Terminal change in cognitive function: an updated review of longitudinal studies

Loneliness, Dementia Status, and Their Association with All-Cause Mortality Among Older US Adults

Background

Loneliness, dementia, and mortality are interconnected.

Objective

We aimed at understanding mediating pathways and interactions between loneliness and dementia in relation to mortality risk.

Methods

The study tested bi-directional relationships between dementia, loneliness, and mortality, by examining both interactions and mediating effects in a large sample of older US adults participating in the nationally representative Health and Retirement Study. Out of≤6,468 older participants selected in 2010, with mean baseline age of 78.3 years and a follow-up time up to the end of 2020, 3,298 died at a rate of 64 per 1,000 person-years (P-Y). Cox proportional hazards and four-way decomposition models were used.

Results

Algorithmically defined dementia status (yes versus no) was consistently linked with a more than two-fold increase in mortality risk. Dementia status and Ln(odds of dementia) were strongly related with mortality risk across tertiles of loneliness score. Loneliness z-score was also linked to an elevated risk of all-cause mortality regardless of age, sex, or race or ethnicity, and its total effect (TE) on mortality was partially mediated by Ln(odds of dementia), z-scored, (≤40% of the TE was a pure indirect effect). Conversely, a small proportion (<5%) of the TE of Ln(odds of dementia), z-scored, on mortality risk was explained by the loneliness z-score.

Conclusions

In sum, dementia was positively associated with all-cause mortality risk, in similar fashion across loneliness score tertiles, while loneliness was associated with mortality risk. TE of loneliness on mortality risk was partially mediated by dementia odds in reduced models.

Cognitive Trajectories in Community-Dwelling Older Adults and Incident Dementia, Disability and Death: A 10-Year Longitudinal Study

Objective

The inter-individual variability in cognitive changes may be early indicators of major health events. We aimed to determine whether late-life cognitive trajectories were associated with incident dementia, persistent physical disability and all-cause mortality.

Methods

Data came from a cohort of older community-dwelling individuals aged 70 years or above in Australia and the United States. Global cognition, verbal fluency, episodic memory and psychomotor speed were assessed regularly at up to seven waves between 2010 and 2017. Dementia, disability in activities of daily living, and death were adjudicated between 2017 and 2020. Latent classes of cognitive trajectories over seven years were determined using group-based trajectory modeling. Multivariable logistic regression was used for the prospective associations between cognitive trajectories and these outcomes.

Results

Cognitive trajectories were defined for 16,174 participants (mean age: 78.9 years; 56.7% female) who were alive and without incident dementia or disability by 2017, among which 14,655 participants were included in the association analysis. Between three and five trajectory classes were identified depending on the cognitive test. Cognitive trajectories were strongly associated with the risk of dementia. For example, compared to those in the highest-functioning trajectory, the worst performers of episodic memory had a 37-fold increased risk of dementia (95% CI: 17.23–82.64). The lowest trajectories of both global cognition and episodic memory also predicted increased mortality risk (OR: 1.80, 95% CI: 1.28–2.52; OR: 1.61, 95% CI: 1.09–2.36, respectively), while only slow psychomotor speed was marginally associated with physical disability (OR: 2.39, 95% CI: 0.99–5.77).

Conclusions

In older individuals, cognitive trajectories appear to be early indicators of clinically relevant health outcomes. Systematic cognitive assessments as part of routine geriatric evaluation may facilitate early identification and interventions for those individuals at highest risk.

Associations between race, APOE genotype, cognition, and mortality among urban middle-aged white and African American adults

We examined associations between cognition and mortality and how these relationships vary by race and Apolipoprotein E (APOE) genotype, in a longitudinal study of 2346 middle-aged White and African American adults (30–64 years at baseline) from the Healthy Aging in Neighborhoods of Diversity across the Life Span cohort study. Baseline cognition spanned global mental status, and several domains obtained using principal components analysis (PCA; PCA1: verbal memory/fluency; PCA2: attention/working memory; PCA3: executive function/visuo-spatial abilities). Cox regression models evaluated associations between cognition and all-cause and cardiovascular disease (CVD)-mortality. Interactions between cognition and APOE2 as well as APOE4 allelic dose were tested, and race was a key effect modifier. Higher APOE4 dose was associated with increased CVD-mortality (hazard ratio [HR] per allele = 1.37; 95% CI 1.01–1.86, p = 0.041); APOE2 dosage’s association with CVD-mortality was non-significant (HR = 0.60; 95% CI 0.35–1.03, p = 0.065). Higher PCA3 was associated with lower all-cause (HR = 0.93; 95% CI 0.87–0.99, p = 0.030) and CVD (HR = 0.85; 95% CI 0.77–0.95, p = 0.001) mortality risks, the latter association being more pronounced among Whites. PCA2 interacted synergistically with APOE2 dosage, reducing risks for all-cause mortality (PCA2 × APOE2: − 0.33 ± 0.13, p = 0.010) and CVD mortality (PCA2 × APOE2: − 0.73 ± 0.31, p = 0.019). In conclusion, greater executive function/visuo-spatial abilities were associated with reduced CVD-specific mortality, particularly among Whites. Greater “attention/working memory” coupled with higher APOE2 dosage was linked with reduced all-cause and CVD mortality risks.

