Neurodegenerative basis of age-related cognitive decline

Conscientiousness, dementia related pathology, and trajectories of cognitive aging

The study aim was to determine the contribution of dementia related pathologies to the association of conscientiousness with late-life cognitive health. At enrollment in 2 longitudinal clinical-pathologic cohort studies, 309 older individuals without cognitive impairment completed a standard conscientiousness measure. Annually thereafter, they completed a battery of 17 cognitive tests. On death, they underwent a uniform neuropathologic examination from which measures of neurofibrillary tangles, Lewy bodies, chronic gross cerebral infarction, and hippocampal sclerosis were derived. The relation of conscientiousness and the neuropathologic markers to cognitive decline was assessed in mixed-effects change point models to accommodate nonlinear cognitive decline. During a mean of 10.7 years of follow-up, annual decline on a composite measure of global cognition (baseline M = 0.082, SD = 0.499) was gradual (estimated M = -0.036, 95% CI [-0.046, -0.025]) until a mean of 3.2 years before death (95% CI [-3.6, -2.8]) when it accelerated to a mean annual loss of 0.369 unit (95% CI [-0.426, -0.317]), a tenfold increase. Higher conscientiousness (baseline M = 33.6, SD = 5.1) was associated with slower terminal decline (estimate = 0.064, 95% CI [0.024, 0.103]) but not preterminal decline (estimate = 0.005, 95% CI [-0.003, 0.013]). After adjustment for neuropathologic burden, conscientiousness was still related to terminal decline (estimate = 0.057, 95% CI [0.019, 0.094]) and accounted for 4% of the variance in terminal slopes. In addition, the association of neocortical Lewy bodies with terminal cognitive decline was attenuated in those with higher conscientiousness. The results suggest that higher conscientiousness is protective of late-life cognitive health.

Eight-year parallel change in baroreflex sensitivity and memory function in a sample of healthy older adults

OBJECTIVES

To examine whether changes in the cardiac autonomic nervous system (ANS) over time, as expressed by baroreflex sensitivity (BRS), were associated with long-term changes in cognitive performance in elderly individuals without dementia.

DESIGN

Community-based 8-year longitudinal study.

SETTING

Clinical settings.

PARTICIPANTS

Individuals aged 66.9 ± 0.9 (N = 425).

MEASUREMENTS

At baseline and follow-up, subjects underwent a clinical interview, autonomic and vascular measurements, and a neuropsychological evaluation including attentional, executive, and memory tests using standardized Z-scores. BRS was defined as being normal, moderate, or severe alteration at each evaluation. On the basis of the longitudinal changes subjects were stratified as being stable, moderate or improved.

RESULTS

Mean attentional, executive, and memory change Z-scores were -0.41 ± 0.9, -0.15 ± 0.7, and -0.14 ± 0.8, respectively. BRS of 56% of the subjects remained unchanged, of 20% decreased, and of 24% improved. After regression analysis, the worsened BRS group was 1.88 times as likely to have greater memory change as the group with stable BRS (P = .02). No significant association was found between longitudinal change in BRS and attentional and executive changes.

CONCLUSION

In healthy elderly individuals, BRS decrease was associated with a weak but significant decrease in memory function. The long-term effect of BRS on memory changes may suggest a role of the ANS in cognitive decline.

Sleep breathing disorders and cognitive function in the elderly: an 8-year follow-up study. the proof-synapse cohort

STUDY OBJECTIVES

Sleep breathing disorder (SBD) may be an important factor in age-related cognitive decline. In a cohort of healthy elderly subjects, we performed an 8-y longitudinal study to assess whether changes in cognitive function occur in untreated elderly patients with SBD and without dementia and the factors implicated in these changes.

DESIGN

A population-based longitudinal study.

SETTING

Clinical research settings.

PARTICIPANTS

A total of 559 participants of the PROOF study aged 67 y at the study entry and free from neurological disorders were examined.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Abnormal breathing events were defined by an apnea-hypopnea index (AHI) > 15. The raw cognitive data and averaged Z-scores for the attentional, executive, and memory functions were collected at the baseline and follow-up. At baseline, AHI > 15 was found in 54% of subjects with 18% having an AHI > 30. At follow-up, the presence of abnormal breathing events was associated with a slight but significant decline in the attentional domain (P = 0.01), which was more evident in the subjects with an AHI > 30 (P = 0.004). No significant changes over time were observed in the executive and memory functions. Several indices of chronic hypoxemia, defined either as a cumulative peripheral oxygen saturation (SpO2) < 90% or a minimal SpO2, accounted for portions of the variance in the decline in attention. All observed effects were small, accounting for 4-7% of variance in multivariate models.

CONCLUSION

In healthy elderly subjects, various components of sleep breathing disorder at baseline were associated with small changes in selected cognitive functions specific to the attention domain after controlling for multiple comorbidities, such as sleepiness, hypertension, diabetes, anxiety, and depression.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifiers NCT 00759304 and NCT 00766584.

Prospective study of sedentary behavior, risk of depression, and cognitive impairment

INTRODUCTION

Modern-day lifestyles are characterized by large amounts of prolonged sedentary activities, which may pose a risk to health in its own right, although little is known about their effects on mental health. We examined the association between several types of common sedentary behaviors (TV viewing, Internet use, reading) and different aspects of mental health.

METHODS

We conducted a 2-yr follow-up of 6359 (age 64.9 ± 9.1 yr) men and women from the English Longitudinal Study of Ageing, a cohort of community-dwelling older adults. Self-reported TV viewing time, reading, and use of the Internet was assessed at baseline. Mental health was assessed using the eight-item Centre of Epidemiological Studies Depression scale to measure depressive symptoms and neuropsychological tests of memory and verbal fluency to assess cognitive function.

RESULTS

At baseline, TV viewing time (≥ 6 vs. <2 h · d(-1)) was associated with higher depressive symptoms (coefficient = 0.49, 95% confidence interval [CI] = 0.63 to 0.35) and poorer global cognitive function (coefficient = -1.16, 95% CI = -1.00 to -1.31). Conversely, participants using the Internet reported lower depressive symptoms (coefficient = -0.58, 95% CI = -0.50 to -0.66) and higher global cognitive function (coefficient = 1.27, 95% CI = 1.37 to 1.18). There was no association between any sedentary behaviors at baseline and change in mental health measures over follow-up, suggesting that the difference in scores persisted but did not increase over time.

CONCLUSIONS

Some, but not all sedentary behaviors, are linked to adverse mental health. It is likely that these associations are being driven by the contrasting environmental and social contexts in which they occur.

