Context Growing evidence suggests that nurse staffing affects the quality of
care in hospitals, but little is known about whether the educational composition
of registered nurses (RNs) in hospitals is related to patient outcomes.
Objective To examine whether the proportion of hospital RNs educated at the baccalaureate
level or higher is associated with risk-adjusted mortality and failure to
rescue (deaths in surgical patients with serious complications).
Design, Setting, and Population Cross-sectional analyses of outcomes data for 232 342 general,
orthopedic, and vascular surgery patients discharged from 168 nonfederal adult
general Pennsylvania hospitals between April 1, 1998, and November 30, 1999,
linked to administrative and survey data providing information on educational
composition, staffing, and other characteristics.
Main Outcome Measures Risk-adjusted patient mortality and failure to rescue within 30 days
of admission associated with nurse educational level.
Results The proportion of hospital RNs holding a bachelor's degree or higher
ranged from 0% to 77% across the hospitals. After adjusting for patient characteristics
and hospital structural characteristics (size, teaching status, level of technology),
as well as for nurse staffing, nurse experience, and whether the patient's
surgeon was board certified, a 10% increase in the proportion of nurses holding
a bachelor's degree was associated with a 5% decrease in both the likelihood
of patients dying within 30 days of admission and the odds of failure to rescue
(odds ratio, 0.95; 95% confidence interval, 0.91-0.99 in both cases).
Conclusion In hospitals with higher proportions of nurses educated at the baccalaureate
level or higher, surgical patients experienced lower mortality and failure-to-rescue
rates.
Nurse understaffing is ranked by the public and physicians as one of
the greatest threats to patient safety in US hospitals.1 Last
year we reported the results of a study of 168 Pennsylvania hospitals showing
that each additional patient added to the average workload of staff registered
nurses (RNs) increased the risk of death following common surgical procedures
by 7%, and that the risk of death was more than 30% higher in hospitals where
nurses' mean workloads were 8 patients or more each shift than in hospitals
where nurses cared for 4 or fewer patients.2 These
findings are daunting given the widespread shortage of nurses, increasing
concern about recruiting an adequate supply of new nurses to replace those
expected to retire over the next 15 years,3 and
constrained hospital budgets. These findings also raise questions about whether
characteristics of the hospital RN workforce other than ratios of nurses to
patients are important in achieving excellent patient outcomes.
Nurses constitute the surveillance system for early detection of complications
and problems in care, and they are in the best position to initiate actions
that minimize negative outcomes for patients.4 That
the exercise of clinical judgment by nurses, as well as staffing adequacy,
is key to effective surveillance may explain the link between higher nursing
skill mix (ie, a higher proportion of RNs among the nursing personnel of a
hospital) and better patient outcomes.5-10
Registered nurses in the United States generally receive their basic
education in 1 of 3 types of programs: 3-year diploma programs in hospitals,
associate degree nursing programs in community colleges, and baccalaureate
nursing programs in colleges and universities. In 1950, 92% of new RNs graduated
from hospital diploma programs,11 whereas by
2001, only 3% graduated from hospital diploma programs, 61% came from associate
degree programs, and 36% were baccalaureate program graduates.12 Surprisingly
little is known about the benefits, if any, of the substantial growth in the
numbers of nurses with bachelor's degrees. Indeed the conventional wisdom
is that nurses' experience is more important than their educational levels.
Despite the diversity of educational programs preparing RNs, and a logical
(but unconfirmed) connection between education and clinical judgment, little
if anything is known about the impact of nurses' education on patient outcomes.13 Results of some studies have suggested that baccalaureate-prepared
nurses are more likely to demonstrate professional behaviors important to
patient safety such as problem solving, performance of complex functions,
and effective communication.14-16 However,
few studies have examined the effect of nurse education on patient outcomes,
and their findings have been inconclusive.17
The 168 Pennsylvania hospitals included in our previous study2 of patient-to-nurse staffing and patient mortality
varied substantially in the proportion of staff nurses holding baccalaureate
or higher degrees. This variability provides an opportunity to conduct a similar
study examining the association between the educational composition of a hospital's
RN staff and patient outcomes. Specifically, we tested whether hospitals with
higher proportions of direct-care RNs educated at the baccalaureate level
or above have lower risk-adjusted mortality rates and lower rates of failure
to rescue (deaths in patients with serious complications). We also examined
whether the educational backgrounds of hospital RNs are a predictor of patient
mortality beyond factors such as nurse staffing and experience. These findings
offer insights into the potential benefits of a more highly educated nurse
workforce.
