Trajectories of cognitive decline following dementia onset: what accounts for variation in progression?

Post-Hoc Assessment of Cognitive Efficacy in Alzheimer's Disease Using a Latent Growth Mixture Model in AMBAR, a Phase 2B Randomized Controlled Trial

BACKGROUND

Disease progression in Alzheimer's Dementia (AD) is typically characterized by accelerated cognitive and functional decline, where heterogeneous trajectories can impact the observed treatment response.

METHODS

We hypothesized that unobserved heterogeneity could obscure treatment benefits in AD. The effect of unobserved heterogeneity was empirically quantified within the Alzheimer's Management By Albumin Replacement (AMBAR) phase 2b trial data. The ADAS-Cog 12 cognition endpoint was reanalyzed in a 2-class latent growth mixture model initially fit to the treatment arm. The model with the best fit was then applied across both treatment arms to a larger (n=1000) simulated dataset that was representative of AMBAR trial cognitive data.

RESULTS

Two classes of patients were observed: a stable cognitive trajectory class and a highly variable class. Removal of the latter (n=48, 22%) from the analysis and refitting efficacy models comparing the stable class to full placebo yielded significant treatment efficacy on cognition (p=0.007, Cohen's D=-0.4). Comparison of the stable class of each arm within the simulated dataset revealed a significant difference in treatment efficacy favoring the simulated stable treatment arm.

CONCLUSION

This post hoc exploratory analysis suggests that prespecified strategies for addressing unobserved heterogeneity may yield improved effect detection in AD trials. The generalizability of the analytic strategy is limited by latent stratification in only the treatment arm, a requirement given the small placebo arm in AMBAR. This limitation was partially addressed by the simulation modeling.

Heritability of cognitive abilities and regional brain structures in middle-aged to elderly East Asians

This study examined the single-nucleotide polymorphism heritability and genetic correlations of cognitive abilities and brain structural measures (regional subcortical volume and cortical thickness) in middle-aged and elderly East Asians (Korean) from the Gwangju Alzheimer's and Related Dementias cohort study. Significant heritability was found in memory function, caudate volume, thickness of the entorhinal cortices, pars opercularis, superior frontal gyri, and transverse temporal gyri. There were 3 significant genetic correlations between (i) the caudate volume and the thickness of the entorhinal cortices, (ii) the thickness of the superior frontal gyri and pars opercularis, and (iii) the thickness of the superior frontal and transverse temporal gyri. This is the first study to describe the heritability and genetic correlations of cognitive and neuroanatomical traits in middle-aged to elderly East Asians. Our results support the previous findings showing that genetic factors play a substantial role in the cognitive and neuroanatomical traits in middle to advanced age. Moreover, by demonstrating shared genetic effects on different brain regions, it gives us a genetic insight into understanding cognitive and brain changes with age, such as aging-related cognitive decline, cortical atrophy, and neural compensation.

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.

The role of intraindividual cognitive variability in posttraumatic stress syndromes and cognitive aging: a literature search and proposed research agenda

OBJECTIVES

Cognitive impairments are directly related to severity of symptoms and are a primary cause for functional impairment. Intraindividual cognitive variability likely plays a role in both risk and resiliency from symptoms. In fact, such cognitive variability may be an earlier marker of cognitive decline and emergent psychiatric symptoms than traditional psychiatric or behavioral symptoms. Here, our objectives were to survey the literature linking intraindividual cognitive variability, trauma, and dementia and to suggest a potential research agenda.

DESIGN

A wide body of literature suggests that exposure to major stressors is associated with poorer cognitive performance, with intraindividual cognitive variability in particular linked to the development of posttraumatic stress disorder (PTSD) in the aftermath of severe trauma.

MEASUREMENTS

In this narrative review, we survey the empirical studies to date that evaluate the connection between intraindividual cognitive variability, PTSD, and pathological aging including dementia.

RESULTS

The literature suggests that reaction time (RT) variability within an individual may predict future cognitive impairment, including premature cognitive aging, and is significantly associated with PTSD symptoms.

CONCLUSIONS

Based on our findings, we argue that intraindividual RT variability may serve as a common pathological indicator for trauma-related dementia risk and should be investigated in future studies.

