Limitations
A limitation of the study was that readmissions through
other EDs in the region were not detected by the present
study design, though hospital management and clinical
staff claim that this fraction is small. Some bias may also
have been introduced since no cases from December
2012 were included; however, most of the winter season
was included and the study period covered 2 years,
which would limit the effects of such bias to some extent.
Moreover, even though the 30-day readmission rate
is frequently used as a quality measure [20–22], it is too
blunt to capture all aspects of quality of care. We chose
the 30-day readmission rate as the outcome measure
since it has been studied before and is considered to reflect
various insufficiencies in a healthcare system. Several
patient factors [20], inter-hospital variation [21, 22], and
specific interventions aimed at reducing hospital readmissions
[23–25] have been suggested to affect readmission
rates. Many of these were not adjusted for (e.g. diagnosis,
co-morbidity, and occupational status), since they are unfortunately
unavailable from the data sources available to
us. The limited predictive ability of the multivariable
models is also implied by the fairly low areas under the
ROC-curves and the values of the Nagelkerke's R2 coefficients.
Despite this, we view the agreement between crude-
, multivariable and sensitivity analyses as a relevant signal
in the data not to be neglected. Moreover, some of the effect
may reflect the undifferentiated status of the study
population, suggesting that future studies should aim at describing
the effect for limited groups of patients.
Conclusions
Study results indicate a positive association between inpatient
bed occupancy at discharge from inpatient wards
and the 30-day readmission rate. Though the prematurity
of hospital discharges may not be measurable by a
single outcome measure, our results provide support for
the hypothesis that high inpatient bed occupancy is associated
with premature discharges from inpatient wards
and points to the need of studying the subject closer.
Competing interest
KI was the head of the division responsible for the Emergency Department
where the study was conducted. FJ is currently the chair of the Emergency
Department where the study was conducted. All other authors declare that
they have no competing interests in relation to the study.
Authors’ contributions
MB, MLO, and KI all participated in developing the study design. LG
collected and concatenated data. KI and FJ granted access to data. MB
performed the statistical analyses. MB also prepared all versions of the
manuscript. All authors read and approved the final version of the manuscript