Data Sources, and Variables
We analyzed outcomes data derived from hospital discharge abstracts
that were merged with information on the characteristics of the treating hospitals,
including unique data obtained from surveys of hospital nurses.2 The
institutional review board of the University of Pennsylvania approved the
study protocol.
Hospitals. The sample consisted of 168 (80%)
of the 210 adult acute-care general hospitals operating in Pennsylvania in
1999 that (1) reported surgical discharges to the Pennsylvania Health Care
Cost Containment Council in the specific categories studied here, (2) had
data on structural characteristics available from 2 external administrative
databases (American Hospital Association [AHA] annual survey18 and
Pennsylvania Department of Health Hospital Questionnaire19),
and (3) had at least 10 nurses responding to our questionnaire, which previous
empirical work demonstrated was sufficient to provide reliable estimates of
survey-based organizational characteristics of the hospitals. Six of the excluded
hospitals were Veterans Affairs hospitals, which do not report discharge data
to the state. Twenty-six hospitals were excluded because of missing data,
most often because their reporting to external administrative sources was
done as aggregate multihospital entities. Ten small hospitals, most of which
had 50 or fewer beds, had an insufficient number of nurses responding to the
questionnaire to be included.
A 50% random sample of RNs residing in Pennsylvania and on the rolls
of the Pennsylvania Board of Nursing received questionnaires at their homes
in the spring of 1999. Surveys were completed by 10 184 nurses, an average
of more than 60 nurses per hospital, and the 52% response rate compares favorably
with other voluntary, anonymous surveys of health professionals.20 We
compared our data with information from the AHA annual survey and found that
the number of nurses from each hospital responding to our survey was directly
proportional to the number of RN positions in each hospital. This suggests
similar response rates across hospitals and no response bias at the hospital
level. Moreover, demographic characteristics of the respondents paralleled
those of Pennsylvania hospital nurses in the National Sample Survey of Registered
Nurses.21 For example, the mean ages of Pennsylvania
hospital nurses in our sample and in the National Sample Survey of Registered
Nurses were 40 and 41 years, respectively; the percentages of Pennsylvania
hospital nurses working full-time were 66% and 69%, respectively; and those
having earned bachelor of science in nursing (BSN) degrees were 30% and 31%,
respectively.
Hospital staff nurses were asked to indicate whether their highest credential
in nursing was a hospital school diploma, an associate degree, a bachelor's
degree, a master's degree, or another degree. The proportion of nurses in
each hospital who held each type of credential was computed. Because the educational
preparation of the 4.3% of nurses who checked "other" was unknown, their answers
were not included in our hospital-level measures of educational qualifications.
It was later verified that this decision did not bias the results. Because
there was no evidence that the relative proportions of nurses holding diplomas
and associate degrees affected the patient outcomes studied, those 2 categories
of nurses were collapsed into a single category and the educational composition
of the hospital staff was characterized in terms of the percentage of nurses
holding bachelor's or master's degrees.
Two further variables were derived from the nurse survey. Nursing workload
was computed as the mean number of patients assigned to all staff nurses who
reported caring for at least 1 but fewer than 20 patients on the last shift
they worked. Because nurse experience was an important potential confounding
variable related to both clinical judgment and education, the mean number
of years of experience working as an RN for nurses from each hospital was
also calculated and used in the analyses.
