An evaluation of analytical approaches for understanding change in cognition in the context of aging and health

A comparison of two approaches for modeling dementia progression in a changing patient context

OBJECTIVES

To explain the heterogeneity in dementia disease trajectory, we studied the influence of changing patient characteristics on disease course by comparing the association of dementia progression with baseline comorbidity and frailty, and with time-varying comorbidity and frailty.

METHODS

We used individual growth models to study baseline and time-varying associations in newly diagnosed dementia patients (n = 331) followed for 3 years. We measured cognition using the Mini-Mental State Examination (MMSE), daily functioning using the Disability Assessment for Dementia (DAD), frailty using the Fried criteria and comorbidity using the Cumulative Illness Rating Scale for Geriatrics (CIRS-G).

RESULTS

Although baseline comorbidity and frailty were associated with decreased daily functioning at diagnosis, their effects clearly diminished over time. In contrast, when incorporating comorbidity and frailty as time-varying covariates, comorbidity was associated with lower daily functioning, and frailty with both lower cognition and daily functioning. Being frail was associated with a 0.9-point lower MMSE score (p = 0.03) and a 14.9-point lower DAD score (p < 0.01). A 1-point increase in CIRS-G score was associated with a 1.1-point lower DAD score (p < 0.01).

CONCLUSIONS

Time-varying comorbidity and frailty were more consistently associated with dementia disease course than baseline comorbidity and frailty. Therefore, modeling only baseline predictors is insufficient for understanding the course of dementia in a changing patient context.

Coordinated data analysis: Knowledge accumulation in lifespan developmental psychology

Coordinated analysis is a powerful form of integrative analysis, and is well suited in its capacity to promote cumulative scientific knowledge, particularly in subfields of psychology that focus on the processes of lifespan development and aging. Coordinated analysis uses raw data from individual studies to create similar hypothesis tests for a given research question across multiple datasets, thereby making it less vulnerable to common criticisms of meta-analysis such as file drawer effects or publication bias. Coordinated analysis can sometimes use random effects meta-analysis to summarize results, which does not assume a single true effect size for a given statistical test. By fitting parallel models in separate datasets, coordinated analysis preserves the heterogeneity among studies, and provides a window into the generalizability and external validity of a set of results. The current article achieves three goals: First, it describes the phases of a coordinated analysis so that interested researchers can more easily adopt these methods in their labs. Second, it discusses the importance of coordinated analysis within the context of the credibility revolution in psychology. Third, it encourages the use of existing data networks and repositories for conducting coordinated analysis, in order to enhance accessibility and inclusivity. Subfields of research that require time- or resource- intensive data collection, such as longitudinal aging research, would benefit by adopting these methods. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

A Coordinated Multi-study Analysis of the Longitudinal Association Between Handgrip Strength and Cognitive Function in Older Adults

OBJECTIVE

Handgrip strength, an indicator of overall muscle strength, has been found to be associated with slower rate of cognitive decline and decreased risk for cognitive impairment and dementia. However, evaluating the replicability of associations between aging-related changes in physical and cognitive functioning is challenging due to differences in study designs and analytical models. A multiple-study coordinated analysis approach was used to generate new longitudinal results based on comparable construct-level measurements and identical statistical models and to facilitate replication and research synthesis.

METHODS

We performed coordinated analysis on 9 cohort studies affiliated with the Integrative Analysis of Longitudinal Studies of Aging and Dementia (IALSA) research network. Bivariate linear mixed models were used to examine associations among individual differences in baseline level, rate of change, and occasion-specific variation across grip strength and indicators of cognitive function, including mental status, processing speed, attention and working memory, perceptual reasoning, verbal ability, and learning and memory. Results were summarized using meta-analysis.

RESULTS

After adjustment for covariates, we found an overall moderate association between change in grip strength and change in each cognitive domain for both males and females: Average correlation coefficient was 0.55 (95% CI = 0.44-0.56). We also found a high level of heterogeneity in this association across studies.

DISCUSSION

Meta-analytic results from nine longitudinal studies showed consistently positive associations between linear rates of change in grip strength and changes in cognitive functioning. Future work will benefit from the examination of individual patterns of change to understand the heterogeneity in rates of aging and health-related changes across physical and cognitive biomarkers.

Cognitive and functional progression of dementia in two longitudinal studies

OBJECTIVES

Previous studies have identified several subgroups (ie, latent trajectories) with distinct disease progression among people with dementia. However, the methods and results were not always consistent. This study aims to perform a coordinated analysis of latent trajectories of cognitive and functional progression in dementia across two datasets.

METHODS

Included and analyzed using the same statistical approach were 1628 participants with dementia from the US National Alzheimer's Coordinating Center (NACC) and 331 participants with dementia from the Dutch Clinical Course of Cognition and Comorbidity study (4C-Study). Trajectories of cognition and instrumental activities of daily living (IADL) were modeled jointly in a parallel-process growth mixture model.

