Lower Extremity Motor Function and Disability in Mild Cognitive Impairment

Development of a Longitudinal Model for Disability Prediction in Older Adults in China: Analysis of CHARLS Data (2015-2020)

Background

Disability profoundly affects older adults' quality of life and imposes considerable burdens on health care systems in China's aging society. Timely predictive models are essential for early intervention.

Objective

We aimed to build effective predictive models of disability for early intervention and management in older adults in China, integrating physical, cognitive, physiological, and psychological factors.

Methods

Data from the China Health and Retirement Longitudinal Study (CHARLS), spanning from 2015 to 2020 and involving 2450 older individuals initially in good health, were analyzed. The dataset was randomly divided into a training set with 70% data and a testing set with 30% data. LASSO regression with 10-fold cross-validation identified key predictors, which were then used to develop an Extreme Gradient Boosting (XGBoost) model. Model performance was evaluated using receiever operating characteristic curves, calibration curves, and clinical decision and impact curves. Variable contributions were interpreted using SHapley Additive exPlanations (SHAP) values.

Results

LASSO regression was used to evaluate 36 potential predictors, resulting in a model incorporating 9 key variables: age, hand grip strength, standing balance, the 5-repetition chair stand test (CS-5), pain, depression, cognition, respiratory function, and comorbidities. The XGBoost model demonstrated an area under the curve of 0.846 (95% CI 0.825-0.866) for the training set and 0.698 (95% CI 0.654-0.743) for the testing set. Calibration curves demonstrated reliable predictive accuracy, with mean absolute errors of 0.001 and 0.011 for the training and testing sets, respectively. Clinical decision and impact curves demonstrated significant utility across risk thresholds. SHAP analysis identified pain, respiratory function, and age as top predictors, highlighting their substantial roles in disability risk. Hand grip and the CS-5 also significantly influenced the model. A web-based application was developed for personalized risk assessment and decision-making.

Conclusions

A reliable predictive model for 5-year disability risk in Chinese older adults was developed and validated. This model enables the identification of high-risk individuals, supports early interventions, and optimizes resource allocation. Future efforts will focus on updating the model with new CHARLS data and validating it with external datasets.

Cross-cultural adaptation, validity and reliability of the Turkish version of the Cognitive Functioning Self-Assessment Scale (CFSS)

The Cognitive Functioning Self-Assessment Scale (CFSS) is a scale that enables individuals to assess their subjective cognitive performance. The study aimed to cross-culturally adapt the CFSS to Turkish (CFSS-TR) and prove its psychometric properties. The study included 180 community-dwelling adults over 18 years of age with no psychological or neurological disorders. Participants were assessed using the CFSS-TR, Hospital Anxiety Depression Scale (HADS), and the Cognitive Failures Questionnaire (CFQ) via online survey. Two weeks later, the CFSS-TR was taken from the participants for the second time. The mean age of the individuals was 41.06 ± 13.34 years. The CFSS-TR had good test-retest reliability (ICC: 0.84, CI 95%: 0.78-0.88) and good internal consistency (α = 0.88). The standard error of measurement (SEM) and the 95% confidence interval minimal detectable change (MDC95) values for the total score were 0.11 and 0.30, respectively. CFSS-TR had a strong correlation with CFQ, moderate correlation with HADS depression subscore, and weak correlation with HADS anxiety subscore (respectively r = 0.71, r = 0.52, r = 0.39, p < 0.001). CFSS-TR is a reliable and valid questionnaire for self-assessment of cognitive function in Turkish-speaking community-dwelling adults.

Reduced inhibitory synaptic transmission onto striatopallidal neurons may underlie aging-related motor skill deficits

Human beings are living longer than ever before and aging is accompanied by an increased incidence of motor deficits, including those associated with the neurodegenerative conditions, Parkinson's disease (PD) and Huntington's disease (HD). However, the biological correlates underlying this epidemiological finding, especially the functional basis at the synapse level, have been elusive. This study reveals that motor skill performance examined via rotarod, beam walking and pole tests is impaired in aged mice. This study, via electrophysiology recordings, further identifies an aging-related reduction in the efficacy of inhibitory synaptic transmission onto dorsolateral striatum (DLS) indirect-pathway medium spiny neurons (iMSNs), i.e., a disinhibition effect on DLS iMSNs. In addition, pharmacologically enhancing the activity of DLS iMSNs by infusing an adenosine A2A receptor (A2AR) agonist, which presumably mimics the disinhibition effect, impairs motor skill performance in young mice, simulating the behavior in aged naïve mice. Conversely, pharmacologically suppressing the activity of DLS iMSNs by infusing an A2AR antagonist, in order to offset the disinhibition effect, restores motor skill performance in aged mice, mimicking the behavior in young naïve mice. In conclusion, this study identifies a functional inhibitory synaptic plasticity in DLS iMSNs that likely contributes to the aging-related motor skill deficits, which would potentially serve as a striatal synaptic basis underlying age being a prominent risk factor for neurodegenerative motor deficits.

Admission Cognition and Function Predict Change in Physical Function Following Skilled Nursing Rehabilitation

OBJECTIVES

Many older adults are discharged from skilled nursing facilities (SNFs) at functional levels below those needed for safe, independent home and community mobility. There is limited evidence explaining this insufficient recovery. The purpose of this secondary analysis was to determine predictors of physical function change following SNF rehabilitation.

DESIGN

Secondary analysis of a prospective observational cohort study.

SETTING AND PARTICIPANTS

Across 4 SNFs, data were collected from 698 adults admitted for physical rehabilitation following an acute hospitalization.

METHODS

Physical function recovery was evaluated as change from admission to discharge in Short Physical Performance Battery (SPPB) scores (N = 698) and gait speed (n = 444). Demographic and clinical characteristics collected at admission served as potential predictors of physical function change. Following imputation, a standardized model selection estimator was calculated for predictors per physical function outcome. Predictor estimates and 95% CIs were calculated for each outcome model.

RESULTS

Higher cognitive scores [standardized β (βSTD) = 0.11, 95% CI: 0.0004, 0.20] and higher activities of daily living (ADL) independence at admission (βSTD = 0.22, 95% CI: 0.05, 0.34) predicted greater SPPB change; higher SPPB scores at admission (βSTD = -0.26, 95% CI: -0.35, -0.14) predicted smaller SPPB change. Higher ADL independence at admission (βSTD = 0.17, 95% CI: 0.01, 0.37) predicted greater gait speed change; faster gait speed at admission (βSTD = -0.30, 95% CI: -0.44, -0.15) predicted smaller gait speed change.

CONCLUSIONS AND IMPLICATIONS

Admission cognition, ADL independence, and physical function predicted physical function change following post-hospitalization rehabilitation. Inverse findings for admission physical function and ADL independence predictors suggest independence with ADL is not necessarily aligned with mobility-related function. Findings highlight that functional recovery is multifactorial and requires comprehensive assessment throughout SNF rehabilitation.

