Effects of transcranial direct current stimulation on motor learning in healthy elderly individuals: a systematic review and meta-analysis.

BACKGROUND: Transcranial direct current stimulation (tDCS) is widely used in motor recovery. Nevertheless, whether tDCS improves motor learning in healthy older adults is still controversial. This review aims to investigate the effectiveness of tDCS on motor learning in healthy elderly individuals. METHODS: The PubMed, Cochrane Library, Web of Science and Embase databases were initially searched from inception to December 5, 2022. The standard mean difference (SMD) with the corresponding 95% confidence intervals (CIs) were analysed via random-effect models. RESULTS: Compared with the sham group, no significant effects were found regarding improvement in motor learning based on the speed or accuracy of the task and reaction time for the tDCS intervention group. After subgroup analysis, a significant effect was found for improved motor learning based on reaction time in the primary motor cortex (M1)-cerebellar group. CONCLUSIONS: This review revealed that tDCS had no significant effect on improving the speed or accuracy of motor learning in healthy elderly adults. However, it has a significant effect on improving the motor learning ability based on the reaction time of the task (mainly referring to the tDCS stimulation position of M1 and cerebellar), although the results have obvious heterogeneity and uncertainty.

Epigenetic age stratifies the risk of blood pressure elevation related to short-term PM2.5 exposure in older adults.

BACKGROUND: Exposure to fine particulate matter (PM2.5) is a prominent risk factor for cardiovascular aging in older adults and causes mild syndromes or other comorbidities in otherwise healthy older adults. Accordingly, a precise tool for PM2.5 exposure risk stratification is urgently needed. We aimed to address this need by comparing the performances of seven types of epigenetic age and chronological age to classify the effects of short-term PM2.5 exposure on blood pressure (BP), a typical clinical surrogate marker of cardiovascular aging. METHODS: We conducted a panel study of the Chinese healthy adults aged 60-69 years through five monthly visits. Personal PM2.5 exposures were measured using wearable monitoring devices for three consecutive days, and DNA methylation was determined by the Illumina MethylationEPIC BeadChip using blood samples collected at each visit. Systolic BP, diastolic BP, mean arterial pressure and pulse pressure were measured by the electronic BP monitor. Linear mixed models with interaction terms between PM2.5 and different ages were used to assess their potential usefulness for stratification. RESULTS: DNAmPhenoAge, Skin & blood clock, DNAmGrimAge acceleration, and DunedinPoAm had significant modifying effects on the relationship between PM2.5 and BP. For instance, a 10-µg/m3 increase in the 72-h moving mean PM2.5 was significantly associated with 0.30% (95% CI: 0.10%, 0.51%) and -0.07% (95% CI: -0.32%, 0.18%) increases in systolic BP at higher and lower DNAmPhenoAge acceleration, respectively. Joint models further revealed that using a combination of epigenetic ages could more precisely stratify the effect of PM2.5 on BP. CONCLUSIONS: Our research indicates that epigenetic age may be a useful tool for evaluating the effect of short-term PM2.5 exposure on cardiovascular aging status.

A 10-year longitudinal study of deep white matter lesions on magnetic resonance imaging.

PURPOSE: Deep white matter lesions (DWMLs), T2 high-intensity areas in the subcortical white matter on magnetic resonance imaging (MRI), are a clinical phenotype of cerebral small vessel disease. Factors such as age and hypertension have been reported to significantly contribute to the presence and severity of DWMLs in cross-sectional studies. We herein report a 10-year longitudinal study on DWMLs in elderly Japanese subjects to reveal the clinical variables contributing to the progression of DWMLs. METHODS: A total of 469 Japanese subjects were invited to participate in the study. Of the participants at baseline, 259 subjects completed the revisit MRI study 10 years later. In those 259 subjects, we evaluated the correlation between the progression of DWMLs and clinical variables, such as the gender, age, and overt vascular risk factors. To clarify the role of hypertension, 200 subjects with grade 1 DWMLs at baseline were categorized into three groups according to their status of hypertension and its treatment. RESULTS: Of the 200 subjects with grade 1 DWMLs, 47 subjects (23.5%) showed progression of DWMLs (progression group). In the progression group, the percentage of subjects with hypertension and the systolic blood pressure values were higher than in the non-progression group. In addition, subjects ≥ 60 years old at baseline tended to show deterioration of DWMLs in the group with hypertension without antihypertensive treatment. CONCLUSION: The results of this 10-year longitudinal study imply a positive correlation between long-standing hypertension and the progression of DWMLs.

