Proportion of cognitive loss attributable to terminal decline

Life-Course Pathways to Exceptional Longevity: Evidence From the Lothian Birth Cohort of 1921

BACKGROUND

Longevity, a hallmark of successful aging, is a multifactorial trait with influences from birth onwards. However, limited evidence exists on the pathways linking diverse life-course exposures to longevity, especially within a single cohort.

METHODS

We investigated associations between life-course factors and longevity among community-dwelling adults aged 79 (N = 547) from the Lothian Birth Cohort 1921 with a mortality follow-up of 24 years. Cox proportional hazards and structural equation (path) models were used to explore how factors from early life (social class, childhood intelligence quotient [IQ], education), midlife (social class), and later life (health, lifestyle, psychosocial well-being), as well as sex, personality, and apolipoprotein E e4 status, influence survival time in days.

RESULTS

During follow-up (1999-2023), 538 participants (98%) died (mean age of death = 89.3 years) and 9 survived (mean age = 101.6 years). Factors associated with lower mortality risk in the multivariable Cox model were higher cognitive function (hazard ratio [HR] = 0.72; 95% confidence interval [CI]: 0.59-0.88), better physical function (HR = 0.61; 95% CI: 0.44-0.85), and greater physical activity (HR = 0.81; 95% CI: 0.71-0.92), while history of cancer was associated with higher mortality risk (HR = 1.84; 95% CI: 1.22-2.77). The life-course path model identified the same direct predictors, with additional contributions from female sex and nonsmoking status, to greater longevity. Early- and midlife factors (IQ, education, social class), and emotional stability, conscientiousness, and female sex, were indirectly and positively associated with survival trajectories via multiple dimensions of adult health.

CONCLUSIONS

In understanding why people live to very old ages it is necessary to consider factors from throughout the life course, and to include demographic, psychosocial, and health variables.

Diverging Patterns of Cognitive Decline by Sex and Race-Ethnicity in Seriously Ill Older Americans

Objectives

Differences in Cognitive decline are common in older adults in the last years of life, but differences across sex and race-ethnicity are poorly understood. This study investigated if sex and/or race-ethnicity moderated changes in cognitive function in older adults in the last years of life.

Methods

Data from the Health and Retirement Study (HRS) from 1993 to 2016 were used to analyze imputed cognition summary scores for total word recall and mental status of older adults aged 60-99. Loss of cognitive function was estimated using a multilevel mixed-effects model and accelerated cognitive decline was approximated by incorporating a change-point model using a restricted sample of decedent respondents who died aged 65-99.

Results

Notable disparities were seen in the rates of cognitive decline across sex and race-ethnic groups in the last years of life. Women consistently scored lower than men in word recall but higher in mental status, regardless of race-ethnicity. Non-Hispanic White respondents, men and women, consistently outperformed Hispanic and Black respondents in word recall tasks and mental status.

Conclusions

Our study shows that sex and race-ethnicity moderate cognitive decline in older adults during the last years of life. Older adults from underserved communities are at higher risk of cognitive decline. Our study could inform clinical practice and policy focused on mitigating the adverse impact of cognitive decline experienced by marginalized populations of older adults in the last years of life.

Terminal trajectory of HbA1c for 10 years supports the HbA1c paradox: a longitudinal study using Health and Retirement Study data

Objectives

We aimed to assess the potential time-varying associations between HbA1c and mortality, as well as the terminal trajectory of HbA1c in the elderly to reveal the underlying mechanisms.

Design

The design is a longitudinal study using data from the Health and Retirement Study.

Setting and participants

Data were from the Health and Retirement Study. A total of 10,408 participants aged ≥50 years with available HbA1c measurements at baseline (2006/2008) were included.

Methods

Longitudinal HbA1c measured at 2010/2012 and 2014/2016 were collected. HbA1c values measured three times for their associations with all-cause mortality were assessed using Cox regression and restricted cubic splines. HbA1c terminal trajectories over 10 years before death were analyzed using linear mixed-effect models with a backward time scale.