Amyloid-beta and depression in healthy older adults: a systematic review

OBJECTIVE

Depression has been shown to be a risk factor for Alzheimer's disease (AD), and in older adults may provide a marker for the beginning of the prodromal phase of AD. The purpose of this systematic review is to examine the relationship between amyloid-β (Aβ), a key biomarker of AD, and depression in older adults.

METHOD

The literature search was limited to studies conducted from 2006 to 2014 that were published in English in peer-reviewed journals. Studies were selected if they included a group of older adults who either met established criteria for Major Depressive Disorder or Dysthymia; or were assessed for depressive symptoms on a standardised measure. Studies were also required to include an outcome variable that was a direct measure of Aβ levels in either blood or cerebrospinal fluid (CSF) samples, or via neuroimaging techniques such as positron emission tomography (PET).

RESULTS

Nineteen studies were identified, 15 of which found significant differences in Aβ levels between depressed and non-depressed older adults. However, studies were limited by their cross-sectional design, reliance on blood-based measures of Aβ, and potential sample bias.

CONCLUSIONS

Future investigations should consider prospective longitudinal design using neuroimaging and CSF measures of Aβ.

Validity of a screening tool for detecting subtle cognitive impairment in the middle-aged and elderly

The present study tested 121 middle-aged and elderly community-dwelling individuals on the computer-based Subtle Cognitive Impairment Test (SCIT) and compared their performance with that on several neuropsychological tests. The SCIT had excellent internal consistency, as demonstrated by a high split-half reliability measure (0.88-0.93). Performance on the SCIT was unaffected by the confounding factors of sex, education level, and mood state. Many participants demonstrated impaired performance on one or more of the neuropsychological tests (Controlled Oral Word Association Task, Rey Auditory and Verbal Learning Task, Grooved Pegboard [GP], Complex Figures). Performance on SCIT subtests correlated significantly with performance on many of the neuropsychological subtests, and the best and worst performing quartiles on the SCIT subtest discriminated between good and poor performers on other subtests, collectively indicating concurrent validity of the SCIT. Principal components analysis indicated that SCIT performance does not cluster with performance on most of the other cognitive tests, and instead is associated with decision-making efficacy, and processing speed and efficiency. Thus, the SCIT is responsive to the processes that underpin multiple cognitive domains, rather than being specific for a single domain. Since the SCIT is quick and easy to administer, and is well tolerated by the elderly, it may have utility as a screening tool for detecting cognitive impairment in middle-aged and elderly populations.

Brain pathology contributes to simultaneous change in physical frailty and cognition in old age

OBJECTIVE

First, we tested the hypothesis that the rate of change of physical frailty and cognitive function in older adults are correlated. Next, we examined if their rates of change are associated with the same brain pathologies.

METHODS

About 2,167 older adults participating in the Religious Orders Study and the Rush Memory and Aging Project had annual clinical evaluations. Bivariate random coefficient models were used to estimate simultaneously the rates of change in both frailty and cognition, and the correlation of change was characterized by a joint distribution of the random effects. Then, we examined whether postmortem indices from deceased were associated with the rate of change of frailty and cognition.

RESULTS

During an average follow-up of 6 years, frailty worsened by 0.09 unit/y and cognition declined by 0.08 unit/y. Most individuals showed worsening frailty and cognition (82.8%); 17% showed progressive frailty alone and <1% showed only cognitive decline. The rates of change of frailty and cognition were strongly correlated (ρ = -0.73, p < .001). Among deceased (N = 828), Alzheimer's disease pathology, macroinfarcts, and nigral neuronal loss showed independent associations with the rate of change in both frailty and cognition (all ps < .001). In these models, demographics explained about 9% of the variation in individual rate of change in frailty, and neuropathologies explained about 8%. In contrast, demographics and neuropathologies accounted for 2% and 30%, respectively, of the variance in the cognitive decline.

CONCLUSION

The rates of change in frailty and cognition are strongly correlated and this may be due in part because they share a common pathologic basis.

Emerging concepts in Alzheimer's disease

Alzheimer's disease/senile dementia of the Alzheimer type (AD/SDAT) is the most common neuropathologic substrate of dementia. It is characterized by synapse loss (predominantly within neocortex) as well as deposition of certain distinctive lesions (the result of protein misfolding) throughout the brain. The latter include senile plaques, composed mainly of an amyloid (Aβ) core and a neuritic component; neurofibrillary tangles, composed predominantly of hyperphosphorylated tau; and cerebral amyloid angiopathy, a microangiopathy affecting both cerebral cortical capillaries and arterioles and resulting from Aβ deposition within their walls or (in the case of capillaries) immediately adjacent brain parenchyma. In this article, I discuss the hypothesized role these lesions play in causing cerebral dysfunction, as well as CSF and neuroimaging biomarkers (for dementia) that are especially relevant as immunotherapeutic approaches are being developed to remove Aβ from the brain parenchyma. In addition, I address the role of neuropathology in characterizing the sequelae of new AD/SDAT therapies and helping to validate CSF and neuroimaging biomarkers of disease. Comorbidity of AD/SDAT and various types of cerebrovascular disease is a major theme in dementia research, especially as cognitive impairment develops in the oldest old, who are especially vulnerable to ischemic and hemorrhagic brain lesions.

Age-specific population frequencies of cerebral β-amyloidosis and neurodegeneration among people with normal cognitive function aged 50-89 years: a cross-sectional study

BACKGROUND

As preclinical Alzheimer's disease becomes a target for therapeutic intervention, the overlap between imaging abnormalities associated with typical ageing and those associated with Alzheimer's disease needs to be recognised. We aimed to characterise how typical ageing and preclinical Alzheimer's disease overlap in terms of β-amyloidosis and neurodegeneration.

METHODS

We measured age-specific frequencies of amyloidosis and neurodegeneration in individuals with normal cognitive function aged 50-89 years. Potential participants were randomly selected from the Olmsted County (MN, USA) population-based study of cognitive ageing and invited to participate in cognitive and imaging assessments. To be eligible for inclusion, individuals must have been judged clinically to have no cognitive impairment and have undergone amyloid PET, (18)F-fluorodeoxyglucose ((18)F-FDG) PET, and MRI. Imaging results were obtained from March 28, 2006, to Dec 3, 2013. Amyloid status (positive [A(+)] or negative [A(-)]) was determined by amyloid PET with (11)C Pittsburgh compound B. Neurodegeneration status (positive [N(+)] or negative [N(-)]) was determined by an Alzheimer's disease signature (18)F-FDG PET or hippocampal volume on MRI. We determined age-specific frequencies of the four groups (amyloid negative and neurodegeneration negative [A(-)N(-)], amyloid positive and neurodegeneration negative [A(+)N(-)], amyloid negative and neurodegeneration positive [A(-)N(+)], or amyloid positive and neurodegeneration positive [A(+)N(+)]) cross-sectionally using multinomial regression models. We also investigated associations of group frequencies with APOE ɛ4 status (assessed with DNA extracted from blood) and sex by including these covariates in the multinomial models.

