THE CONTRIBUTION OF PREDISPOSING AND SITUATIONAL RISK-FACTORS TO SERIOUS FALL INJURIES

OBJECTIVES: The objectives were to identify situational risk factors associated with suffering a serious fall injury and to determine whether, and to what extent, predisposing and situational risk factors contributed independently to risk of suffering a serious fall injury. DESIGN: Nested cohort study. SETTING: General community. PARTICIPANTS: 568 members of a representative sample of community-living persons 72 years of age or older who fell during a median follow-up of 36 months. MEASUREMENTS: Candidate predisposing factors, identified during a baseline face-to-face home assessment, were the demographic, cognitive, medical, and physical performance measures associated with an increased risk of serious injury among fallers in a previous analysis of the cohort. Acute host, behavioral, and environmental factors present at the time of the participants' first reported fall constituted potential situational risk factors. The primary outcome was occurrence of a serious fall injury, defined as a fracture, joint dislocation, or head injury resulting in loss of consciousness and hospitalization, during the first fall recorded during follow-up. RESULTS: Sixty-nine subjects (12%) suffered a serious injury during their first reported fall. No acute host factor was associated with increased risk of injury. The environmental and activity factors associated independently with serious injury in multivariate analysis included falling on stairs (adjusted relative risk 2.0; 95% confidence intervals 1.1 - 3.5), during displacing activity (1.8; 1.0 - 3.0), and from at least body height (2.1; 1.0 - 4.7). The independent predisposing factors included female gender (2.1; 1.0 - 4.4), low body mass index (1.8; 1.2 - 2.9), and cognitive impairment (2.8; 1.7 - 4.7). Although 12% of first falls resulted in a serious injury overall, this percentage ranged from 0% to 36% as the number of predisposing risk factors increased from zero to three and from 5% to 40% as the number of situational risk factors increased from zero to three. Further, for any given number of predisposing risk factors, the percentage of fallers suffering a serious injury increased with the number of situational risk factors CONCLUSIONS: Several environmental and behavioral factors contributed to the risk of serious fall injury; this contribution was independent of the effect of chronic predisposing risk factors. Preventive programs that address both predisposing and situational risk factors may result in the greatest injury reduction. These findings support previously recommended multicomponent intervention programs that combine medical, rehabilitative, and environmental components.