Multi-session anodal tDCS enhances the effects of postural training on balance and postural stability in older adults with high fall risk: Primary motor cortex versus cerebellar stimulation
Graphical abstract
Introduction
The population of the older adults continues to grow globally due to quality improvements in healthcare systems [1]. Relevant literature indicates that 50% of the older adults in nursing homes fall at least once a year [2,3]. Also, various studies have shown that balance disorders in older adults play a vital role in increasing the rate of falls [[4], [5], [6]]. Because falling may lead to the loss of independence, severe injuries and even death [6], any treatment which leads to improvement in balance and postural control in older adults with high fall risk may play an essential role in the reduction of falls and its consequences. In this regard, some studies have examined the effects of balance and postural training in healthy older adults [7,8]. These studies have shown that 12–20 weeks of postural training could improve balance and muscle performance and increase strength and improve in older adults [7,8]. However, older adults with high fall risk were not explicitly investigated in any of these studies [7,8]. Gusi et al. reported dynamic postural stability improvement and a decreased fear of falling following 12 weeks of postural training in older adults with high fall risk [9]. The findings in the studies mentioned above indicate that more extended periods of training may lead to an improvement in postural stability and balance in older adults [[7], [8], [9]]. Nonetheless, it might be difficult for this population to adhere to an extended training schedule [[7], [8], [9]].
Literature indicates that the cerebellar vermis plays a vital role in the maintenance of standing posture [[10], [11], [12], [13], [14]]. The cerebellum regulates both cognitive and automatic processes of postural control by acting on the cerebral cortex, via the thalamocortical projections, and on the brainstem [10,15]. Various studies have reported changes in the structure and function of different areas of the brain in older adults [12,13]. These changes can adversely affect balance and postural adjustments and therefore increase the risk of falling in older adults [16]. Hence, a treatment strategy could be the restoration of these changes using neuromodulatory techniques such as transcranial direct current stimulation (tDCS). In this regard, a series of studies have used anodal tDCS (a-tDCS) as a non-invasive neuro-modulatory technique for improvement of balance and postures deficits in older adults [17,18] and have shown the positive effects of bilateral cerebellar a-tDCS on posture and balance in healthy older adults [17,18]. These studies concluded that static and dynamic postural stability, balance and functional performance are improved following bilateral cerebellar a-tDCS. Likewise, some other studies have investigated the effects of unilateral primary motor cortex (M1) a-tDCS and reported positive effects of stimulation on postural stability and balance [19,20]. Overall, it can be concluded that both cerebellum and M1 may have a role in the restoration of balance and posture in human adults.
To the best of the authors' knowledge, there is no study to compare the effects of a-tDCS of cerebellum and M1 on the balance and postural control of older adults with high fall risk. Consequently, this study aims to compare the enhancing effects of a dominant M1 and bilateral cerebellar a-tDCS on postural training towards improving balance and postural control in older adults with a high fall risk. We hypothesised as follows:
- 1.
In older adults with high fall risk, M1 and bilateral cerebellar a-tDCS will have a significant enhancing effect on postural training compared to that of sham stimulation.
- 2.
In older adults with high fall risk, bilateral cerebellar a-tDCS will have a significantly stronger enhancing effect on postural training than that of M1 a-tDCS.
- 3.
Compared to the training paired with a-tDCS, two weeks of postural training alone or bilateral cerebellar a-tDCS alone does not significantly improve static and dynamic postural stability indices and Berg Balance Score (BBS) in older adults with high fall risk.
Section snippets
Methods and materials
Seventy-three older adult participants with the high fall risk who were aged between 60 and 85 (66.07 ± 4.37) were assessed against the inclusion and exclusion criteria in this study (Fig. 1).
Inclusion criteria were older adults aged 60–85 years who scored five or higher based on the falls risk assessment scale [21]. This scale is a valid and repeatable measure for assessment of falling rate in older adults [21]. Exclusion criteria included any history of neurological diseases, such as
Results
The demographic details and baseline data for each group are presented in Table 1. There were no significant differences between the groups with regard to variables of age, gender, body mass index, BBS and postural indices at the static or dynamic levels of 8 and 3 of the Biodex Balance System, and conditions corresponding to the eyes being opened or closed (p > 0.05).