Medically actionable pathogenic variants in a population of 13,131 healthy elderly individuals.

PURPOSE: To measure the prevalence of medically actionable pathogenic variants (PVs) among a population of healthy elderly individuals. METHODS: We used targeted sequencing to detect pathogenic or likely pathogenic variants in 55 genes associated with autosomal dominant medically actionable conditions, among a population of 13,131 individuals aged 70 or older (mean age 75 years) enrolled in the ASPirin in Reducing Events in the Elderly (ASPREE) trial. Participants had no previous diagnosis or current symptoms of cardiovascular disease, physical disability or dementia, and no current diagnosis of life-threatening cancer. Variant curation followed American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) standards. RESULTS: One in 75 (1.3%) healthy elderly individuals carried a PV. This was lower than rates reported from population-based studies, which have ranged from 1.8% to 3.4%. We detected 20 PV carriers for Lynch syndrome (MSH6/MLH1/MSH2/PMS2) and 13 for familial hypercholesterolemia (LDLR/APOB/PCSK9). Among 7056 female participants, we detected 15 BRCA1/BRCA2 PV carriers (1 in 470 females). We detected 86 carriers of PVs in lower-penetrance genes associated with inherited cardiac disorders. CONCLUSION: Medically actionable PVs are carried in a healthy elderly population. Our findings raise questions about the actionability of lower-penetrance genes, especially when PVs are detected in the absence of symptoms and/or family history of disease.

Handedness of healthy elderly and patients with Alzheimer's disease.

Purpose/Aim of the study: Research has suggested decreasing proportions of non-right handers in older age groups and reduced incidence of non-right handedness among individuals with Alzheimer's disease (AD). We hypothesized that healthy elderly individuals would have a higher proportion of non-right handers than individuals with AD and that the proportion of non-right handers would decrease with increasing age. Further, we investigated whether the proportions of non-right handers differed between those with early and late onset of AD.Materials and Methods: Two-hundred and fifty-six healthy elderly and 182 individuals with AD served as participants. Hand dominance was recorded based on side of writing during testing and self-report. We analyzed proportions of right handers and non-right handers for three age ranges (≤ 69, 70 - 79, and ≥ 80 years). A second analysis focused on the proportions of right and non-right handers among patients with AD classified as either early or late disease onset.Results: Handedness proportions did not differ between the controls and ADs. For AD but not for controls, there was a trend towards reduced proportions of non-right handers with increasing age. Early onset AD was associated with a larger proportion of non-right handers compared to those with late onset AD.Conclusions: Results did not support a trend of decreasing non-right handedness with increasing age in controls, but did provide support for such a trend in individuals with AD. The results provided support for the hypothesis of increased incidence of non-right handedness in early onset vs. late onset AD.

Relationship between Psychological Distress and Continuous Sedentary Behavior in Healthy Older Adults.

Background: Our purpose is to clarify whether psychological distress (PD) affects the rate of continuous sedentary behavior (CSB). Materials and Methods: In this secondary analysis, a sample population of 80 healthy older adults aged 65 years or older participated in a health club of college A from 2016 to 2017. We conducted Structural Equation Modeling (SEM) using the cross-lagged and synchronous effects models. We adopted the following as proxy variables: CSB (based on the ratio of 1.5 METs sessions or more continuing for over 30 min) CSB and PD (based on the Kessler psychological distress scale: K6). Results: "2016 K6" had a significant influence on "2017 CSB" (standardization factor (ß) = 0.136, p = 0.020) using the cross-lagged effects model, and "2017 K6" significantly influenced "2017 CSB" (ß = 0.166, p = 0.039) using the synchronous effects model. Fit indices were Adjusted Goodness-of-Fit Index (AGFI) = 0.990, Confirmatory Fit Index (CFI) = 1.000, and Root Mean Square Error of Approximation (RMSEA) = 0.000. Conclusion: The results suggest that PD may affect the ratio of CSB one year later.