FINDINGS

The study population consisted of 985 eligible participants. The population frequency of A(-)N(-) was 100% (n=985) at age 50 years and fell to 17% (95% CI 11-24) by age 89 years. The frequency of A(+)N(-) increased to 28% (24-32) at age 74 years, then decreased to 17% (11-25) by age 89 years. The frequency of A(-)N(+) increased from age 60 years, reaching 24% (16-34) by age 89 years. The frequency of A(+)N(+) increased from age 65 years, reaching 42% (31-52) by age 89 years. The results from our multinomial models suggest that A(+)N(-) and A(+)N(+) were more frequent in APOE ɛ4 carriers than in non-carriers and that A(+)N(+) was more, and A(+)N(-) less frequent in men than in women.

INTERPRETATION

Accumulation of amyloid and neurodegeneration are nearly inevitable by old age, but many people are able to maintain normal cognitive function despite these imaging abnormalities. Changes in the frequency of amyloidosis and neurodegeneration with age, which seem to be modified by APOE ɛ4 and sex, suggest that pathophysiological sequences might differ between individuals.

FUNDING

US National Institute on Aging and Alexander Family Professorship of Alzheimer's Disease Research.

Building a pipeline to discover and validate novel therapeutic targets and lead compounds for Alzheimer's disease

Cognitive decline, Alzheimer's disease (AD) and other causes are major public health problems worldwide. With changing demographics, the number of persons with dementia will increase rapidly. The treatment and prevention of AD and other dementias, therefore, is an urgent unmet need. There have been considerable advances in understanding the biology of many age-related disorders that cause dementia. Gains in understanding AD have led to the development of ante-mortem biomarkers of traditional neuropathology and the conduct of several phase III interventions in the amyloid-β cascade early in the disease process. Many other intervention strategies are in various stages of development. However, efforts to date have met with limited success. A recent National Institute on Aging Research Summit led to a number of requests for applications. One was to establish multi-disciplinary teams of investigators who use systems biology approaches and stem cell technology to identify a new generation of AD targets. We were recently awarded one of three such grants to build a pipeline that integrates epidemiology, systems biology, and stem cell technology to discover and validate novel therapeutic targets and lead compounds for AD treatment and prevention. Here we describe the two cohorts that provide the data and biospecimens being exploited for our pipeline and describe the available unique datasets. Second, we present evidence in support of a chronic disease model of AD that informs our choice of phenotypes as the target outcome. Third, we provide an overview of our approach. Finally, we present the details of our planned drug discovery pipeline.

Plasma vitamin D levels and cognitive function in aging women: the nurses' health study

BACKGROUND

Vitamin D may play a role in preserving cognitive function. However, there is a paucity of prospective studies on the relationship between vitamin D and cognition with aging. The aim of this study was to examine the association between plasma levels of vitamin D and subsequent cognitive function.

METHODS

This is a prospective study including 1,185 women aged 60-70 years from the Nurses' Health Study, who had plasma 25-hydroxy-vitamin D levels measured in 1989-1990 and completed an initial Telephone Interview of Cognitive Status approximately 9 years later. Subsequently, three follow-up cognitive assessments were conducted at 1.5-2.0 years intervals. We used multivariable-adjusted linear regression to model initial cognitive function, and mixed linear regression to model change in cognitive function over time.

RESULTS

Lower vitamin D levels were associated with significantly worse cognitive function 9 years later. For example, the mean global composite score averaging all the cognitive tests was 0.20 lower (95% Confidence Interval (CI):-0.33,-0.08; p-trend=0.009) in women in the lowest quintile (median=14.1 ng/mL) compared with women in the highest quintile of vitamin D (median=38.4 ng/mL). The observed differences were equivalent to the effect estimates we found for women who were approximately 4-6 years apart in age. However, vitamin D levels were not significantly associated with subsequent cognitive decline during 6 years of follow-up.

CONCLUSIONS

Higher levels of plasma vitamin D in women aged 60-70 years were associated with better cognitive function about a decade later but were not associated with cognitive decline during 6 years of follow-up.

Midlife type 2 diabetes and poor glycaemic control as risk factors for cognitive decline in early old age: a post-hoc analysis of the Whitehall II cohort study

BACKGROUND

Type 2 diabetes increases the risk for dementia, but whether it affects cognition before old age is unclear. We investigated whether duration of diabetes in late midlife and poor glycaemic control were associated with accelerated cognitive decline.

METHODS

5653 participants from the Whitehall II cohort study (median age 54.4 years [IQR 50.3-60.3] at first cognitive assessment), were classified into four groups: normoglycaemia, prediabetes, newly diagnosed diabetes, and known diabetes. Tests of memory, reasoning, phonemic and semantic fluency, and a global score that combined all cognitive tests, were assessed three times over 10 years (1997-99, 2002-04, and 2007-09). Mean HbA1c was used to assess glycaemic control during follow-up. Analyses were adjusted for sociodemographic characteristics, health-related behaviours, and chronic diseases.

FINDINGS

Compared with normoglycaemic participants, those with known diabetes had a 45% faster decline in memory (10 year difference in decline -0.13 SD, 95% CI -0.26 to -0.00; p=0.046), a 29% faster decline in reasoning (-0.10 SD, -0.19 to -0.01; p=0.026), and a 24% faster decline in the global cognitive score (-0.11 SD, -0.21 to -0.02; p=0.014). Participants with prediabetes or newly diagnosed diabetes had similar rates of decline to those with normoglycaemia. Poorer glycaemic control in participants with known diabetes was associated with a significantly faster decline in memory (-0.12 [-0.22 to -0.01]; p=0.034) and a decline in reasoning that approached significance (-0.07 [-0.15 to 0.00]; p=0.052).

INTERPRETATION

The risk of accelerated cognitive decline in middle-aged patients with type 2 diabetes is dependent on both disease duration and glycaemic control.

FUNDING

US National Institutes of Health, UK Medical Research Council.

Alcohol consumption and cognitive decline in early old age

Objective:

To examine the association between alcohol consumption in midlife and subsequent cognitive decline.