Association between serum lipid levels and lower-extremity functions in older adults with and without Alzheimer's dementia in South Korea: A cross-sectional analysis

PURPOSE

Older adults with Alzheimer's dementia (AD) experience lower-extremity dysfunction. High serum lipid levels are a risk factor for AD. We investigated the association between serum lipid levels and lower-extremity function in older individuals with and without AD.

METHODS

In this cross-sectional study, we enrolled 33,185 senior citizens (aged 66 years) who participated in the National Geriatric Screening Program, sampled from the Korean National Health Insurance Service-National Health Screening Cohort Database, between 2009 and 2015. Participants were dichotomized into 1) an AD group comprising individuals with the International Classification of Diseases, Tenth Revision, diagnostic codes F00, F00.0-F00.9, and G30, G30.0-G30.9; and 2) a control group comprising individuals without AD. Differences in the Timed Up and Go and One-Leg Standing results among the three levels (low, moderate, and high) of total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol were evaluated between the groups. Logistic regression analysis was performed to estimate the odds of gait disorder considering clinical and lifestyle variables.

RESULTS

In participants with low LDL-C levels, increased LDL-C levels correlated with higher gait speed. In the AD group, balancing time with eyes open (BT-EO) was inversely correlated with TG levels in participants with low TG levels. In the control group, BT-EO was negatively correlated with TC levels in participants with low TC levels.

CONCLUSION

Serum lipid levels were significantly correlated with lower-extremity function in participants with and without AD but not with gait disorder in participants with AD.

Relation of Motor Impairments to Neuropathologic Changes of Limbic-Predominant Age-Related TDP-43 Encephalopathy in Older Adults

BACKGROUND AND OBJECTIVES

Limbic-predominant age-related transactive response DNA-binding protein 43 (TDP-43) encephalopathy neuropathologic change (LATE-NC) is common and is a major contributor to cognitive decline and Alzheimer dementia in older adults. The objective of the current study was to examine whether LATE-NC was also associated with declining motor function in older adults.

METHODS

Participants were from 2 longitudinal clinical pathologic studies of aging who did not have dementia at the time of enrollment. Postmortem pathologic examination included immunohistochemical staining for TDP-43 in 8 brain regions, which was summarized as a dichotomous variable indicating advanced LATE-NC stages at which TDP-43 pathology had accumulated in the hippocampus, entorhinal, or neocortical regions. Annual motor testing included maximal inspiratory and expiratory pressures (summarized as respiratory muscle strength), grip and pinch strength (summarized as hand strength), finger tapping speed and the Purdue Pegboard Test (summarized as hand dexterity), and walking 8 feet and turning 360° (summarized as gait function). The severity of parkinsonism was also assessed and summarized as a global parkinsonism score. Global cognition was a summary of standardized scores of 19 neuropsychological tests. We used linear mixed-effect models to examine the associations of LATE-NC with longitudinal changes of motor decline and used multivariate random coefficient models to simultaneously examine the associations of LATE-NC with cognitive and motor decline.

RESULTS

Among 1,483 participants (mean age at death 90.1 [SD = 6.4] years, 70% women, mean follow-up 7.4 [SD = 3.8] years), LATE-NC was present in 34.0% (n = 504). In separate linear mixed-effect models controlling for demographics and other brain pathologies, LATE-NC was associated with faster decline in respiratory muscle strength (estimate = -0.857, SE = 0.322, p = 0.008) and hand strength (estimate = -0.005, SE = 0.002, p = 0.005) but was not related to hand dexterity, gait function, or parkinsonism. In multivariate random coefficient models including respiratory muscle strength, hand strength, and global cognition as the outcomes, LATE-NC remained associated with a faster respiratory muscle strength decline rate (estimate = -0.021, SE = 0.009, p = 0.023), but the association with hand strength was no longer significant (estimate = -0.002, SE = 0.003, p = 0.390).

DISCUSSION

Motor impairment, specifically respiratory muscle weakness, may be an unrecognized comorbidity of LATE-NC that highlights the potential association of TDP-43 proteinopathy with noncognitive phenotypes in aging adults.

Neurodegenerative and Cerebrovascular Brain Pathologies Are Differentially Associated With Declining Grip Strength and Gait In Older Adults

BACKGROUND

Understanding the pathological bases underlying the heterogeneity of motor decline in old age may lead to targeted treatments. We examined whether different brain pathologies are related to declining grip strength and gait function.

METHODS

We examined postmortem brains of older adults who underwent annual motor testing. Postmortem exam measured 6 neurodegenerative and 5 cerebrovascular disease (CVD) pathologies. Grip strength was measured twice bilaterally using a hand-held dynamometer, and gait function was a composite measure based on time and steps taken to walk 8 ft and perform a 360° turn twice.

RESULTS

In separate linear mixed-effects models including all autopsied adults (N = 1 217), neurodegenerative pathologies including tau tangles, TDP-43, and nigral neuronal loss were associated with declining grip strength, but not CVD pathologies. In contrast, although both CVD and neurodegenerative pathologies were associated with declining gait function, CVD pathologies accounted for 75% of the variance of declining rate of gait function explained by brain pathologies and neurodegenerative pathologies accounted for 25%. These findings were unchanged in adults (n = 970) without a history of stroke. Restricting analyses to only adults without dementia (n = 661), CVD pathologies continued to account for the majority of the variance of declining gait. However, we failed to detect in this subgroup the variance of declining grip strength explained by neurodegenerative or CVD pathologies.

CONCLUSION

Different pathologies accumulating in aging brains may contribute to the phenotypic heterogeneity of motor decline. Larger studies are needed in older adults without dementia to assess differences in the motor consequences of varied brain pathologies.

The Value of Handgrip Strength and Self-Rated Squat Ability in Predicting Mild Cognitive Impairment: Development and Validation of a Prediction Model

Early identification of individuals with mild cognitive impairment (MCI) is essential to combat worldwide dementia threats. Physical function indicators might be low-cost early markers for cognitive decline. To establish an early identification tool for MCI by combining physical function indicators (upper and lower limb function) via a clinical prediction modeling strategy. A total of 5393 participants aged 60 or older were included in the model. The variables selected for the model included sociodemographic characteristics, behavioral factors, mental status and chronic conditions, upper limb function (handgrip strength), and lower limb function (self-rated squat ability). Two models were developed to test the predictive value of handgrip strength (Model 1) or self-rated squat ability (Model 2) separately, and Model 3 was developed by combining handgrip strength and self-rated squat ability. The 3 models all yielded good discrimination performance (area under the curve values ranged from 0.719 to 0.732). The estimated net reclassification improvement values were 0.3279 and 0.1862 in Model 3 when comparing Model 3 to Model 1 and Model 2, respectively. The integrated discrimination improvement values were estimated as 0.0139 and 0.0128 when comparing Model 3 with Model 1 and Model 2, respectively. The model that contains both upper and lower limb function has better performance in predicting MCI. The final prediction model is expected to assist health workers in early identification of MCI, thus supporting early interventions to reduce future risk of AD, particularly in socioeconomically deprived communities.

Functional mobility decline and incident mild cognitive impairment and early dementia in community-dwelling older adults: the Singapore Longitudinal Ageing Study

BACKGROUND

Motor and gait disturbances are evident in early Alzheimer and non-Alzheimer dementias and may predict the likelihood of mild cognitive impairment (MCI) or progression to dementia.

