Naturalistic assessment of reaction time variability in older adults at risk for Alzheimer's disease

OBJECTIVE

Maintaining attention underlies many aspects of cognition and becomes compromised early in neurodegenerative diseases like Alzheimer's disease (AD). The consistency of maintaining attention can be measured with reaction time (RT) variability. Previous work has focused on measuring such fluctuations during in-clinic testing, but recent developments in remote, smartphone-based cognitive assessments can allow one to test if these fluctuations in attention are evident in naturalistic settings and if they are sensitive to traditional clinical and cognitive markers of AD.

METHOD

Three hundred and seventy older adults (aged 75.8 +/- 5.8 years) completed a week of remote daily testing on the Ambulatory Research in Cognition (ARC) smartphone platform and also completed clinical, genetic, and conventional in-clinic cognitive assessments. RT variability was assessed in a brief (20-40 seconds) processing speed task using two different measures of variability, the Coefficient of Variation (CoV) and the Root Mean Squared Successive Difference (RMSSD) of RTs on correct trials.

RESULTS

Symptomatic participants showed greater variability compared to cognitively normal participants. When restricted to cognitively normal participants, APOE ε4 carriers exhibited greater variability than noncarriers. Both CoV and RMSSD showed significant, and similar, correlations with several in-clinic cognitive composites. Finally, both RT variability measures significantly mediated the relationship between APOE ε4 status and several in-clinic cognition composites.

CONCLUSIONS

Attentional fluctuations over 20-40 seconds assessed in daily life, are sensitive to clinical status and genetic risk for AD. RT variability appears to be an important predictor of cognitive deficits during the preclinical disease stage.

The Beneficial, Formative Role of Lifetime Exposures across Cognitive Domains in Barbados Using Data from the SABE Study

This study tested the hypothesis that within older Barbadian adults, sex, education, and occupation type lessen age-related cognitive decline. The analyses used a cross-sectional data set from 1325 people collected in the 2006 SABE Study (Health, Well-being, and Aging). Cognition was assessed as scores in each subdomain of the Mini-Mental State Exam. The loss of a single point in each subdomain was predicted by sex, years of education, job type, and their interactions with age. Results demonstrated that age and protective factors affect each cognitive domain differently. High education combined with mentally complex employment helped maintain cognitive performance in later life. Beneficial lifetime exposures are additive, providing combined benefits. Findings provide insight into public policy aiming to minimize the number of adults with cognitive decline and dementia in Barbados and the Caribbean.

Social and Leisure Activities Predict Transitions in Cognitive Functioning in Older Mexican Adults: A Latent Transition Analysis of the Mexican Health and Aging Study

OBJECTIVES

Mexico has a rapidly aging population at risk for cognitive impairment. Social and leisure activities may protect against cognitive decline in older adults. The benefits of these behaviors may vary by patterns of cognitive impairment. The objectives of this study were to identify latent states of cognitive functioning, model the incidence of transitions between these states, and investigate how social and leisure activities were associated with state transitions over a 6-year period in Mexican adults aged 60 and older.

METHODS

We performed latent transition analyses to identify distinct cognitive statuses in the 2012 and 2018 waves of the Mexican Health and Aging Study (N = 9,091). We examined the transition probabilities between these states and their associations with social and leisure activities.

RESULTS

We identified 4 cognitive statuses at baseline: normal cognition (43%), temporal disorientation (30%), perceptual-motor function impairment (7%), and learning and memory impairment (20%). Various social and leisure activities were associated with reduced odds of death and disadvantageous cognitive transitions, as well as increased odds of beneficial transitions.

DISCUSSION

Mapping the effects of popular social and leisure activities onto common patterns in cognitive functioning may inform the development of more enjoyable and effective health-protective behavioral interventions.

The effect of acute exercise on objectively measured sleep and cognition in older adults

Background

Exercise can improve cognition in aging, however it is unclear how exercise influences cognition, and sleep may partially explain this association. The current study aimed to investigate whether objectively measured sleep mediates the effect of an acute exercise intervention on cognition in older adults.

