Nurse Staffing and Patient Outcomes:
Examining the Evidence in Acute Care and Nursing Homes
December 2006 (download pdf file)

Written by
Dr. Sandra A. LeVasseur, PhD, RN
Associate Director, Research
Hawaii State Center for Nursing - School of Nursing and Dental Hygiene
University of Hawai‘i at Mānoa, Honolulu, Hawai‘i

I. Introduction

The Senate Concurrent Resolution (S.C.R. NO.76, S.D.1) is titled “Urging Healthcare Facilities in the State of Hawaii to Implement the ‘Utilization Guide for the American Nurses Association Principles for Safe Staffing.’”

The Institute of Medicine’s (IOM) report, “To Err is Human: Building a Safer Health System” (2000) ¹ acknowledges

‘the availability of nurses, the organization of nursing care, and the types of nursing interventions vary by institution. Structuring nurse staffing (e.g., availability of nurses, organizational models of nursing care) and care interventions to meet “safe thresholds” could be considered a patient safety practice. However, no studies have evaluated thresholds explicitly.’ (p. 424.)

Many are concerned with the capacity of registered nurses to maintain patient safety. The registered nurse role encompasses both surveillance and care for early identification and intervention of complications and problems in care. As Aiken ² has reports ‘as the registered nurse shortage continues, with burdensome nurse workloads, high turnover, and many unfilled hospital positions, concern is growing about the ability of nurses to fill the role effectively’.

In 2000, the American Nurses Association ³ reported that health care containment costs were affecting hospitals in three ways. First, patients have a higher acuity throughout their inpatient stay compared to previous years and require more intense nursing care. Second, the number of patients cared for by the nursing workforce (i.e., registered nurses (RNs), licensed practical nurses (LPNs), and certified nurse assistants or nurse assistants (CNA/ NAs) has increased in many settings. Third, the education and training requirements of many nurses in clinical settings is not sufficient. Since this time, staffing issues facing the profession have grown more complex as a result of numerous issues such as the shortage of registered nurses. There is concern as to whether the increased acuity of patients, the increased workload, the declining levels of training among nursing staff, and the nursing workforce shortage threatens the quality of care in acute care settings.

Table 1. The Nurse Workforce and Nurse Staffing Levels

A number of states across the country have engaged in dialogue concerning the implementation of nurse-patient ratios. In 1999, the California State Legislature passed Assembly Bill 394 and became the first state in the nation to establish minimum nurse-patient ratios. Thus, limiting the number of patients that a registered nurse (RNs) or licensed practical nurse (LPN) may care for at any one time. That legislation, AB 394, charged the California Department of Health Services (CDHS) with determining those staffing standards. The CDHS regulations implementing the new ratios requirements went into effect in January, 2004. The bill’s proponents cited a growing body of research linking nurse staffing levels and positive patient care outcomes.

However, the quality of the research evidence concerning the impact of nurse staffing levels on patient outcomes requires rigorous evaluation to inform policy. Thus, the primary purpose of this paper is to identify and discuss the quality of evidence concerning effects of nurse staffing on patient outcomes and determine whether the literature supports setting specific nurse-patient ratios in acute care hospitals. The paper will also identify work related to staffing levels and quality in nursing homes. Three systematic reviews and other supporting evidence will be used to appraise the evidence concerning nurse staffing levels and patient outcomes primarily in acute care and secondarily in nursing homes.

Measuring Staff Levels and Patient Outcomes
The challenge faced in attempting to synthesize information, and establishing what the evidence is concerning staff levels and impact on patient safety, is the lack of standardization in definition 3 and measurement of constructs such as ‘nurse staffing levels’. This lack of consistency creates major limitations when attempting to compare variables across studies. As shown in Table 3 studies can use a variety of variables to measure nurse staffing. Of these measures, many investigators choose to examine the structural elements of nursing care. ^1,4-7 However, a variety of different concepts can be used to represent this construct including number of nurses, number of nurse hours, percentage or ratios of nurses to patients, skill mix, organization of nursing care delivery or organizational culture, nurse workload, nurse stress, or qualification of nurses.

Table 2. Measures of Nurse Staffing

Other, less frequently used constructs are the intervention or process measures of care including studies based on the ‘science of nursing’ or ‘nurses as the intervention’. For the purposes of this paper the intervention or process measures of care will not be discussed in this paper.

Systematic Reviews
Healthcare providers, consumers, researchers, and policy makers are inundated with unmanageable amounts of information. We need systematic reviews to efficiently integrate valid information and provide a basis for rational decision making. ⁸ Systematic reviews establish where the effects of healthcare are consistent and where they may vary significantly. Systematic reviews are valuable in informing policy and decision making. They are useful where there is uncertainty regarding the potential benefits or harm of an intervention and when there are variations in practice. By locating and synthesizing evidence from primary studies, systematic reviews provide empirical answers to focused questions.

Systematic Reviews versus Traditional Reviews
Systematic reviews differ from other types of review in that they adhere to a strict scientific design in order to make them more comprehensive, to minimize the chance of bias, and so ensure their reliability. They use a replicable, scientific and transparent approach which seeks to minimize bias. Rather than reflecting the views of the authors or being based on only a (possibly biased) selection of the published literature, they contain a comprehensive summary of the available evidence. The techniques used to ensure the reliability of the review results will vary according to whether the review is quantitative or qualitative. However, the techniques are comparable and serve to define the systematic review genre, regardless of whether it is intended to be qualitative or quantitative. All systematic reviews will include some qualitative elements. However, not all systematic reviews contain statistical analysis or synthesis.

The Hierarchy of Evidence
A simple assessment of the appropriateness of a study design is often used to guarantee a minimum level of quality. Study designs that are included in a review should be clearly stated in the inclusion/exclusion criteria in the protocol of the systematic review. As shown in Table 1 the quality threshold of primary studies can be determined by generating a hierarchy of study designs and setting a cut-off level for study selection. This hierarchy of study designs in Table 1 will be cited in tables of evidence used throughout this paper.

Table 3. Hierarchy of study designs*

Table 4. The Hierarchy of outcome measures