Three hospital characteristics were used as control variables: size,
teaching status, and technology. Hospital-level data were obtained from the
1999 AHA annual survey and the 1999 Pennsylvania Department of Health Hospital
Survey. Three size categories (<100 beds, 101-250 beds, ≥251 beds) were
used. Hospitals without any postgraduate medical residents or fellows (nonteaching)
were distinguished from those with 1:4 or smaller trainee-to-bed ratios (minor
teaching) and those with ratios higher than 1:4 (major teaching). High-technology
hospitals were those that had facilities for either open-heart surgery, major
organ transplantations, or both.
Patients and Patient Outcomes. Discharge abstracts
for the universe of 232 342 patients aged 20 to 85 years who underwent
general surgical, orthopedic, or vascular procedures from April 1, 1998, to
November 30, 1999, in the 168 nonfederal hospitals were obtained from the
Pennsylvania Health Care Cost Containment Council, which checks the data for
completeness and quality. A list of the diagnosis related groups studied was
provided previously.2
We examined the association between the educational attainments of nurses
across hospitals and both deaths within 30 days of hospital admission (derived
by linking discharge abstract data and Pennsylvania vital statistics data)
and deaths within 30 days of admission among patients who experienced complications
(failure to rescue). Patient complications were determined with International Classification of Diseases, Ninth Revision, Clinical Modification
(ICD-9-CM) codes in the secondary diagnosis and procedure fields of
discharge abstracts indicative of 39 clinical events using protocols drawing
on expert consensus as well as empirical evidence to distinguish complications
from preexisting comorbidities.22-24
The 2 patient outcomes studied were risk-adjusted by including 133 variables
in our models, including age, sex, whether the admission was a transfer from
another hospital, whether it was an emergency admission, a series of 48 variables
indicating surgery type, dummy variables indicating the presence of 28 chronic
preexisting conditions as classified by ICD-9-CM codes,
and interaction terms chosen on the basis of their ability to predict mortality
and failure to rescue in the present data set. Construction of the patient
risk adjustment models used an approach similar to that reported by Silber
and colleagues.22-26 The c statistic for the mortality risk adjustment model was
0.89 and for the failure to rescue model, 0.81.
We also estimated and controlled for the effect of having a board-certified
surgeon on risk for mortality and failure to rescue. For each patient, the
license number of the operating physician of record was matched to a physician's
name using a public use file from the Pennsylvania Bureau of Professional
and Occupational Affairs, and subsequently to records from the American Board
of Medical Specialties directory of board-certified medical specialists.27 A dummy variable was constructed to indicate whether
or not the operating physician was board-certified in general surgery or another
surgical specialty. A second dummy variable was used to identify patients
(8% of all patients) with operating physicians whose license numbers could
not be linked to names to determine board-certification status. Use of these
2 variables in tandem produced a reasonable way of controlling for surgeon
qualifications in our models.
Descriptive statistics (means, SDs, and percentages) and significance
tests (χ2 and F tests) were computed to compare groups of hospitals
that varied in terms of their educational composition on hospital characteristics,
including nurse experience and nurse staffing, and patient characteristics.
Logistic regression models were used to estimate the effects of a 10% increase
in the proportion of nurses who had a bachelor's or master's degree on patient
mortality and failure to rescue, and to estimate the effects of nurse staffing,
nurse experience, and surgeon board certification. The associations of educational
composition, staffing, experience of nurses, and surgeon board certification
with patient outcomes were computed before and after controlling for patient
characteristics (demographic characteristics, nature of the hospital admission,
comorbidities, and relevant interaction terms) and hospital characteristics
(bed size, teaching status, and technology).
To account for the clustering of patients within hospitals in our sample,
all model estimates were computed using Huber-White (robust) procedures to
adjust the SEs of the estimated parameters. Direct standardization estimates
derived from the final model are presented to indicate the size of the effects
of educational composition of nursing staff independently of and jointly with
nurse staffing levels. With all patients and using the final fully adjusted
models for predicting death and failure to rescue, the probabilities of poor
outcomes were calculated for patients in hospitals assuming that 20%, 40%,
and 60% of the hospital RNs held bachelor's or master's degrees and under
various patient-to-nurse ratios (4, 6, and 8 patients per nurse), with all
other patient and hospital characteristics unchanged.28 All
analyses were conducted using STATA version 7.0 (STATA Corp, College Station,
Tex), using P<.05 as the level of statistical
significance.
