident experiencing an antibiotic-related adverse event (adjusted odds ratio, 1.24; 95% CI, 1.07-1.42; P = .003). A sensitivity analysis examining nursing home-level antibiotic use as a continuous variable confirmed an increased risk of resident-level antibiotic-related harms (adjusted odds ratio, 1.004 per additional day of nursing home antibiotic use; 95% CI, 1.001-1.006; P = .01). CONCLUSIONS AND RELEVANCE Antibiotic use is highly variable across nursing homes; residents of high-use homes are exposed to an increased risk of antibiotic-related harms even if they have not directly received these agents. Antibiotic stewardship is needed to improve the safety of all nursing home residents.