Evidence Report/Technology Assessment: Number 74
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Under its Evidence-based Practice Program, the Agency for Healthcare Research and Quality (AHRQ) is developing scientific information for other agencies and organizations on which to base clinical guidelines, performance measures, and other quality improvement tools. Contractor institutions review all relevant scientific literature on assigned clinical care topics and produce evidence reports and technology assessments, conduct research on methodologies and the effectiveness of their implementation, and participate in technical assistance activities.
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Overview / Reporting the Evidence / Methodology / Findings / Future Research / Availability of Full Report
Do the working conditions of health care
personnel contribute to the incidence of medical
errors? This question is often raised during public
discussion of ways to improve patient safety. How
much do issues of nurse staffing and doctors'
hours, for example, contribute to the estimated
44,000 to 98,000 deaths per year in hospitals due
to medical errors?
The objective of this report is to identify and
summarize evidence from the scientific literature
on the effects of health care working conditions on
patient safety. The report also identifies relevant
information from industries outside of heath care.
Working conditions were classified into five
- Workforce staffing.
- Workflow design.
- Personal/social factors.
- Physical environment.
- Organizational factors.
The classification system for
working conditions was derived from existing
literature and advice from an expert panel. It is
consistent with human factors research in multiple
disciplines and industries such as aviation and
nuclear power. Workforce staffing refers to job
assignments and includes four principal aspects of
job duties: the volume of work assigned to
individuals, the professional skills required for
particular job assignments, the duration of
experience in a particular job category, and work
schedules. Workflow design focuses on the job
activities of health care workers, including
interactions among workers and the nature and
scope of the work as tasks are completed.
Personal/social factors refer to individual and
group factors such as stress, job satisfaction, and
professionalism. Physical environment includes
aspects of the health care workplace such as light,
aesthetics, and sound. Organizational factors are
structural and process aspects of the organization
as a whole, such as use of teams, division of labor,
and shared beliefs.
The researchers developed an analytic
framework to define how working conditions are
related to patient safety. Antecedent conditions,
which are external factors such as personal
characteristics of workers and fixed structural
characteristics of the system (e.g., geographic
location, regulations, and legislation), can affect
the impact of working conditions on patient
safety. Working conditions are viewed either as
resources that improve work quality or as demands
that impede work quality. Working conditions
potentially affect patient safety, which leads to
The researchers also developed a model of
patient safety to help frame the key questions and
provide a way to synthesize data reported in
studies. The model is drawn from injury analysis
and incorporates elements of both processes and
outcomes. It is based on the relationships between
medical errors (defined as the failure of a planned
action to be completed as intended, or the use of a
wrong plan) and adverse outcomes (injuries caused
by health care rather than underlying disease).
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Reporting the Evidence
The key questions derive directly from the
analytic framework. Each key question applies to
all five categories of working conditions; specific
working conditions are inserted into the key
questions for each of the five categories. The key
questions permitted the research team to classify
the entire body of evidence for each category and
to derive a judgment about the strength of
evidence regarding the contribution of the
working condition categories to overall patient safety.
The six key questions are:
- Do working conditions affect patient outcomes that are
related to patient safety?
- Do working conditions affect the rate of medical errors?
- Do working conditions affect the rate of recognition of
medical errors after they occur?
- Do working conditions affect the probability that adverse
events will occur following detected or undetected medical
- Does the complexity of the plan of care influence whether
working conditions affect patient outcomes that are
related to patient safety?
- Do working conditions affect measures of service quality
in industries other than health care?
The populations of interest for this report include health care
workers, patients, and workers in industries other than health
care. The outcomes considered are defined in the analytic
framework and model of patient safety and hence the key
questions. They include patient outcomes, medical errors, and
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To identify relevant literature the researchers searched five
databases: MEDLINE® (with HealthSTAR), CINAHL®,
PsycINFO, EBSCO, and the Campbell Collaboration. The
Campbell Collaboration is an international effort modeled on
the Cochrane Collaboration. The Campbell Collaboration
prepares, maintains, and disseminates systematic reviews of the
effectiveness of social and educational policies and practices. Its
Social, Psychological, Educational and Criminological Trials
Register (C2-SPECTR) is a registry of randomized and possibly
randomized trials in education, social work and welfare, and
criminal justice. The researchers searched MEDLINE® (1980 to
2002) and CINAHL® (1982 to 2002) to capture the health care
literature, and they searched PsycINFO (1984 to 2002) and
EBSCO (1980 to 2002) to capture literature outside of health
care. The searches were limited to the years 1980 to 2002
because most contemporary quality management and
accreditation systems have been implemented since 1980.