Methods

Participants were 30 cognitively unimpaired, physically active older adults (69.2 ± 4.3 years) with poor sleep (determined via self-report). After a triple baseline cognitive assessment to account for any natural fluctuation in cognitive performance, participants completed either a single bout of 20-minutes of high intensity exercise on a cycle ergometer, or a control condition, in a cross-over trial design. Cognition was measured immediately post-intervention and the following day, and sleep (total sleep time, sleep onset latency, sleep efficiency, % of rapid eye movement sleep, light sleep and deep sleep) was characterized using WatchPAT™ at baseline (5 nights) and measured for one night after both exercise and control conditions.

Results

Results showed no effect of the exercise intervention on cognition immediately post-intervention, nor an effect of acute exercise on any sleep variable. There was no mediating effect of sleep on associations between exercise and cognition. However, a change from baseline to post-intervention in light sleep and deep sleep did predict change in episodic memory at the ~24 h post-intervention cognitive assessment, regardless of intervention condition.

Discussion

There was no effect of acute high intensity exercise on sleep or cognition in the current study. However, results suggest that associations between sleep and cognition may exist independently of exercise in our sample. Further research is required, and such studies may aid in informing the most effective lifestyle interventions for cognitive health.

Adherence type impacts completion rates of frequent mobile cognitive assessments among older adults with and without cognitive impairment

Background

Prior to a diagnosis of Alzheimer's disease, many individuals experience cognitive and behavioral fluctuations that are not detected during a single session of traditional neuropsychological assessment. Mobile applications now enable high-frequency cognitive data to be collected remotely, introducing new opportunities and challenges. Emerging evidence suggests cognitively impaired older adults are capable of completing mobile assessments frequently, but no study has observed whether completion rates vary by assessment frequency or adherence type.

Methods

Thirty-three older adults were recruited from the Boston University Alzheimer's Disease Research Center (mean age = 73.5 years; 27.3% cognitively impaired; 57.6% female; 81.8% White, 18.2% Black). Participants remotely downloaded and completed the DANA Brain Vital application on their own mobile devices throughout the study. The study schedule included seventeen assessments to be completed over the course of a year. Specific periods during which assessments were expected to be completed were defined as subsegments, while segments consisted of multiple subsegments. The first segment included three subsegments to be completed within one week, the second segment included weekly subsegments and spanned three weeks, and the third and fourth segments included monthly subsegments spanning five and six months, respectively. Three distinct adherence types - subsegment adherence, segment adherence, and cumulative adherence - were examined to determine how completion rates varied depending on assessment frequency and adherence type.

Results

Adherence type significantly impacted whether the completion rates declined. When utilizing subsegment adherence, the completion rate significantly declined (p = 0.05) during the fourth segment. However, when considering completion rates from the perspective of segment adherence, a decline in completion rate was not observed. Overall adherence rates increased as adherence parameters were broadened from subsegment adherence (60.6%) to segment adherence (78.8%), to cumulative adherence (90.9%).

Conclusions

Older adults, including those with cognitive impairment, are able to complete remote cognitive assessments at a high-frequency, but may not necessarily adhere to prescribed schedules.

Daily Physical Activity: Associations With Memory and Affect

PURPOSE

Little is known about effects of moderate to vigorous physical activity (MVPA) and resistance training on daily variations in memory and affect. This study examined the relationship of MVPA and resistance training to memory and affect in daily life.

DESIGN

Short-term longitudinal 7-day diary.

SETTING

Northeast; primarily Boston-area communities.

SAMPLE

Adults aged 25 to 94.

MEASURES

For seven days, MVPA was assessed with an Actigraph. and resistance training was self-reported. Each evening, memory failures, positive and negative affect were recorded in a written diary and objective memory performance was assessed by telephone.

ANALYSIS

Multilevel linear regression analyses examined the between and within person associations of MVPA and resistance training with memory performance, memory failures, and affect.

RESULTS

Those who engaged in more MVPA had better memory performance across the week (b = 0.0163, SE = 0.0076, f2 = 0.004, p = 0.033). Participants reported higher levels of positive affect on days in which they spent more time in MVPA than usual (b = 0.003, SE = 0.001, f2 = 0.144, p < .001) and on days they engaged in resistance training (b = 0.1547, SE = 0.079, f2 = 0.007; p = 0.049).

CONCLUSIONS

Those who spent more time in MVPA had better memory performance, and on days with greater than usual MVPA time and resistance training, affect was more positive than on days with less activity. Implications for motivating physical exercise are considered.

