Reaction Time and Postural Sway Modify the Effect of Executive Function on Risk of Falls in Older People with Mild to Moderate Cognitive Impairment

Abstract

To explore the relationship between cognitive performance and falls in older people with mild to moderate cognitive impairment (CI) by investigating the mediational effects of medical, medication, neuropsychological, and physiological factors. Secondary analysis, prospective cohort study. Community and low-level care. 177 older people (aged 82 ± 7 years) with mild to moderate CI (MMSE 11-23; ACE-R < 83). Global cognition and six neuropsychological domains (memory, language, visuospatial, processing speed, executive function [EF], and affect) were assessed. Participants also underwent sensorimotor and balance assessments. Falls were recorded prospectively for 12 months. The EF domain was most strongly associated with multiple falls (relative risk [RR]: 1.50, 95% CI: 1.18-1.91). Global cognition was not associated with falls (RR: 1.09, 95% CI: 0.92-1.30). Additional analyses showed that participants with poorer EF (median cutpoint) were more likely to be taking centrally acting medications and were less physically active. They also had significantly worse vision, reaction time, knee extension strength, balance (postural sway, controlled leaning balance), and higher physiological fall risk scores. Participants with poorer EF were 1.5 times (RR: 1.50, 95% CI: 1.03-2.18) more likely to have multiple falls. Mediational analyses demonstrated that reaction time and postural sway reduced the relative risk of EF on multiple falls by 31% (RR: 1.19, 95% CI: 0.81-1.74). Within this sample of older people with mild to moderate CI, poorer EF increased the risk of multiple falls. This relationship was mediated by reaction time and postural sway,suggesting cognitively impaired older people with poorer EF may benefit from fall prevention programs targeting these mediating factors.