OBJECTIVE

We investigated the Timed-Up-and-Go (TUG) measure of functional mobility in predicting cognitive decline and incident MCI or early dementia (MCI-dementia).

DESIGN

Prospective cohort study with 4.5 years follow-up.

SETTING

Population based.

PARTICIPANTS

2,544 community-dwelling older adults aged 55+ years.

METHODS

Participants with baseline data on TUG, fast gait speed (GS), knee extension strength (KES) and performance-oriented mobility assessment (POMA) gait and balance were followed up for cognitive decline (Mini-Mental State Exam; MMSE drop of ≥2, among 1,336 dementia-free participants) and incident MCI-dementia (among 1,208 cognitively normal participants). Odds ratio (OR) and 95% confidence intervals (95% CI) were adjusted for age, sex, education, smoking, physical, social and productive activity, multi-morbidity, metabolic syndrome and MMSE.

RESULTS

Per standard deviation increase in TUG, POMA, GS and KES were significantly associated with incident MCI-dementia: TUG (OR = 2.84, 95% CI = 2.02-3.99), GS (OR = 2.17, 95% CI = 1.62-2.91), POMA (OR = 1.88, 95% CI = 1.22-2.92) and KES (OR = 1.52, 95% CI = 1.15-2.02). Adjusted OR remained significant only for TUG (OR = 1.52, 95% CI = 1.01-2.31) and GS (OR = 1.53, 95% CI = 1.08-2.16). Areas under the curve (AUC) for TUG (AUC = 0.729, 95% CI = 0.671-0.787) were significantly greater than GS (AUC = 0.683, 95% CI = 0.619-0.746), KES (AUC = 0.624, 95% CI = 0.558-0.689) and POMA (AUC = 0.561, 95% CI = 0.485-0.637). Similar associations with cognitive decline were significant though less pronounced, and adjusted ORs remained significant for TUG, GS and POMA.

CONCLUSION

Functional mobility decline precedes incident MCI and early dementia. The TUG appears to be especially accurate in predicting the future risks of adverse cognitive outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03405675. Registered 23 January 2018 (retrospectively registered).

Segmental Bioimpedance Variables in Association With Mild Cognitive Impairment

Objective

To examine the changes in body composition, water compartment, and bioimpedance in mild cognitive impairment (MCI) individuals.

Methods

We obtained seven whole-body composition variables and seven pairs of segmental body composition, water compartment, and impedance variables for the upper and lower extremities from the segmental multi-frequency bioelectrical impedance analysis (BIA) of 939 elderly participants, including 673 cognitively normal (CN) people and 266 individuals with MCI. Participants’ characteristics, anthropometric information, and the selected BIA variables were described and statistically compared between the CN participants and those with MCI. The correlations between the selected BIA variables and neuropsychological tests such as the Korean version of the Mini-Mental State Examination and Seoul Neuropsychological Screening Battery – Second Edition were also examined before and after controlling for age and sex. Univariate and multivariate logistic regression analyses with estimated odds ratios (ORs) were conducted to investigate the associations between these BIA variables and MCI prevalence for different sexes.

Results

Participants with MCI were slightly older, more depressive, and had significantly poorer cognitive abilities when compared with the CN individuals. The partial correlations between the selected BIA variables and neuropsychological tests upon controlling for age and sex were not greatly significant. However, after accounting for age, sex, and the significant comorbidities, segmental lean mass, water volume, resistance, and reactance in the lower extremities were positively associated with MCI, with ORs [95% confidence interval (CI)] of 1.33 (1.02–1.71), 1.33 (1.03–1.72), 0.76 (0.62–0.92), and 0.79 (0.67–0.93), respectively; with presumably a shift of water from the intracellular area to extracellular space. After stratifying by sex, resistance and reactance in lower extremities remained significant only in the women group.

Conclusion

An increase in segmental water along with segmental lean mass and a decrease in body cell strength due to an abnormal cellular water distribution demonstrated by reductions in resistance and reactance are associated with MCI prevalence, which are more pronounced in the lower extremities and in women. These characteristic changes in BIA variables may be considered as an early sign of cognitive impairment in the elderly population.

Changes in Physical and Cognitive Function Predict Sedentary Behavior in Older Adults With Mild Cognitive Impairment

The current longitudinal study examined the influence of cognitive and lower extremity function on sedentary behavior continuously over 6 months in community-dwelling older adults with mild cognitive impairment (MCI). Multilevel models examined Montreal Cognitive Assessment (MoCA) change scores and the Short Physical Performance Battery (SPPB) on percent time in sedentary behavior among 17 older adults with MCI (50 to 74 observations for analysis). Sedentary behavior was measured daily and averaged monthly using wrist-worn actigraphy. Each 1-unit decrease in MoCA score was associated with an increase of 2 percentage points in sedentary behavior (p ≤ 0.01). In addition, each 1-unit decrease in chair stand score (lower extremity strength) was associated with an increase of 5 percentage points in sedentary behavior (p ≤ 0.01). Older adults experiencing cognitive decline and concurrent changes in lower extremity strength had the sharpest increase in sedentary behavior. Findings suggest lower body strengthening interventions may reduce sedentary behavior time and subsequently preserve physical functioning in this vulnerable population. [Research in Gerontological Nursing, 14(6), 285-291.].

Clinical assessment of gait and functional mobility in Italian healthy and cognitively impaired older persons using wearable inertial sensors

AIM

The main purpose of the present study was to verify the feasibility of wearable inertial sensors (IMUs) in a clinical setting to screen gait and functional mobility in Italian older persons. In particular, we intended to verify the capability of IMUs to discriminate individuals with and without cognitive impairments and assess the existence of significant correlations between mobility parameters extracted by processing trunk accelerations and cognitive status.

METHODS

This is a cross-sectional study performed on 213 adults aged over 65 years (mean age 77.0 ± 5.4; 62% female) who underwent cognitive assessment (through Addenbrooke's Cognitive Examination Revised, ACE-R) instrumental gait analysis and the Timed Up and Go (TUG) test carried out using a wearable IMU located in the lower back.

RESULTS

Individuals with cognitive impairments exhibit a peculiar gait pattern, characterized by significant reduction of speed (- 34% vs. healthy individuals), stride length (- 28%), cadence (- 9%), and increase in double support duration (+ 11%). Slight, but significant changes in stance and swing phase duration were also detected. Poorer performances in presence of cognitive impairment were observed in terms of functional mobility as overall and sub-phase TUG times resulted significantly higher with respect to healthy individuals (overall time, + 38%, sub-phases times ranging from + 22 to + 34%), although with some difference associated with age. The severity of mobility alterations was found moderately to strongly correlated with the ACE-R score (Spearman's rho = 0.58 vs. gait speed, 0.54 vs. stride length, 0.66 vs. overall TUG time).

CONCLUSION

The findings obtained in the present study suggest that wearable IMUs appear to be an effective solution for the clinical assessment of mobility parameters of older persons screened for cognitive impairments within a clinical setting. They may represent a useful tool for the clinician in verifying the effectiveness of interventions to alleviate the impact of mobility limitations on daily life in cognitively impaired individuals.

