To examine whether healthcare-associated infections (HAIs) and nurse staffing are associated using unit-level staffing data.
Previous studies of the association between HAIs and nurse staffing are inconsistent and limited by methodological weaknesses.
Cross-sectional data between 2007 and 2012 from a large urban hospital system were analyzed. HAIs were diagnosed using the Centers for Disease Control and Prevention's National Healthcare Safety Network definitions. We used Cox proportional-hazards regression model to examine the association of nurse staffing (2 days before HAI onset) with HAIs after adjusting for individual risks.
Fifteen percent of patient-days had 1 shift understaffed, defined as staffing below 80% of the unit median for a shift, and 6.2% had both day and night shifts understaffed. Patients on units with both shifts understaffed were significantly more likely to develop HAIs 2 days later.
Understaffing is associated with increased risk of HAIs.