Influence of Nursing Time and Staffing on Medication Errors: A Cross-Sectional Analysis of Administrative Data.

: Medication errors cause adverse events; however, studies have yet to examine medication errors related to nursing hours while considering ward characteristics in Japan. Purpose: This study investigated medication errors caused by nurses to quantitatively assess ward activity as busyness in nursing duties. : This study considered patients hospitalized in the general wards of 10 National Hospital Organization institutions between April 2019 and March 2020. The study data were obtained from the Diagnosis Procedure Combination system, incident report system, and reports on nurse staffing and work hours. Data for 27,629 ward days with 88,475 patients were analyzed. Multivariate analysis was performed to determine the impact of factors on medication errors. : The mean patient age was 71.43 years (SD = 15.08). The medication error rate in nursing wards was 13.71%. The mean nursing time per patient during day shift was 1.95 h (SD = 0.58) in the non-medication error group and 2.06 h (SD = 0.58) in the medication error group ( < 0.01). The nursing time per patient in the medication error group compared to that in the non-medication error group had an odds ratio of 1.31 ( < 0.01) during day shifts. : Contrary to evidence, the results showed that medication errors caused by nurses related to increased nurse time with patients during day shifts. Further investigation is needed on the relationship of busyness with nursing duties to ensure an adequate nurse-patient ratio, nursing time, and improved patient safety.