Predictors of rehospitalization among elderly patients admitted to a rehabilitation hospital: the role of polypharmacy, functional status, and length of stay.

Objectives: Rehospitalizations for elderly patients are an increasing health care burden. Nonetheless, we have limited information on unplanned rehospitalizations and the related risk factors in elderly patients admitted to in-hospital rehabilitation facilities after an acute hospitalization.

Setting: In-hospital rehabilitation and aged care unit.

Design: Retrospective cohort study.

Participants: Elderly patients 65 years or older admitted to an in-hospital rehabilitation hospital after an acute hospitalization between January 2004 and June 2011.

Measurements: The rate of 30-day unplanned rehospitalization to hospitals was recorded. Risk factors for unplanned rehospitalization were evaluated at rehabilitation admission: age, comorbidity, serum albumin, number of drugs, decline in functional status, delirium, Mini Mental State Examination score, and length of stay in the acute hospital. A multivariable Cox proportional regression model was used to identify the effect of these risk factors for time to event within the 30-day follow-up.

Results: Among 2735 patients, with a median age of 80 years (interquartile range 74-85), 98 (4%) were rehospitalized within 30 days. Independent predictors of 30-day unplanned rehospitalization were the use of 7 or more drugs (hazard ratio [HR], 3.94; 95% confidence interval, 1.62-9.54; P = .002) and a significant decline in functional status (56 points or more at the Barthel Index) compared with the month before hospital admission (HR 2.67, 95% CI: 1.35-5.27; P = .005). Additionally, a length of stay in the acute hospital of 13 days or more carried a twofold higher risk of rehospitalization (HR 2.67, 95% CI: 1.39-5.10); P = .003).

Conclusions: The rate of unplanned rehospitalization was low in this study. Polypharmacy, a significant worsening of functional status compared with the month before acute hospital admission, and hospital length of stay are important risk factors.