Results

Women constitute 59.6% of the participants with a mean age of 69 years, with 3,070 decedents during the follow-up (8.9 years). The mortality rate during follow-up was 29.5%. Increased mortality risk became insignificant for the highest quartile of HbA1c compared to the third quartile (aHR 1.148, 1.302, and 1.069 for a follow-up of 8.9, 6.5, and 3.2 years, respectively) with a shorter follow-up, while it became higher for the lowest quartile of HbA1c (aHR 0.986, 1.068, and 1.439 for a follow-up of 8.9, 6.5, and 3.2 years, respectively). Accordingly, for both decedents with and without diabetes, an initial increase in HbA1c was followed by an accelerating terminal decline starting 5-6 years before death.

Conclusions and implications

The time-varying association between HbA1c and mortality mapped to the terminal trajectory in HbA1c. High and low HbA1c may have different clinical relationships with mortality. The HbA1c paradox may be partially explained by reverse causation, namely, early manifestation of death.

APOE Genotype Modifies the Association between Midlife Adherence to the Planetary Healthy Diet and Cognitive Function in Later Life among Chinese Adults in Singapore

BACKGROUND

It remains unclear if adherence to the planetary healthy diet (PHD), designed to improve human and environmental health, is associated with better cognitive function in aging, and if this association differs by apolipoprotein E (APOE) genotype.

OBJECTIVES

We aimed to examine the association between the PHD pattern and risk of poor cognitive function, and to further assess whether the APOE ε4 allele could modify this association.

METHODS

The study included 16,736 participants from the Singapore Chinese Health Study. The PHD score was calculated using data from a validated 165-item food frequency questionnaire at baseline (1993-1998), with higher scores indicating greater adherence to the PHD. Cognitive function was assessed by the Singapore-modified Mini-Mental State Examination at follow-up 3 visits (2014-2016). A subset of 9313 participants had APOE genotype data. Logistic regression models were used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs), with adjustment for potential confounders.

RESULTS

We identified 2397 (14.3%) cases of poor cognitive function. In the total population, OR (95% CI) of poor cognitive function for each one-SD increment in the PHD score was 0.89 (0.85, 0.93). Carriers of APOE ε4 allele had increased risk of poor cognitive function (OR: 1.36, 95% CI: 1.15, 1.61). There was a significant interaction between the PHD score and the APOE ε4 allele (P-interaction = 0.042). Each one-SD increment in the PHD score was significantly associated with lower risk of poor cognitive function (OR: 0.89; 95% CI: 0.83, 0.96) in non-carriers of APOE ε4 allele, but not in APOE ε4 allele carriers (OR: 1.04, 95% CI: 0.89, 1.23).

CONCLUSIONS

Midlife adherence to the PHD was associated with reduced risk of poor cognitive function in later life. However, this was not observed in carriers of APOE ε4 allele who had higher risk of poor cognitive function.

Quantifying longitudinal cognitive resilience to Alzheimer's disease and other neuropathologies

INTRODUCTION

Cognitive resilience (CR) has been defined as the continuum of better (or worse) than expected cognition, given the degree of neuropathology. To quantify this concept, existing approaches focus on either cognitive level at a single time point or slopes of cognitive decline.

METHODS

In a prospective study of 1215 participants, we created a continuous measure of CR defined as the mean of differences between estimated person-specific and marginal cognitive levels over time, after accounting for neuropathologies.

RESULTS

Neuroticism and depressive symptoms were associated with all CR measures (P-values < .012); as expected, cognitive activity and education were only associated with the cognitive-level approaches (P-values < .0002). However, compared with the existing CR measures focusing on a single measure or slopes of cognition, our new measure yielded stronger relations with risk factors.

DISCUSSION

Defining CR based on the longitudinal differences between person-specific and marginal cognitive levels is a novel and complementary way to quantify CR.