Cognition-Mortality Associations Are More Pronounced When Estimated Jointly in Longitudinal and Time-to-Event Models

With aging populations worldwide, there is growing interest in links between cognitive decline and elevated mortality risk—and, by extension, analytic approaches to further clarify these associations. Toward this end, some researchers have compared cognitive trajectories of survivors vs. decedents while others have examined longitudinal changes in cognition as predictive of mortality risk. A two-stage modeling framework is typically used in this latter approach; however, several recent studies have used joint longitudinal-survival modeling (i.e., estimating longitudinal change in cognition conditionally on mortality risk, and vice versa). Methodological differences inherent to these approaches may influence estimates of cognitive decline and cognition-mortality associations. These effects may vary across cognitive domains insofar as changes in broad fluid and crystallized abilities are differentially sensitive to aging and mortality risk. We compared these analytic approaches as applied to data from a large-sample, repeated-measures study of older adults (N = 5,954; ages 50–87 years at assessment; 4,453 deceased at last census). Cognitive trajectories indicated worse performance in decedents and when estimated jointly with mortality risk, but this was attenuated after adjustment for health-related covariates. Better cognitive performance predicted lower mortality risk, and, importantly, cognition-mortality associations were more pronounced when estimated in joint models. Associations between mortality risk and crystallized abilities only emerged under joint estimation. This may have important implications for cognitive reserve, which posits that knowledge and skills considered well-preserved in later life (i.e., crystallized abilities) may compensate for declines in abilities more prone to neurodegeneration, such as recall memory and problem solving. Joint longitudinal-survival models thus appear to be important (and currently underutilized) for research in cognitive epidemiology.

Cognition in Healthy Aging

The study of cognitive change across a life span, both in pathological and healthy samples, has been heavily influenced by developments in cognitive psychology as a theoretical paradigm, neuropsychology and other bio-medical fields; this alongside the increase in new longitudinal and cohort designs, complemented in the last decades by the evaluation of experimental interventions. Here, a review of aging databases was conducted, looking for the most relevant studies carried out on cognitive functioning in healthy older adults. The aim was to review not only longitudinal, cross-sectional or cohort studies, but also by intervention program evaluations. The most important studies, searching for long-term patterns of stability and change of cognitive measures across a life span and in old age, have shown a great range of inter-individual variability in cognitive functioning changes attributed to age. Furthermore, intellectual functioning in healthy individuals seems to decline rather late in life, if ever, as shown in longitudinal studies where age-related decline of cognitive functioning occurs later in life than indicated by cross-sectional studies. The longitudinal evidence and experimental trials have shown the benefits of aerobic physical exercise and an intellectually engaged lifestyle, suggesting that bio-psycho-socioenvironmental factors concurrently with age predict or determine both positive or negative change or stability in cognition in later life.

Proportion of cognitive loss attributable to terminal decline

OBJECTIVE

To estimate the proportion of late-life cognitive loss attributable to impending death.

METHODS

Older persons (n = 1,071) in a longitudinal cohort study without dementia at enrollment underwent annual cognitive assessments (mean 10.6 years, SD 4.6, range 4-24) prior to death. We estimated the onset of terminal acceleration in cognitive decline and rates of decline before and after this point in change point models that allowed calculation of the percent of cognitive loss attributable to terminal decline. Outcomes were composite measures of global and specific cognitive functions. We also estimated dementia and mild cognitive impairment (MCI) incidence before and during the terminal period.

RESULTS

A mean of 3.7 years before death (95% credible interval [CI] -3.8 to -3.5), the rate of global cognitive decline accelerated to -0.313 unit per year (95% CI -0.337 to -0.290), a more than 7-fold increase indicative of terminal decline. The mean global cognitive score dropped 0.377 unit (SD 0.516) assuming no terminal decline and 1.192 units (SD 1.080) with terminal decline. As a result, 71% (95% bootstrapped CI 0.70, 0.73) of overall global cognitive loss was terminal. In subsequent analyses, terminal decline accounted for 70% of episodic memory loss, 65% of semantic memory loss, 57% of working memory loss, 52% of perceptual speed loss, and 53% of visuospatial loss. MCI incidence in the preterminal and terminal periods was similar, but dementia incidence was more than 6-fold higher in the terminal period than preterminal.

CONCLUSION

Most late-life cognitive loss is driven by terminal decline.

Socioeconomic Inequalities in Frailty among Older Adults: Results from a 10-Year Longitudinal Study in the Netherlands

BACKGROUND

Frailty is an important risk factor for adverse outcomes in older people. Substantial variation in frailty prevalence between socioeconomic groups exists, but longitudinal evidence for the association between socioeconomic position (SEP) and frailty is scarce.

