Extensive research has established a strong link between overall nurse staffing levels and certain patient safety outcomes. In contrast, the impact of agency nurse staffing on patient outcomes has been studied less frequently, with inconsistent results. US studies examining agency hours often rely on cross-sectional designs, which, along with similarly limited research on overtime hours, highlight the need for more comprehensive and methodologically rigorous investigations.

This article explores the relationship between overtime and agency nursing hours and 10 patient safety indicators developed by the US Agency for Healthcare Research and Quality (AHRQ).