大高 洋平

BACKGROUND: Gait-a frequently performed activity of daily living-is thought to reflect multiple dimensions of an individual's physical and cognitive status. Individuals with frailty or mild cognitive impairment (MCI) show decreased gait speed. However, previous studies have not simultaneously considered both statuses, although they frequently co-occur and may act as confounders. The direct association between frailty and gait is well-understood. In contrast, the association between cognitive decline-independent of physical function-and decreased gait speed, as well as the relationship among these three factors (frailty, cognitive decline, and gait speed), is not fully understood. METHODS: This study examined the effect of MCI on gait speed after accounting for frailty. Older individuals were categorized as (1) frailty with MCI, (2) frailty without MCI, (3) pre-frailty with MCI, (4) pre-frailty without MCI, (5) non-frailty with MCI, and (6) non-frailty without MCI. Frailty was assessed using the Kihon checklist and MCI using the Montreal Cognitive Assessment. Participants completed a 10-m walk test under two conditions: comfortable walking and fast walking. Two types of analyses were conducted: mediation analysis and two-way analysis of covariance (ANCOVA). RESULTS: Mediation analysis supported independent relationships between frailty and MCI status and gait speed, suggesting a direct association between MCI and gait speed, even when accounting for frailty. In addition, two-way analysis of covariance indicated significant main effects of both frailty and MCI on gait speed, with no significant interaction between them under the two walking conditions. CONCLUSIONS: These findings suggest that the observed association between MCI and gait speed is largely independent from frailty status, providing additional evidence supporting the association between cognitive function and gait performance.

Abstract Background Patients with hip fractures are at high risk of falling. In hospitals, identifying high-risk patients based on their capabilities and implementing targeted prevention strategies is essential. Because fall risk changes with functional recovery, it should be assessed longitudinally rather than at a single time point. This study aimed to determine whether the risk of falls (falls per 1,000 person-days) was stratified by motor and cognitive functional status and to examine the relationship between fall incidence rates and the actual number of falls in each functional status. Methods This retrospective observational study included 824 consecutive patients with hip fractures admitted to a rehabilitation hospital. Data on falls during hospitalization and Functional Independence Measure (FIM) scores were retrieved from medical records. Average FIM scores for the motor and cognitive items were obtained and categorized into complete dependence, modified dependence, and independence. Fall rates and number of observed falls in each combined condition were investigated. Results The highest fall rate was observed when patients were in states of modified motor dependence and complete cognitive dependence (11.4 falls/1,000 person-days; 17 falls; 9.3% of all falls). In contrast, patients in independent motor and cognitive states had a lower fall rate (2.0 falls/1,000 person-days) but accounted for a larger proportion of total falls (32 falls; 17.6% of all falls), representing 1.9 times the total number of falls observed in the highest fall-rate group. Conclusion This study successfully demonstrated that fall risk in patients with hip fractures varies according to functional status, peaking during phases of modified motor dependence and complete cognitive dependence. However, owing to longer observation periods, a greater number of falls occurred among those in low-risk states than among those in high-risk states, demonstrating the “prevention paradox.” Effective management requires a dual strategy: intensive interventions targeting high-risk phases and standardized preventive measures for all patients to address cumulative risk during the recovery process.