OBJECTIVE

To investigate the course of socioeconomic inequalities in frailty among older adults during 10 years of follow-up.

METHODS

Data were used from the Longitudinal Aging Study Amsterdam (n = 1,509). Frailty was measured with the functional domains approach, based on deficiencies in four domains: physical, nutritive, cognitive, and sensory. Mixed-model analyses were performed to estimate the course of frailty and its association with SEP during a 10-year follow-up. We investigated whether similar patterns of associations held in different scenarios, comparing results of survivor analyses with those based on two imputation methods accounting for dropout due to death (substitution of first missing value and missing values imputed with a prediction model).

RESULTS

All scenarios showed a linear increase in frailty with aging (survivor analyses OR = 1.87, 95% CI = 1.66-2.11) and associations of low education and low income with frailty (adjusted OR for low education = 1.76, 95% CI = 1.05-2.97; adjusted OR for low income = 1.90, 95% CI = 1.20-3.01; both for survivor analyses). Sex-stratified analyses indicated that socioeconomic inequalities were mainly present in men, not in women. Similar patterns of associations of SEP with frailty were observed in all scenarios, but the increase in frailty prevalence over time differed substantially between the scenarios. There were no statistically significant interactions between time and SEP on frailty (all scenarios), suggesting that inequalities in frailty did not increase or decrease during follow-up.

CONCLUSION

SEP inequalities in frailty among older adults were observed, mainly among men, and persisted during 10 years of follow-up.

Synergistic effects of cognitive impairment on physical disability in all-cause mortality among men aged 80 years and over: Results from longitudinal older veterans study

Objective

We evaluated effects of the interrelationship between physical disability and cognitive impairment on long-term mortality of men aged 80 years and older living in a retirement community in Taiwan.

Methods

This prospective cohort study enrolled older men aged 80 and older living in a Veterans Care Home. Those with confirmed diagnosis of dementia were excluded. All participants received comprehensive geriatric assessment, including sociodemographic data, Charlson’s Comorbidity Index (CCI), geriatric syndromes, activities of daily living (ADL) using the Barthel index and cognitive function using the Mini-Mental State Examination (MMSE). Subjects were categorized into normal cognitive function, mild cognitive deterioration, and moderate-to-severe cognitive impairment and were further stratified by physical disability status. Kaplan-Meier log-rank test was used for survival analysis. After adjusting for sociodemographic characteristics and geriatric syndromes, Cox proportional hazards model was constructed to examine associations between cognitive function, disability and increased mortality risk.

Results

Among 305 male subjects aged 85.1 ± 4.1 years, 89 subjects died during follow-up (mean follow-up: 1.87 ± 0.90 years). Kaplan-Meier unadjusted analysis showed reduced survival probability associated with moderate-to-severe cognitive status and physical disability. Mortality risk increased significantly only for physically disabled subjects with simultaneous mild cognitive deterioration (adjusted HR 1.951, 95% CI 1.036–3.673, p = 0.038) or moderate-to-severe cognitive impairment (aHR 2.722, 95% CI 1.430–5.181, p = 0.002) after adjusting for age, BMI, education levels, smoking status, polypharmacy, visual and hearing impairment, urinary incontinence, fall history, depressive symptoms and CCI. Mortality risk was not increased among physically independent subjects with or without cognitive impairment, and physically disabled subjects with intact cognition.

Conclusions

Physical disability is a major risk factor for all-cause mortality among men aged 80 years and older, and risk increased synergistically when cognitive impairment was present. Cognitive impairment alone without physical disability did not increase mortality risk in this population.

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.

Long-term Cognitive Trajectories and Mortality in Older Women

BACKGROUND

Few studies have examined whether change in cognition is linked to mortality. This study examined the relationship between cognitive trajectories in older age and risk of death.

METHODS

We studied community-dwelling, nondemented women aged 65+ (mean age = 71) enrolled in a prospective study of aging and followed up to 25 years. A modified Mini-Mental State Examination (mMMSE) and Trail Making Task Part B (TMTB) were administered at multiple visits during follow-up. We examined the association between cognitive trajectories (analyzed by quintiles) from baseline to age 80 (n = 7,477 for mMMSE and n = 6,503 for TMTB) and all-cause mortality after age 80 using Cox regression models, both unadjusted and adjusted for education, physical activity, alcohol, depression score, current smoking and history of hypertension and diabetes. Cause of death was determined from death certificates, classified as cardiovascular, cancer and other.

RESULTS

Women with greater rate of decline were older, less educated, less physically active, had higher depression score and were more likely to have a history of hypertension and diabetes (all p < .01). Participants with the greatest decline (quintile 1) had an increased risk of death (mMMSE hazard ratio [HR] = 1.28; TMTB HR = 1.43] and those with the least decline (quintile 5) had a decreased risk of death (mMMSE HR = 0.73; TMTB HR = 0.61) compared with intermediate decliners (quintiles 2-4). Cognitive trajectories were associated with cardiovascular mortality and other causes of death, but not cancer deaths.

