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The Association of Registered Nurse Staffing Levels and Patient Outcomes: Systematic Review and Meta-Analysis

Kane, Robert L. MD*; Shamliyan, Tatyana A. MD, MS*; Mueller, Christine PhD, RN; Duval, Sue PhD*; Wilt, Timothy J. MD, MPH

doi: 10.1097/MLR.0b013e3181468ca3
Review Article

Objective: To examine the association between registered nurse (RN) staffing and patient outcomes in acute care hospitals.

Study Selection: Twenty-eight studies reported adjusted odds ratios of patient outcomes in categories of RN-to-patient ratio, and met inclusion criteria. Information was abstracted using a standardized protocol.

Data Synthesis: Random effects models assessed heterogeneity and pooled data from individual studies. Increased RN staffing was associated with lower hospital related mortality in intensive care units (ICUs) [odds ratios (OR), 0.91; 95% confidence interval (CI), 0.86–0.96], in surgical (OR, 0.84; 95% CI, 0.80–0.89), and in medical patients (OR, 0.94; 95% CI, 0.94–0.95) per additional full time equivalent per patient day. An increase by 1 RN per patient day was associated with a decreased odds ratio of hospital acquired pneumonia (OR, 0.70; 95% CI, 0.56–0.88), unplanned extubation (OR, 0.49; 95% CI, 0.36–0.67), respiratory failure (OR, 0.40; 95% CI, 0.27–0.59), and cardiac arrest (OR, 0.72; 95% CI, 0.62–0.84) in ICUs, with a lower risk of failure to rescue (OR, 0.84; 95% CI, 0.79–0.90) in surgical patients. Length of stay was shorter by 24% in ICUs (OR, 0.76; 95% CI, 0.62–0.94) and by 31% in surgical patients (OR, 0.69; 95% CI, 0.55–0.86).

Conclusions: Studies with different design show associations between increased RN staffing and lower odds of hospital related mortality and adverse patient events. Patient and hospital characteristics, including hospitals’ commitment to quality of medical care, likely contribute to the actual causal pathway.

Supplemental Digital Content is Available in the Text.

From the *University of Minnesota School of Public Health; †University of Minnesota School of Nursing; and ‡VA Medical Center, Minneapolis, Minnesota.

Supported by Agency for Healthcare Research and Quality, US Department of Health and Human Services, Contract No. 290-02-0009, Task Order 1.

The authors of this report are responsible for its content. Statements in the report should not be construed as endorsement by the Agency for Healthcare Research and Quality or the US Department of Health and Human Services.

Reprints: Robert L. Kane, MD, University of Minnesota School of Public Health, D351 Mayo (MMC 197), 420 Delaware Street SE, Minneapolis, MN 55455. E-mail:

© 2007 Lippincott Williams & Wilkins, Inc.