Long-Term Care Service Trajectories and Their Predictors for Persons Living With Dementia: Results From a Canadian Study

OBJECTIVE

We used latent transition analysis to explore common long-term care (LTC) service trajectories and their predictors for older adults with dementia.

METHOD

Using linked administrative data collected over a 4-year interval (2008-2011), the study sample included 3,541 older persons with dementia who were clients of publicly funded LTC in British Columbia, Canada.

RESULTS

Our results revealed relatively equal reliance on home care (HC) and facility-based residential care (RC) as starting points. HC service users were further differentiated into "intermittent HC" and "continuous HC" groups. Mortality was highest for the RC group. Age, changes in cognitive performance, and activities of daily living were important predictors of transitions into HC or RC.

DISCUSSION

Reliance on HC and RC by persons with dementia raises critical questions about ensuring that an adequate range of services is available in local communities to support aging in place and to ensure appropriate timing for entry into institutions.

Association Between Accelerated Multimorbidity and Age-Related Cognitive Decline in Older Baltimore Longitudinal Study of Aging Participants without Dementia

OBJECTIVES

To explore the association between rate of physical health deterioration, operationalized as rising multimorbidity overtime, and longitudinal decline in cognitive function in older adults without dementia.

DESIGN

Longitudinal (Baltimore Longitudinal Study of Aging (BLSA)).

SETTING

Community.

PARTICIPANTS

BLSA participants aged 65 and older followed for an average of 3 years and free of dementia or mild cognitive impairment (MCI) at baseline and follow-up (N = 756).

MEASUREMENTS

Standardized neurocognitive tests evaluating mental status, memory, executive function, processing speed, and verbal fluency were administered. Multimorbidity was assessed at each visit as number of diagnosed chronic diseases from a predefined list. Faster accumulation of chronic diseases was defined as upper quartile of rate of change in number of diseases over time (≥0.25 diseases/year).

RESULTS

Faster accumulation of chronic diseases was significantly associated with greater rate of decline on the Category (P = .01) and Letter (P = .01) Fluency Tests. Similar trends were also found for the Trail-Making Test Parts A (P = .08) and B (P = .07); no association was found with rate of change in visual and verbal memory.

CONCLUSION

Although further investigations are required to validate the results and fully understand the underlying mechanisms, these findings suggest that accelerated deterioration of physical health is associated with accelerated decline with aging in specific cognitive domains in older adults without dementia.

Selective attrition and intraindividual variability in response time moderate cognitive change

OBJECTIVES

Selection of a developmental time metric is useful for understanding causal processes that underlie aging-related cognitive change and for the identification of potential moderators of cognitive decline. Building on research suggesting that time to attrition is a metric sensitive to non-normative influences of aging (e.g., subclinical health conditions), we examined reason for attrition and intraindividual variability (IIV) in reaction time as predictors of cognitive performance.

METHOD

Three hundred and four community dwelling older adults (64-92 years) completed annual assessments in a longitudinal study. IIV was calculated from baseline performance on reaction time tasks. Multilevel models were fit to examine patterns and predictors of cognitive change.

RESULTS

We show that time to attrition was associated with cognitive decline. Greater IIV was associated with declines on executive functioning and episodic memory measures. Attrition due to personal health reasons was also associated with decreased executive functioning compared to that of individuals who remained in the study.

DISCUSSION

These findings suggest that time to attrition is a useful metric for representing cognitive change, and reason for attrition and IIV are predictive of non-normative influences that may underlie instances of cognitive loss in older adults.

Aging-related magnification of genetic effects on cognitive and brain integrity

Heritability studies document substantial genetic influences on cognitive performance and decline in old age. Increasing evidence shows that effects of genetic variations on cognition, brain structure, and brain function become stronger as people age. Disproportionate impairments are typically observed for older individuals carrying disadvantageous genotypes of different candidate genes. These data support the resource-modulation hypothesis, which states that genetic effects are magnified in persons with constrained neural resources, such as older adults. However, given that findings are not unequivocal, we discuss the need to address several factors that may resolve inconsistencies in the extant literature (gene-gene and gene-environment interactions, study populations, gene-environment correlations, and epigenetic mechanisms).

Vascular risk as a predictor of cognitive decline in a cohort of elderly patients with mild to moderate dementia

Background/Aims

The purpose of our study was to evaluate vascular risk factors and other clinical variables as predictors of cognitive and functional decline in elderly patients with mild to moderate dementia.