CONCLUSIONS

Our study suggests that greater decline in general cognition or executive function is associated with higher rates of mortality in oldest-old women.

Think Fast, Feel Fine, Live Long: A 29-Year Study of Cognition, Health, and Survival in Middle-Aged and Older Adults

In a 29-year study of 6,203 individuals ranging in age from 41 to 96 years at initial assessment, we evaluated the relative and combined influence of 65 mortality risk factors, which included sociodemographic variables, lifestyle attributes, medical indices, and multiple cognitive abilities. Reductions in mortality risk were most associated with higher self-rated health, female gender, fewer years as a smoker, and smaller decrements in processing speed with age. Thus, two psychological variables-subjective health status and processing speed-were among the top predictors of survival. We suggest that these psychological attributes, unlike risk factors that are more narrowly defined, reflect (and are influenced by) a broad range of health-related behaviors and characteristics. Information about these attributes can be obtained with relatively little effort or cost and-given the tractability of these measures in different cultural contexts-may prove expedient for prevention, diagnosis, and treatment of conditions related to increased mortality risk in diverse human populations.

Pre-Operative Cognitive Functioning and Inflammatory and Neuroendocrine Responses to Cardiac Surgery

Background

Cognitive functioning is linked to cardiac mortality and morbidity, but the mechanisms underlying this relationship are unclear.

Purpose

To examine the relationship between pre-operative cognitive functioning and post-operative inflammatory and neuroendocrine responses in patients undergoing coronary artery bypass graft (CABG) surgery.

Methods

One-hundred ninety-three outpatients were screened to assess their cognitive function using the Montreal Cognitive Assessment (MoCA) on average 30 days prior to CABG surgery and provided blood samples for the measurement of interleukin (IL)-6 and C-reactive protein (CRP) and saliva samples for the measurement of diurnal cortisol. Participants were followed-up 4–8 days following surgery for the repeat measurement of IL-6 and CRP and 60 days after surgery for the measurement of diurnal salivary cortisol.

Results

Patients with low cognitive function (MoCA < 26) prior to surgery reached higher IL-6 concentrations in the days after surgery (β = −0.212, p = 0.021) and had greater cortisol output across the day 2 months after surgery (β = −0.179, p = 0.044).

Conclusions

Low cognitive functioning is associated with a more negative pattern of biological response to surgery, indicative of poorer physical recovery. These pathways may contribute to the links between cognitive function and cardiovascular pathology.

Cognition and mortality in older people: the Sydney Memory and Ageing Study

BACKGROUND

Both cognitive ability and cognitive decline have been shown to predict mortality in older people. As dementia, a major form of cognitive decline, has an established association with shorter survival, it is unclear the extent to which cognitive ability and cognitive decline predict mortality in the absence of dementia.

OBJECTIVE

To determine whether cognitive ability and decline in cognitive ability predict mortality in older individuals without dementia.

DESIGN

The Sydney Memory and Ageing Study is an observational population-based cohort study. Participants completed detailed neuropsychological assessments and medical examinations to assess for risk factors such as depression, obesity, hypertension, diabetes, hypercholesterolaemia, smoking and physical activity. Participants were regularly assessed at 2-year intervals over 8 years.

SETTING

A community sample in Sydney, Australia.

SUBJECTS

One thousand and thirty-seven elderly people without dementia.

RESULTS

Overall, 236 (22.8%) participants died within 8 years. Both cognitive ability at baseline and decline in cognitive ability over 2 years predicted mortality. Decline in cognitive ability, but not baseline cognitive ability, was a significant predictor of mortality when depression and other medical risk factors were controlled for. These relationships also held when excluding incident cases of dementia.

CONCLUSIONS

The findings indicate that decline in cognition is a robust predictor of mortality in older people without dementia at a population level. This relationship is not accounted for by co-morbid depression or other established biomedical risk factors.

The utility of estimating population-level trajectories of terminal wellbeing decline within a growth mixture modelling framework

PURPOSE

Mortality-related decline has been identified across multiple domains of human functioning, including mental health and wellbeing. The current study utilised a growth mixture modelling framework to establish whether a single population-level trajectory best describes mortality-related changes in both wellbeing and mental health, or whether subpopulations report quite different mortality-related changes.

METHODS

Participants were older-aged (M = 69.59 years; SD = 8.08 years) deceased females (N = 1,862) from the dynamic analyses to optimise ageing (DYNOPTA) project. Growth mixture models analysed participants' responses on measures of mental health and wellbeing for up to 16 years from death.