A Decade Later on How to "Use It" So We Don't "Lose It": An Update on the Unanswered Questions about the Influence of Activity Participation on Cognitive Performance in Older Age

Activity engagement is a modifiable factor that has been widely-cited as being good for the aging brain and cognition and represents a valuable target for reducing dementia risk. However, specific issues about activity engagement (mental, social, and physical) and cognition in older adulthood remain, and Bielak [Gerontology 2010;56: 507-519] reviewed seven major methodological and theoretical questions about this relationship. We present an updated reflection on these key questions, focusing on research published in the last 10 years. For some questions, a significant amount of work has been done and conclusions have become clearer; for others, there have been few additions to the literature and our knowledge remains much the same as it was a decade ago. We review the issues identified in the 2010 paper including the directionality and temporal nature of the relationship; whether specific activity domains offer different benefits to cognition and what domain(s) of cognition are affected; variation in the relation by age, gender, or education; potential mechanisms involved; and how activity engagement is assessed. For each, we present the most up-to-date research, discuss remaining challenges and possible future directions. This formal unifying of the information in the field is intended as a guide to support continued progress by spurring on studies addressing specific questions while reminding researchers of critical issues. We conclude with recommendations that future studies investigating the link between activity engagement and cognitive performance in adulthood should consider.

Smartphone-Based Neuropsychological Assessment in Parkinson's Disease: Feasibility, Validity, and Contextually Driven Variability in Cognition

OBJECTIVES

The prevalence of neurodegenerative disorders demands methods of accessible assessment that reliably captures cognition in daily life contexts. We investigated the feasibility of smartphone cognitive assessment in people with Parkinson's disease (PD), who may have cognitive impairment in addition to motor-related problems that limit attending in-person clinics. We examined how daily-life factors predicted smartphone cognitive performance and examined the convergent validity of smartphone assessment with traditional neuropsychological tests.

METHODS

Twenty-seven nondemented individuals with mild-moderate PD attended one in-lab session and responded to smartphone notifications over 10 days. The smartphone app queried participants 5x/day about their location, mood, alertness, exercise, and medication state and administered mobile games of working memory and executive function.

RESULTS

Response rate to prompts was high, demonstrating feasibility of the approach. Between-subject reliability was high on both cognitive games. Within-subject variability was higher for working memory than executive function. Strong convergent validity was seen between traditional tests and smartphone working memory but not executive function, reflecting the latter's ceiling effects. Participants performed better on mobile working memory tasks when at home and after recent exercise. Less self-reported daytime sleepiness and lower PD symptom burden predicted a stronger association between later time of day and higher smartphone test performance.

CONCLUSIONS

These findings support feasibility and validity of repeat smartphone assessments of cognition and provide preliminary evidence of the effects of context on cognitive variability in PD. Further development of this accessible assessment method could increase sensitivity and specificity regarding daily cognitive dysfunction for PD and other clinical populations.

Variability in Cognitive Performance on Mobile Devices Is Sensitive to Mild Cognitive Impairment: Results From the Einstein Aging Study

Background and Objective: Within-person variability in cognitive performance has emerged as a promising indicator of cognitive health with potential to distinguish normative and pathological cognitive aging. We use a smartphone-based digital health approach with ecological momentary assessments (EMA) to examine differences in variability in performance among older adults with mild cognitive impairment (MCI) and those who were cognitively unimpaired (CU). Method: A sample of 311 systematically recruited, community-dwelling older adults from the Einstein Aging Study (Mean age = 77.46 years, SD = 4.86, Range = 70-90; 67% Female; 45% Non-Hispanic White, 40% Non-Hispanic Black) completed neuropsychological testing, neurological assessments, and self-reported questionnaires. One hundred individuals met Jak/Bondi criteria for MCI. All participants performed mobile cognitive tests of processing speed, visual short-term memory binding, and spatial working memory on a smartphone device up to six times daily for 16 days, yielding up to 96 assessments per person. We employed heterogeneous variance multilevel models using log-linear prediction of residual variance to simultaneously assess cognitive status differences in mean performance, within-day variability, and day-to-day variability. We further tested whether these differences were robust to the influence of environmental contexts under which assessments were performed. Results: Individuals with MCI exhibited greater within-day variability than those who were CU on ambulatory assessments that measure processing speed (p < 0.001) and visual short-term memory binding (p < 0.001) performance but not spatial working memory. Cognitive status differences in day-to-day variability were present only for the measure of processing speed. Associations between cognitive status and within-day variability in performance were robust to adjustment for sociodemographic and contextual variables. Conclusion: Our smartphone-based digital health approach facilitates the ambulatory assessment of cognitive performance in older adults and the capacity to differentiate individuals with MCI from those who were CU. Results suggest variability in mobile cognitive performance is sensitive to MCI and exhibits dissociative patterns by timescale and cognitive domain. Variability in processing speed and visual short-term memory binding performance may provide specific detection of MCI. The 16-day smartphone-based EMA measurement burst offers novel opportunity to leverage digital technology to measure performance variability across frequent assessments for studying cognitive health and identifying early clinical manifestations of cognitive impairment.