Methods:

Data are from 5,054 men and 2,099 women from the Whitehall II cohort study with a mean age of 56 years (range 44–69 years) at first cognitive assessment. Alcohol consumption was assessed 3 times in the 10 years preceding the first cognitive assessment (1997–1999). Cognitive tests were repeated in 2002–2004 and 2007–2009. The cognitive test battery included 4 tests assessing memory and executive function; a global cognitive score summarized performances across these tests. Linear mixed models were used to assess the association between alcohol consumption and cognitive decline, expressed as z scores (mean = 0, SD = 1).

Results:

In men, there were no differences in cognitive decline among alcohol abstainers, quitters, and light or moderate alcohol drinkers (<20 g/d). However, alcohol consumption ≥36 g/d was associated with faster decline in all cognitive domains compared with consumption between 0.1 and 19.9 g/d: mean difference (95% confidence interval) in 10-year decline in the global cognitive score = −0.10 (−0.16, −0.04), executive function = −0.06 (−0.12, 0.00), and memory = −0.16 (−0.26, −0.05). In women, compared with those drinking 0.1 to 9.9 g/d of alcohol, 10-year abstainers showed faster decline in the global cognitive score (−0.21 [−0.37, −0.04]) and executive function (−0.17 [−0.32, −0.01]).

Conclusions:

Excessive alcohol consumption in men (≥36 g/d) was associated with faster cognitive decline compared with light to moderate alcohol consumption.

Genome-wide association study of the rate of cognitive decline in Alzheimer's disease

BACKGROUND

Substantial interindividual variability exists in the disease trajectories of Alzheimer's disease (AD) patients. Some decline rapidly whereas others decline slowly, and there are no known explanations for this variability. We describe the first genome-wide association study to examine rate of cognitive decline in a sample of AD patients with longitudinal measures of cognition.

METHODS

The discovery sample was 303 AD cases recruited in the Alzheimer's Disease Neuroimaging Initiative and the replication sample was 323 AD cases from the Religious Orders Study and Rush Memory and Aging Project. In the discovery sample, Alzheimer's Disease Assessment Scale-cognitive subscale responses were tested for association with genome-wide single-nucleotide polymorphism (SNP) data using linear regression. We tested the 65 most significant SNPs from the discovery sample for association in the replication sample.

RESULTS

We identified SNPs in the spondin 1 gene (SPON1), the minor alleles of which were significantly associated with a slower rate of decline (rs11023139, P = 7.0 × 10(-11)) in the discovery sample. A SPON1 SNP 5.5 kb upstream was associated with decline in the replication sample (rs11606345, P = .002).

CONCLUSION

SPON1 has not been previously associated with AD risk, but is plausibly related because the gene product binds to the amyloid precursor protein and inhibits its cleavage by β-secretase. These data suggest that SPON1 may be associated with the differential rate of cognitive decline in AD.

Brainstem aminergic nuclei and late-life depressive symptoms

IMPORTANCE

The neurobiologic basis of late-life depressive symptoms is not well understood.

OBJECTIVE

To test the hypothesis that neurodegeneration and neuronal density in brainstem aminergic nuclei are related to late-life depressive symptoms. DESIGN, SETTING, PARTICIPANTS, AND EXPOSURE: Longitudinal clinicopathological cohort study at residences of participants in the Chicago, Illinois, metropolitan area. Participants included 124 older persons without dementia in the Rush Memory and Aging Project who had annual evaluations for a mean (SD) of 5.7 (2.8) years, died, and underwent a postmortem neuropathological examination that provided estimates of the densities of Lewy bodies, neurofibrillary tangles, and aminergic neurons in the locus ceruleus, dorsal raphe nucleus, substantia nigra, and ventral tegmental area.

MAIN OUTCOMES AND MEASURES

The number of depressive symptoms (mean [SD], 1.61 [1.48]; range, 0-6; skewness, 0.94) on the Center for Epidemiological Studies Depression Scale averaged across annual evaluations.

RESULTS

Brainstem Lewy bodies were associated with depressive symptoms, and the association was attenuated in those taking antidepressant medication. Brainstem tangles were associated with more depressive symptoms in those without cognitive impairment but with fewer symptoms in those with mild cognitive impairment. Lower density of tyrosine hydroxylase-immunoreactive neurons in the ventral tegmental area was robustly associated with a higher level of depressive symptoms (mean [SE] estimate, -0.014 [0.003]; P < .001; 16.3% increase in adjusted R2). The association was not modified by medication use or cognitive impairment. Neither tyrosine hydroxlyase-immunoreactive neurons in the locus ceruleus nor tryptophan hydroxlyase-immunoreactive neurons in the dorsal raphe nucleus were related to depressive symptoms.

CONCLUSIONS AND RELEVANCE

The results suggest that the mesolimbic dopamine system, especially the ventral tegmental area, has an important role in late-life depressive symptoms.

APOE ε4, Alzheimer's disease pathology, cerebrovascular disease, and cognitive change over the years prior to death

The goal of this study was to examine the association of the APOE ε4 allele with the late-life cognitive trajectory and test the hypothesis that the association of ε4 with cognitive decline is explained by Alzheimer's disease (AD) neuropathology. Participants (N = 581) came from 2 longitudinal clinical-pathologic studies of aging and dementia, the Religious Orders Study (ROS) and the Memory and Aging Project (MAP). Longitudinal measures of cognition were derived from detailed annual neuropsychological testing. Uniform neuropathologic evaluations provided quantitative measures of AD pathology, chronic cerebral infarctions, and Lewy bodies. Participants with 1 or more copies of the ε4 allele (ε2/4 excluded) were considered ε4 carriers. Random change point models were applied to examine the association of the ε4 allele with onset of terminal decline as well as preterminal and terminal slopes. On average, the onset of terminal decline occurred around 3 years before death, and the rate of terminal decline was eightfold faster than the preterminal decline. The presence of the ε4 allele was associated with an earlier onset of terminal decline and faster rates of decline before and after its onset. After adjusting for AD pathology, the ε4 allele was no longer associated with onset of terminal decline or preterminal slope, and the association with terminal slope became marginal. The APOE ε4 allele is an important determinant of late-life change in cognition, including terminal decline, and works primarily through AD pathology.

Taking up physical activity in later life and healthy ageing: the English longitudinal study of ageing

Background

Physical activity is associated with improved overall health in those people who survive to older ages, otherwise conceptualised as healthy ageing. Previous studies have examined the effects of mid-life physical activity on healthy ageing, but not the effects of taking up activity later in life. We examined the association between physical activity and healthy ageing over 8 years of follow-up.

Methods

Participants were 3454 initially disease-free men and women (aged 63.7±8.9 years at baseline) from the English Longitudinal Study of Ageing, a prospective study of community dwelling older adults. Self-reported physical activity was assessed at baseline (2002–2003) and through follow-up. Healthy ageing, assessed at 8 years of follow-up (2010-2011), was defined as those participants who survived without developing major chronic disease, depressive symptoms, physical or cognitive impairment.