Characteristics of Hospitals and Patients
Table 1 provides information
on characteristics of the 168 hospitals in our sample. About 19% of the hospitals
had more than 250 beds, 36% were teaching hospitals, and 28% had high-technology
facilities. Across all hospitals, nurses had a mean (SD) of 14.2 (2.7) years
of experience and a mean (SD) workload on their last shift of 5.7 (1.1) patients.
The proportion of staff nurses with bachelor's degrees or higher degrees ranged
from 0% to 70% across the hospitals. In 20% of the hospitals (34/168) less
than 20% of staff nurses had BSN or higher degrees, while in 11% of the hospitals
(19/168) 50% or more of the nurses had BSN or higher degrees. Hospitals with
higher percentages of nurses with BSN or master's degrees tended to be larger
and have postgraduate medical training programs, as well as high-technology
facilities. Hospitals with higher proportions of baccalaureate- and master's-prepared
nurses also had slightly less experienced nurses on average and significantly
lower mean workloads. The strong association between the educational composition
of hospitals and other hospital characteristics, including nurse workloads,
makes clear the need to control for these latter characteristics in estimating
the effects of nurse education on patient mortality.
Table 2 describes characteristics
of the patients in our sample and how they varied across hospitals with different
nurse educational compositions. Of the patients studied, 43.7% were men and
the mean (SD) age was 59.3 (16.9) years. Of the 232 342 patients, 53 813
(23.2%) experienced a major complication not present on admission, 4535 (2.0%)
died within 30 days of admission, and the death rate among patients with complications
(failure to rescue) was 8.4%. The 2 largest categories of surgical procedures
patients underwent were orthopedic (51.2%) and digestive tract/hepatobiliary
(36.4%) procedures.
The most common patient comorbidities were hypertension (34.4%) and
diabetes (13.5%). While the largest proportion of patients (58 329 or
25%) were cared for in hospitals in which 30% to 39% of the nurses were at
least BSN-educated, the numbers ranged across the sample (Table 2). Moreover, characteristics of patients, including whether
the operating physician was a board-certified surgeon, differed across the
groups of hospitals defined by the percentage of nurses with BSN or higher
degrees, although few of these characteristics varied across groups in a consistent
pattern.
Effects of Hospital RN Education on Mortality and Failure to Rescue
Table 3 presents odds ratios
(ORs) representing the raw or unadjusted effects of nurse education, staffing,
and experience, and the effect of a board-certified surgeon as operating physician.
Also in Table 3 the adjusted ORs
show the effects of those factors in a model controlling for all of these
factors and for other hospital and patient characteristics. There was a statistically
significant relationship between the proportion of nurses in a hospital with
bachelor's and master's degrees and the risks of both mortality and failure
to rescue, both before and after controlling for other hospital and patient
characteristics.
Each 10% increase in the proportion of nurses with higher degrees decreased
the risk of mortality and of failure to rescue by a factor of 0.95, or by
5%, after controlling for patient and hospital characteristics. This adjusted
OR of 0.95 (95% confidence interval, 0.91-0.99) is a multiplicative parameter.
To estimate how much of a difference would be expected between hospitals in
which 20% vs 60% of the nurses had at least BSNs, it should be taken to the
fourth power (since the difference between 20% and 60% is equivalent to four
10% intervals). The resultant ratio (0.954 = 0.81) indicates that
all else being equal, the odds of 30-day mortality and failure to rescue would
be 19% lower in hospitals where 60% of the nurses had BSNs or higher degrees
than in hospitals where only 20% of nurses did.
All 3 of the other clinician characteristics studied (nurse staffing,
experience, and board-certified surgeon as operating physician) had significant
associations with mortality before controlling for each other, the educational
composition of RNs, and all other patient and hospital characteristics. The
final model indicates only very slight changes in the parameters estimating
the nurse staffing effect that we previously reported2 when
nurse education is added (from a 7% increase in risk of both negative outcomes
with a 1 patient-per-nurse increase in mean workload originally reported to
a 6% increase in mortality risk and a 5% increase in risk of failure to rescue).