Narrative Review of Sensory Changes as a Biomarker for Alzheimer's Disease

Early recognition of Alzheimer's disease (AD) in the prodromal period has not been robust yet will be necessary if effective disease-modifying drugs are to be useful in preventing or delaying the condition. The objective of this narrative review was to describe the current, evidenced based understanding of alterations in sensory data as potential biomarkers for AD. Review of empirical studies that tested senses as biomarkers for AD and were published in English within the past 50 years was completed. Eighteen empirical studies were identified that met the strict criteria for inclusion, with 12 of these studies being related to the olfactory system. Two studies examined auditory, two examined vision, one examined proprioception, and one examined taste. Thus, only olfaction has been studied to any extent, leaving a clear gap in the literature for the use of other senses. A promising area of research has begun to be reported concerning differences in responses to pain stimuli in AD relative to cognitively normal subjects. Pain is not a single sense like the others but integrates several senses and may allow for use as an early biomarker for AD, as it integrates several brain areas and pathways. Unlike the other senses, simple devices can be used to measure changes in pain perception in cognitively normal adults with genetic predispositions for possible AD, making this potentially useful for clinicians in the future.

Skeletal Muscle Health and Cognitive Function: A Narrative Review

Sarcopenia is the loss of skeletal muscle mass and function with advancing age. It involves both complex genetic and modifiable risk factors, such as lack of exercise, malnutrition and reduced neurological drive. Cognitive decline refers to diminished or impaired mental and/or intellectual functioning. Contracting skeletal muscle is a major source of neurotrophic factors, including brain-derived neurotrophic factor, which regulate synapses in the brain. Furthermore, skeletal muscle activity has important immune and redox effects that modify brain function and reduce muscle catabolism. The identification of common risk factors and underlying mechanisms for sarcopenia and cognition may allow the development of targeted interventions that slow or reverse sarcopenia and also certain forms of cognitive decline. However, the links between cognition and skeletal muscle have not been elucidated fully. This review provides a critical appraisal of the literature on the relationship between skeletal muscle health and cognition. The literature suggests that sarcopenia and cognitive decline share pathophysiological pathways. Ageing plays a role in both skeletal muscle deterioration and cognitive decline. Furthermore, lifestyle risk factors, such as physical inactivity, poor diet and smoking, are common to both disorders, so their potential role in the muscle-brain relationship warrants investigation.

Characteristics of Mild Cognitive Impairment in Northern Japanese Community-Dwellers from the ORANGE Registry

A gradually increasing prevalence of mild cognitive impairment (MCI) is recognized in the super-aging society that Japan faces, and early detection and intervention in community-dwellers with MCI are critical issues to prevent dementia. Although many previous studies have revealed MCI/non-MCI differences in older individuals, information on the prevalence and characteristics of MCI in rural older adults is limited. The aim of this study was to investigate differential characteristics between older adults with and without MCI. The investigation was conducted over one year from 2018 to 2019. Participants were recruited from Akita in northern Japan. Neuropsychological assessments were applied to classify MCI, including the National Center for Geriatrics and Gerontology Functional Assessment Tool (NCGG-FAT) and the Touch panel-type Dementia Assessment Scale (TDAS) based on the Alzheimer's disease assessment scale. Our samples consisted of 103 older adults divided into 54 non-MCI and 49 MCI. The MCI group had lower scores of all cognitive items. Our results showed that individuals with MCI had significantly slower walking speed (WS) and worse geriatric depression scale (GDS) compared to non-MCI. In addition, WS was significantly associated with some cognitive items in non-MCI, but not in MCI. Finally, we showed that predictive variables of MCI were WS and GDS. Our study provides important information about MCI in rural community-dwellers. We suggest that older adults living in a super-aging society should receive lower limb training, and avoiding depression in older adults through interaction of community-dwellers may contribute to preventing the onset of MCI.

Genetic background modifies CNS-mediated sensorimotor decline in the AD-BXD mouse model of genetic diversity in Alzheimer's disease

Many patients with Alzheimer's dementia (AD) also exhibit noncognitive symptoms such as sensorimotor deficits, which can precede the hallmark cognitive deficits and significantly impact daily activities and an individual's ability to live independently. However, the mechanisms underlying sensorimotor dysfunction in AD and their relationship with cognitive decline remains poorly understood, due in part to a lack of translationally relevant animal models. To address this, we recently developed a novel model of genetic diversity in Alzheimer's disease, the AD-BXD genetic reference panel. In this study, we investigated sensorimotor deficits in the AD-BXDs and the relationship to cognitive decline in these mice. We found that age- and AD-related declines in coordination, balance and vestibular function vary significantly across the panel, indicating genetic background strongly influences the expressivity of the familial AD mutations used in the AD-BXD panel and their impact on motor function. Although young males and females perform comparably regardless of genotype on narrow beam and inclined screen tasks, there were significant sex differences in aging- and AD-related decline, with females exhibiting worse decline than males of the same age and transgene status. Finally, we found that AD motor decline is not correlated with cognitive decline, suggesting that sensorimotor deficits in AD may occur through distinct mechanisms. Overall, our results suggest that AD-related sensorimotor decline is strongly dependent on background genetics and is independent of dementia and cognitive deficits, suggesting that effective therapeutics for the entire spectrum of AD symptoms will likely require interventions targeting each distinct domain involved in the disease.

Slow gait as a motor marker of mild cognitive impairment? the relationships between functional mobility and mild cognitive impairment

The purpose of this study was to evaluate the association between functional mobility and mild cognitive impairment in older adults. A total of 800 older adults were recruited (653 controls and 147 subjects with MCI [88 subjects with aMCI and 59 subjects with naMCI]). Motor performance was measured with the Timed Up and Go test (TUG). The demographic factors associated with MCI were: age (OR = 1.05; 95% CI: 1.01-1.09) and the level of education (OR = 0.73; 95% CI: 0.68-0.79). An independent clinical factor associated with MCI was the TUG (OR = 1.14; 95% CI: 1.03-1.27). In the aMCI group, the relation between the TUG and cognitive status occurred (OR = 1.15; 95% CI: 1.02-1.31), whereas in the naMCI group this relationship was not observed. There is an association between cognitive dysfunction and impaired motor performance in older adults with MCI.

Motor deficits are independent of axonopathy in an Alzheimer's disease mouse model of TgCRND8 mice

There have been an increasing number of reports of non-cognitive symptoms in Alzheimer's disease (AD). Some symptoms are associated with the loss of motor functions, e.g. gait disturbances, disturbed activity level and balance. Consistent with clinical findings, several AD mouse models harboring amyloid pathology develop motor impairment. Although the factors that contribute to the motor deficits have not yet been determined, it has been suggested that axonopathy is one of the key factors that may contribute to this particular feature of the disease. Our previous study found that TgCRND8 mice exhibited profound motor deficits as early as 3 months old. In this study, we explored the possible factors that may be related to motor deficits in TgCRND8 mice. Results from silver, neurofilament and amyloid precursor protein (APP) staining revealed no axonopathy occurred in the brain and spinal cord of TgCRND8 mice at the age of 3 months. Anterograde labeling of corticospinal tract of spinal cord and electronic microscopy (EM) analysis showed that no axonopathy occurred in TgCRND8 mice at the age of 3 months. According to these results, it could be concluded that no axonal alterations were evident in the TgCRND8 mice when motor deficits was overt. Thus, axonopathy may play a less prominent role in motor deficits in AD. These results suggest that mechanisms by which motor function undergo impairment in AD need to be further studied.