Long-Term Relationship between Psychological Distress and Continuous Sedentary Behavior in Healthy Older Adults: A Three Panel Study.

Background and objectives: Psychological distress (PD) is associated with continuous sedentary behaviors (CSB; based on the ratio of 1.5 metabolic equivalents (METs) sessions or more continuing for over 30 min) in older adults, but the long-term relation is not sufficiently clarified. This study aims to clarify the long-term relationship between PD and the rate of CSB. Materials and Methods: In this secondary analysis, a sample population of 72 healthy elderly people aged 65 years or older participated in a health club of college A from 2016 to 2018. We conducted structural equation modeling (SEM) using the cross-lagged and synchronous effects models. We adopted the following as proxy variables: CSB and PD (based on the Kessler 6 scale (K6) scores). Results: "2016 K6" to"2017 CSB" (standardization factor (ß = 0.141, p = 0.025), "2017 K6" to "2018 CSB" (ß = 0.187, p < 0.001) and "2016 CSB" to "2018 CSB" (ß = 0.188, p < 0.001) were all statistically significant using the cross-lagged effects models. Fit indices were adjusted goodness of fit index (AGFI) = 0.961, comparative fit index (CFI) = 1.000, and root mean square error of approximation (RMSEA) = 0.000. Conclusion: The results suggest that PD may affect the ratio of CSB one year later, and CSB may affect the ratio of PD two year later.

γ-Aminobutyric acid type A receptor binding affinity in the right inferior frontal gyrus at resting state predicts the performance of healthy elderly people in the visual sustained attention test.

ABSTRACTBackground:Although recent studies have suggested that the γ-aminobutyric acid type A (GABAA) receptor binding affinity can be a more sensitive marker of age-related neuronal loss than regional gray matter (GM) volume, knowledge about the relationship between decreased GABAA receptor binding affinity and cognitive decline during normal aging is still limited. METHODS: Thirty-seven healthy elderly individuals (aged 50-77 years (mean, 64.5 ± 7.3 years); 15 males and 22 females) were enrolled in this study. We investigated the association of the performance of the healthy elderly in the attentional function test with regional GM volume, regional cerebral bold flow (rCBF), and GABAA receptor binding affinity in the resting state by structural magnetic resonance imaging (MRI), arterial spin labeling (ASL), and 123I-iomazenil (IMZ) SPECT, with the analysis focusing on the bilateral inferior frontal gyri. RESULTS: The score of the rapid visual information processing (RVP) test, which is used to assess visual sustained attention, showed a positive correlation with GABAA receptor binding affinity in the right inferior frontal gyrus. No significant correlation was found between RVP test score and regional GM volume or rCBF. CONCLUSION: The findings of 123I-IMZ SPECT, but not those of structural MRI or ASL, suggest that a decreased GABAA receptor binding affinity can be a sensitive marker of cognitive impairment.

Type and Location of Wearable Sensors for Monitoring Falls during Static and Dynamic Tasks in Healthy Elderly: A Review.

In recent years, the meaning of successful living has moved from extending lifetime to improving the quality of aging, mainly in terms of high cognitive and physical functioning together with avoiding diseases. In healthy elderly, falls represent an alarming accident both in terms of number of events and the consequent decrease in the quality of life. Stability control is a key approach for studying the genesis of falls, for detecting the event and trying to develop methodologies to prevent it. Wearable sensors have proved to be very useful in monitoring and analyzing the stability of subjects. Within this manuscript, a review of the approaches proposed in the literature for fall risk assessment, fall prevention and fall detection in healthy elderly is provided. The review has been carried out by using the most adopted publication databases and by defining a search strategy based on keywords and boolean algebra constructs. The analysis aims at evaluating the state of the art of such kind of monitoring, both in terms of most adopted sensor technologies and of their location on the human body. The review has been extended to both dynamic and static analyses. In order to provide a useful tool for researchers involved in this field, the manuscript also focuses on the tests conducted in the analyzed studies, mainly in terms of characteristics of the population involved and of the tasks used. Finally, the main trends related to sensor typology, sensor location and tasks have been identified.