Potential Mechanisms Underlying Resistance to Dementia in Non-Demented Individuals with Alzheimer's Disease Neuropathology

Alzheimer’s disease (AD) is the most common form of dementia and typically characterized by the accumulation of amyloid-β plaques and tau tangles. Intriguingly, there also exists a group of elderly which do not develop dementia during their life, despite the AD neuropathology, the so-called non-demented individuals with AD neuropathology (NDAN). In this review, we provide extensive background on AD pathology and normal aging and discuss potential mechanisms that enable these NDAN individuals to remain cognitively intact. Studies presented in this review show that NDAN subjects are generally higher educated and have a larger cognitive reserve. Furthermore, enhanced neural hypertrophy could compensate for hippocampal and cingulate neural atrophy in NDAN individuals. On a cellular level, these individuals show increased levels of neural stem cells and ‘von Economo neurons’. Furthermore, in NDAN brains, binding of Aβ oligomers to synapses is prevented, resulting in decreased glial activation and reduced neuroinflammation. Overall, the evidence stated here strengthens the idea that some individuals are more resistant to AD pathology, or at least show an elongation of the asymptomatic state of the disease compared to others. Insights into the mechanisms underlying this resistance could provide new insight in understanding normal aging and AD itself. Further research should focus on factors and mechanisms that govern the NDAN cognitive resilience in order to find clues on novel biomarkers, targets, and better treatments of AD.

The "cognitive clock": A novel indicator of brain health

INTRODUCTION

We identified a "cognitive clock," a novel indicator of brain health that provides person-specific estimates of cognitive age, and tested the hypothesis that cognitive age is a better predictor of brain health than chronological age in two independent datasets.

METHODS

The initial analyses were based on 1057 participants from the Rush Memory and Aging Project and the Religious Orders Study who began without impairment and underwent cognitive assessments up to 24 years. A shape invariant model characterized the latent pattern of cognitive decline, conceptualized here as the "cognitive clock," and yielded person-specific estimates of cognitive age. Survival analyses examined cognitive versus chronological age for predicting Alzheimer's disease dementia, mild cognitive impairment and mortality, and regression analyses examined associations of cognitive versus chronological age with neuropathology and brain atrophy. Finally, we applied the cognitive clock to an independent validation sample of 2592 participants from the Chicago Health and Aging Project, a biracial population-based study, to confirm the predictive utility of cognitive age.

RESULTS

The "cognitive clock" showed that cognition remained stable until a cognitive age of about 80, then declined moderately until 90, then declined precipitously. In the initial dataset, cognitive age was a better predictor of dementia, mild cognitive impairment and mortality than chronological age, and was more strongly associated with neuropathology and brain atrophy. Application of the cognitive clock to the independent validation sample provided further support for the utility of cognitive age as a strong prognostic indicator of adverse outcomes.

DISCUSSION

Cognitive age is a robust prognostic indicator of adverse health outcomes and may serve as a useful biomarker in aging research.

Similar mortality risk in incident cognitive impairment and dementia: Evidence from the ASPirin in Reducing Events in the Elderly (ASPREE) trial

BACKGROUND

This study examined the risk of mortality in older adults with newly detected cognitive impairment or dementia.

METHODS

Data from the Australian cohort of the ASPirin in Reducing Events in the Elderly (ASPREE) trial were examined. The ASPREE clinical trial compared daily low-dose aspirin to a placebo and involved 16,703 individuals aged 70 years and over, who were without major cognitive impairment, physical disability, or cardiovascular disease at recruitment. During the trial, evidence of cognitive impairment, based on cognitive testing and medical record information, triggered dementia adjudication of participants using DSM-IV criteria. Cox proportional hazard models were used to compare mortality rates across the dementia, trigger-only, and no-trigger groups.

RESULTS

Over a median 4.7-year follow-up period, 806 participants triggered dementia adjudication, with 485 (60.2%) judged to have dementia. Following recruitment, mortality risks were 32.9, 33.6, and 10.8 events per 1000 person-years in the dementia, trigger-no-dementia, and no-trigger groups, respectively. In the fully adjusted model, mortality risks remained higher in the dementia and trigger-no-dementia groups, with hazard ratios of 1.7 (95% CI: 1.3-2.1) and 1.9 (95% CI: 1.5-2.6), respectively. There was no discernible difference between the dementia and trigger-no-dementia groups in mortality rates following recruitment, or following a dementia trigger. These two groups were more likely to die from sepsis, respiratory disease, and dementia, but less likely to die from cancer than the no-trigger group, χ²  = 161.5, p < 0.001.