Daily social interactions related to daily performance on mobile cognitive tests among older adults

The lack of social contact or good social relationships has been linked with cognitive decline and higher risk for Alzheimer’s disease and related dementias. One important but unexamined question is how daily social interactions relate to older adults’ cognitive function in daily life. The present study examined how changes in daily social interactions related to fluctuations in older adults’ performance on mobile cognitive tests from day to day. Using an ecological momentary assessments approach, 312 older adults (aged 70 to 90 years) completed surveys on social interactions and mobile cognitive tests five times a day for 16 consecutive days using smartphones. Multilevel modeling was used for analyses. Results demonstrated that having more daily social interactions, especially more pleasant social interactions, related to better cognitive performance the same day and over the subsequent two days. Cognitive performance, however, did not predict subsequent changes in social interactions across days. At the between-person level, older adults who had more (vs. less) frequent interactions with close partners on average, especially with their friends, had better cognitive performance. Finally, the average levels of social interactions also moderated the within-person associations between daily social interactions and the same-day cognitive performance. In sum, results from this study highlight the importance of having pleasant social interactions and frequent interactions with friends for older adults’ cognitive function in daily life, and have important implications for future behavioral interventions targeting certain features of daily social interactions to reduce risk of cognitive decline and Alzheimer’s disease and related dementias.

Rich and Balanced Experiences of Daily Emotions are Associated with Activity Diversity Across Adulthood

OBJECTIVES

Studies demonstrate the association between diverse emotions and health. However, we know little about how these emotions are related to activities in daily life. This study examined whether the diversity of daily activities ("activity diversity") is associated with the diversity of both positive and negative daily emotions ("emodiversity") in adulthood. We also examined if these associations differed by age.

METHODS

Two separate samples of participants from the Midlife in the United States Study II (M2: 2004-2009, n=2,012, Mage=56yrs) and Refresher (MR: 2012-2016, n=779, Mage=47yrs) provided activity and emotion data for eight consecutive days. Using Shannon's entropy, we constructed activity diversity and emodiversity (positive, negative) scores. Analyses adjusted for sociodemographic and health characteristics, total activity time, mean positive/negative emotions, and number of days with positive/negative emotion data.

RESULTS

Greater activity diversity was associated with greater positive emodiversity and greater negative emodiversity in both samples. In the M2 sample, the association between activity diversity and positive emodiversity was stronger among relatively younger adults, such the positive association among those aged 33-44 years was greater than that observed among those aged 68-84 years. Results held after adjusting for time spent in each of the activities or when using different emodiversity metrics (Gini or Simpson coefficients).

DISCUSSION

Broad and even participation of daily activities may provide more opportunities to experience rich and balanced emotions. Findings suggest that the association between activity diversity and emodiversity exists across adulthood, underscoring the value of including information about daily activities when examining emotional experiences across the lifespan.

Environmental factors related to sleep latency among inpatients in rehabilitation wards according to functional independence measure cognitive scores

BACKGROUND

No study has investigated sleep-related environmental factors in patients according to their functional independence measure (FIM) cognitive scores.

AIMS

The aim of this study is to examine the associations between environmental factors such as noise and sleep latency according to the FIM cognitive scores among inpatients in rehabilitation wards.

DESIGN

This is a prospective longitudinal study.

METHODS

This study measured the sleep state using a bed-based actigraphy, environmental data from Environmental Sensor®, and medical record information of 33 inpatients in the rehabilitation wards during 2018. A linear mixed-effect model was used to analyse the associations between sleep latency and environmental factors. Participants were grouped according to high or low FIM cognitive scores.