RESULTS

Cognition and IADL tended to decline in unison across the two samples. Slow decline in both domains was observed in 26% of the US sample and 74% of the Dutch sample. Rapid decline in cognition and IADL was observed in 7% of the US sample and 26% of the Dutch sample. The majority (67%) of the US sample showed moderate cognitive decline and rapid IADL decline.

CONCLUSIONS

Trajectories of slow and rapid dementia progression were identified in both samples. Despite using the same statistical methods, the number of latent trajectories was not replicated and the relative class sizes differed considerably across datasets. These results call for careful consideration when comparing progression estimates in the literature. In addition, the observed discrepancy between cognitive and functional decline stresses the need to monitor dementia progression across multiple domains.

Cognitive activity mediates the association between social activity and cognitive performance: A longitudinal study

Social activity is 1 aspect of an active lifestyle and some evidence indicates it is related to preserved cognitive function in older adulthood. However, the potential mechanisms underlying this association remain unclear. We investigate 4 potential mediational pathways through which social activity may relate to cognitive performance. A multilevel structural equation modeling approach to mediation was used to investigate whether cognitive activity, physical activity, depressive symptoms, and vascular health conditions mediate the association between social activity and cognitive function in older adults. Using data from the Victoria Longitudinal Study, we tested 4 cognitive outcomes: fluency, episodic memory, reasoning, and vocabulary. Three important findings emerged. First, the association between social activity and all 4 domains of cognitive function was significantly mediated by cognitive activity at the within-person level. Second, we observed a significant indirect effect of social activity on all domains of cognitive function through cognitive activity at the between-person level. Third, we found a within-person indirect relationship of social activity with episodic memory performance through physical activity. For these older adults, engagement in social activities was related to participation in everyday cognitive activities and in turn to better cognitive performance. This pattern is consistent with the interpretation that a lifestyle of social engagement may benefit cognitive performance by providing opportunities or motivation to participate in supportive cognitively stimulating activities. (PsycINFO Database Record

Decline in Memory, Visuospatial Ability, and Crystalized Cognitive Abilities in Older Adults: Normative Aging or Terminal Decline?

The aim of this study is to explore the pattern of change in multiple measures of cognitive abilities in a sample of oldest-old adults, comparing two different time metrics (chronological age and time to death) and therefore examining both underlying conceptual assumptions (age-related change and terminal decline). Moreover, the association with individual characteristics as sex, education, and dementia diagnosis was also examined. Measures of cognitive status (Mini-Mental State Examination and the Swedish Clock Test) and tests of crystallized (knowledge and synonyms), memory (verbal memory, nonverbal long-term memory, recognition and correspondence, and short-term memory), and visuospatial ability were included. The sample consisted of 671 older Swedish adult participants of the OCTO Twin Study. Linear mixed models with random coefficients were used to analyse change patterns and BIC indexes were used to compare models. Results showed that the time to death model was the best option in analyses of change in all the cognitive measures considered (except for the Information Test). A significant cognitive decline over time was found for all variables. Individuals diagnosed with dementia had lower scores at the study entrance and a faster decline. More educated individuals performed better in all the measures of cognition at study entry than those with poorer education, but no differences were found in the rate of change. Differences were found in age, sex, or time to death at baseline across the different measures. These results support the terminal decline hypothesis when compared to models assuming that cognitive changes are driven by normative aging processes.

Personality and global cognitive decline in Japanese community-dwelling elderly people: A 10-year longitudinal study

OBJECTIVES

To examine the longitudinal associations between the big five personality and changes in global cognitive function among community-dwelling elderly people involved in the National Institute for Longevity Sciences - Longitudinal Study of Aging.

METHODS

The participants were 594 individuals (age range 60-81years) and followed for 10years and tested six times. Personality was assessed by the Japanese version of NEO five factor inventory at baseline. Cognitive function was assessed by the Japanese version of Mini Mental State Examination (MMSE) at all visits. For participants with a baseline MMSE score≥28, logistic generalized estimating equation models estimated the odds ratio (OR) and 95% confidence interval (CI) for MMSE score≤27 at each follow-up visit, according to a 1-SD increase of the baseline personality score. Post hoc analyses were performed for mild cognitive deficits, baseline MMSE score≥24 and ≤27, to estimate the OR and CI for MMSE score≤23.

RESULTS

The adjusted OR for MMSE score≤27 was 0.78 (95% CI, 0.69-0.88), with a 1-SD increase in Openness to Experience score. In post hoc analyses, the adjusted OR for MMSE score≤23 was 0.50 (95% CI, 0.35-0.72) with a 1-SD increase in Conscientiousness score. Relationships between other personality traits and the decline in MMSE score were not significant.

CONCLUSIONS

Higher Openness to Experience was associated with a reduction in risk for cognitive decline in community-dwelling older adults. Higher Conscientiousness might also predict lower risk for severe cognitive decline, especially for individuals with mild cognitive deficits.

Predictors of Long-Term Change in Adult Cognitive Performance: Systematic Review and Data from the Northern Finland Birth Cohort 1966

OBJECTIVE

Several social life events and challenges have an impact on cognitive development. Our goal was to analyze the predictors of change in cognitive performance in early midlife in a general population sample. Additionally, systematic literature review was performed.

