Intraindividual variability and falls in older adults.

OBJECTIVE: We investigated whether a simple measure of reaction time (RT) intraindividual variability (IIV) was associated with falls in older adults. Falls and fall-related injuries represent a major cost to health care systems, it is therefore critically important to find measures that can readily identify older adults at greater risk of falling. METHOD: Cognitive and motor function were investigated in 108 adults aged 53 to 93 years (M = 73.49) recruited across the local community and hospital outpatient department. Forty-two participants had experienced either an injurious fall, or multiple falls, in the previous 2 years. RESULTS: Logistic regression suggested that fallers could be distinguished from nonfallers by greater medication use, IIV, postural sway, weaker grip strength and slower gait speed. Structural equation models revealed that IIV was predictive of falls via the mediating variable of motor function (e.g., gait). IIV also predicted higher order cognition (executive function) but higher order cognitive function did not uniquely predict falls or account for the associations between IIV and falls. CONCLUSIONS: These findings indicate that IIV measures capture important aspects of cognitive and motor decline and may have considerable potential in identifying older adults at risk of falling in health care and community settings. (PsycINFO Database Record

Intraindividual Reaction Time Variability, Falls, and Gait in Old Age: A Systematic Review.

OBJECTIVES: Intraindividual variability (IIV) refers to the variation in reaction time (RT) performance across a given cognitive task. As greater IIV may reflect compromise of the frontal circuitry implicated in falls and gait impairment in older adults, we conducted a systematic review of the literature relating to this issue. METHODS: Searches were conducted of electronic databases that identified empirical investigations of IIV, falls, and gait in older adult samples with a mean age of 65 years or older. Data were extracted relating to IIV measures, study population, and outcomes. RESULTS: Of 433 studies initially identified, 9 met inclusion criteria for IIV and falls (n = 5), and gait (n = 4). Representing a total of 2,810 older participants, all of the studies of IIV and falls showed that elevated variability was associated with increased risk of falling, and half of the studies of gait indicated greater IIV was related to gait impairment. DISCUSSION: Across studies, IIV measures were consistently associated with falls in older persons and demonstrated some potential in relation to gait. IIV metrics may, therefore, have considerable potential in clinical contexts and supplement existing test batteries in the assessment of falls risk and gait impairment in older populations.