Abstract
The aim of this study was to address whether deficits in the central cholinergic activity may contribute to the increased difficulty to allocate attention during gait in the elderly with heightened risk of falls. We recruited 50 participants with a history of two or more falls (33 patients with Parkinson’s Disease and 17 older adults) and 14 non-fallers age-matched adults. Cholinergic activity was estimated by means of short latency afferent inhibition (SAI), a transcranial magnetic stimulation (TMS) technique that assesses an inhibitory circuit in the sensorimotor cortex and is regarded as a global marker of cholinergic function in the brain. Increased difficulty to allocate attention during gait was evaluated by measuring gait performance under single and dual-task conditions. Global cognition was also assessed. Results showed that SAI was reduced in patients with PD than in the older adults (fallers and non-fallers) and in older adults fallers with respect to non-fallers. Reduction in SAI indicates less inhibition i.e., less cholinergic activity. Gait speed was reduced in the dual task gait compared to normal gait only in our faller population and changes in gait speed under dual task significantly correlated with the mean value of SAI. This association remained significant after adjusting for cognitive status. These findings suggest that central cholinergic activity may be a predictor of change in gait characteristics under dual tasking in older adults and PD fallers independently of cognitive status.
Highlights
Falls are a major cause of morbidity among older adults and individuals with neurodegenerative diseases, such as Parkinson’s disease (PD)
Gait speed was significantly lower in PD-F than in OLD-NF (p < 0.001) and in OLD-F than in OLD-NF (p = 0.003) with no difference between PD-F and OLD-F (p = 0.12)
Consistent with this, PD-F and OLD-F significantly reduced their gait speed under dual task gait with respect to normal gait (PD-F, dual vs. normal p < 0.001; OLD-F, dual vs. normal p = 0.022), whereas OLD-NF did not significantly reduced gait speed under dual task gait (p = 0.18)
Summary
Falls are a major cause of morbidity among older adults and individuals with neurodegenerative diseases, such as Parkinson’s disease (PD). One potential mechanism underlying the increased fall risk in those populations is reduced attentional resource allocation, which can compromise postural and gait stability (Montero-Odasso et al, 2012). Many studies have used the ‘‘dual-task paradigm’’ (i.e., observing people walking while they perform a secondary attention-demanding task) to assess the interactions between cognition ( reduced capacity to sustain and divide attention), gait and propensity to fall. A dysfunction of the cholinergic system has been identified as potentially contributing to the increased fall propensity and reduced attentional capacity in aging and neurodegeneration. An association between cholinergic dysfunction and gait disturbances in older adults with moderate to severe cognitive impairment has been reported (Morris et al, 1987; MonteroOdasso et al, 2015). Recent pilot work intriguingly suggested that treatment with anti-cholinergic medications may the risk of falls (Mancini et al, 2015; Henderson et al, 2016)
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