Association between body composition parameters and risk of mild cognitive impairment in older Japanese adults

AIM

The aim of the present study was to investigate the association between various body composition parameters and the risk of mild cognitive impairment (MCI) in older Japanese adults, as well as potential sex-related differences in the risk of MCI.

METHODS

Participants underwent cognitive tests, and were divided into 840 participants with MCI (mean age 71.9 ± 5.5 years) and 1740 without MCI (mean age 71.3 ± 5.2 years). Body composition parameters were measured using a bioelectrical impedance analyzer. Multiple logistic regression analysis was then carried out to examine the associations between body composition parameters and risk of MCI.

RESULTS

After adjusting for confounding factors, those in the lowest quartile for fat-free mass had a higher risk of MCI than those in the highest quartile (men: odds ratio [OR] 1.96, 95% confidence interval CI 1.24-3.10; women: OR 1.49, 95% CI 1.01-2.19). Loss of muscle mass in the upper (OR 2.17, 95% CI 1.40-3.37) and lower (OR 1.99, 95% CI 1.25-3.15) limbs was associated with a higher MCI risk in men. However, only loss of muscle mass in the lower limbs was associated with a higher MCI risk (OR 1.61, 95% CI 1.06-2.44) in women. No associations were found between obesity measures and MCI.

CONCLUSIONS

We found that loss of fat-free mass was associated with MCI in older adults, regardless of sex. We also found that appendicular muscle mass was more closely associated with MCI in men than in women. These results suggest that the association between appendicular muscle mass and MCI might have different underlying mechanisms based on sex. Geriatr Gerontol Int 2017; 17: 2053-2059.

[Do you measure gait speed in your daily clinical practice? A review]

Gait speed (GS), measured at usual pace, is an easy, quick, reliable, non-expensive and informative measurement. With a standard chronometer, like those that currently found in mobile phones, and with two marks on the floor, trained health professionals obtain a more objective and quick measurement compared with many geriatric scales used in daily practice. GS is one of the pillars of the frailty phenotype, and is closely related to sarcopenia. It is a powerful marker of falls incidence, disability and death, mostly useful in the screening of older adults that live in the community. In recent years, the evidence is reinforcing the usefulness of GS in acute care and post-surgical patients. Its use in patients with cognitive impairment is suggested, due to the strong link between cognitive and physical function. Although GS meets the criteria for a good geriatric screening tool, it is not much used in clinical practice. Why? This review has different aims: (i)disentangling the relationship between GS and frailty; (ii)reviewing the protocols to measure GS and the reference values; (iii)reviewing the evidence in different clinical groups (older adults with frailty, with cognitive impairment, with cancer or other pathologies), and in different settings (community, acute care, rehabilitation), and (iv)speculating about the reasons for its poor use in clinical practice and about the gaps to be filled.

Frailty in Relation to the Risk of Alzheimer's Disease, Dementia, and Death in Older Chinese Adults: A Seven-Year Prospective Study

OBJECTIVES

To explore the relationship of general health decline assessed by frailty and risk of dementia and Alzheimer's disease (AD).

DESIGN

A seven-year prospective cohort study.

SETTING

Secondary analysis of data from the Beijing Longitudinal Study on Aging.

PARTICIPANTS

Urban and rural community-dwelling people aged 60 and older at baseline.

MEASUREMENTS

Frailty was quantified using the deficit accumulation-based frailty index (FI), constructed from 40 health deficits at baseline. Dementia was diagnosed by DSM-IIIR. AD and vascular dementia (VaD) were diagnosed by NINCDS-ADRDA and NINDS-AIREN. The relationships between frailty and the risk of dementia, AD and death were evaluated through multivariable models.

RESULTS

Of 2788 participants at baseline (1997), 171 (11.1%) reported a history of dementia. In seven years, 351 people developed dementia (13%: 223 AD and 128 other types of dementia) and 813 died (29%). After adjustment for age, sex, education, and baseline cognition, baseline frailty status significantly associated with Alzheimer's disease and dementia and death. For each deficit accumulated, the odds ratio of death increased by 5.7%, and the odds ratio of dementia increased by 2.9% (p < 0.001).

CONCLUSION

Frailty was associated with Alzheimer's disease and dementia over a seven years period. Frailty index might facilitate the identification of older adults at high risk of dementia for the application of the most effective, targeted prevention strategies.

Associations between Physical Activity and Cognitive Functioning among Middle-Aged and Older Adults

OBJECTIVES

To describe aerobic physical activity among middle-aged and older adults by their self-reported cognitive decline and their receipt of informal care for declines in cognitive functioning and most common type of physical activity.

DESIGN

Cross-sectional study using data from the 2011 Behavioral Risk Factor Surveillance System.

SETTING

Landline and cellular telephone survey.

PARTICIPANTS

93,082 respondents aged 45 years and older from 21 US states in 2011.

MEASUREMENTS

Subjective cognitive decline (SCD) was defined as experiencing confusion or memory loss that was happening more often or getting worse during the past 12 months. Regular care was defined as always, usually, or sometimes receiving care from family or friends because of SCD. Using the 2008 Physical Activity Guidelines for Americans, respondents were classified as being inactive, insufficiently active, or sufficiently active based on their reported aerobic exercise. We calculated weighted proportions and used chi-square tests for differences across categories by SCD status and receipt of care. We estimated the prevalence ratio (PR) for being inactive, insufficiently active, and sufficiently active using separate log-binomial regression models, adjusting for covariates.

RESULTS

12.3% of respondents reported SCD and 23.1% of those with SCD received regular care. 29.6% (95%CI: 28.9-30.4) of respondents without SCD were inactive compared to 37.1% (95%CI: 34.7-39.5) of those with SCD who did not receive regular care and 50.2% (95%CI: 45.2-55.1) of those with SCD who received regular care. 52.4% (95%CI: 51.6-53.2) of respondents without SCD were sufficiently active compared to 46.4% (95%CI: 43.8-49.0) of respondents with SCD and received no regular care and 30.6% (95%CI: 26.1-35.6) of respondents with SCD who received regular care. After adjusting for demographic and health status differences, people receiving regular care for SCD had a significantly lower prevalence of meeting aerobic guidelines compared to people without SCD (PR=0.80, 95%CI: 0.69-0.93, p=0.005). The most prevalent physical activity was walking for adults aged ≥ 45 years old (41-52%) regardless of SCD status or receipt of care.

CONCLUSION

Overall, the prevalence of inactivity was high, especially among people with SCD. These findings suggest a need to increase activity among middle-aged and older adults, particularly those with SCD who receive care. Examining ways to increase walking, potentially by involving informal caregivers, could be a promising way for people with SCD to reduce inactivity and gain the health benefits associated with meeting physical activity guidelines.