Searches were performed separately for each of the five
categories of working conditions (workforce staffing, workflow
design, personal/social factors, physical environment, and
organizational factors). Search strategies were developed by the
lead investigator for each working condition category, using
MeSH® terms where possible. Searches were limited to human
studies and those in the English language or with English
abstracts. The searches resulted in a total of 23,179 citations.
The lead investigator for each working condition category
applied a set of inclusion/ exclusion criteria to the
titles/abstracts in their area. To assess the interobserver
reliability of this process, dual reviews were performed on
random samples of citations. Full-text papers were retrieved for
studies judged to be possibly relevant and assessed again for
relevance using the same inclusion/exclusion criteria.
Studies were then abstracted using data-abstraction
guidelines, and quality ratings were applied. The researchers
rated design suitability and quality of study execution. They
constructed evidence tables, and a second investigator reviewed
the studies to verify the accuracy of the summary information
and quality ratings.
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After the investigators had reviewed all citations for possible
relevance, over 1,000 papers were retrieved and read; of these,
912 papers were excluded from further review. Of the excluded
papers, 730 were health care related and 182 focused on
industries outside of health care. The bibliography includes the
A total of 115 studies were found to have evidence relevant
for answering the key questions and were included in evidence
tables. In some cases, additional studies were found to provide
evidence that was indirectly related to key questions. The
volume of available evidence varied considerably among the
categories of working conditions, which reflects extensive
variability in the amount of research conducted in these
With the exception of Key Question 4 (regarding impact on
the probability of adverse events), valid evidence was found for
all key questions. The largest amount of available evidence
applied to Key Question 1, and there was sufficient evidence to
conclude that several different specific working conditions
affect outcomes that are related to patient safety. There also was
sufficient evidence to conclude that some working conditions
affect rates of medical errors (Key Question 2).
The results of studies of factory and office workers are
generally consistent with similar studies performed in health
care settings (Key Question 6). These findings suggest that
studies of working conditions in other industries are relevant to
health care and can be used to expand the fund of knowledge
about working conditions in health care.
The systematic literature review provided sufficient evidence
to make specific recommendations about strategies for
improving patient safety. These recommendations can be
summarized as follows:
- Strategies to increase staffing levels of licensed and
unlicensed nurses in both acute-care hospitals and nursing
homes will likely lead to improved patient outcomes.
- Preventable complications are lower when complex
technical procedures are performed by physicians who
conduct them frequently (i.e., high-volume physicians).
- Duration of experience of the health professional is
associated with better patient outcomes for some types of
- Systems to reduce interruptions and distractions will likely
reduce the incidence of medical errors.
- Systems to improve information exchange, transfer of
responsibility, and continuity of care between hospital and
nonhospital settings ("hand offs") decrease medication
errors and, in some settings, hospital re-admissions.
- Levels of ambient noise in health care settings do not
adversely affect patient safety.
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For several specific working conditions, there is evidence that
the working condition affects patient safety, but the evidence
comes from few studies and is insufficient to draw clear
conclusions. Further research to clarify and confirm the
findings from existing studies will permit judgments to be
made about the importance of these working conditions. The
areas in which such targeted research is indicated include
workplace stress, workplace lighting conditions, and several
aspects of organizational factors.
With the exception of selected work processes pertaining to
workflow design, most of the evidence on the relationship of
working conditions to patient safety is derived from non-experimental
studies. Thus, there remain unanswered questions
about the magnitude of improvement in patient safety that can
be achieved by improving working conditions. There is a need
for significant future research that evaluates how specific
workplace interventions will affect patient outcomes. Such
research could be conducted as clinical trials or as carefully
designed demonstration projects and program evaluation
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Availability of Full Report
The full evidence report from which this summary was
taken was prepared for AHRQ by the Oregon Health and Science University Evidence-based Practice Center under contract number 290-97-0018. Printed copies may be obtained free of charge
from the AHRQ Publications Clearinghouse by calling 1-800-358-9295. Requesters should ask for Evidence Report/Technology Assessment No. 74, The Effect of Health Care Working Conditions on Patient Safety.
The Evidence Report is also online on the National Library of Medicine Bookshelf, or can be downloaded as a PDF File (735 KB) [Plugin Software Help].
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Current as of March 2003
AHRQ Publication No. 03-E024