Methods

The clinical characteristics of 82 elderly patients (mean age 79.0 ± 5.9 years; 67.1% females) with mild to moderate dementia were obtained at baseline, including years of education, Framingham Coronary Heart Disease Risk score, Hachinski Ischemic Score (HIS), Clinical Dementia Rating (CDR), Mini-Mental State Examination (MMSE) score, Functional Activities Questionnaire (FAQ) score, Burden Interview Scale score, and Neuropsychiatric Inventory (NPI) score. Changes in MMSE and FAQ scores over time were assessed annually. The association between baseline clinical variables and cognitive and functional decline was investigated during 3 years of follow-up through the use of generalized linear mixed effects models.

Results

A trend was found towards steeper cognitive decline in patients with less vascular burden according to the HIS (β = 0.056, p = 0.09), better cognitive performance according to the CDR score (β = 0.313, p = 0.06) and worse caregiver burden according to the Burden Interview Scale score (β = −0.012, p = 0.07) at baseline.

Conclusion

Further studies with larger samples are necessary to confirm and expand our findings.

The influence of multimorbidity on clinical progression of dementia in a population-based cohort

Introduction

Co-occurrence with other chronic diseases may influence the progression of dementia, especially in case of multiple chronic diseases. We aimed to verify whether multimorbidity influenced cognitive and daily functioning during nine years after dementia diagnosis compared with the influence in persons without dementia.

Methods

In the Kungsholmen Project, a population-based cohort study, we followed 310 persons with incident dementia longitudinally. We compared their trajectories with those of 679 persons without dementia. Progression was studied for cognition and activities of daily life (ADLs), measured by MMSE and Katz Index respectively. The effect of multimorbidity and its interaction with dementia status was studied using individual growth models.

Results

The mean (SD) follow-up time was 4.7 (2.3) years. As expected, dementia related to both the decline in cognitive and daily functioning. Irrespective of dementia status, persons with more diseases had significantly worse baseline daily functioning. In dementia patients having more diseases also related to a significantly faster decline in daily functioning. Due to the combination of lower functioning in ADLs at baseline and faster decline, dementia patients with multimorbidity were about one to two years ahead of the decline of dementia patients without any co-morbidity. In persons without dementia, no significant decline in ADLs over time was present, nor was multimorbidity related to the decline rate. Cognitive decline measured with MMSE remained unrelated to the number of diseases present at baseline.

Conclusion

Multimorbidity was related to baseline daily function in both persons with and without dementia, and with accelerated decline in people with dementia but not in non-demented individuals. No relationship of multimorbidity with cognitive functioning was established. These findings imply a strong interconnection between physical and mental health, where the greatest disablement occurs when both somatic and mental disorders are present.

Alzheimer's disease with vascular component: a distinct clinical entity?

Background

Longitudinal reports on the clinical features of patients with Alzheimer's disease (AD) and concomitant cerebrovascular disease are scarce.

Methods

We elaborated a working definition of AD with vascular component (ADVC), and this definition was retrospectively investigated in a cohort of patients with cognitive deterioration who were prescribed a cholinesterase inhibitor during usual practice.

Results

A total of 137 patients with probable AD and 66 patients with ADVC were studied during a mean follow-up period of 2.8 years. Univariate analyses demonstrated worse functional evolution and anticipation of psychotic symptoms and agitation in the ADVC group.

Conclusions

The present results are consistent with an additive model of predominantly frontal-subcortical vascular damage in AD.

Predictors of future cognitive decline in persons with mild cognitive impairment

This study sought first to identify individual items of the Mini-Mental State Examination (MMSE) and demographic variables at baseline that predicted the trajectories of cognitive change among patients with mild cognitive impairment (MCI), and second to quantify the risk of cognitive decline in such patients based on their pattern of failure of MMSE items. 187 MCI patients were evaluated serially with the MMSE for up to 3.5 years. Patients who followed a declining cognitive trajectory differed from the stable reference group in their baseline profile of MMSE test performance. Patient age and performance on delayed recall, constructional praxis, attention, and orientation to time and floor predicted future cognitive decline with good accuracy (79.9%) and specificity (86.4%), and moderate sensitivity (67.2%). These results are presented in the form of a simple clinical tool for quantifying risk of future cognitive decline in MCI.