Evaluation of postural balance in mild cognitive impairment through a three-dimensional electromagnetic system

Introduction

Elderly people with cognitive impairment are at greater risk for falls; thus, an understanding of the earliest stages of cognitive decline is necessary.

Objective

To compare postural balance between elderly people with and without mild cognitive impairment using a three-dimensional system.

Methods

Thirty elderly people with mild cognitive impairment and thirty healthy elderly subjects were selected. Static posturography was performed using three-dimensional electromagnetic equipment and the following parameters were evaluated: maximum displacement, mean speed and total trajectory. Open- and closed-eye stabilometric variable comparisons between groups and within each group were carried out, and a relationship between the Mini Mental State Examination and the total trajectory of all elderly subjects was determined.

Results

The analysis among open- and closed-eye conditions showed a significant difference in maximum anteroposterior displacement in the control group and a significant difference in all stabilometric variables in the mild cognitive impairment group. A significant difference between the groups in all variables in the closed-eye condition was observed. There was a strong correlation between cognitive performance and total trajectory.

Conclusion

Evaluations showed decrease in balance in elderly people with mild cognitive impairment. Presence of anteroposterior displacement can be an early sign of postural control impairment, and the evaluation with visual restriction can be useful in detecting small postural instabilities.

Relationships between balance and cognition in patients with subjective cognitive impairment, mild cognitive impairment, and Alzheimer disease

BACKGROUND

Balance impairments are common in patients with Alzheimer disease (AD), but which aspects of balance are affected, at which stage of cognitive impairment, and their associations with cognitive domains remain unexplored.

OBJECTIVES

The aims of this study were: (1) to explore differences in balance abilities among patients with subjective cognitive impairment (SCI) or mild cognitive impairment (MCI), mild AD, and moderate AD and (2) to examine the relationship between the various aspects of balance and cognitive domains.

DESIGN

This was a cross-sectional study.

METHODS

Home-dwelling patients with SCI or MCI (n=33), mild AD (n=99), and moderate AD (n=38) participated in this study. The Balance Evaluation Systems Test (BESTest), comprising 6 subscales-"Biomechanical Constraints," "Stability Limits/Verticality," "Anticipatory Postural Adjustments," "Postural Responses," "Sensory Orientation," and "Stability in Gait"-was used to assess balance. Cognitive domains were assessed using the following measures: Mini-Mental Status Examination, Word-List Learning Test from the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), Verbal Fluency Test, Clock Drawing Test, and Trail Making Test, parts A and B (TMT-A and TMT-B, respectively). Two-way between-group analyses of variance, adjusted for age, were used to analyze differences among the groups. Multiple linear regression analysis was used to explore the associations between balance and cognition.

RESULTS

Differences were found between the groups on all BESTest subscales; the moderate AD group had the worst scores. The TMT-B (measuring executive function) was associated with all of the BESTest subscales after controlling for demographic factors.

LIMITATIONS

The cross-sectional design hampered interpretation of the development of balance impairments.

CONCLUSIONS

The study findings indicate that all aspects of balance control deteriorate with increasing severity of cognitive impairment and that executive function plays an important role in balance control. Physical therapists should pay attention to these findings both in clinical practice and in future research.

Development of a frailty framework among vulnerable populations

Frailty is a public health issue that is experienced by homeless and other vulnerable populations; to date, a frailty framework has not been proposed to guide researchers who study hard-to-reach populations. The Frailty Framework among Vulnerable Populations has been developed from empirical research and consultation with frailty experts in an effort to characterize antecedents, that is, situational, health-related, behavioral, resource, biological, and environmental factors that contribute to physical, psychological, and social frailty domains and impact adverse outcomes. As vulnerable populations continue to age, a greater understanding of frailty will enable the development of nursing interventions.

Effectiveness of exercise on cognitive impairment and Alzheimer's disease

Physical activity has a protective effect on brain function in older people. Here, we briefly reviewed the studies and results related to the effects of exercise on cognitive impairment and Alzheimer's disease. The main findings from the current body of literature indicate positive evidence for structured physical activity (cardiorespiratory and resistance exercise) as a promising non-pharmacological intervention for preventing cognitive decline. More studies are needed to determine the mechanisms involved in this preventative effect, including on strength, cardiorespiratory, and other types of exercise. Thus, the prevention of Alzheimer's disease may depend on healthy lifestyle habits, such as a structured physical fitness program.

Physical impairments in cognitively impaired older people: implications for risk of falls

BACKGROUND

Cognitively impaired older people fall twice as often as their cognitively intact counterparts. There is, however, limited information on factors that increase the risk of falls in this population. This study aimed to determine whether a group of cognitively impaired older people (CIG) perform worse than a matched group of cognitively intact older people (NCIG) on a profile of physical performance and mobility tests.

METHODS

One hundred and thirty-eight cognitively impaired and 276 age and gender matched cognitively intact community-dwelling older adults (>60 years) took part in the study. Participants completed a detailed physical performance battery from which composite fall risk scores were derived. Falls were measured prospectively for 12 months with monthly falls diaries, telephone calls, and by regularly contacting participants' "person responsible."

RESULTS

The CIG performed worse than the NCIG in tests of reaction time, muscle strength (grip and quadriceps), balance (sway on floor, sway on foam, controlled leaning balance and near tandem standing ability), and mobility (sit to stand, timed up and go (TUG) and steps required to turn 180 degrees). The CIG had significantly higher composite fall risk scores than the NCIG and fell significantly more during follow-up (Multiple falls (2+): CIG 43%; NCIG 21%).

CONCLUSIONS

Fall risk in the CIG was significantly increased due to multiple physical impairments. Physical profiles provide a means of quantifying the extent of impairment in older people with cognitive impairment and potential direction for targeting interventions for reducing fall risk.

Overview and findings from the rush Memory and Aging Project

The Memory and Aging Project is a longitudinal, epidemiologic clinical-pathologic cohort study of common chronic conditions of aging with an emphasis on decline in cognitive and motor function and risk of Alzheimer's disease (AD). In this manuscript, we first summarize the study design and methods. Then, we present data on: (1) the relation of motor function to cognition, disability, and death; (2) the relation of risk factors to cognitive and motor outcomes, disability and death; (3) the relation of neuropathologic indices to cognitive outcomes; (4) the relation of risk factors to neuropathologic indices; and (5) additional study findings. The findings are discussed and contextualized.

Life space and risk of Alzheimer disease, mild cognitive impairment, and cognitive decline in old age

OBJECTIVE

To test the hypothesis that a constricted life space, the extent of movement through the environment covered during daily functioning, is associated with increased risk of incident Alzheimer disease (AD), increased risk of mild cognitive impairment (MCI), and more rapid cognitive decline in older adults.

DESIGN

Two prospective cohort studies.

SETTING

Retirement communities, community-based organizations, churches, and senior subsidized housing facilities across the Chicago metropolitan area.

PARTICIPANTS

A total of 1,294 community-dwelling elders without baseline clinical dementia.