Results

At follow-up, 19.3% of the sample was defined as healthy ageing. In comparison with inactive participants, moderate (OR, 2.67, 95% CI 1.95 to 3.64), or vigorous activity (3.53, 2.54 to 4.89) at least once a week was associated with healthy ageing, after adjustment for age, sex, smoking, alcohol, marital status and wealth. Becoming active (multivariate adjusted, 3.37, 1.67 to 6.78) or remaining active (7.68, 4.18 to 14.09) was associated with healthy ageing in comparison with remaining inactive over follow-up.

Conclusions

Sustained physical activity in older age is associated with improved overall health. Significant health benefits were even seen among participants who became physically active relatively late in life.

TDP-43 pathology, cognitive decline, and dementia in old age

IMPORTANCE

Cognitive decline is a leading cause of disability and death in old age but its neurobiological bases are not well understood.

OBJECTIVE

To test the hypothesis that transactive response DNA-binding protein 43 (TDP-43) is related to late-life cognitive decline.

DESIGN, SETTING, AND PARTICIPANTS

Longitudinal clinical-pathologic cohort study involving more than 40 Catholic groups across the United States. A total of 130 older Catholic nuns, priests, and monks underwent annual clinical evaluations, including detailed cognitive testing, for a mean of 10.1 years prior to death. On neuropathologic examination, we collected semiquantitative measures of TDP-43 pathology, density of neuronal neurofibrillary tangles, area occupied by amyloid-beta plaques, and the presence of alpha-synuclein Lewy bodies from multiple brain regions. Gross and microscopic cerebral infarcts and hippocampal sclerosis were also identified.

MAIN OUTCOMES AND MEASURES

Annual rate of change in a previously established composite measure of global cognition during a mean of 10.1 years of annual observation before death.

RESULTS

Transactive response DNA-binding protein 43 pathology, ranging from sparse to severe, was identified in 46% of participants and was associated with amyloid plaques, tangles, and hippocampal sclerosis but not neocortical Lewy bodies or cerebral infarcts. After controlling for amyloid plaques, tangles, and hippocampal sclerosis, TDP-43 pathology was associated with more rapid cognitive decline and accounted for nearly as much of the variability in rates of global cognitive decline as did tangles. Transactive response DNA-binding protein 43 pathology had a distinct cognitive profile that differed from other neuropathologic processes (related to decline in episodic and working memory but not in other cognitive domains), and it was elevated in those who developed dementia but not in those with mild cognitive impairment.

CONCLUSION AND RELEVANCE

The results suggest that TDP-43 is an important brain pathology underlying cognitive decline and dementia in old age.

Disentangling the effects of age and APOE on neuropathology and late life cognitive decline

Age and APOE are the most robust risk factors for dementia and cognitive decline, but the underlying neurobiology remains unclear. We examined the extent to which the hallmark pathologies of Alzheimer's disease, Lewy body disease, and cerebrovascular diseases account for the association of age and APOE with decline in episodic memory versus nonepisodic cognitive abilities. Up to 20 waves of longitudinal cognitive data were collected from 858 autopsied participants in 2 ongoing clinical-pathologic cohort studies of aging. Neuropathologic examinations quantified measures of beta amyloid (Aβ) plaque, mesial temporal and neocortical neurofibrillary tangles, macro- and microinfarcts, and neocortical Lewy bodies. Random coefficient models estimated person-specific slopes of decline in episodic memory and nonepisodic cognition. Path analysis examined the relation of age, APOE, and the 6 pathologic indices to the slopes of cognitive decline. The effect of age on decline in episodic memory was mediated by Aβ, mesial temporal and neocortical tau tangles, and macroscopic infarcts; age on decline in nonepisodic cognition was mediated by Aβ, neocortical tangles, and macroscopic infarcts. The effect of APOE on decline in episodic memory was mediated by Aβ, mesial temporal and neocortical tangles, and neocortical Lewy bodies; APOE on nonepisodic cognition was mediated by Aβ, neocortical tangles, and neocortical Lewy bodies. There were no direct effects of age and APOE on decline after accounting for these pathologic pathways.

Association of lower hemoglobin level and neuropathology in community-dwelling older persons

Lower hemoglobin levels have been associated with cognitive decline in older persons. The objective of this study was to investigate the relationship between lower hemoglobin levels and common, age-related neuropathologies associated with cognitive decline. Hemoglobin and neuropathology measures were available in 113 deceased, community-dwelling, older adults participating in the Rush Memory and Aging Project, a prospective, observational, clinical pathology study of aging. The mean hemoglobin level was 13.0 g/dL (SD = 1.4) and was measured 3.2 (SD = 1.3) years prior to death. Thirty-five participants had at least one chronic macroscopic infarction and twenty-nine had at least one chronic microscopic infarction. Eleven participants had Lewy Bodies. The mean Alzheimer's disease pathology score based on a summary measure of neuritic plaques, diffuse plaques, and neurofibrillary tangles was 0.56 unit (SD = 0.56; range = 0, 2.34). Using logistic regression models adjusted for age at death, gender, and education, each g/dL lower hemoglobin level increased the odds for having a chronic macroscopic infarction by 37% (95% CI = 1.01, 1.86) but not for having a chronic microscopic infarction (OR = 1.11; 95% CI = 0.82, 1.52) or Lewy Bodies (OR = 1.07; 95% CI = 0.68, 1.68). In an adjusted multiple regression model, hemoglobin level was not associated with the global AD pathology measure (parameter estimate = -0.02, SE = 0.03, p = 0.6). In secondary analyses, lower hemoglobin levels were associated with higher odds of having a chronic macroscopic infarction in a subcortical region but not with higher total subcortical chronic macroscopic infarction volume. In conclusion, lower hemoglobin levels appear to be associated with chronic macroscopic infarctions but not other common age-related neuropathologies.