RESULTS

The average patient age was 77.2 ± 10.9 years, and 48.5% were male. In the high FIM cognitive score group, the loudness and frequency of noise exceeding 40 dB during sleep latency were significantly associated with sleep latency. In the low FIM cognitive score group, only the noise frequency was associated with sleep latency, and intra-individual variance was larger than that of the high group.

CONCLUSION

These findings suggest that providing night care with attention to subdued noise is important, particularly for patients with low cognitive functional independence levels measured by the FIM cognitive score.

Leveraging Daily Social Experiences to Motivate Healthy Aging

Models of healthy aging highlight the motivating influence of social connections. Social experiences constantly shape our thoughts and behaviors throughout daily life, and these daily processes slowly and consistently influence our health and well-being. In this paper, we discuss research that has moved from cross-sectional laboratory designs emphasizing individual behaviors to more naturalistic within-person paradigms linking daily social experiences to emotional, cognitive, and physical well-being. We mention research gaps that need to be filled to advance our knowledge of the powerful forces of the social environment for motivating healthy aging. We also offer future directions to move this research forward. We conclude with an outlook on how to leverage these powerful forces in novel intervention approaches that are sensitive to the constantly changing nature of the person and the environment.

How do personality traits manifest in daily life of older adults?

The present study examined how personality traits manifest in daily life of older adults and distinguished between the manifestations of experiences and behaviors. We used data from an ambulatory assessment study over 10 days with assessments of trait-related experiences and behaviors obtained from 136 older adults aged between 60 and 91 years (41.2% male; M = 70.45 years). Multilevel models revealed that on average, 61.2% of variance in trait-related experiences and 39.6% of variance in behaviors were due to consistent differences between persons. Older adults were rather variable and diverse in their trait manifestations, while they also showed relative stability in trait manifestations. Across older age, some age effects for trait manifestations were found. Moreover, within-person variation of experiences and behaviors showed, with one exception, joint fluctuations in daily life. The findings portray a nuanced picture of trait manifestations in older adulthood. The findings complement the literature on within-person variability in older adulthood and might encourage further studies from a within-person perspective to better understand how older adults navigate through daily life.

Features of daily social interactions that discriminate between older adults with and without mild cognitive impairment

OBJECTIVES

Detecting subtle behavioral changes in everyday life as early signs of cognitive decline and impairment is important for effective early intervention against Alzheimer's disease. This study examined whether features of daily social interactions captured by ecological momentary assessments could serve as more sensitive behavioral markers to distinguish older adults with mild cognitive impairment (MCI) from those without MCI, as compared to conventional global measures of social relationships.

METHOD

Participants were 311 community dwelling older adults (aged 70 to 90 years) who reported their social interactions and socializing activities five times daily for 14 consecutive days using smartphones.

RESULTS

Compared to those with normal cognitive function, older adults classified as MCI reported less frequent total and positive social interactions and less frequent in-person socializing activities on a daily basis. Older adults with and without MCI, however, did not show differences in most features of social relationships assessed by conventional global measures.

DISCUSSION

These results suggest that certain features of daily social interactions (quality and quantity) could serve as sensitive and ecologically valid behavioral markers to facilitate the detection of MCI.

Diagnosing developmental prosopagnosia: repeat assessment using the Cambridge Face Memory Test

Developmental prosopagnosia (DP) is a cognitive condition characterized by a relatively selective impairment in face recognition. Currently, people are screened for DP via a single attempt at objective face-processing tests, usually all presented on the same day. However, several variables probably influence performance on these tests irrespective of actual ability, and the influence of repeat administration is also unknown. Here, we assess, for the first known time, the test-retest reliability of the Cambridge Face Memory Test (CFMT)-the leading task used worldwide to diagnose DP. This value was found to fall just below psychometric standards, and single-case analyses revealed further inconsistencies in performance that were not driven by testing location (online or in-person), nor the time-lapse between attempts. Later administration of an alternative version of the CFMT (the CFMT-Aus) was also found to be valuable in confirming borderline cases. Finally, we found that performance on the first 48 trials of the CFMT was equally as sensitive as the full 72-item score, suggesting that the instrument may be shortened for testing efficiency. We consider the implications of these findings for existing diagnostic protocols, concluding that two independent tasks of unfamiliar face memory should be completed on separate days.