Nurses' years of experience were not found to be a significant predictor
of mortality or failure to rescue in the full models. The strong and significant
decrease in mortality associated with having a board-certified surgeon as
operating physician is largely explained by the tendency of patients with
board-certified surgeons to be treated at hospitals with other characteristics
associated with better outcomes. None of the interaction terms created by
combining these 4 variables achieved statistical significance, suggesting
that nurse education, nurse staffing, and surgeon board certification operate
independently of each other in predicting mortality and failure to rescue.
These effects imply that altering the educational background of hospital
nurses by increasing the percentage of those earning a BSN would produce substantial
decreases in mortality rates for surgical patients generally and for patients
who develop complications. Direct standardization techniques were used to
predict the excess deaths in all patients and patients with complications
that would be expected with varying levels of nurse educational levels and
workloads. As Table 4 shows, if
the proportion of BSN nurses in all hospitals was 60% rather than 20%, 3.6
fewer deaths per 1000 patients (21.1 − 17.5) and 14.2 fewer deaths per
1000 patients with complications (failure to rescue) would be expected. Moreover, Table 4 indicates that the effect on mortality
of a 20% increase in the percentage of BSNs in the workforce would be roughly
equivalent to the effect of a reduction in mean nurse workload of 2 patients,
and that both the mortality and failure-to-rescue rates would be decidedly
lower if both the workloads were lighter and the workforce were composed of
higher percentages of BSN-prepared nurses.
To our knowledge, this study provides the first empirical evidence that
hospitals' employment of nurses with BSN and higher degrees is associated
with improved patient outcomes. Our findings indicate that surgical patients
cared for in hospitals in which higher proportions of direct-care RNs held
bachelor's degrees experienced a substantial survival advantage over those
treated in hospitals in which fewer staff nurses had BSN or higher degrees.
Similarly, surgical patients experiencing serious complications during hospitalization
were significantly more likely to survive in hospitals with a higher proportion
of nurses with baccalaureate education.
When the proportions of RNs with hospital diplomas and associate degrees
as their highest educational credentials were examined separately, the particular
type of educational credential for nurses with less than a bachelor's degree
was not a factor in patient outcomes. Furthermore, mean years of experience
did not independently predict mortality or failure to rescue, nor did it alter
the association between educational background or of staffing and either patient
outcome. These findings suggest that the conventional wisdom that nurses'
experience is more important than their educational preparation may be incorrect.
The improved outcomes associated with higher levels of BSNs in a hospital
was found to be independent of and additive to the associations of superior
outcomes in hospitals with better nurse staffing we reported previously.2 Thus, both lower patient-to-nurse ratios and having
a majority of RNs educated at the baccalaureate level appear to be jointly
associated with substantially lower mortality and failure-to-rescue rates
for patients undergoing common surgical procedures.
In our sample of 168 Pennsylvania hospitals in which the proportion
of nurses with bachelor's degrees and mean patient-to-nurse ratios varied
widely, 2% (4535/232 342) of the surgical patients undergoing the procedures
we studied died within 30 days of hospital admission. Our results imply that
had the proportion of nurses with BSN or higher degrees been 60% and had the
patient-to-nurse ratio been 4:1, possibly 3810 of these patients (725 fewer)
might have died, and had the proportion of baccalaureate nurses been 20% and
had staffing uniformly been at 8:1 patient-to-nurse ratios, 5530 (995 more)
might have died. While this difference of more than 1700 deaths across 2 educational
and staffing scenarios is approximate, it represents a conservative estimate
of preventable deaths potentially attributable to nurses' education and RN
staffing levels because our patient sample represents only about half of all
surgical cases in the study hospitals.