Cognitive decline impairs financial and health literacy among community-based older persons without dementia

Literacy is an important determinant of health and well-being across the life span but is critical in aging, when many influential health and financial decisions are made. Prior studies suggest that older persons exhibit lower literacy than younger persons, particularly in the domains of financial and health literacy, but the reasons why remain unknown. The objectives of this study were to: (a) examine pathways linking diverse resources (i.e., education, word knowledge, cognitive function, and decision making style) to health and financial literacy among older persons and determine the extent to which the relation of age with literacy represents a direct effect versus an indirect effect due to decrements in specific cognitive functions (i.e., executive functions and episodic memory); and (b) test the hypothesis that declines in executive function and episodic memory are associated with lower literacy among older persons without dementia. Six-hundred and forty-five community-based older persons without dementia underwent detailed assessments of diverse resources, including education, word knowledge, cognitive function (i.e., executive function, episodic memory) and decision making style (i.e., risk aversion), and completed a measure of literacy that included items similar to those used in the Health and Retirement Study, such as numeracy, financial concepts such as compound inflation and knowledge of stocks and bonds, and important health concepts such as understanding of drug risk and Medicare Part D. Path analysis revealed a strong effect of age on literacy, with about half of the effect of age on literacy due to decrements in executive functions and episodic memory. In addition, executive function had an indirect effect on literacy via decision making style (i.e., risk aversion), and education and word knowledge had independent effects on literacy. Finally, among (n = 447) persons with repeated cognitive assessments available for up to 14 years, regression analysis supported the association of multiple resources with literacy; moreover, more rapid declines in executive function and episodic memory over an average of 6.4 years prior to the literacy assessment predicted lower literacy scores (ps < 0.02), but rate of decline in word knowledge did not. These findings suggest that diverse individual resources contribute to financial and health literacy and lower literacy in old age is partially due to declines in executive function and episodic memory.

Much of late life cognitive decline is not due to common neurodegenerative pathologies

OBJECTIVE

The pathologic indices of Alzheimer disease, cerebrovascular disease, and Lewy body disease accumulate in the brains of older persons with and without dementia, but the extent to which they account for late life cognitive decline remains unknown. We tested the hypothesis that these pathologic indices account for the majority of late life cognitive decline.

METHODS

A total of 856 deceased participants from 2 longitudinal clinical-pathologic studies, Rush Memory and Aging Project and Religious Orders Study, completed a mean of 7.5 annual evaluations, including 17 cognitive tests. Neuropathologic examinations provided quantitative measures of global Alzheimer pathology, amyloid load, tangle density, macroscopic infarcts, microinfarcts, and neocortical Lewy bodies. Random coefficient models were used to examine the linear relation of pathologic indices with global cognitive decline. In subsequent analyses, random change point models were used to examine the relation of the pathologic indices with the onset of terminal decline and rates of preterminal and terminal decline (ie, nonlinear decline).

RESULTS

Cognition declined a mean of about 0.11 U per year (estimate = -0.109, standard error [SE] = 0.004, p < 0.001), with significant individual differences in rates of decline; the variance estimate for the individual slopes was 0.013 (SE = 0.112, p < 0.001). In separate analyses, global Alzheimer pathology, amyloid, tangles, macroscopic infarcts, and neocortical Lewy bodies were associated with faster rates of decline and explained 22%, 6%, 34%, 2%, and 8% of the variation in decline, respectively. When analyzed simultaneously, the pathologic indices accounted for a total of 41% of the variation in decline, and the majority remained unexplained. Furthermore, in random change point models examining the influence of the pathologic indices on the onset of terminal decline and the preterminal and terminal components of the cognitive trajectory, the common pathologic indices accounted for less than a third of the variation in the onset of terminal decline and rates of preterminal and terminal decline.

INTERPRETATION

The pathologic indices of the common causes of dementia are important determinants of cognitive decline in old age and account for a large proportion of the variation in late life cognitive decline. Surprisingly, however, much of the variation in cognitive decline remains unexplained, suggesting that other important determinants of cognitive decline remain to be identified. Identification of the mechanisms that contribute to the large unexplained proportion of cognitive decline is urgently needed to prevent late life cognitive decline.

Vascular and Alzheimer's disease markers independently predict brain atrophy rate in Alzheimer's Disease Neuroimaging Initiative controls

This study assessed relationships among white matter hyperintensities (WMH), cerebrospinal fluid (CSF), Alzheimer's disease (AD) pathology markers, and brain volume loss. Subjects included 197 controls, 331 individuals with mild cognitive impairment (MCI), and 146 individuals with AD with serial volumetric 1.5-T MRI. CSF Aβ1-42 (n = 351) and tau (n = 346) were measured. Brain volume change was quantified using the boundary shift integral (BSI). We assessed the association between baseline WMH volume and annualized BSI, adjusting for intracranial volume. We also performed multiple regression analyses in the CSF subset, assessing the relationships of WMH and Aβ1-42 and/or tau with BSI. WMH burden was positively associated with BSI in controls (p = 0.02) but not MCI or AD. In multivariable models, WMH (p = 0.003) and Aβ1-42 (p = 0.001) were independently associated with BSI in controls; in MCI Aβ1-42 (p < 0.001) and tau (p = 0.04) were associated with BSI. There was no evidence of independent effects of WMH or CSF measures on BSI in AD. These data support findings that vascular damage is associated with increased brain atrophy in the context of AD pathology in pre-dementia stages.

Combined impact of smoking and heavy alcohol use on cognitive decline in early old age: Whitehall II prospective cohort study

BACKGROUND

Identifying modifiable risk factors for cognitive decline may inform prevention of dementia.

AIMS

To examine the combined impact of cigarette smoking and heavy alcohol consumption on cognitive decline from midlife.

METHOD

Prospective cohort study (Whitehall II cohort) with three clinical examinations in 1997/99, 2002/04 and 2007/09. Participants were 6473 adults (72% men), mean age 55.76 years (s.d. = 6.02) in 1997/99. Four cognitive tests, assessed three times over 10 years, combined into a global z-score (mean 0, s.d. = 1).

RESULTS

Age-related decline in the global cognitive score was faster in individuals who were smoking heavy drinkers than in non-smoking moderate alcohol drinkers (reference group). The interaction term (P = 0.04) suggested that the combined effects of smoking and alcohol consumption were greater than their individual effects. Adjusting for age, gender, education and chronic diseases, 10-year decline in global cognition was -0.42 z-scores (95% CI -0.45 to -0.39) for the reference group. In individuals who were heavy alcohol drinkers who also smoked the decline was -0.57 z-scores (95% CI -0.67 to -0.48); 36% faster than the reference group.

CONCLUSIONS

Individuals who were smokers who drank alcohol heavily had a 36% faster cognitive decline, equivalent to an age-effect of 2 extra years over 10-year follow-up, compared with individuals who were non-smoking moderate drinkers.

Neuropathologic basis of age-associated brain atrophy

IMPORTANCE

While brain volume changes are used as surrogate markers for Alzheimer disease neuropathology in clinical studies, the extent to which these changes are due to pathologic features of Alzheimer disease in the aging brain is not well established. This study aims to clarify the neuropathologic correlates of longitudinal brain atrophy.

OBJECTIVE

To examine the association between brain atrophy during life and neuropathology in an elderly population.

DESIGN

Autopsy study of a cohort of elderly individuals.

