Print “PDF version

What’s New in the Patient Safety World

July 2019

HAI’s and Nurse Staffing



Do nurse staffing levels impact rates of healthcare-associated infections (HAI’s)? Last year a systematic review of the literature (Mitchell 2018) identified 54 articles dealing with the issue. The majority of the studies found nurse staffing variables to be associated with an increase in HAI rates. But the authors noted studies varied in design and methodology, as well as in their use of operational definitions and measures of staffing and HAI’s. Also, only 5 studies addressed non-nurse staffing, and those had mixed results. The authors concluded that more rigorous and consistent research designs, definitions, and risk-adjusted HAI data are needed in future studies exploring this area.


So a new study (Shang 2019) has addressed some of the methodological weaknesses of previous studies. Shang and colleagues analyzed data from a large urban hospital system. HAI’s were diagnosed using the Centers for Disease Control and Prevention's National Healthcare Safety Network definitions and Cox proportional-hazards regression model was used to examine the association of nurse staffing (2 days before HAI onset) with HAI’s 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. They found that patients on units with both shifts understaffed with RN’s were 15 percent more likely to develop HAI’s on or after the third day of exposure to periods of understaffing compared to patients in units with both day and night shifts adequately staffed. In addition, units understaffed with nursing supporting staff (LPN’s and nurse assistants) had increased patients’ risk of HAI’s.


This is one more study that adds to the evidence base on the importance of adequate nurse:patient staffing ratios. Nursing staffing levels have also been shown to correlate with patient mortality rates. But, as we’ve discussed in so many columns, the issue is more complex than simple nurse:patient ratios. Those ratios do not take into account actual nurse workload nor do they take into account the fatigue factor that may accompany long work shifts or forced overtime. One factor that comes into play in those conditions is the concept of “missed nursing care” or “care left undone” (see our Patient Safety Tips of the Week for November 26, 2013 “Missed Care: New Opportunities?” and May 9, 2017 “Missed Nursing Care and Mortality Risk”).


We discussed the issue of nursing workload in detail in our Patient Safety Tips of the Week for March 6, 2018 “Nurse Workload and Mortality” and May 29, 2018 “More on Nursing Workload and Patient Safety” and our February 2019 What's New in the Patient Safety World column “Nurse Staffing, Workload, Missed Care, Mortality”. In those columns we discussed the issue of how to best measure workload.




Some of our other columns on nursing workload and missed nursing care/care left undone:


November 26, 2013    “Missed Care: New Opportunities?

May 9, 2017                “Missed Nursing Care and Mortality Risk

March 6, 2018             “Nurse Workload and Mortality

May 29, 2018              “More on Nursing Workload and Patient Safety

October 2018               “Nurse Staffing Legislative Efforts

February 2019             “Nurse Staffing, Workload, Missed Care, Mortality






Mitchell BG, Gardner A, Stone PW, at al. Hospital Staffing and Health Care–Associated Infections: A Systematic Review of the Literature. Joint Commission Journal on Quality and Patient Safety 2018; 44(10): 613-622



Shang J, Needleman J, Liu J, et al. Nurse Staffing and Healthcare-Associated Infection, Unit-Level Analysis. JONA: The Journal of Nursing Administration 2019; 49(5): 260-265






Print “PDF version











Tip of the Week Archive


What’s New in the Patient Safety World Archive