Discussion
The findings in the current study supported the first hypothesis which indicated that compared to sham a-tDCS, bilateral cerebellar and M1 a-tDCS significantly enhance the effects of postural training on postural stability indices and BBS in older adults with high fall risk. This finding is supported by many studies which have shown the enhancing effects of multi-session M1 and cerebellar a-tDCS on the postural training effects on both static and dynamic postural stability as well as balance in
Conclusion
The findings in the current study indicate that two weeks of M1 or bilateral cerebellar a-tDCS during postural training can significantly improve postural stability and balance in older adults with high fall risk. Also, the enhancing effect of concurrent bilateral cerebellar a-tDCS with postural training on dynamic postural control is significantly higher than concurrent dominant M1 a-tDCS with postural training in older adults with high fall risk. Moreover, the results also indicate that two
Declaration of interests
None.
Acknowledgments
We would like to thank the Research Centre of Neuromuscular Rehabilitation of Semnan University of Medical Sciences for their cooperation and providing the facilities for this work.
References (43)
- et al.
Effect of exercise on balance, strength and reaction time in older people
Aust J Physiother
(1994) - et al.
Balance training reduces fear of falling and improves dynamic balance and isometric strength in institutionalised older people: a randomised trial
J Physiother
(2012) - et al.
Task-specific changes in motor evoked potentials of lower limb muscles after different training interventions
Brain Res
(2007) - et al.
Brain activity during observation and motor imagery of different balance tasks: an fMRI study
Cortex
(2015) - et al.
Long-term effects of motor training on resting-state networks and underlying brain structure
Neuroimage
(2011) - et al.
Validation of the Hendrich II Fall Risk Model: a large concurrent case/control study of hospitalized patients
Appl Nurs Res
(2003) - et al.
Acquisition of conditioned eye blink responses is modulated by cerebellar tDCS
Brain Stimul
(2014) - et al.
Modelling the electric field and the current density generated by cerebellar transcranial DC stimulation in humans
Clin Neurophysiol
(2014) - et al.
Safety criteria for transcranial direct current stimulation (tDCS) in humans
Clin Neurophysiol
(2003) - et al.
Transcranial DC stimulation (tDCS): a tool for double-blind sham-controlled clinical studies in brain stimulation
Clin Neurophysiol
(2006)
Transcranial direct current stimulation
Brain stimuli
Size of the neocerebellar vermis is associated with cognition in healthy elderly men
Brain Cognit
Relative contributions of the cerebellar vermis and prefrontal lobe volumes on cognitive function across the adult lifespan
Neurobiol Aging
Global aging: the challenge of success
Popul Bull
Falls in the elderly
Am Fam Physician
Interventions for preventing falls in older people living in the community
Cochrane Database Syst Rev
Posturography and risk of recurrent falls in healthy non-institutionalized persons aged over 65
Gerontology
Force platform measurements as predictors of falls among older people - a review
Gerontology
Balance improvements in older women: effects of exercise training
Phys Ther
Brain activation during maintenance of standing postures in humans
Brain
Cited by (57)
The comparative effects of anodal and cathodal trans-cranial direct current stimulation on balance and posture: A systematic review of literature and meta-analysis
2023, Journal of Clinical NeuroscienceCitation Excerpt :There is evidence that the impact of tDCS is polarity dependent, with increases in the excitability by anodal stimulation and inhibitory effect by cathodal stimulation [28]. In this regard, some studies determined that anodal tDCS (a-tDCS) can develop static and dynamic postural stability [6,18,27,29], but did not improve postural control in complex whole-body dynamic balance tasks [30,31]. On the other hand, some studies reported that cathodal tDCS (c-tDCS) improved standing body sway and balance in healthy people [2,26], whereas another study showed that c-tDCS impaired the keeping of standing balance [32].
Sensory system-specific associations between brain structure and balance
2022, Neurobiology of AgingConsensus Paper: Cerebellum and Ageing
2024, Cerebellum