RESULTS

Multi-level models confirmed overall terminal decline and terminal drop in both mental health and wellbeing. However, modelling data from the same participants within a latent class growth mixture framework indicated that most participants reported stability in mental health (90.3 %) and wellbeing (89.0 %) in the years preceding death.

CONCLUSIONS

Whilst confirming other population-level analyses which support terminal decline and drop hypotheses in both mental health and wellbeing, we subsequently identified that most of this effect is driven by a small, but significant minority of the population. Instead, most individuals report stable levels of mental health and wellbeing in the years preceding death.

Investigating terminal decline: results from a UK population-based study of aging

The terminal decline hypothesis states that in the proximity of death, an individual's decline in cognitive abilities accelerates. We aimed at estimating the onset of faster rate of decline in global cognition using Mini Mental State Examination (MMSE) scores from participants of the Cambridge City over 75 Cohort Study (CC75C), a U.K. population-based longitudinal study of aging where almost all participants have died. The random change point model fitted to MMSE scores structured as a function of distance to death allowed us to identify a potentially different onset of change in rate of decline before death for each individual in the sample. Differences in rate of change before and after the onset of change in rate of decline by sociodemographic variables were investigated. On average, the onset of a faster rate of change occurred about 7.7 years before death and varied across individuals. Our results show that most individuals experience a period of slight decline followed by a much sharper decline. Education, age at death, and cognitive impairment at study entry were identified as modifiers of rate of change before and after change in rate of decline. Gender differences were found in rate of decline in the final stages of life. Our study suggests that terminal decline is a heterogeneous process, with its onset varying between individuals.

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

OBJECTIVES

In this article, we discuss the importance of studying the relationship between health and cognitive function, and some of the methods with which this relationship has been studied.

METHODS

We consider the challenges involved, in particular operationalization of the health construct and causal inference in the context of observational data. We contrast the approaches taken, and review the questions addressed: whether health and cognition are associated, whether changes in health are associated with changes in cognition, and the degree of interdependency among their respective trajectories.

RESULTS

A variety of approaches for understanding the association between cognition and health in aging individuals have been used. Much of the literature on cognitive change and health has relied on methods that are based at least in part on the reorganization of between-person differences (e.g., cross-lag analysis) rather than relying more fully on analysis of within-person change and joint analysis of individual differences in within-person change in cognition and health.

DISCUSSION

We make the case for focusing on the interdependency between within-person changes in health and cognition and suggest methods that would support this.

Successful aging and longevity in older old women: the role of depression and cognition

Based in successful aging theory and terminal cognitive drop research, this paper investigates cerebrovascular burden (CVB), depressive symptoms, and cognitive decline as threats to longevity. A subsample of stroke-free women over the age of 80 was identified in the Health and Retirement Survey (years 2000–2008). Mortality at 2, 6, and 8 year intervals was predicted using CVB (diabetes, heart disease, hypertension), depressive symptoms (Center for Epidemiological Studies Depression Scale), and cognitive decline (decline of 1 standard deviation or more on the 35-point Telephone Interview for Cognitive Status over 2 years). At most waves (2002, 2004, and 2006) mortality was predicted by CVB, depressive symptoms, and cognitive drop measured 2 years prior. CVB and depressive symptoms at the 2000 wave predicted mortality at 6 and 8 years. Older women with the greatest longevity had low CVB, robust cognitive functioning, and few depression symptoms, supporting successful aging theory and terminal cognitive drop.

Consequences of age-related cognitive declines

Adult age differences in a variety of cognitive abilities are well documented, and many of those abilities have been found to be related to success in the workplace and in everyday life. However, increased age is seldom associated with lower levels of real-world functioning, and the reasons for this lab-life discrepancy are not well understood. This article briefly reviews research concerned with relations of age to cognition, relations of cognition to successful functioning outside the laboratory, and relations of age to measures of work performance and achievement. The final section discusses several possible explanations for why there are often little or no consequences of age-related cognitive declines in everyday functioning.

Are terminal decline and its potential indicators detectable in population studies of the oldest old?

OBJECTIVES

To explore whether it is possible to detect decline in global scores of cognitive function in the proximity of death whilst simultaneously investigating potential risk profiles.

METHODS

Using the Mini Mental State Examination in a population study of the oldest old in which 99% of participants have died, a linear and quadratic time-to-death repeated measures random effects models were used to detect decline and potential factors which might indicate individual variation.

RESULTS

Decline and acceleration of this decline were detectable in the period before death. Some between person variation was detected in this pattern, which included differences in cognitive performance by age at death (-0.2 (SE = 0.02)), sex (-1.2 (SE = 0.2)), initial cognitive impairment (-7.5 (SE = 0.2)) and mobility (-0.6 (SE = 0.2)), in rate of decline by age at death (-0.04 (SE = 0.005)), sex (-0.1 (SE = 0.06)), initial cognitive impairment (-0.3 (SE = 0.07)) and mobility (-0.1 (SE = 0.05)) and differences in change in rate of decline by sex (-0.008 (SE = 0.004)), initial cognitive impairment (-0.02 (SE = 0.04)) and mobility (-0.01 (SE = 0.003)).