MAIN OUTCOME MEASURES

Detailed annual clinical evaluation to diagnose incident AD and MCI, and document change in cognitive function.

RESULTS

During a mean (SD) follow-up of 4.4 (1.7) years, 180 persons developed AD. In a proportional hazards model controlling for age, sex, race, and education, a more constricted life space was associated with an increased risk of AD (hazard ratio = 1.21, confidence interval: 1.08-1.36). A person with a life space constricted to their home was almost twice as likely to develop AD than a person with the largest life space (out of town). The association did not vary along demographic lines and persisted after the addition of terms for performance-based physical function, disability, depressive symptoms, social network size, vascular disease burden, and vascular risk factors. The association remained consistent after excluding persons with MCI at baseline and who developed AD in the first 2 years of observation. A constricted life space was also associated with an increased risk of MCI (hazard ratio = 1.17, confidence interval: 1.06-1.28), and a more rapid rate of global cognitive decline (estimate: -0.012, standard error: 0.003, t[5033] = -3.58, p <0.001).

CONCLUSIONS

A constricted life space is associated with increased risk of AD, MCI, and cognitive decline among older persons.

Loss of motor function in preclinical Alzheimer's disease

Accumulating evidence suggests that Alzheimer's disease (AD) has a long preclinical phase, during which time its characteristic pathology accumulates and patient function declines, but symptoms are insufficient to warrant a clinical diagnosis of dementia. There have been increasing reports of noncognitive symptoms, including loss of motor function, reported to be associated with incident AD. To understand the link between motor function and preclinical AD, this article examines: our understanding of motor function and its clinical assessment in cohort studies; the relationship of motor function and loss of cognition in older persons; risk factors for cognitive and motor decline; and the relation of post-mortem indices of AD and motor function prior to death. Together, these data suggest that age-related cognitive and motor decline may share a common causation. Furthermore, individuals with a clinical diagnosis of AD may represent the 'tip of the iceberg', since AD pathology may also account for a substantial proportion of cognitive and motor dysfunction currently considered 'normal aging' in older persons without dementia. Thus, AD may have a much larger impact on the health and wellbeing of our aging population.

Physical frailty predicts future cognitive decline - a four-year prospective study in 2737 cognitively normal older adults

OBJECTIVE

To examine the association between baseline frailty measurements and cognitive function 4 years later.

DESIGN

Prospective observational study.

SETTING

Community.

PARTICIPANTS

Two thousand seven hundred and thirty seven cognitively normal older adults.

MEASUREMENT

The appendicular muscle mass (ASM), hand grip strength, timed chair-stand test, walking speed and step length were measured at baseline. The Mini-mental state examination (MMSE) was administered at baseline and 4 years later.

RESULTS

In men, all baseline frailty measurements, namely, being underweight, lower ASM, weaker grip strength, slower chair-stand test, shorter step length, slower timed walk were significantly associated with a lower MMSE score 4 years afterwards. After adjustment for age, years of education and baseline MMSE score, ASM and timed walk became insignificant. In women, all frailty measurements except underweight and low ASM were significantly associated with MMSE score 4 years later. Moreover, only weaker grip strength persisted to be significant after adjustment for age, years of education and baseline MMSE score.

CONCLUSION

Physical frailty, as represented by being underweight, weaker grip strength, slower chair-stand test, shorter step-length in men and weaker grip strength in women, was associated with cognitive decline over a four year period.

Sensorimotor function, balance abilities and pain influence Timed Up and Go performance in older community-living people

BACKGROUND AND AIMS

The Timed up and Go Test (TUG) is recommended as a screening tool for fall risk in older people. It is assumed that this general mobility test is underpinned by physiological factors such as strength, coordination and balance. However, no studies have examined the range of physiological and psychological factors which influence performance on this test. The aim of this study was to examine the relative contributions of a range of sensorimotor, balance and psychological factors to TUG performance in a large sample of older people.

METHODS

280 community-dwelling people aged 65 plus years (mean age 74.9, SD=6.4) underwent the TUG test, as well as quantitative tests of vision, peripheral sensation, strength, reaction time, balance, fear of falling, pain and vitality.

RESULTS

The time required to complete the TUG was significantly related to limitations in instrumental activities of daily living and fear of falling. Many physiological and psychological factors were significantly associated with TUG performance in univariate analyses. Stepwise multiple regression analyses identified knee strength, postural sway, reaction time, edge contrast sensitivity, MMSE score, SF12 body pain and general health scores, number of medical conditions and age as significant and independent predictors of TUG performance. Of these measures, the lower limb strength measure explained most variance in TUG times. However, other sensorimotor, balance, psychological and health measures provided important independent information. The combined set of variables explained 43.5% of the variance in TUG times (multiple r=0.65).

CONCLUSIONS

Findings indicate that, in community-dwelling older people, TUG performance is influenced by lower limb strength, balance, reaction time, vision and pain, in addition to cognitive function and health status.

Association between life space and risk of mortality in advanced age

OBJECTIVES

To examine the association between life space, a measure of functional status that describes the range of movement through the environment covered during daily functioning, and the risk of mortality in older community-based persons.

DESIGN

Two ongoing, prospective observational cohort studies of aging.

SETTING

Greater metropolitan Chicago area.

PARTICIPANTS

One thousand four hundred forty-five community-based older persons without dementia.

MEASUREMENTS

Life space was measured at baseline using a series of questions designed to measure the extent of participants' movement throughout their environment, ranging from the bedroom to out of town. The association between life space and mortality was examined using proportional hazards models adjusted for age, sex, race, and education.

RESULTS

Over up to 8 years of follow-up (mean 4.1 years), 329 of 1,445 (22.8%) participants died. In a proportional hazards model adjusted for age, sex, race, and education, a more-constricted life space was associated with a greater risk of death (hazard ratio=1.18, 95% confidence interval=1.09-1.27, P<.001), such that people with life spaces constricted to their immediate home environment (score=3) were approximately 1.6 times as likely to die as those whose life spaces included trips out of town (score=0). This association persisted after the addition of terms for several potential confounders, including physical activity, performance-based physical function, disability, depressive symptoms, social networks, body mass index, and number of chronic medical conditions.

CONCLUSION

Constricted life space is associated with greater risk of death in older community-based persons.

Lower-extremity function in cognitively healthy aging, mild cognitive impairment, and Alzheimer's disease

OBJECTIVE

To examine differences in lower-extremity function in cognitive healthy older persons, older persons with mild cognitive impairment (MCI), and older persons with Alzheimer's disease (AD).

DESIGN

Descriptive study.

SETTING

University Alzheimer's disease clinical and research program.

PARTICIPANTS

Older persons (N=66) were studied (mean age, 76.7y); 22 were cognitively normal, 22 were diagnosed with probable MCI, 22 were diagnosed with probable AD.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Lower-extremity function was assessed by the four-meter walk test (4MWT), Timed Up & Go (TUG) test, and sit-to-stand (STS) test.

RESULTS

Analysis of variance, adjusting for covariates, revealed that performance on the 4MWT was significantly lower in the MCI and AD groups as compared with controls. TUG test performance was worse in the AD group compared with controls. No significant group differences were found for STS performance.