Factors Associated with Undergoing Regular Dental Check-ups in Healthy Elderly Individuals.

The purpose of this study was to determine the distribution of healthy elderly individuals undergoing regular dental check-ups and identify any environmental or associated oral factors. A cross-sectional questionnaire survey was used to interview 216 individuals attending 2 welfare facilities for the elderly, of whom 160 were included in the final analysis. Items comprised age, sex, number of residual teeth, frequency of teeth/denture cleaning, subjective chewing ability, denture use, oral status, regular dental check-ups, visitation of the same dentist, number of dental visits in the past year, General Oral Health Assessment Index (GOHAI) (Japanese version) score, living situation, and use of routine medication. Individuals undergoing regular dental check-ups were defined as those with a primary dentist whom they saw for dental check-ups at least once a year. The rate of individuals undergoing regular dental check-ups was 75.0% in men aged 60-74 years, 58.8% in women aged 60-74 years, 70.0% in men aged 75 years or over, and 45.3% in women aged 75 years or over. Logistic regression analysis revealed a higher number of residual teeth (odds ratio [OR]=2.664 in comparison with those with fewer than 20 teeth, p=0.0427); cleaning teeth/dentures 3 or more times per day (OR=2.546 in comparison with cleaning them twice per day or less, p=0.0157); and a higher GOHAI score (OR=2.742 in comparison with those with a GOHAI score of less than 58, p=0.0263) as factors significantly correlated with undergoing regular dental check-ups. In conclusion, the results revealed that individuals undergoing regular dental check-ups had 20 or more residual teeth, cleaned their teeth/denture 3 or more times per day, and had a higher GOHAI score. This indicates that the best predictive factor for undergoing regular dental check-ups in healthy elderly individuals is their GOHAI score.

Free water elimination improves test-retest reproducibility of diffusion tensor imaging indices in the brain: A longitudinal multisite study of healthy elderly subjects.

Free water elimination (FWE) in brain diffusion MRI has been shown to improve tissue specificity in human white matter characterization both in health and in disease. Relative to the classical diffusion tensor imaging (DTI) model, FWE is also expected to increase sensitivity to microstructural changes in longitudinal studies. However, it is not clear if these two models differ in their test-retest reproducibility. This study compares a bi-tensor model for FWE with DTI by extending a previous longitudinal-reproducibility 3T multisite study (10 sites, 7 different scanner models) of 50 healthy elderly participants (55-80 years old) scanned in two sessions at least 1 week apart. We computed the reproducibility of commonly used DTI metrics (FA: fractional anisotropy, MD: mean diffusivity, RD: radial diffusivity, and AXD: axial diffusivity), derived either using a DTI model or a FWE model. The DTI metrics were evaluated over 48 white-matter regions of the JHU-ICBM-DTI-81 white-matter labels atlas, and reproducibility errors were assessed. We found that relative to the DTI model, FWE significantly reduced reproducibility errors in most areas tested. In particular, for the FA and MD metrics, there was an average reduction of approximately 1% in the reproducibility error. The reproducibility scores did not significantly differ across sites. This study shows that FWE improves sensitivity and is thus promising for clinical applications, with the potential to identify more subtle changes. The increased reproducibility allows for smaller sample size or shorter trials in studies evaluating biomarkers of disease progression or treatment effects. Hum Brain Mapp 38:12-26, 2017. © 2016 Wiley Periodicals, Inc.

Long-lasting active lifestyle and successful cognitive aging in a healthy elderly population: The PROOF cohort.