CONCLUSION

Using an extension of existing methods for exploring terminal decline, the phenomenon of decline in global cognition measures in the proximity of death was clearly detected as well as potential variables which could influence that pattern. Further work is required to explore whether similar methods can be used to detect the onset of the acceleration of this decline in each individual together with the potential to identify individual level factors that can allow clinicians to distinguish between the normal and preterminal phases of change in extreme old age.

A population-based study on the influence of brain atrophy on 20-year survival after age 85

BACKGROUND

Individuals aged 80 years and older is the fastest growing segment of the population worldwide. To understand the biology behind increasing longevity, it is important to examine factors related to survival in this age group. The relationship between brain atrophy and survival after age 85 remains unclear.

METHODS

A population-based sample (n = 239) had head CT scans at age 85 and was then followed until death. Cortical atrophy and ventricular size were assessed. Statistical analyses included Cox proportional hazards models with time to death as the outcome and considering a large number of possible confounders, including baseline cognitive function, incident dementia, and somatic disorders.

RESULTS

Mean survival time (±SD) was 5.0 ± 3.6 years (range 0.10-19.8 years). Decreased survival was associated with temporal, and frontal atrophy, sylvian fissure width and a number of ventricular measures after adjustment for potential confounders. In participants without dementia at baseline (n = 135), decreased survival was associated with temporal lobe atrophy and bifrontal ratio. In those with dementia (n = 104), decreased survival was associated with third ventricle width, cella media ratio, and ventricle-to-brain and ventricle-to-cranial ratio.

CONCLUSIONS

Several indices of brain atrophy were related to decreased survival after age 85, regardless of dementia status. Brain atrophy is rarely mentioned as a significant indicator of survival in the elderly, independent of traditional predictors such as cardiovascular disease or cancer. The biology behind the influence of brain atrophy on survival needs to be further scrutinized.

Personality and personal control make a difference for life satisfaction in the oldest-old: findings in a longitudinal population-based study of individuals 80 and older

This study investigates life satisfaction in relation to impending death among the oldest-old using overall disease load, self-rated health, and personality as interacting covariates of level and change. We used data from a sample of 370 healthy individuals who completed the Life Satisfaction Index-Z at four measurement occasions during a 6-year period in the Swedish OCTO-Twin study of individuals aged 80 and older. Growth curve analyses showed a linear decrease in life satisfaction as individuals approached death. The decrease was not related to level or change in self-rated health and disease load. High disease load was, however, related to lower levels of life satisfaction, but, this association was moderated by locus of control, such that those with high disease load and high locus of control did not show lower life satisfaction. Poor self-rated health was also associated with lower life satisfaction, but, this association was moderated by neuroticism, such that those with poor-rated health and low neuroticism did not show lower live satisfaction. Personality factors such as locus of control and neuroticism can influence the association between health and life satisfaction. The findings suggest further investigations of the role of personality characteristics in late life satisfaction and whether interventions aimed to increase personal control can improve life satisfaction in old age.

Fluid cognitive ability is associated with greater exposure and smaller reactions to daily stressors

The authors of this study investigated whether fluid cognitive ability predicts exposure and emotional reactivity to daily stressors. A national sample of adults from the Midlife in the United States study and the National Study of Daily Experiences (N = 1,202) who had a mean age of 57 years (SD = 12; 56% women, 44% men) completed positive and negative mood reports as well as a stressor diary on 8 consecutive evenings via telephone. Participants also completed a telephone-based battery of tests measuring fluid cognitive ability. Higher levels of fluid cognitive ability were associated with greater exposure to work- and home-related overload stressors. Possessing higher levels of fluid cognitive ability was associated with smaller stressor-related increases in negative mood, primarily for interpersonal tensions and network stressors, and smaller stressor-related decreases in positive mood for interpersonal tensions. Furthermore, fluid cognitive ability was unrelated to subjective severity ratings of the stressors reported. Discussion focuses on the role of fluid cognitive ability in daily stress processes.

Sex differences in the level and rate of change of physical function and grip strength in the Danish 1905-cohort study

OBJECTIVE

The study was conducted to examine sex differences in the initial level and rate of change in physical function and grip strength.

METHOD

The baseline survey included 2,262 Danes born in 1905 and alive in 1998 and followed-up in 2000, 2003, and 2005. Hence, the authors fully used the power of having a cohort with multiple assessments in late life and virtually complete follow-up of lifespan (through December 2008). Latent growth curve modeling was used.

RESULTS

Men had higher initial levels and rates of decline in strength score and grip strength. Lifespan was positively correlated with intercepts and slopes.

DISCUSSION

The Danish data suggested that the longest-living individuals have higher initial levels of strength score and grip strength and smaller rate of change. The data further suggested that the initial level of strength score and grip strength was more predictive of mortality than the rate of change was, and the predictive effects were similar in men and women.

