title: Nurse staffing levels revisited: a consideration of key issues in nurse staffing levels and skill mix research.
abstract: OBJECTIVE
  This paper revisits the published evidence relating to how nurse staffing levels impact on patient, nurse and service outcomes and considers the implications of this body of research for nurse managers in their quest to determine optimum nursing numbers.
  
  
  BACKGROUND
  Within the context of the recognized global nursing shortage and particular local pressures within international health services, questions of appropriate nurse staffing levels and skill mix are once again becoming increasingly important. It would seem that the determination of optimum nurse staffing levels and skill mix is a central issue in relation to health service governance, service user involvement, as well as in the recruitment, retention and well-being of nursing staff across the service sectors.
  
  
  METHODS
  A review of published evidence was carried out, applying key principles of the systematic method, in order to facilitate the identification of current factors and issues in nurse staffing levels research. The review did not seek to address a specific research question. The search covered 10 years from 1998 to 2008 and identified more than 500 relevant papers, giving a wide international perspective.
  
  
  RESULTS
  The majority of research in the field relates to the acute service sector and there are considerable similarities in issues that transcend international boundaries. Much of the research focuses on the impact on patients and nurses of 'poor' nurse staffing levels. More recent studies have explored the impact of nurse staffing levels on the service organization itself. However, while there may be an association between models of nurse staffing and outcomes, there is insufficient evidence to establish a causal relationship between these factors. In this context it is perhaps time to reconsider how nursing outcomes are defined and measured. IMPLICATIONS FOR NURSING MANAGEMENT AND CONCLUSION: Nurse managers, commissioners of services and workforce planners need to be cognisant of key issues and analyses in the consideration of nurse staffing levels. Not least of these is the need for a healthy degree of caution regarding the supposed objectivity, scientific basis, or evidence base, for rational calculation of optimum nurse staffing levels.
authors.affiliation: School of Health Sciences, Thompson Yates Building, University of Liverpool, Liverpool L69 3GB, UK. m.flynn@liverpool.ac.uk
authors.forename: Maria
authors.initials: M
authors.lastname: Flynn
authors.forename: Mick
authors.initials: M
authors.lastname: McKeown
mesh_terms: D054976:Clinical Governance; D015986:Confounding Factors, Epidemiologic; D055318:Evidence-Based Nursing; D006272:Health Facility Environment; D006301:Health Services Needs and Demand; D006801:Humans; D038622:Internationality; D016294:Models, Nursing; D017146:Models, Organizational; D009718:Nurse Administrators / Q000458:organization & administration; D015401:Nursing Administration Research / Q000458:organization & administration*; D009740:Nursing Staff / Q000193:education / Q000600:supply & distribution; D017063:Outcome Assessment, Health Care / Q000458:organization & administration*; D010560:Personnel Selection / Q000458:organization & administration; D010561:Personnel Staffing and Scheduling / Q000458:organization & administration*; D011787:Quality of Health Care / Q000458:organization & administration; D012107:Research Design; D006113:United Kingdom; D016526:Workload; D017132:Workplace / Q000458:organization & administration