What is the impact of professional nursing on patients' outcomes globally? An overview of research evidence.

Background: Nursing is an integral part of all healthcare services, and has the potential of having a wide and enduring impact on health outcomes for a global ageing population. Over time nurses have developed new roles and assumed greater responsibilities. It is increasingly important to demonstrate the safety and overall impact of nurses' practice through research, to support the case for greater investment and development of nursing services around the world.

Objective: To provide an overview of existing research evidence on the impact of nursing on patient outcomes, identify gaps in evidence, and point to future priorities for global research. Specifically to address two questions: what is the evidence that nursing contributes to improving the health and well-being of populations?; and where should research activity be focused to strengthen the evidence base for the impact of nursing?

Methods: A search of the literature from 1996 using CINAHL, MEDLINE, the Cochrane Library, Google Scholar and the NICE evidence databases using the key words: nursing, nurse led, nursing interventions and patient outcomes. Initial analysis of the retrieved citations to reveal clusters of evidence of nursing impact in clinical areas which had been subject to systematic/integrative reviews or meta-analyses. Further analysis of these reviews to provide an overview of the research evidence for nurses' contributions to healthcare to inform discussion on future research agendas. We use the terms low, moderate and high quality evidence to reflect the assessments made by the review authors whose work is presented throughout.

Results: Analysis of 61 reviews, including ten Cochrane reviews and two scoping/selective reviews to provide a summary of the research evidence for nurses' contributions to healthcare in the following areas of practice: nursing in acute care settings; nurses' involvement in public health; the contribution of specialist nurse and nurse-led services to the management of chronic disease; comparison of care provided by nurses and doctors; and task shifting to invasive procedures.

Conclusions: There is evidence that adequate numbers of well-educated nurses working in acute care areas can reduce the risk of patient mortality, although the evidence for this is confined to studies in high income countries and the evidence is not sufficiently robust to draw up definitive nurse: patient ratios. There is also moderate evidence that well trained nurses can produce health outcomes that are equivalent to those of doctors for patients with a range of chronic health problems, particularly for those patients managed in primary care, and that nurse-led care may be more effective than medical care in promoting patient adherence to treatment and patient satisfaction. There is low to moderate evidence for the benefits of parenting support programmes delivered by nurses on a range of health outcomes; and for the impact of home visiting on improving function and other health service outcomes for older people. The wider societal benefits of home visiting by nurses and the impact of this on long term outcomes and related cost-effectiveness of home visiting has not been established. There is limited available information regarding the wider global impact of increasing the numbers of nurses and their contribution to healthcare through improved education. Moreover there is very little evidence for the cost-effectiveness of changing care providers from doctors to nurses and as the majority of cost data available has tended to come from studies based in higher income countries, their external validity in terms of applicability to settings in low and middle income countries is questionable. In addition to effectiveness, cost and safety, future research needs to address how implementing expanded nursing roles and task shifting impacts on the morale, retention, and professional development of nurses and the other workforces, and the longer term implications of these developments both locally and internationally.