Application of a joint multivariate longitudinal-survival analysis to examine the terminal decline hypothesis in the Swiss Interdisciplinary Longitudinal Study on the Oldest Old

In this work I aim at extending current knowledge on the terminal decline hypothesis by applying a joint multivariate longitudinal-survival analysis to the cognitive data of the Swiss Interdisciplinary Longitudinal Study on the Oldest Old. (In that study, 529 individuals between 79 and 85 years of age at study inception were assessed up to five times on a task of perceptual speed and one of verbal fluency.) I simultaneously estimated a multivariate, multilevel longitudinal model and a Weibull survival model to test whether individual performance and change in speed and fluency predict survival, controlling for retest effects, initial age, gender, overall health, socioeconomic status, and sensory functioning. Results revealed that age and performance level in fluency predicted survival, whereas level in speed and change in both cognitive variables did not. I discuss the relevance of fluency tasks in predicting mortality.

Decline in life satisfaction in old age: longitudinal evidence for links to distance-to-death

Using 12-year longitudinal data from deceased participants of the Berlin Aging Study (N = 414; age 70-103 years, at first occasion; M = 87 years, SD = 8.13), the authors examined whether and how old and very old individuals exhibit terminal decline in reported life satisfaction at the end of life. Relative to age-related decline, mortality-related decline (i.e., distance-to-death) accounted for more variance in interindividual differences in life satisfaction change and revealed steeper average rates of decline, by a factor of 2. By applying change-point growth models, the authors identified a point, about 4 years before death, at which decline showed a two-fold increase in steepness relative to the preterminal phase. For the oldest old (85+ years), a threefold increase was observed. Established mortality predictors, including sex, comorbidities, dementia, and cognition, accounted for only small portions of interindividual differences in mortality-related change in life satisfaction. The authors conclude that late-life changes in subjective well-being are related to mechanisms predicting death and suggest routes for further inquiry.

Association between mortality and cognitive change over 7 years in a large representative sample of UK residents

OBJECTIVE

To examine the association between change in reaction time and cognitive performance over 7 years and the risk of death from all causes and some specific causes after controlling for known risk factors.

METHODS

The sample comprised members of the Health and Lifestyle Survey (HALS) of community-dwelling adults in England, Scotland, and Wales. Baseline testing (HALS1), involving 9003 people, took place in 1985 and 1986. Sociodemographic, lifestyle, health, and physiological information was collected. Cognitive functioning was measured using tests of simple and choice reaction time, a short memory test, and a test of visual-spatial reasoning. Follow-up testing (HALS2) took place in 1991 and 1992, when 5352 members of the study were administered the same questionnaires, physiological examinations, and cognitive tests. The sample has been followed for mortality up to June 2005.

RESULTS

After controlling for age, gender, and the relevant baseline cognitive test scores, greater declines between HALS1 and HALS2 on simple reaction time mean and variability, choice reaction time mean and variability, memory and visual-spatial reasoning were associated with significantly increased risks of death from all causes, all cardiovascular diseases (CVDs), coronary heart disease (CHD), stroke, and respiratory disease. These associations were only slightly attenuated after adjusting for occupational social class, educational, smoking, alcohol consumption, physical activity, body mass index, blood pressure, and lung function.

CONCLUSIONS

Decline in performance of reaction times and simple cognitive tasks across a 7-year period was associated with an increased risk of death from all causes, all CVDs, CHD, stroke, and respiratory disease up to 13 years later, even after adjustment for known risk factors.

Population Inference with Mortality and Attrition in Longitudinal Studies on Aging: A Two-Stage Multiple Imputation Method

A major challenge for inference regarding aging-related change in longitudinal studies is that of study attrition and population mortality. Inferences in longitudinal studies can account for attrition and mortality-related change as distinct processes, but this is made difficult when follow-up of all individuals (i.e., age at death) is not complete. This is a common problem because most longitudinal studies of aging either have incomplete follow-up or are still collecting data on subsequent outcomes, including time of death. A statistical approach is suggested for including time-to-death as a predictor in models with incomplete follow-up using a two-stage multiple-imputation procedure. An empirical example using data from the OCTO-Twin study is presented that shows the utility of his procedure for making inferences conditional on mortality when mortality data are incomplete.

Terminal cognitive decline: accelerated loss of cognition in the last years of life

OBJECTIVE

To test the hypothesis that rate of cognitive decline accelerates in the last years of life.

METHODS

Participants are 853 older persons without dementia at study onset. For up to 8 years, they underwent annual clinical evaluations that included a battery of 19 cognitive tests from which previously established composite measures of global cognition and specific cognitive domains were derived. In analyses, we used linear mixed-effects models that allowed rate of cognitive decline to change at a given point before death to estimate the onset of a terminal decline period and rate of cognitive decline before and after that point. In subsequent analyses, we tested potential modifiers of terminal decline.

