Motor and cognitive status exert non-linear effect on risk for falls during inpatient rehabilitation

We aimed to examine in which manner motor and cognitive domains of the Functional Independence Measure (FIM) contribute to the risk for falls during inpatient rehabilitation. This retrospective study was conducted in a 124-bed tertiary care rehabilitation center providing comprehensive rehabilitation services located in the southeast United States. The sample included 1,472 patients consecutively admitted over 18 months. A 13-item motor FIM score (range 13 to 91) and a 5-item cognitive FIM score (range 5 to 35) were retrieved from the admission records. Each instance of fall was reported by clinical staff and databased for research purposes. Generalized Additive Model was used to determine relationship between the FIM scores and falls.

After controlling for age, gender, race, co-morbidities, and severity of impairment, GAM plots indicated that the risk for falls increases with increasing motor FIM, reaches a peak at motor FIM of 37 points, and then declines. Similar pattern persisted for the cognitive FIM with peak at 14 points. Log-hazard ratio was greater than zero between 20 and 40 for the motor FIM and 5 and 18 for the cognitive FIM. Significantly higher prevalence of falls within this high risk area was observed among patients admitted for stroke or brain dysfunction and with more than 9 co-morbidities.

Our results suggest that the influence of motor and cognitive status at admission on the risk for inpatient falls is neither linear nor monotonic. The established non-linear relationship may be useful for identifying those at high risk and for planning preventive strategies.