METHOD

The study sample was drawn from the Northern Finland Birth Cohort 1966 at the ages of 34 and 43 years. Primary school performance, sociodemographic factors and body mass index (BMI) were used to predict change in cognitive performance measured by the California Verbal Learning Test, Visual Object Learning Test, and Abstraction Inhibition and Working Memory task. Analyses were weighted by gender and education, and p-values were corrected for multiple comparisons using Benjamini-Hochberg procedure (B-H).

RESULTS

Male gender predicted decrease in episodic memory. Poor school marks of practical subjects, having no children, and increase in BMI were associated with decrease in episodic memory, though non-significantly after B-H. Better school marks, and higher occupational class were associated with preserved performance in visual object learning. Higher vocational education predicted preserved performance in visual object learning test, though non-significantly after B-H. Likewise, having children predicted decreased performance in executive functioning but non-significantly after B-H.

CONCLUSIONS

Adolescent cognitive ability, change in BMI and several sociodemographic factors appear to predict cognitive changes in early midlife. The key advantage of present study is the exploration of possible predictors of change in cognitive performance among general population in the early midlife, a developmental period that has been earlier overlooked.

I forgot when I lost my grip-strong associations between cognition and grip strength in level of performance and change across time in relation to impending death

An association between level of cognitive function and grip strength is well established, whereas evidence for longitudinal associations of change in the 2 functions is still unclear. We examined associations between cognition and grip strength in levels of performance and in longitudinal change in late life in a population-based sample, aged ≥80 years at baseline, followed until death. The sample consisted of 449 nondemented individuals drawn from the OCTO-Twin Study. A test battery assessing 6 cognitive domains and grip strength was administered at 5 occasions with measurements intervals of 2 years. We fitted time to death bivariate growth curve models, adjusted for age, education, and sex which resulted in associations between grip strength and cognition in both levels of performance (across all cognitive domains) and rates of change (in 4 of 6 domains). These results show that cognition and grip strength change conjointly in later life and that the association between cognition and grip strength is stronger before death than earlier in life.

Causal associations between depression symptoms and cognition in a community-based cohort of older adults

OBJECTIVE

To evaluate the temporal association between depression symptoms and cognitive function in older adults over a 4-year period.

METHODS

Using a longitudinal, cross-lagged, population-based design, we studied depression symptoms and cognitive domains (including processing speed, verbal fluency, face and word recognition, episodic memory, and simple and choice reaction time) in 896 community-dwelling adults aged 70-97 years.

RESULTS

Cross-lagged structural equation models suggested that initial depression symptoms affected subsequent processing speed and simple and choice reaction time but that cognition did not predict depression symptoms over time. The associations between depression and cognitive variables were attenuated when the models were adjusted for sensory impairment, physical health, and locus of control.

CONCLUSION

The findings suggest that, causally, depression precedes cognitive impairment in this age group and that the association is related to physical health and perceptions of a lack of control.

Fighting for Intelligence: A Brief Overview of the Academic Work of John L. Horn

John L. Horn (1928-2006) was a pioneer in multivariate thinking and the application of multivariate methods to research on intelligence and personality. His key works on individual differences in the methodological areas of factor analysis and the substantive areas of cognition are reviewed here. John was also our mentor, teacher, colleague, and friend. We overview John Horn's main contributions to the field of intelligence by highlighting 3 issues about his methods of factor analysis and 3 of his substantive debates about intelligence. We first focus on Horn's methodological demonstrations describing (a) the many uses of simulated random variables in exploratory factor analysis; (b) the exploratory uses of confirmatory factor analysis; and (c) the key differences between states, traits, and trait-changes. On a substantive basis, John believed that there were important individual differences among people in terms of cognition and personality. These sentiments led to his intellectual battles about (d) Spearman's g theory of a unitary intelligence, (e) Guilford's multifaceted model of intelligence, and (f) the Schaie and Baltes approach to defining the lack of decline of intelligence earlier in the life span. We conclude with a summary of John Horn's unique approaches to dealing with common issues.

Coordinated analysis of age, sex, and education effects on change in MMSE scores

OBJECTIVES

We describe and compare the expected performance trajectories of older adults on the Mini-Mental Status Examination (MMSE) across six independent studies from four countries in the context of a collaborative network of longitudinal studies of aging. A coordinated analysis approach is used to compare patterns of change conditional on sample composition differences related to age, sex, and education. Such coordination accelerates evaluation of particular hypotheses. In particular, we focus on the effect of educational attainment on cognitive decline.

METHOD

Regular and Tobit mixed models were fit to MMSE scores from each study separately. The effects of age, sex, and education were examined based on more than one centering point.

RESULTS

Findings were relatively consistent across studies. On average, MMSE scores were lower for older individuals and declined over time. Education predicted MMSE score, but, with two exceptions, was not associated with decline in MMSE over time.

CONCLUSION

A straightforward association between educational attainment and rate of cognitive decline was not supported. Thoughtful consideration is needed when synthesizing evidence across studies, as methodologies adopted and sample characteristics, such as educational attainment, invariably differ.