CONCLUSION

ASPREE participants who triggered for a dementia evaluation experienced a substantially higher mortality rate than those who remained cognitively intact. The increase was indistinguishable among persons who met DSM-IV criteria for dementia vs. those who triggered for a dementia evaluation but failed to meet DSM-IV criteria. Future work should investigate whether earlier detection of cognitive decline can be used to identify and prevent early mortality.

To what degree is late life cognitive decline driven by age-related neuropathologies?

The ageing brain is vulnerable to a wide array of neuropathologies. Prior work estimated that the three most studied of these, Alzheimer's disease, infarcts, and Lewy bodies, account for ∼40% of the variation in late life cognitive decline. However, that estimate did not incorporate many other diseases that are now recognized as potent drivers of cognitive decline [e.g. limbic predominant age-related TDP-43 encephalopathy (LATE-NC), hippocampal sclerosis, other cerebrovascular conditions]. We examined the degree to which person-specific cognitive decline in old age is driven by a wide array of neuropathologies. Deceased participants (n = 1164) from two longitudinal clinical-pathological studies, the Rush Memory and Aging Project and Religious Orders Study, completed up to 24 annual evaluations including 17 cognitive performance tests and underwent brain autopsy. Neuropathological examinations provided 11 pathological indices, including markers of Alzheimer's disease, non- Alzheimer's disease neurodegenerative diseases (i.e. LATE-NC, hippocampal sclerosis, Lewy bodies), and cerebrovascular conditions (i.e. macroscopic infarcts, microinfarcts, cerebral amyloid angiopathy, atherosclerosis, and arteriolosclerosis). Mixed effects models examined the linear relation of pathological indices with global cognitive decline, and random change point models examined the relation of the pathological indices with the onset of terminal decline and rates of preterminal and terminal decline. Cognition declined an average of about 0.10 unit per year (estimate = -0.101, SE = 0.003, P < 0.001) with considerable heterogeneity in rates of decline (variance estimate for the person-specific slope of decline was 0.0094, P < 0.001). When considered separately, 10 of 11 pathological indices were associated with faster decline and accounted for between 2% and 34% of the variation in decline, respectively. When considered simultaneously, the 11 pathological indices together accounted for 43% of the variation in decline; Alzheimer's disease-related indices accounted for 30-36% of the variation, non-Alzheimer's disease neurodegenerative indices 4-10%, and cerebrovascular indices 3-8%. Finally, the 11 pathological indices combined accounted for less than a third of the variation in the onset of terminal decline (28%) and rates of preterminal (32%) and terminal decline (19%). Although age-related neuropathologies account for a large proportion of the variation in late life cognitive decline, considerable variation remains unexplained even after considering a wide array of neuropathologies. These findings highlight the complexity of cognitive ageing and have important implications for the ongoing effort to develop effective therapeutics and identify novel treatment targets.

Terminal decline in objective and self-reported measures of motor function before death: 10 year follow-up of Whitehall II cohort study

OBJECTIVES

To examine multiple objective and self-reported measures of motor function for their associations with mortality.

DESIGN

Prospective cohort study.

SETTING

UK based Whitehall II cohort study, which recruited participants aged 35-55 years in 1985-88; motor function component was added at the 2007-09 wave.

PARTICIPANTS

6194 participants with motor function measures in 2007-09 (mean age 65.6, SD 5.9), 2012-13, and 2015-16.

MAIN OUTCOME MEASURES

All cause mortality between 2007 and 2019 in relation to objective measures (walking speed, grip strength, and timed chair rises) and self-reported measures (physical component summary score of the SF-36 and limitations in basic and instrumental activities of daily living (ADL)) of motor function.