CONCLUSIONS

These results suggest an association between cognitive impairment and lower-limb function in older persons. Walking speed could be evaluated for its possible utility in screening older persons at risk for cognitive impairment and falls.

The association between choice stepping reaction time and falls in older adults--a path analysis model

BACKGROUND

choice stepping reaction time (CSRT) is a functional measure that has been shown to significantly discriminate older fallers from non-fallers.

OBJECTIVE

to investigate how physiological and cognitive factors mediate the association between CSRT performance and multiple falls by use of path analysis.

METHODS

294 retirement-village residents, aged 62-95 years, undertook CSRT tests, requiring them to step onto one of four randomly illuminated panels, in addition to physiological and cognitive tests. Number of falls was collected during 1-year follow-up.

RESULTS

79 participants (27%) reported two or more falls during the follow-up period. Regression analyses indicated CSRT was able to predict multiple falls by a factor of 1.76 for each SD change. The path analysis model revealed that the association between CSRT and multiple falls was mediated entirely by the physiological parameters reaction time and balance (postural sway) performance. These two parameters were in turn mediated over a physiological path (by quadriceps strength and visual contrast sensitivity) and a cognitive path (cognitive processing).

CONCLUSIONS

this study provides an example of how path analysis can reveal mediators for the association between a functional measure and falls. Our model identified inter-relationships (with relative weights) between physiological and cognitive factors, CSRT and multiple falls.

Spatial and temporal gait parameters in Alzheimer's disease and aging

Spatial and temporal gait parameters in 40 patients with early Alzheimer's disease (AD) were compared to that of 34 normal controls (NC) on a level ground and on a treadmill. Over-ground velocity, cycle-time, cadence, stride-length, stride-width and double-support time were captured on an electronic walkway. On the treadmill, cadence, cycle-time and double-support time were recorded at a preferred velocity using footswitches. The AD group were significantly slower on the Timed Up and Go task compared to NC (p<0.05). AD patients differed significantly from the NC on their over-ground gait velocity (99+/-19 cm/s vs 119+15 cm/s, p<0.001), cadence (101+/-9 steps/min vs 109+/-9 steps/min, p=0.001) and stride-length (118+/-18 cm vs 131+/-17 cm, p<0.01). On the treadmill, only preferred speed was significantly different in the AD group compared to the NC group (60+/-20 cm/s vs 74+/-23 cm/s, p=0.02). These results indicate that patients with early AD walk slower and with shorter strides than healthy older adults.

NOvelty-related motivation of anticipation and exploration by dopamine (NOMAD): implications for healthy aging

Studies in humans and animals show that dopaminergic neuromodulation originating from the substantia nigra/ventral tegmental area (SN/VTA) of the midbrain enhances hippocampal synaptic plasticity for novel events and has a motivationally energizing effect on actions through striatal mechanisms. In this review, we discuss how these mechanisms of dopaminergic neuromodulation connect to the behavioural and functional consequences that age-related structural degeneration of the SN/VTA exerts on declarative memory. We propose a framework called 'NOvelty-related Motivation of Anticipation and exploration by Dopamine' (NOMAD) which captures existing links between novelty, dopamine, long-term memory, plasticity, energization and their relation to aging. We propose that maximizing the use of this mechanism by maintaining mobility and exploration of novel environments could be a potential mechanism to slow age-related decline of memory.

Functional decline in cognitive impairment--the relationship between physical and cognitive function

BACKGROUND

Physical function decline is associated with dementia, which might either be mediated by the coexisting sarcopenia or directly related to the impaired cognition. Our objectives are to examine the relationship between cognitive function and performance-based physical function and to test the hypothesis that cognitive function is related to poor physical function independent of muscle mass.

METHODS

We measured muscle strength, performance-based physical function and muscle mass using dual-energy X-ray absorptiometry and cognitive function using the cognitive part of the Community Screening Instrument of Dementia (CSI-D) in 4,000 community-dwelling Chinese elderly aged >65 years. A CSI-D cognitive score of >28.40 was considered as cognitively impaired. The effect of cognitive impairment on muscle strength and physical function was analyzed by multivariate analysis with adjustment for age, appendicular skeletal mass (ASM), the Physical Activity Scale for the Elderly (PASE) and other comorbidities.

RESULTS

In both genders, the cognitively impaired (CSI-D cognitive score >28.40) group had a weaker grip strength (-5.10 kg, p < 0.001 in men; -1.08 kg in women, p < 0.001) and performed worse in the two physical function tests (in men, 6-meter walk speed, -0.13 m/s, p < 0.001, chair stand test, 1.42 s, p < 0.001; in women, 6-meter walk speed, -0.08 m/s, p < 0.001, chair stand test, 1.48 s, p < 0.001). After adjustment for age, ASM, PASE and other comorbidities, significant differences in grip strength (-2.60 kg, p < 0.001 in men; -0.49 kg, p = 0.011 in women) and the two physical function tests persisted between the cognitively impaired and nonimpaired group (in men, 6-meter walk speed, -0.072 m/s, p < 0.001, chair stand test, 0.80 s, p = 0.045; in women, 6-meter walk speed, -0.049 m/s, p < 0.001, chair stand test, 0.98 s, p < 0.001).

CONCLUSIONS

Poor physical function and muscle strength coexisted with cognitive impairment. This relationship was independent of muscle mass. It is likely therefore that the functional decline in dementia might be related directly to factors resulting in cognitive impairment independently of the coexisting sarcopenia.

Gait dysfunction in mild cognitive impairment syndromes

OBJECTIVES

To conduct a systematic clinical and quantitative assessment of gait in older adults with mild cognitive impairment (MCI) syndromes.

DESIGN

Cross-sectional.

SETTING

Einstein Aging Study, a community-based longitudinal aging study.

PARTICIPANTS

Fifty-four individuals with amnestic MCI (a-MCI), 62 with nonamnestic-MCI (na-MCI), and 295 healthy controls identified from the Einstein Aging Study participants.

MEASUREMENTS

Comparison of clinical and quantitative gait performance in subjects with MCI subtypes with that of cognitively normal older adults.

RESULTS

Neurological gaits were more common in a-MCI (31.5%, P=.008) but not in na-MCI (19.4%, P=.55), than in controls (16.3%). Quantitative gait in multiple parameters was worse in both MCI subtypes than in controls. Factor analysis revealed three independent factors representing pace, rhythm, and variability. Subjects with a-MCI had worse rhythm and variability scores than those with na-MCI and controls. Subjects with na-MCI had worse performance on the pace domain than the other two groups. Subjects with MCI and gait abnormalities had higher disability scores than subjects with MCI without gait abnormalities.

CONCLUSION

Gait dysfunction is common in older individuals with amnestic and nonamnestic subtypes of MCI.

Gait, aging and dementia

Cognitive impairment has been recognized as a risk factor for falls and for increasing the severity of injury following a fall, but the mechanisms by which cognitive impairment influences gait and postural control have been unclear. A recent report that galantamine improves gait parameters in older adults may help to untangle this.