RESULTS

There were 115 deaths. Those who died did not differ from survivors in their level of global cognitive function at study onset, but beginning a mean of 42 months before death, their rate of global cognitive decline sharply increased. The duration and rapidity of terminal decline in global cognition differed from person to person. Terminal cognitive decline was not modified by age, sex, education, or the presence of mild cognitive impairment, but it was not present in those with vascular disease (e.g., stroke and heart attack) or in those without at least one copy of the apolipoprotein E epsilon4 allele, suggesting that Alzheimer's disease pathology may contribute to the phenomenon.

CONCLUSIONS

In old age, cognitive decline markedly accelerates during the last 3 to 4 years of life, consistent with the terminal decline hypothesis.

Population-based cohorts of the 50s and over: a summary of worldwide previous and ongoing studies for research on health in ageing

As most countries face the ageing of their population, understanding successful and pathologic ageing is a research priority. Longitudinal studies examining the ageing process from middle-age are required to establish causal and valid relationships. This systematic review of the literature aimed at identifying large community-based longitudinal studies either including exclusively elderly people or following people from middle-age (50+ years at enrolment) to death, and resulted in a selection of 72 cohort studies. Design features of selected studies show that most were conducted in North America or Northern Europe, most included both genders, and follow-up period was often less than 10 years. Many cohorts focused on cardiovascular health, cognitive decline or osteoporosis. Usually collected variables comprise of self-reported data on socio-demographics, chronic diseases and functional status, as well as measures of cognition, anthropometrics and physical performances. Biological samples were taken in about 60% of the studies, and a third also undertook genetic analyses. This review summarises information on design and content of large population-based cohorts of older persons, and represents a valuable background from which additional data may be retrieved.

Longitudinal Cognition-Survival Relations in Old and Very Old Age

We use a statistical model that combines longitudinal and survival analyses to estimate the influence of level and change in cognition on age at death in old and very old individuals. Data are from the Berlin Aging Study, in which an initial sample of 516 elderly individuals with an age range of 70 to 103 years was assessed up to 11 times across a period of up to 13 years. Four cognitive ability domains were assessed by two variables each: perceptual speed (Digit Letter and Identical Pictures), episodic memory (Paired Associates and Memory for Text), fluency (Categories and Word Beginnings), and verbal knowledge (Vocabulary and Spot-a-Word). Longitudinal models on cognition controlled for dementia diagnosis and retest effects, while survival models on age at death controlled for age, sex, socioeconomic status, sensory and motor performance, and broad personality characteristics. Results indicate: (1) Individual differences in the level of and in the linear change in performance are present for all cognitive variables; (2) when analyzed independently of cognitive performance, all covariates, except broad personality factors, predict survival; (3) when cognitive performance is accounted for, age, sex, and motor performance do predict survival, while socioeconomic status and broad personality factors do not, and sensory performance does only at times; (4) when cognitive variables are analyzed independently of each other, both level and change in speed and fluency, as well as level in memory and knowledge predict survival; (5) when all cognitive variables are analyzed simultaneously using a two-stage procedure, none of them is significantly associated to survival. In agreement with others, our findings suggest that survival is related to cognitive development in old and very old age in a relatively global, rather than ability-specific, manner.

Aging and Late-Life Terminal Decline in Perceptual Speed

Individual changes in perceptual speed were modeled as a conditional function of age and time-to-death. Alternative time-structured models were evaluated in a Swedish population-based, age-homogeneous sample (Gothenburg H70; N = 764) of individuals assessed at ages 70, 75, 79, 85, 88, 90, 92, 95, 97, and 99. Modeling time as proximity to death accounted better for the heterogeneity of individual changes than an age-based time structure. Time-to-death was a significant predictor of individual differences in rates of change in the age-based model but age did not significantly predict individual differences in rates of change in the model structured by proximity to death. In both the age-based and death-based time-structured models, accelerated changes prior to time of death were observed and provide support for the terminal-decline hypothesis. Identification of health-related factors and other sources of causal heterogeneity of aging-related change can make productive use of alternative time specifications that emphasize congruency between within-person change processes and aggregate population change.

Change in cognitive capabilities in the oldest old: the effects of proximity to death in genetically related individuals over a 6-year period

Change in cognitive abilities was assessed over a 6-year period in a sample of monozygotic and same-sex dizygotic twin pairs (N = 507 individuals), aged 80 and older (mean age = 83.3 years: SD = 3.1). who remained nondemented over the course of the study. Latent growth models (LGMs) show that chronological age and time to death are consistent predictors of decline in measures of memory, reasoning, speed, and verbal abilities. Multivariate LGM analysis resulted in weak and often negative correlations among rates of change between individuals within twin pairs, indicating greater differential change within twin pairs than occurs on average across twin pairs. These findings highlight several challenges for estimating genetic sources of variance in the context of compromised health and mortality-related change.