SETTING

Community-based population.

PARTICIPANTS

Seventy-one healthy elderly individuals were selected from participants of the Oregon Brain Aging Study for having an autopsy, more than 1 magnetic resonance imaging scan, and the last magnetic resonance imaging scan within 36 months of death.

MAIN OUTCOMES AND MEASURES

The associations between brain volume trajectories (ventricular, total brain, and hippocampal) and time interaction terms for neurofibrillary tangles, neuritic plaques, gross infarcts, microinfarcts, amyloid angiopathy, Lewy bodies, APOE ε4 presence, and clinical diagnosis (no cognitive impairment, mild cognitive impairment, or dementia as time-varying covariates) were examined in mixed-effects models, adjusting for duration of follow-up and age at death.

RESULTS

Ventricular volume trajectory was significantly associated with age, presence of infarcts, neurofibrillary tangle and neuritic plaque scores, APOE ε4 allele presence, and dementia diagnosis. Total brain volume trajectory was significantly associated with age and mild cognitive impairment diagnosis. Hippocampal volume trajectory was significantly associated with amyloid angiopathy.

CONCLUSIONS AND RELEVANCE

Ventricular volume trajectory is more sensitive than total brain and hippocampal volume trajectories as a marker of accruing Alzheimer disease and vascular pathology in elderly individuals. The association between brain volume trajectories and cognitive impairment (mild cognitive impairment and dementia) remained after controlling for the degree of neuropathology and other covariates. This suggests that there may be other factors not measured in this study that could be contributing to brain atrophy in those with cognitive impairment.

Overview and findings from the rush Memory and Aging Project

The Memory and Aging Project is a longitudinal, epidemiologic clinical-pathologic cohort study of common chronic conditions of aging with an emphasis on decline in cognitive and motor function and risk of Alzheimer's disease (AD). In this manuscript, we first summarize the study design and methods. Then, we present data on: (1) the relation of motor function to cognition, disability, and death; (2) the relation of risk factors to cognitive and motor outcomes, disability and death; (3) the relation of neuropathologic indices to cognitive outcomes; (4) the relation of risk factors to neuropathologic indices; and (5) additional study findings. The findings are discussed and contextualized.

AD pathology and cerebral infarctions are associated with memory and executive functioning one and five years before death

We provide rigorous psychometric evidence for distinct patterns of cognitive impairment for Alzheimer's disease (AD) and cerebral infarctions using 440 participants from the Religious Order Study. Latent variable models were used to decompose the effects of AD pathology and cerebral infarctions assessed at autopsy on overall cognition and specific neuropsychological tests at one and five years prior to death. Results support clinical and univariate psychometric analyses that memory impairment is more pronounced in AD, and executive impairment is more pronounced in the presence of cerebral infarctions. These specific effects are subtle relative to the stronger associations of both AD neuropathology and cerebral infarctions with overall levels of cognitive impairment.

Comparing measures of decline to dementia in amnestic MCI subjects in the National Alzheimer's Coordinating Center (NACC) Uniform Data Set

BACKGROUND

Many studies have investigated factors associated with the rate of decline and evolution from mild cognitive impairment (MCI) to Alzheimer's disease (AD) dementia in elderly patients. In this analysis, we compared the rates of decline to dementia estimated from three common global measures of cognition: Mini-Mental State Examination (MMSE) score, Clinical Dementia Rating sum of boxes (CDR-SB) score, and a neuropsychological tests composite score (CS).

METHODS

A total of 2,899 subjects in the National Alzheimer's Coordinating Center Uniform Data Set aged 65+ years diagnosed with amnestic mild cognitive impairment (aMCI) were included in this analysis. Population-averaged decline to dementia rates was estimated and compared for standardized MMSE, CDR-SB, and CS using Generalized Estimating Equations (GEE). Associations between rate of decline and several potential correlates of decline were also calculated and compared across measures.

RESULTS

The CDR-SB had the steepest estimated slope, with a decline of 0.49 standard deviations (SD) per year, followed by the MMSE with 0.22 SD per year, and finally the CS with 0.07 SD per year. The rate of decline of the three measures differed significantly in a global test for differences (p < 0.0001). Age at visit, body mass index (BMI) at visit, Apolipoprotein E (APOE) ɛ4 allele status, and race (black vs. white) had significantly different relationships with rate of decline in a global test for difference among the three measures.

CONCLUSIONS

These results suggest that both the rate of decline and the effects of AD risk factors on decline to dementia can vary depending on the evaluative measure used.

Impact of smoking on cognitive decline in early old age: the Whitehall II cohort study

CONTEXT

Smoking is a possible risk factor for dementia, although its impact may have been underestimated in elderly populations because of the shorter life span of smokers.

OBJECTIVE

To examine the association between smoking history and cognitive decline in the transition from midlife to old age.

DESIGN

Cohort study.

SETTING

The Whitehall II study. The first cognitive assessment was in 1997 to 1999, repeated over 2002 to 2004 and 2007 to 2009.

PARTICIPANTS

Data are from 5099 men and 2137 women in the Whitehall II study, mean age 56 years (range, 44-69 years) at the first cognitive assessment.

MAIN OUTCOME MEASURES

The cognitive test battery was composed of tests of memory, vocabulary, executive function (composed of 1 reasoning and 2 fluency tests), and a global cognitive score summarizing performance across all 5 tests. Smoking status was assessed over the entire study period. Linear mixed models were used to assess the association between smoking history and 10-year cognitive decline, expressed as z scores.

RESULTS

In men, 10-year cognitive decline in all tests except vocabulary among never smokers ranged from a quarter to a third of the baseline standard deviation. Faster cognitive decline was observed among current smokers compared with never smokers in men (mean difference in 10-year decline in global cognition=-0.09 [95% CI, -0.15 to -0.03] and executive function=-0.11 [95% CI, -0.17 to -0.05]). Recent ex-smokers had greater decline in executive function (-0.08 [95% CI, -0.14 to -0.02]), while the decline in long-term ex-smokers was similar to that among never smokers. In analyses that additionally took dropout and death into account, these differences were 1.2 to 1.5 times larger. In women, cognitive decline did not vary as a function of smoking status.

CONCLUSIONS

Compared with never smokers, middle-aged male smokers experienced faster cognitive decline in global cognition and executive function. In ex-smokers with at least a 10-year cessation, there were no adverse effects on cognitive decline.

