Shared neural substrates of cognitive function and postural control in older adults

Effects of resistance training associated with a verbal fluency task on physical performance and cognitive function in frail nursing home residents

OBJECTIVES

Studies examining the effects of dual-task resistance training (RT) on nursing-home residents are still scarce. To add knowledge to this field, the present study compared the effects of 12-week RT and RT plus cognitive task (COG) programs on physical performance and cognitive function in a sample of frail nursing home residents.

METHODS

This is an experimental study that combined data from two studies that examined older adults living in nursing home residences in Brazil. Exercise groups performed a 12-week RT protocol that included four exercises, with 3-4 times (sets) of 8-10 repetitions at 70 %-75 % of 1-repetition maximum (1RM), twice a week. The RT+COG group evoked as many words was possible for specific categories during concentric actions of the squat on the chair (until 90° knee flexion) and seated unilateral knee extension exercises. Global cognitive function and physical performance were evaluated using the Mini-Mental State Examination (MMSE) and Short Physical Performance Battery (SPPB) tests, respectively.

RESULTS

After interventions, participants in the RT+COG and RT groups had significantly greater lower-limb muscle strength compared with the control group (CG). Those in the RT+COG group had greater tandem performance in comparison to RT and CG groups.

CONCLUSIONS

Our findings indicate that RT preserves lower-limb muscle strength in frail nursing home residents, regardless of performance of cognitive tasks. Better balance was exclusively observed in the RT+COG, whereas significant improvements in mobility status were only found in the RT group. The present investigation was based on a small sample of nursing home residents. Larger and more structured studies are necessary to confirm our results.

Postural Control Characteristics in Alzheimer's Disease, Dementia With Lewy Bodies, and Vascular Dementia

BACKGROUND

Dementia often results in postural control impairment, which could signify central nervous system dysfunction. However, no studies have compared postural control characteristics among various types of dementia. This study aimed to compare static postural control in patients with Alzheimer's disease (AD), dementia with Lewy bodies (DLB), and vascular dementia (VaD).

METHODS

Cross-sectional relationship between the clinical diagnoses (AD, DLB, VaD, or normal cognition [NC]) of outpatients at a memory clinic and their upright postural control characteristics were examined. In the postural control test, participants were instructed to maintain a static upright standing on a stabilometer for 60 seconds under the eyes-open and eyes-closed conditions. Forty postural control parameters, including distance, position, and velocity in the anterior-posterior and medio-lateral directions, derived from the trajectory of the center of mass sway, were calculated. The characteristics of each type of dementia were compared to those of NC, and the differences among the 3 types of dementia were evaluated using linear regression models.

RESULTS

The study included 1 789 participants (1 206 with AD, 111 with DLB, 49 with VaD, and 423 with NC). Patients with AD exhibited distinct postural control characteristics, particularly in some distance and velocity parameters, only in the eyes-closed condition. Those with DLB exhibited features in the mean position in the anterior-posterior direction. In patients with VaD, significant differences were observed in most parameters, except the power spectrum.

CONCLUSIONS

Patients with AD, DLB, and VaD display disease-specific postural control characteristics when compared to cognitively normal individuals.

Neurometabolic correlates of posturography in normal aging and older adults with mild cognitive impairment: Evidence from a 1H-MRS study

Proton magnetic resonance spectroscopy (¹H-MRS) holds promise for revealing and understanding neurodegenerative processes associated with cognitive and functional impairments in aging. In the present study, we examined the neurometabolic correlates of balance performance in 42 cognitively intact older adults (healthy controls - HC) and 26 older individuals that were diagnosed with mild cognitive impairment (MCI). Neurometabolite ratios of total N-acetyl aspartate (tNAA), glutamate-glutamine complex (Glx), total choline (tCho) and myo-inositol (mIns) relative to total creatine (tCr) were assessed using single voxel ¹H-MRS in four different brain regions. Regions of interest were the left hippocampus (HPC), dorsal posterior cingulate cortex (dPCC), left sensorimotor cortex (SM1), and right dorsolateral prefrontal cortex (dlPFC). Center-of-pressure velocity (Vcop) and dual task effect (DTE) were used as measures of balance performance. Results indicated no significant group differences in neurometabolite ratios and balance performance measures. However, our observations revealed that higher tCho/tCr and mIns/tCr in hippocampus and dPCC were generic predictors of worse balance performance, suggesting that neuroinflammatory processes in these regions might be a driving factor for impaired balance performance in aging. Further, we found that higher tNAA/tCr and mIns/tCr and lower Glx/tCr in left SM1 were predictors of better balance performance in MCI but not in HC. The latter observation hints at the possibility that individuals with MCI may upregulate balance control through recruitment of sensorimotor pathways.

