Abstract & Commentary
Functional Status and the Risk for Readmission
By Kenneth P. Steinberg, MD, FACP, Editor
Professor of Medicine, University of Washington School of Medicine, Seattle, WA
Dr. Steinberg reports no financial relationships in this field of study.
SOURCE: Hoyer EH, et al. Association of impaired functional status at hospital discharge and subsequent rehospitalization. J Hosp Med 2014; 9:277-282.
Reducing 30-day hospital readmission rates is an important goal in improving healthcare quality and reducing healthcare costs. While causes of hospital readmission are myriad and multifactorial, some previous studies have suggested that impairments in functional status experienced during an acute care hospitalization may increase the risk of readmission. The presumed causal pathway is that patients who become debilitated during an acute care hospitalization may be vulnerable to post-discharge complications and thus to hospital readmission.
To further explore this issue, the authors conducted a single-center, retrospective study of patients admitted to an inpatient rehabilitation facility at a community hospital over a six-year period of time. Patients were excluded if they died during the inpatient rehabilitation stay or if they were not admitted directly from an acute care hospital. Data were collected from a standard rehabilitation medicine administrative database that included demographic data, Functional Independence Measure (FIM) score on admission to the rehabilitation facility, and a validated case-mix system as defined by the acute care hospital primary discharge diagnosis. A system developed by the University HealthSystem Consortium (UHC), patients were stratified by diagnosis groups and severity of illness. The primary outcome was all-cause readmission defined as a patient transfer to an acute care hospital during the inpatient rehabilitation stay within 30 days of admission to the rehabilitation center. Functional status was measured using the FIM score, an 18-item measure of functional status that allows patients to be divided into low, medium, and high functional groups. Logistic regression was used to evaluate the association between FIM score category and readmission status adjusting for potentially confounding variables available from the administrative databases.
Over the six-year study period, 9,405 consecutive eligible patients were admitted to the acute inpatient rehabilitation facility and a total of 1,182 (13%) were readmitted back to an acute care hospital within 30 days. Median time to readmission was 6 days (interquartile range 3 10 days). Patients were divided by diagnosis into neurologic, orthopedic, and medical categories. Patients in the low FIM score category had the highest unadjusted rate of readmission for each diagnostic category and as a continuous variable, FIM scores were linearly associated with readmission. Compared to patients with high admission FIM scores, patients with low and middle FIM scores had higher unadjusted odds of readmission (OR 4.0; 95% CI 3.4 4.7; P < 0.001 and OR 1.8; 95% CI 1.5 2.1; P < 0.001).
In the multivariable analyses, patients with a primary medical diagnosis had higher odds of readmission to the hospital (OR 1.8; 95% CI 1.6 2.1, P < 0.001) relative to patients with a neurologic or orthopedic diagnosis. Across all diagnoses, the adjusted odds ratios (95% CI) for the low and middle versus high FIM score category were 3.0 (2.5 3.6; P < 0.001) and 1.5 (1.3 1.8; P < 0.001) respectively. Patients in the lowest FIM group with a medical diagnosis had the highest adjusted readmission rate of 28.7%. The authors did not observe a statistical interaction between age and FIM score in predicting readmission. Finally, there were similar significant associations between admission FIM score group and readmission status that did not differ significantly across the 3 major diagnostic categories, suggesting that the effect of functional status was similar across various types of patients. Of the components of the FIM score, only those items related to transfers (to chair/wheelchair, toilet, and tub/shower), locomotion, and self-care were significantly associated with readmission.
COMMENTARY
This study demonstrated that low functional status at the time of discharge from an acute care hospital was strongly associated with higher 30-day readmission rates. This observation was consistent across major diagnostic groups with low-functioning medical patients having the highest rate of readmission (28.7%). The authors found that the motor subscales of the FIM score (transfers, locomotion, and self-care) were independently associated with readmissions. They interpret that observation as suggesting that lower motor scores may be a marker of poor physiologic reserve. Limitations of this study are primarily related to its observational design that allows for detection of associations but does not allow attribution of cause-and-effect. In addition, there may be residual confounding due to limitations in the administrative databases. The study also only evaluated patients discharged to an acute rehabilitation facility and not all patients discharged from an acute care hospital. Nevertheless, the study is consistent with prior literature in this field.
The results of this study are not particularly shocking in that it falls into that category of studies showing that sicker patients do worse. But the importance of this study, in my mind, lies in its identification of a potentially modifiable risk factor for 30-day readmission. Routine inpatient medical practice may not fully address the debilitation that occurs with acute illness as functional assessments might not be made and physical therapy (PT) and occupational therapy (OT) services may be underutilized or understaffed. Incorporating functional status into routine medical care may allow hospitalists to identify patients at higher risk of readmission. For those patients, the integration of early activity and mobility may be a means of decreasing their risk for readmission. This study does not address this hypothesis directly, but it makes me wonder.