OBJECTIVES: The aim of this study was to determine whether cognitive reserve in the elderly affects the evolution of cognitive performance and what its relationship is with active lifestyles in later life. METHODS: Cognitive performance was evaluated at baseline and 8 years later in 543 participants of the PROOF cohort, initially aged 67 years. Subjects were categorized as Cognitively Elite (CE), Cognitively Normal (CN) or Cognitively Impaired (CI) at each evaluation. At follow-up, demographic data and lifestyle, including social, intellectual and physical behaviors, were collected by questionnaires. RESULTS: As much as 69% (n=375) remained unchanged, while 25.5% (n=138) decreased and 5.5% (n=30) improved. When present, the reduction in cognitive status was most often limited to one level, but was dependent on the initial level, affecting up to 73% of the initially CN, but only 58% of the initially CE. Cognitive stability was significantly associated with the degree of social engagement at follow-up (CE: P=0.009; CN: P=0.025). CONCLUSION: In the healthy elderly, high cognitive ability predicts both cognitive ability and social involvement in later life. Cognitive decline by only one level may also extend the time to reach impairment, underlining the importance of the so-called cognitive reserve.

Adaptation of multijoint coordination during standing balance in healthy young and healthy old individuals.

Standing balance requires multijoint coordination between the ankles and hips. We investigated how humans adapt their multijoint coordination to adjust to various conditions and whether the adaptation differed between healthy young participants and healthy elderly. Balance was disturbed by push/pull rods, applying two continuous and independent force disturbances at the level of the hip and between the shoulder blades. In addition, external force fields were applied, represented by an external stiffness at the hip, either stabilizing or destabilizing the participants' balance. Multivariate closed-loop system-identification techniques were used to describe the neuromuscular control mechanisms by quantifying the corrective joint torques as a response to body sway, represented by frequency response functions (FRFs). Model fits on the FRFs resulted in an estimation of time delays, intrinsic stiffness, reflexive stiffness, and reflexive damping of both the ankle and hip joint. The elderly generated similar corrective joint torques but had reduced body sway compared with the young participants, corresponding to the increased FRF magnitude with age. When a stabilizing or destabilizing external force field was applied at the hip, both young and elderly participants adapted their multijoint coordination by lowering or respectively increasing their neuromuscular control actions around the ankles, expressed in a change of FRF magnitude. However, the elderly adapted less compared with the young participants. Model fits on the FRFs showed that elderly had higher intrinsic and reflexive stiffness of the ankle, together with higher time delays of the hip. Furthermore, the elderly adapted their reflexive stiffness around the ankle joint less compared with young participants. These results imply that elderly were stiffer and were less able to adapt to external force fields.

A novel accelerometry-based algorithm for the detection of step durations over short episodes of gait in healthy elderly.

BACKGROUND: The assessment of short episodes of gait is clinically relevant and easily implemented, especially given limited space and time requirements. BFS (body-fixed-sensors) are small, lightweight and easy to wear sensors, which allow the assessment of gait at relative low cost and with low interference. Thus, the assessment with BFS of short episodes of gait, extracted from dailylife physical activity or measured in a standardised and supervised setting, may add value in the study of gait quality of the elderly. The aim of this study was to evaluate the accuracy of a novel algorithm based on acceleration signals recorded at different human locations (lower back and heels) for the detection of step durations over short episodes of gait in healthy elderly subjects. METHODS: Twenty healthy elderly subjects (73.7 ± 7.9 years old) walked twice a distance of 5 m, wearing a BFS on the lower back, and on the outside of each heel. Moreover, an optoelectronic three-dimensional (3D) motion tracking system was used to detect step durations. A novel algorithm is presented for the detection of step durations from low-back and heel acceleration signals separately. The accuracy of the algorithm was assessed by comparing absolute differences in step duration between the three methods: step detection from the optoelectronic 3D motion tracking system, step detection from the application of the novel algorithm to low-back accelerations, and step detection from the application of the novel algorithm to heel accelerations. RESULTS: The proposed algorithm successfully detected all the steps, without false positives and without false negatives. Absolute average differences in step duration within trials and across subjects were calculated for each comparison, between low-back accelerations and the optoelectronic system were on average 22.4 ± 7.6 ms (4.0 ± 1.3 % of average step duration), between heel accelerations and the optoelectronic system were on average 20.7 ± 11.8 ms (3.7 ± 1.9 %), and between low-back accelerations and heel accelerations were on average 27.8 ± 15.1 ms (4.9 ± 2.5 % of average step duration). CONCLUSIONS: This study showed that the presented novel algorithm detects step durations over short episodes of gait in healthy elderly subjects with acceptable accuracy from low-back and heel accelerations, which provides opportunities to extract a range of gait parameters from short episodes of gait.