RESULTS

One sex specific standard deviation poorer motor function in 2007-09 (cases/total, 610/5645) was associated with an increased mortality risk of 22% (95% confidence interval 12% to 33%) for walking speed, 15% (6% to 25%) for grip strength, 14% (7% to 23%) for timed chair rises, and 17% (8% to 26%) for physical component summary score over a mean 10.6 year follow-up. Having basic/instrumental ADL limitations was associated with a 30% (7% to 58%) increased mortality risk. These associations were progressively stronger when measures were drawn from 2012-13 (mean follow-up 6.8 years) and 2015-16 (mean follow-up 3.7 years). Analysis of trajectories showed poorer motor function in decedents (n=484) than survivors (n=6194) up to 10 years before death for timed chair rises (standardised difference 0.35, 95% confidence interval 0.12 to 0.59; equivalent to a 1.2 (men) and 1.3 (women) second difference), nine years for walking speed (0.21, 0.05 to 0.36; 5.5 (men) and 5.3 (women) cm/s difference), six years for grip strength (0.10, 0.01 to 0.20; 0.9 (men) and 0.6 (women) kg difference), seven years for physical component summary score (0.15, 0.05 to 0.25; 1.2 (men) and 1.6 (women) score difference), and four years for basic/instrumental ADL limitations (prevalence difference 2%, 0% to 4%). These differences increased in the period leading to death for timed chair rises, physical component summary score, and ADL limitations.

CONCLUSION

Motor function in early old age has a robust association with mortality, with evidence of terminal decline emerging early in measures of overall motor function (timed chair rises and physical component summary score) and late in basic/instrumental ADL limitations.

Consumption of dietary nuts in midlife and risk of cognitive impairment in late-life: the Singapore Chinese Health Study

BACKGROUND

evidence from prospective studies investigating the association between consumption of nuts in midlife and risk of cognitive impairment in late life is limited.

METHODS

this study analysed data from 16,737 participants in a population-based cohort, the Singapore Chinese Health Study. Intake of nuts was assessed using a validated food-frequency questionnaire at baseline (1993-1998), when participants were 45-74 years old (mean age = 53.5 years). Cognitive function was tested using the Singapore modified Mini-Mental State Examination during the third follow-up visit (2014-2016), when participants were 61-96 years old (mean age = 73.2 years). Cognitive impairment was defined using education-specific cut-off points. Logistic regression models were used to estimate the odds ratio (OR) and the 95% confidence interval (CI) for the association between intake and risk of cognitive impairment.

RESULTS

cognitive impairment was identified in 2,397 (14.3%) participants. Compared with those who consumed <1 serving/month of nuts, participants who consumed 1-3 servings/month, 1 serving/week and ≥2 servings/week had 12% (95% CI 2-20%), 19% (95% CI 4-31%) and 21% (2-36%) lower risk of cognitive impairment, respectively (P-trend = 0.01). Further adjustment for intake of unsaturated fatty acids attenuated the association to non-significance. Mediation analysis showed that the 50.8% of the association between nuts and risk of cognitive impairment was mediated by the intake of total unsaturated fatty acids (P < 0.001).

CONCLUSION

higher intake of nuts in midlife was related to a lower risk of cognitive impairment in late life, which was partly mediated by unsaturated fatty acids.

The Clinician's Interview-Based Impression of Change (Plus caregiver input) and goal attainment in two dementia drug trials: Clinical meaningfulness and the initial treatment response

INTRODUCTION

The Clinician's Interview-Based Impression of Change Plus caregiver input (CIBIC-Plus) has been widely used in dementia drug trials to evaluate cognition, behavior, and function. New trials of symptomatic drugs forecast renewed interest in this measure.

METHODS

To test its clinical meaningfulness, we examined how CIBIC-Plus performed in two cholinesterase inhibitor trials compared to goal attainment scaling Scale (GAS) scores, a patient-reported outcome measure.

RESULTS

Net goal attainment was seen for all but one GAS domains in subjects who improved on the CIBIC-Plus. Subjects who improved initially on CIBIC-Plus scores were likely to remain improved across all other outcomes for each trial's duration, except for Disability Assessment for Dementia scores.

DISCUSSION

The initial response to treatment, as assessed by CIBIC-Plus, remained stable for most outcome measures. Even small CIBIC-Plus improvement changes are associated with clinically meaningful change as assessed by GAS. Other tests detect decline better than improvement.

Association of Low Systolic Blood Pressure with Postmortem Amyloid-β and Tau

BACKGROUND

Vascular mechanisms may contribute to the accumulation of AD pathology.

OBJECTIVE

We examined whether the burden of vascular risk factors proximate to death is associated with amyloid-β and tau levels or modified their known association.

