Needleman et al.

(2002) [40]

Cohort study



Not reported

Administrative data from 1997 for 799 hospitals in 11 states, covering 5,075,969 discharges of medical patients and 1,104,659

surgical patients

A higher proportion of hours of care per day provided by registered nurses and a greater number of hours of care provided per day were associated with a shorter length of stay and lower rates of urinary tract infections and upper gastrointestinal bleeding.

A higher hour of care provided by RNs was associated with a lower rate of pneumonia, shock or cardiac arrest, and “failure to rescue”.

Direct consequences: Patient harm

Person et al.

(2004) [41]

Cross-sectional analysis



Assess the association of nurse staffing with in-hospital mortality for patients with acute myocardial infarction.

118,940 patients admitted with AMI in 6668 hospitals in the US

Patients treated in environments with higher RN staffing were less likely to die in-hospital.

Patients treated in environments with higher LPN (licensed practical nurse) staffing were more likely to die in-hospital. (The data was adjusted with patient demographic, clinical characteristics, treatment, hospital volume, technology index teaching and urban status)

Direct consequences: Mortality

Potter et al.

(2003) [54]


Prospective, correlation study


To determine baseline values of patient outcome measures and the relationship of nurse staffing to patient outcomes.

32 acute inpatient care units

3418 patients

The percentage of RN hours was negatively correlated with patient pain and self-care ability, and positive correlated with patient health status and five out of seven measures of post-discharge patient satisfaction.

Indirect consequences: Poor quality of basic care

Rogowski et al. (2013) [42]

Retrospective cohort study



To study the adequacy of Neo Natal Intensive Care Unit (NICU) nurse staffing in the United States using national guidelines and analyze its association with infant outcomes

newborn very low-birth-weight infants discharged from the NICUs in 2008 (n = 5771) and 2009 (n = 5630)

All registered nurses with infant assignments.

The percentage of Very Low Birth Weight (VLBW) infants with hospital associated infections were 16.4% in 2008 and 13.9% in 2009. Relative to the guidelines, on average, hospitals understaffed 47% of all NICU infants in 2008 and 31% in 2009.

A 1 standard deviation increase in the amount of a nurse per infant to meet the guidelines was associated with higher odds of infection in 2008 and 2009

Direct consequences: Patient harm

Sasicbay-Akkadecbanunt et al.

(2003) [43]

cross-sectional study



To examine the association between in-hospital mortality and four nurse staffing variables.

Data of 2531 patients admitted to seven medical units and 10 surgical units of a 2300 bed university hospital.

The nurse-to-patient ratio was statistically correlated with in-hospital mortality. Nurse-to-patient ratio had an individual effect on in-hospital mortality.

The ratio of total staff to patients was the best predictor of in hospital mortality among four staffing variables.

There was not a significant relationship between in hospital mortality and the proportion of RNs to total nursing staff, the mean years of RN experience and the percentage of bachelor degree prepared nurses.

Direct consequences: Mortality