Sural sensory nerve action potential, epidermal nerve fiber density, and quantitative sudomotor axon reflex in the healthy elderly.

INTRODUCTION: Polyneuropathy evaluation in older patients is often challenging due to conflicting data regarding normative values for peripheral nerve testing. METHODS: We characterized the results of sural nerve conduction studies, intraepidermal nerve fiber density (IENFD), and quantitative sudomotor axon reflex testing (QSART) in a prospective study of 50 healthy subjects aged ≥60 years. RESULTS: Of the 50 subjects, 48 (96%) had an obtainable sural sensory nerve action potential (SNAP). Using quantile regression, we estimated the lower limit of normal (LLN) for sural amplitudes to be 3 µV for patients 60-70 years, 1 µV for those 70-74 years, and <1 µV (absent) for those ≥75 years of age. IENFD and QSART volume were reduced with advancing age, although IENFD was lower in men and QSART volume was lower in women. CONCLUSIONS: We propose that an absent sural SNAP in patients up to 75 years of age should be considered abnormal. Our findings also support age- and gender-stratified normative data for IENFD and QSART.

Cognitive functioning and its influence on sexual behavior in normal aging and dementia.

OBJECTIVE: Motivational aspects, emotional factors, and cognition, all of which require intact cognitive functioning may be essential in sexual functioning. However, little is known about the association between cognitive functioning and sexual behavior. The aim of this article is to review the current evidence for the influence of cognitive functioning on sexual behavior in normal aging and dementia. METHODS: A systematic literature search was conducted in PubMed, Ovid, Cochrane, and PsycINFO databases. The databases were searched for English language papers focusing on human studies published relating cognitive functioning to sexual behavior in the aging population. Keywords included sexual behavior, sexuality, cognitive functioning, healthy elderly, elderly, aging and dementia. RESULTS: Eight studies fulfilled our inclusion criteria. Of these studies, five included dementia patients and/or their partners, whereas only three studies included healthy older persons. Although not consistently, results indicated a trend that older people who are not demented and continue to engage in sexual activity have better overall cognitive functioning. Cognitive decline and dementia seem to be associated with diminished sexual behavior in older persons. CONCLUSIONS: The association between cognitive functioning and sexual behavior in the aging population is understudied. The results found are inconclusive.

Reliability of Isometric Knee Extension Muscle Strength Measurements of Healthy Elderly Subjects Made with a Hand-held Dynamometer and a Belt.

[Purpose] The purpose of this study was to examine the reliability of three isometric knee extension strength measurements (IKE) made with a hand-held dynamometer (HHD) and a belt of healthy elderly living in the community as subjects. [Subjects] The subject cohort consisted of 186 healthy elderly people, aged 65 to 79 years, living in local communities. [Methods] IKE of the leg subjects used to kick a ball was measured. IKE of each subject was measured three times using an HHD-belt at intervals of 30 seconds. The reliability of the larger of the first two measurements (LV2) as well as the third measurement (3V) was investigated. [Results] The intraclass correlation coefficients [ICC (1, 1)] for LV2 and 3V were 0.955. Bland-Altman analysis showed a fixed bias, and the limits of agreement ranged from -5.6 to 4.6. [Conclusion] The ICC results show that the test-retest reproducibility of IKE measurements of healthy elderly subjects using an HHD-belt is high. However, Bland-Altman analysis showed a fixed bias, suggesting the need for three measurements.