Natural History of Social Participation in the Very Old: Findings from the Newcastle 85+ Study

Objective: To describe the natural history of social participation in people aged 85 years and over. Methods: Prospective cohort study; Newcastle 85+ study. Data were collected at baseline (n = 850) and at 18-, 36- and 60-month follow-ups (n = 344). Participation in 19 social activities (e.g. playing bingo, doing volunteer work and watching television) was measured at each time point. Results: The mean number of activities reported at baseline was 8.7 (SD 2.6). The number of activities was higher in those with higher educational attainment and intact walking ability (both p < .001). Social participation decreased significantly over time (p < .001) and at a similar rate in both sexes and for those with/without limited walking ability but at a higher rate in those with higher than lower educational attainment (p = .019). Discussion: Social participation seems to decrease significantly between ages 85 and 90 years; ways of encouraging social participation in this age group are needed.

Cognition in Context: Understanding the Everyday Predictors of Cognitive Performance in a New Era of Measurement

Background

Research suggests that variability in attention and working memory scores, as seen across time points, may be a sensitive indicator of impairment compared with a singular score at one point in time. Given that fluctuation in cognitive performance is a meaningful metric of real-world function and trajectory, it is valuable to understand the internal state-based and environmental factors that could be driving these fluctuations in performance.

Objective

In this viewpoint, we argue for the use of repeated mobile assessment as a way to better understand how context shapes moment-to-moment cognitive performance. To elucidate potential factors that give rise to intraindividual variability, we highlight existing literature that has linked both internal and external modifying variables to a number of cognitive domains. We identify ways in which these variables could be measured using mobile assessment to capture them in ecologically meaningful settings (ie, in daily life). Finally, we describe a number of studies that have already begun to use mobile assessment to measure changes in real time cognitive performance in people’s daily environments and the ways in which this burgeoning methodology may continue to advance the field.

Methods

This paper describes selected literature on contextual factors that examined how experimentally induced or self-reported contextual variables (ie, affect, motivation, time of day, environmental noise, physical activity, and social activity) related to tests of cognitive performance. We also selected papers that used mobile assessment of cognition; these papers were chosen for their use of high-frequency time-series measurement of cognition using a mobile device.

Results

Upon review of the relevant literature, it is evident that contextual factors have the potential to meaningfully impact cognitive performance when measured in laboratory and daily life environments. Although this research has shed light on the question of what gives rise to real-life variability in cognitive function (eg, affect and activity), many of the studies were limited by traditional methods of data collection (eg, involving retrospective recall). Furthermore, cognition has often been measured in one domain or in one age group, which does not allow us to extrapolate results to other cognitive domains and across the life span. On the basis of the literature reviewed, mobile assessment of cognition shows high levels of feasibility and validity and could be a useful method for capturing individual cognitive variability in real-world contexts via passive and active measures.

Conclusions

We propose that, through the use of mobile assessment, there is an opportunity to combine multiple sources of contextual and cognitive data. These data have the potential to provide individualized digital signatures that could improve diagnostic precision and lead to meaningful clinical outcomes in a wide range of psychiatric and neurological disorders.

Associations Between Aging-Related Changes in Grip Strength and Cognitive Function in Older Adults: A Systematic Review

OBJECTIVES

Grip strength and cognitive function reflect upper body muscle strength and mental capacities. Cross-sectional research has suggested that in old age these two processes are moderately to highly associated, and that an underlying common cause drives this association. Our aim was to synthesize and evaluate longitudinal research addressing whether changes in grip strength are associated with changes in cognitive function in healthy older adults.

METHODS

We systematically reviewed English-language research investigating the longitudinal association between repeated measures of grip strength and of cognitive function in community-dwelling older adults to evaluate the extent to which the two indices decline concurrently. We used four search engines: Embase, PsychINFO, PubMed, and Web of Science.

RESULTS

Of 459 unique citations, 6 met our full criteria: 4 studies reported a longitudinal association between rates of change in grip strength and cognitive function in older adults, 2 of which reported the magnitudes of these associations as ranging from low to moderate; 2 studies reported significant cross-sectional but not longitudinal associations among rates of change. All studies concluded that cognitive function and grip strength declined, on average, with increasing age, although with little to no evidence for longitudinal associations among rates of change.

CONCLUSIONS

Future research is urged to expand the study of physical and cognitive associations in old age using a within-person and multi-study integrative approach to evaluate the reliability of longitudinal results with greater emphasis on the magnitude of this association.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42016038544.