[Show abstract][Hide abstract] ABSTRACT: Background: This study set out to verify the hypothesis that geriatric rehabilitation patients are lower functioning and more medically complex than their adult rehabilitation counterparts. Methods: This retrospective study compares 101 Geriatric Rehabilitation Unit (GRU) and 100 Physical Medicine and Rehabilitation Unit (PMRU) patients treated in Ottawa and London, Ontario, in 1999. The measurements used were the Functional Independence Measure (FIM), Cumulative Illness Rating Scale (CIRS), medication changes, discharge medications, number of admission medications, physician progress notes, and days with laboratory tests. Results: As expected, the GRU patients were significantly older than the PMRU patients. They had lower mean admission FIM scores, lower discharge FIM scores, and lower FIM improvements. Because lengths of stay were longer, their rate of FIM change was lower. GRU patients were also more medically complex than PMRU patients in all the dimensions measured. Conclusions: Geriatric Rehabilitation patients have lower functional status and higher medical complexity than their Physical Medicine and Rehabilitation counterparts. As the population ages, more rehabilitation beds may need to be designated "geriatric," and future funding formulas will need to allow for the functional and medical differences of these patients.