One limitation of our analysis is the potential for response bias in
the education and staffing measures derived from the nurse survey, given a
52% response rate. However, examining the Pennsylvania respondents in the
probability-based National Sample Survey of Registered Nurses conducted in
2000,21 we found no evidence of overall differences
between our sample and Pennsylvania hospital staff nurses at large in terms
of job satisfaction or demographic characteristics, including education.
A second limitation relates to study design. Longitudinal data sets,
preferably including hospitals from more than 1 state, will be essential for
establishing the generalizability of these findings as well as establishing
whether and how levels of baccalaureate-prepared nurses and nurse staffing
in a hospital are causally related to patient outcomes. Also, as in any research
drawing on administrative patient outcomes data, there is a potential for
differences in completeness and consistency of diagnostic coding across hospitals
to influence risk adjustment.29
A number of checks on the validity of these findings were completed.
Allowing nurse education to have a nonlinear effect and testing whether the
effect of education varied across levels of educational composition using
quadratic and dummy variables did not significantly improve model fit, suggesting
that incremental increases in more educated nurses in a hospital were associated
with progressively better outcomes. Including the small proportion of nurses
who checked "other" as their highest degree with nurses in the baccalaureate
or higher category or in the associate degree or diploma category rather than
omitting them from calculations yielded no change in the estimated associations
between education and patient outcomes. In an attempt to determine whether
unobserved variables that distinguished patients treated in hospitals with
different levels of nurse education, we computed propensity scores30 representing the likelihood that patients with various
characteristics were treated in hospitals with high and low levels of baccalaureate
nurses. These scores were not a significant predictor of mortality or of failure
to rescue, nor did they significantly alter our estimates of the association
between education and outcomes.
Research suggests that nurse executives in university teaching hospitals
prefer a nurse workforce with approximately 70% prepared at the baccalaureate
level and estimate that current levels average 51%. Also, community hospital
nurse executives prefer to have 55% of their RNs educated at the baccalaureate
level.31 Data are not currently available to
estimate the proportion of hospitals nationally that have 50% or more of their
RN workforces prepared at the BSN level or higher, but since only 11% of Pennsylvania
hospitals met this standard in our sample there appears to be a wide gap between
the preferences of hospital executives and current staffing patterns.
Only 43% of all hospital staff nurses nationally in 2000 were prepared
at the BSN level or higher. Enrollments in baccalaureate nursing programs
declined by almost 10% from 1995 to 2000, although the past few years have
seen an upturn.21,32 The return
of diploma- and associate degree–prepared RNs to colleges and universities
after their initial preparation has been an important source of baccalaureate-prepared
nurses. About 22% of currently employed hospital RNs with BSN or higher degrees
received them after their basic educations.21 However,
the proportion of hospital nurses pursuing further studies declined from 14%
in 1984 to 9% in 2000, as did the proportion of hospital nurses who received
tuition assistance from their employers (from 66% in 1992 to 53% in 2000).21,33 Meeting the demand for baccalaureate-prepared
hospital nurses requires renewed support and incentives by employers to encourage
nurses to pursue education to the level of baccalaureate and beyond.
In the current nurse shortage, as in previous ones, public policy discussion
has centered on how to increase the supply of RNs. However, little attention
has been paid to considering where investments in public funds in the 2 major
educational pathways into nursing practice—associate or bachelor's degree
programs—will best serve the public good and the interests of employers.
Nursing education policy reports published in the past decade concluded that
the United States has an imbalance in the educational preparation of its nurse
workforce with too few RNs with BSN and higher degrees.34-36 Our
findings provide sobering evidence that this imbalance may be harming patients.
Our documentation of significantly better patient outcomes in hospitals
with more highly educated RNs at the bedside underscores the importance of
placing greater emphasis in national nurse workforce planning on policies
to alter the educational composition of the future nurse workforce toward
a greater proportion with baccalaureate or higher education as well as ensuring
the adequacy of the overall supply. Public financing of nursing education
should aim at shaping a workforce best prepared to meet the needs of the population.
Finally, our results suggest that employers' efforts to recruit and retain
baccalaureate-prepared nurses in bedside care and their investments in further
education for nurses may lead to substantial improvements in quality of care.
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