Gait Characteristics during Dual-Task Walking in Elderly Subjects of Different Ages.

BACKGROUND: In older age, walking ability gradually decreases due to factors including impaired balance, reduced muscle strength, and impaired vision and proprioception. Further, cognitive functions play a key role during walking and gradually decline with age. There is greater variability in gait parameters when the demands during walking increase, in dual- and multiple-task situations. The aim of this study was to analyze gait parameters while performing a demanding cognitive and motor dual task in three different age-related healthy elderly subject groups. METHOD: A total of 132 healthy individuals (54 males, 78 females) were divided into three groups-55 to 65, 66 to 75, and 76 to 85 years. The subjects performed a basic walking task, dual motor task, dual mental task, and combined motor and mental task while walking. The gait parameters cycle time, stride length, swing time, and double support time were noted, as well as the variability of those parameters. RESULTS: Cycle time was longer and stride length was shorter in the >76-year-old group than in the 51-65-year-old group in all test conditions. A comparison of all three groups did not show a significant difference in swing time, while double support time was increased in the same group. CONCLUSIONS: Changes are observed when gait is performed simultaneously with an additional motor or cognitive task. Early detection of gait disorders can help identify elderly people at increased risk of falls. Employing a dual-task paradigm during gait assessment in healthy elderly subjects may help identify cognitive impairment early in the course of the disturbance.

Influence of human gut microbiome on the healthy and the neurodegenerative aging.

The gut microbiome plays a crucial role in host health throughout the lifespan by influencing brain function during aging. The microbial diversity of the human gut microbiome decreases during the aging process and, as a consequence, several mechanisms increase, such as oxidative stress, mitochondrial dysfunction, inflammatory response, and microbial gut dysbiosis. Moreover, evidence indicates that aging and neurodegeneration are closely related; consequently, the gut microbiome may serve as a novel marker of lifespan in the elderly. In this narrative study, we investigated how the changes in the composition of the gut microbiome that occur in aging influence to various neuropathological disorders, such as mild cognitive impairment (MCI), dementia, Alzheimer's disease (AD), and Parkinson's disease (PD); and which are the possible mechanisms that govern the relationship between the gut microbiome and cognitive impairment. In addition, several studies suggest that the gut microbiome may be a potential novel target to improve hallmarks of brain aging and to promote healthy cognition; therefore, current and future therapeutic interventions have been also reviewed.

Comparison of IMU set-ups for the estimation of gait spatio-temporal parameters in an elderly population.

The increasing average age emphasizes the importance of gait analysis in elderly populations. Inertial Measurement Units (IMUs) represent a suitable wearable technology for the characterization of gait by estimating spatio-temporal parameters (STPs). However, the location of inertial sensors on the human body and the associated algorithms for the estimation of gait STPs play a fundamental role and are still open challenges. Accordingly, the aim of this work was to compare three IMUs set-ups (trunk, shanks, and ankles) and correspondent algorithms to a gold standard optoelectronic system for the estimation of gait STPs in a healthy elderly population. In total, 14 healthy elderly subjects walked barefoot at three different speeds. Gait parameters were assessed for each IMUs set-up and compared to those estimated with the gold standard. A statistical analysis based on Pearson correlation, Root Mean Square Error and Bland Altman plots was conducted to evaluate the accuracy of IMUs. Even though all tested set-ups produced accurate results, the IMU on the trunk performed better in terms of correlation (R ≥ 0.8), RMSE (0.01-0.06 s for temporal parameters, 0.03-0.04 for the limp index), and level of agreement (-0.01 s ≤ mean error ≤ 0.01 s, -0.02 s ≤ standard deviation error ≤ 0.02 s), also allowing simpler preparation of subjects and minor encumbrance during gait. From the promising results, a similar experiment might be conducted in pathological populations in the attempt to verify the accuracy of IMUs set-ups and algorithms also in non-physiological patterns.