Effects of instability resistance training on static postural control of cognitively impaired older adults

BACKGROUND: Mounting evidence has demonstrated functional and cognitive-related benefits after Instability Resistance Training (IRT) in individuals, healthy as wellas patients presenting with neurological disorders. However, whether IRT may play a significant role in the postural control of older adults has not been established. OBJECTIVE: To evaluate the effects of 12- weeks of IRT on static postural control of older adults with subjective cognitive impairment. METHODS: In this randomized controlled trial, a total of 67 participants (aged 65 years and older) were randomly assigned to either 12 weeks of IRT (n= 22), traditional resistance training (RT) (n= 23), or a health education control group (CON) (n= 22). Static postural control was assessed using a force platform that recorded the displacement amplitude of the center of pressure (CoP) in the anteroposterior (AP) and mediolateral (ML) directions in bipedal support (30 seconds) with eyes open and closed. RESULTS: All groups increased AP displacement in the conditions of eyes open and closed. During the eyes-closed condition, only the IRT group increased the ML displacement. No between-group differences were detected in any postural control (p> 0.05). CONCLUSIONS: 12 weeks of IRT does not improve the static postural control in older adults with cognitive impairment.

Deterioration, Compensation and Motor Control Processes in Healthy Aging, Mild Cognitive Impairment and Alzheimer's Disease

Aging is associated with modifications of several brain structures and functions. These modifications then manifest as modified behaviors. It has been proposed that some brain function modifications may compensate for some other deteriorated ones, thus maintaining behavioral performance. Through the concept of compensation versus deterioration, this article reviews the literature on motor function in healthy and pathological aging. We first highlight mechanistic studies that used paradigms, allowing us to identify precise compensation mechanisms in healthy aging. Subsequently, we review studies investigating motor function in two often-associated neurological conditions, i.e., mild cognitive impairment and Alzheimer's disease. We point out the need to expand the knowledge gained from descriptive studies with studies targeting specific motor control processes. Teasing apart deteriorated versus compensating processes represents precious knowledge that could significantly improve the prevention and rehabilitation of age-related loss of mobility.

Postural Control Dysfunction and Balance Rehabilitation in Older Adults with Mild Cognitive Impairment

Older adults with mild cognitive impairment (MCI) are at an increased risk for falls and fall-related injuries. It is unclear whether current balance rehabilitation techniques largely developed in cognitively intact populations would be successful in older adults with MCI. This mapping review examined the available balance rehabilitation research conducted in older adults with MCI. Databases Medline, Cinahl, Cochrane, PubMed, Scopus, and PsycINFO were systematically searched from inception to August 2020. Twenty-one studies with 16 original randomized controlled trials (RCTs) involving 1201 older adults with MCI (>age 60) met the inclusion criteria, of which 17 studies showed significant treatment effects on balance functions. However, only six studies demonstrated adequate quality (at least single-blind, no significant dropouts, and intervention and control groups are equivalent at baseline) and evidence (medium or large effect size on at least one balance outcome) in improving balance in this population, and none of them are double- or triple-blind. Therefore, more high-quality RCTs are needed to inform future balance rehabilitation program development for older adults with MCI. Moreover, few studies examined the incidence of falls after the intervention, which limits clinical utility. Future RCTs should prospectively monitor falls or changes in risk of falls after the intervention.