Discussion
Both the crude and adjusted results suggest a positive
association between inpatient bed occupancy at the hour
of patient discharge and the 30-day readmission rate.
Even though the differences were smaller than what was
considered clinically meaningful prior to conducting the
study, the post hoc power calculation revealed adequate
statistical power (>85 %) for the detected differences
between each occupancy category and the reference, except
for the smallest subgroup (cases discharged at occupancy
>105 %). We argue that these findings support
the hypothesis that high inpatient bed occupancy is associated
with premature hospital discharges. The most
notable absolute difference is between either of the subgroups
with cases discharged at high inpatient bed occupancy
and the reference category (occupancy 95 % occupied). The results were attenuated
when time of discharge was adjusted for in the sensitivity
analysis. It is hard to say whether the time of discharge
or the occupancy at discharge is the major driver
behind the 30-day readmission rate, since it is possible that
high inpatient bed occupancy causes delays in discharges
(higher census causes longer discharge rounds), so that
some of the effect attributed to time of discharge in the
sensitivity analysis is really mediated by the inpatient bed
occupancy rate. Whichever the case, inpatient bed occupancy
remained a significant predictor of 30-day readmissions
in the sensitivity analysis for all but the smallest
subgroup (cases discharged at occupancy >105 %). This