Auditory event-related potentials in individuals with subjective and mild cognitive impairment.

OBJECTIVE: The analysis of event-related potentials (ERPs) is a useful tool to differentiate between healthy older adults, and individuals with mild cognitive impairment (MCI). Less is known about the ERPs' sensitivity of differentiating between individuals with subjective cognitive impairment (SCI) and MCI, as early evidence indicates similar brain alterations between these two groups. In order, to establish tests that are sensitive to subclinical impairment, this study compared auditory evoked ERPs between individuals with SCI and MCI. METHODS: Besides assessing cognitive performance in four neuropsychological tests (Trail Making Test A + B, verbal fluency letter and category task), latency and amplitude of ERP components evoked by an auditory oddball paradigm were compared between two groups of either individuals with SCI (n = 13) or MCI (n = 13). RESULTS: While individuals with MCI performed significantly worse in all neuropsychological tests (TMT A: p = 0.001, Cohen's d = 1.5; TMT B: p = 0.030, Cohen's d = 0.94; verbal fluency letter: p = 0.0011, Cohen's d = 1.08; verbal fluency category: p = 0.038; Cohen's d = 0.86), no significant differences (p > 0.05) were found in ERP components with small to moderate effect sizes (Cohen's d ranged between 0.11 - 0.59). CONCLUSION: ERPs evoked by an auditory oddball paradigm lack sensitivity to differentiate between individuals with SCI and MCI, although significant differences in cognitive performance were detected by neuropsychological tests. Similar pathophysiological brain alterations may limit utility of ERPs as indicated by previous research and results of this study. Cognitively more challenging tasks than the auditory oddball paradigm may be considered by future investigations.

Rating of perceived exertion - a valid method for monitoring light to vigorous exercise intensity in individuals with subjective and mild cognitive impairment?

In rehabilitation settings, exercise intensity is often monitored with Borg's rating of perceived exertion (RPE). However, previous studies showed that severe cognitive impairment may limit the usability of the RPE. The aim of this study was to assess the relationship between RPE and heart rate (HR), and to establish whether a target RPE can be used to achieve exercise intensity based on an individual's HR-RPE in people with early cognitive impairment. 97 participants (74.7 ± 6 years) with early cognitive impairment completed an incremental exercise test. Of these, 54 were tested during a single, RPE guided exercise session. RPE and HR were monitored throughout. Correlations between HR and RPE were assessed using Spearman's correlation. Mean differences between measured HR and target HR were calculated and compared using a two-way ANOVA with factors cognition and exercise mode. Bland-Altman plots were constructed to analyse the agreement between target and measured HR. HR and RPE correlated moderately with each other (p < 0.001; r = 0.555) and no differences between target and measured HR were observed. Bland-Altman plots revealed a mean difference of 1.2 bpm and a 95% level of agreement was between 24.4 and -22.1 bpm. No differences in rating accuracy were observed between different cognitive impairment levels nor between different exercise modes. Bland-Altman plots revealed some variance between the participants with almost half of them missing target HR by 10bpm or more. Therefore, the RPE should only be applied with caution and, if possible, with other measurements (e.g. heart rate monitors) to ensure that target intensity is reached.

Validation of a widely used heart rate monitor to track steps in older adults.

BACKGROUND: Activity tracking devices gain popularity in research, which is due to their multiple features (e.g. heart rate monitor, step count) and easy handling. Nevertheless, many devices used for research are lacking validation of specific features. This study aimed to assess the validity of the Polar M400© activity tracker to count steps in older adults and, therefore, compared it to a previously validated pedometer (Omron Walking Style©) and observed step count. METHODS: Thirty-two older adults (mean age: 74.8±5.9 years) walked at a self-selected, normal gait speed on a tartan track for 200 meters while wearing the activity tracker and the pedometer. Additionally, steps were counted manually. Data was analysed using Kruskal-Wallis test and Lin's concordance coefficient. Furthermore, Bland Altman plots were employed to evaluate accuracy of the activity tracker. RESULTS: Kruskal-Wallis test revealed significant differences between the step count of the activity tracker and the pedometer (P=0.011) but no further differences were observed. Lin's concordance showed a moderate correlation between activity tracker and pedometer (rc=0.561) and between pedometer and observed step count (rc=0.690). A high correlation was detected between activity tracker and observed step count (rc=0.802). Bland Altman plots revealed good accuracy of the activity tracker. CONCLUSIONS: The Polar M400© activity tracker accurately assesses steps during walking in older adults. Nevertheless, a slight overestimation compared to the pedometer was observed, which should be considered when using the activity tracker for tracking steps over a longer period of time.

Cardiorespiratory Fitness and Cognitive Function are Positively Related Among Participants with Mild and Subjective Cognitive Impairment.

BACKGROUND: By 2030, about 74 million people will be diagnosed with dementia, and many more will experience subjective (SCI) or mild cognitive impairment (MCI). As physical inactivity has been identified to be a strong modifiable risk factor for dementia, exercise and physical activity (PA) may be important parameters to predict the progression from MCI to dementia, but might also represent disease trajectory modifying strategies for SCI and MCI. OBJECTIVE: A better understanding of the relationship between activity, fitness, and cognitive function across the spectrum of MCI and SCI would provide an insight into the potential utility of PA and fitness as early markers, and treatment targets to prevent cognitive decline. METHODS: 121 participants were stratified into three groups, late MCI (LMCI), early MCI (EMCI), and SCI based on the Montreal Cognitive Assessment (MoCA). Cognitive function assessments also included the Trail Making Test A+B, and a verbal fluency test. PA levels were evaluated with an interviewer-administered questionnaire (LAPAQ) and an activity monitor. An incremental exercise test was performed to estimate cardiorespiratory fitness and to determine exercise capacity relative to population normative data. RESULTS: ANCOVA revealed that LMCI subjects had the lowest PA levels (LAPAQ, p = 0.018; activity monitor, p = 0.041), and the lowest exercise capacity in relation to normative values (p = 0.041). Moreover, a modest correlation between MoCA and cardiorespiratory fitness (r = 0.25; p < 0.05) was found. CONCLUSION: These findings suggest that during the earliest stages of cognitive impairment PA and exercise capacity might present a marker for the risk of further cognitive decline. This finding warrants further investigation using longitudinal cohort studies.

Cognitive Impairment Is Reflected by an Increased Difference between Real and Imagined Timed Up and Go Test Performance.

BACKGROUND: Recent research suggests using an imaginary version of the Timed Up and Go test (TUG) for a first assessment of cognitive impairment. By using the time difference between a real (TUGr) and an imagined (TUGi) TUG task, the objective of this study was to examine the effect of cognitive impairment on motor imagery ability. METHODS: Fifty-two participants (mean age 69.3 ± 4.0 years) with mild cognitive impairment or subjective cognitive impairment were included in this study. The time difference between the TUGr and the TUGi was used as the main outcome. The Trail Making Test part B (TMT B), the ratio between TMT A and TMT B, and the Montreal Cognitive Assessment (MoCA) battery were the main independent variables. RESULTS: The difference between TUGr and TUGi performance time and the TMT B performance time increased with decreasing cognitive function (p < 0.01). There was no relationship between TUGr and TUGi performance time and TMT B/A ratio. There were significant correlations between TUG time differences and the MoCA score (r = -0.489, p < 0.01), the TMT B (r = 0.364, p < 0.01), and the TMT B/A ratio (r = 0.377, p < 0.01). CONCLUSION: The combination of TUGr and TUGi may have added value in assessing cognitive impairment, which is a possible pre-stage of dementia.