Association Between Mobility as a Time-Dependent Exposure Factor and Risk of Fall: A Retrospective Cohort Study of Older Patients with Orthopedic Conditions in a Sub-acute Rehabilitation Setting.

Abstract

To examine the frequency of falls during recovery in older patients with orthopedic conditions in a sub-acute rehabilitation setting and to evaluate the association between mobility and fall risk. Observational retrospective cohort study. Single sub-acute rehabilitation hospital. Patients with orthopedic conditions aged ≥65 years admitted between April 1, 2023, and November 30, 2024. Not applicable. Incidence of first fall after admission. Of the 845 participants, 65 (7.7%) experienced a fall during follow-up (median: 42 days [interquartile range: 23-64 days]). The fall rate per 1,000 person-days increased immediately after admission, peaking at 2.41 during weeks 5-6, then declining. The Cox proportional hazards model assessing the association between mobility and fall risk showed no significant difference based on mobility at admission. However, repeated assessments showed a significantly higher hazard ratio (2.65; 95% confidence interval, 1.16-6.04) during light assistance or supervision, defined as requiring minimal physical contact or supervision by a caregiver, compared with independent status. Repeated assessments of mobility as a time-dependent exposure factor revealed that fall risk was highest during periods requiring light assistance or supervision and was most frequent during weeks 5-6 of the sub-acute rehabilitation setting. These findings indicate that evaluating mobility only at admission is inadequate for assessing fall risk, underscoring the importance of continuous reassessment throughout the sub-acute rehabilitation.