METHODS

We examined the brains of 1, 585 participants from two longitudinal community-based studies of older adults. Amyloid-β and tau were quantified by postmortem examination. The burden of vascular risk factors was summarized by calculating the Framingham general cardiovascular risk score (FRS) proximate to death. Using linear regressions, we examined the association of the FRS with the amyloid-β and tau levels and examined if the FRS modified the association of the amyloid-β with tau.

RESULTS

On average, participants were nearly 90 years old and two-thirds were women. The FRS was not associated with amyloid-β (Spearman r  = -0.00, p  = 0.918) or tau (r = 0.01, p = 0.701). However, the FRS as a whole (estimate = -0.022, SE = 0.008, p = 0.009), and specifically the systolic blood pressure (SBP) component (estimate = -0.033, SE = 0.012, p = 0.009), modified the association of the amyloid-β with tau. Further analysis showed that the association between amyloid-β and tau was stronger at lower levels of SBP.

CONCLUSION

Late-life vascular risk scores were not related to postmortem levels of amyloid-β or tau. However, lower levels of vascular risk scores and SBP were associated with a stronger association between amyloid-β and tau. These data suggest that vascular risk factors may modify the relation of AD pathology markers to one another.

Neuropathologic burden and the degree of frailty in relation to global cognition and dementia

OBJECTIVE

To test the hypothesis that degree of frailty and neuropathologic burden independently contribute to global cognition and odds of dementia.

METHODS

This was a secondary analysis of a prospective cohort study of older adults living in Illinois. Participants underwent an annual neuropsychological and clinical evaluation. We included 625 participants (mean age 89.7 ± 6.1 years; 67.5% female) who died and underwent autopsy. We quantified neuropathology using an index measure of 10 neuropathologic features: β-amyloid deposition, hippocampal sclerosis, Lewy bodies, tangle density, TDP-43, cerebral amyloid angiopathy, arteriolosclerosis, atherosclerosis, and gross and chronic cerebral infarcts. Clinical consensus determined dementia status, which we coded as no cognitive impairment, mild cognitive impairment, or dementia. A battery of 19 tests spanning multiple domains quantified global cognition. We operationalized frailty using a 41-item frailty index. We employed regression analyses to model relationships between neuropathology, frailty, and dementia.

RESULTS

Both frailty and a neuropathology index were independently associated with global cognition and dementia status. These results held after controlling for traditional pathologic measures in a sample of participants with Alzheimer clinical syndrome. Frailty improved the fit of the model for dementia status (χ²[2] 72.64; p < 0.0001) and explained an additional 11%-12% of the variance in the outcomes.

CONCLUSION

Dementia is a multiply determined condition, to which both general health, as captured by frailty, and neuropathology significantly contribute. This integrative view of dementia and health has implications for prevention and therapy; specifically, future research should evaluate frailty as a means of dementia risk reduction.

Normative Cognitive Decline in Old Age

OBJECTIVE

To characterize trajectories of normative cognitive aging.

METHODS

Older persons without dementia at study enrollment (n = 1,010) had annual cognitive testing for up to 24 years (mean = 9.9 years, standard deviation = 5.0), died, and underwent a neuropathologic examination to quantify 9 postmortem markers of common neurodegenerative and cerebrovascular conditions. To accommodate the heterogeneity in cognitive trajectories, we used functional mixed effects models, which allow individuals to have different patterns of cognitive decline under a unified model structure.

RESULTS

In a functional mixed effects model, postmortem markers (Alzheimer disease pathology, Lewy bodies, transactive response DNA-binding protein 43 pathology, hippocampal sclerosis, atherosclerosis, gross infarcts) were associated with global cognitive decline. Residual global cognitive decline after adjustment for neuropathologic burden was weakly related to age at death; it occurred in only about one-third of participants, mostly proximate to death. Results were comparable after eliminating the initial cognitive assessments to minimize retest learning or controlling for frailty proximate to death. Analyses were also conducted with composite measures of episodic memory and perceptual speed. Residual decline not attributable to neuropathologic burden was confined to a subset for each outcome and was most evident proximate to death. Age at death was unrelated to residual decline in episodic memory but was related to residual decline in perceptual speed.

INTERPRETATION

Late life cognitive loss mainly reflects non-normative pathologic and mortality-related processes rather than normative age-related processes. ANN NEUROL 2020;87:816-829.