Memory aging and brain maintenance

Episodic memory and working memory decline with advancing age. Nevertheless, large-scale population-based studies document well-preserved memory functioning in some older individuals. The influential ‘reserve’ notion holds that individual differences in brain characteristics or in the manner people process tasks allow some individuals to cope better than others with brain pathology and hence show preserved memory performance. Here, we discuss a complementary concept, that of brain maintenance (or relative lack of brain pathology), and argue that it constitutes the primary determinant of successful memory aging. We discuss evidence for brain maintenance at different levels: cellular, neurochemical, gray- and white-matter integrity, and systems-level activation patterns. Various genetic and lifestyle factors support brain maintenance in aging and interventions may be designed to promote maintenance of brain structure and function in late life.

The natural history of cognitive decline in Alzheimer's disease

The study aim was to describe the temporal course of cognitive decline in Alzheimer's disease (AD). We selected 226 persons from 2 longitudinal clinical-pathological studies who were cognitively healthy at baseline, followed at least 4 years (M = 10.2, SD = 3.5), and clinically diagnosed with AD at some point during follow-up. Each evaluation included a battery of 17 cognitive tests from which a previously established composite measure of global cognition was derived. In those who died, a uniform neuropathologic examination established the pathological diagnoses of Alzheimer's disease and other common conditions that impair cognition. Mixed-effects models with 2 change points were used to assess trajectories of cognitive decline. In the main analysis, there was no change in cognitive function until a mean of 7.5 years before dementia was diagnosed (95% confidence interval [CI]: -8.3, -6.7). The global cognitive measure declined a mean of 0.087-unit per year (95% CI: -0.099, -0.073) until a mean of 2.0 years before the diagnosis (95% CI: -2.2, -1.7) when it increased more than 4-fold to a mean loss of 0.370-unit per year (95% CI: -0.417, -0.334). Of 126 individuals who died and underwent autopsy, 101 (80%) met pathologic criteria for AD, of whom 67 had at least one other pathologic condition. Pathologic measures of AD and cerebral infarction were not strongly related to cognitive trajectories. The results indicate that cognitive decline in AD begins many years before dementia is diagnosed and accelerates during the course of the disease.

Obesity phenotypes in midlife and cognition in early old age: the Whitehall II cohort study

OBJECTIVE

To examine the association of body mass index (BMI) and metabolic status with cognitive function and decline.

METHODS

A total of 6,401 adults (71.2% men), aged 39-63 years in 1991-1993, provided data on BMI (normal weight 18.5-24.9 kg/m(2), overweight 25-29.9 kg/m(2); and obese ≥30 kg/m(2)) and metabolic status (abnormality defined as 2 or more of 1) triglycerides ≥1.69 mmol/L or lipid-lowering drugs, 2) systolic blood pressure ≥130 mm Hg, diastolic blood pressure ≥85 mm Hg, or antihypertensive drugs, 3) glucose ≥5.6 mmol/L or medications for diabetes, and 4) high-density lipoprotein cholesterol <1.04 mmol/L for men and <1.29 mmol/L for women). Four cognitive tests (memory, reasoning, semantic, and phonemic fluency) were administered in 1997-1999, 2002-2004, and 2007-2009, standardized to z scores, and averaged to yield a global score.

RESULTS

Of the participants, 31.0% had metabolic abnormalities, 52.7% were normal weight, 38.2% were overweight, and 9.1% were obese. Among the obese, the global cognitive score at baseline (p = 0.82) and decline (p = 0.19) over 10 years was similar in the metabolically normal and abnormal groups. In the metabolically normal group, the 10-year decline in the global cognitive score was similar (p for trend = 0.36) in the normal weight (-0.40; 95% confidence interval [CI] -0.42 to -0.38), overweight (-0.42; 95% CI -0.45 to -0.39), and obese (-0.42; 95% CI -0.50 to -0.34) groups. However, in the metabolically abnormal group, the decline on the global score was faster among obese (-0.49; 95% CI -0.55 to -0.42) than among normal weight individuals (-0.42; 95% CI -0.50 to -0.34), (p = 0.03).

CONCLUSIONS

In these analyses the fastest cognitive decline was observed in those with both obesity and metabolic abnormality.

Alzheimer disease pathology and longitudinal cognitive performance in the oldest-old with no dementia

OBJECTIVE

It has been hypothesized that individuals without dementia with Alzheimer disease (AD) neuropathology may be in the preclinical stages of dementia and could be experiencing subtle cognitive decline. The purpose of this study was to compare longitudinal cognitive performance in oldest-old individuals without dementia with and without AD neuropathology.

METHODS

The study included 58 individuals without dementia from The 90+ Autopsy Study, a population-based study of aging and dementia in individuals aged 90 and older. Participants had neurologic and neuropsychological testing every 6 months with an average of 3 years of follow-up. We compared the trajectory of cognitive performance on the Modified Mini-Mental State Examination (3MS) and the California Verbal Learning Test II (CVLT) by level of AD neuropathology. Based on Consortium to Establish a Registry for Alzheimer's Disease plaque staging, individuals were categorized as having low (none or sparse) or high (moderate or frequent) plaques. Based on Braak and Braak staging, participants were classified as having low (stages I-III) or high (IV-VI) tangles.

RESULTS

No significant differences were found in 3MS or CVLT cognitive performance over time based on plaque or tangle staging. Both high and low pathology groups showed modest improvements on the 3MS and CVLT consistent with learning effects.

CONCLUSIONS

AD neuropathology at autopsy is not associated with the trajectory of cognitive performance in the 3 years before death in oldest-old without dementia. Despite the presence of AD neuropathology at death, oldest-old without dementia display learning effects on cognitive tests. Further research is necessary to understand factors other than AD neuropathology that may affect cognition in the oldest-old.

The Minority Aging Research Study: ongoing efforts to obtain brain donation in African Americans without dementia

The Minority Aging Research Study (MARS) is a longitudinal, epidemiologic cohort study of decline in cognitive function and risk of Alzheimer's disease (AD) in older African Americans, with brain donation after death added as an optional component for those willing to consider organ donation. In this manuscript, we first summarize the study design and methods of MARS. We then provide details of ongoing efforts to achieve neuropathologic data on over 100 African Americans participating in MARS and in three other clinical-pathologic cohort studies at Rush University Medical Center. The results examine strategies for recruiting and consenting African Americans without dementia; (2) efforts to maintain high rates of follow-up participation; (3) strategies for achieving high rates of agreement to brain donation; and (4) the methodology of obtaining rapid brain autopsy at death. The implications of these efforts are discussed.

Overview and findings from the religious orders study

The Religious Orders Study is a longitudinal clinical-pathologic cohort study of aging and Alzheimer's disease (AD). In this manuscript, we summarize the study methods including the study design and describe the clinical evaluation, assessment of risk factors, collection of ante-mortem biological specimens, brain autopsy and collection of selected postmortem data.

THE RESULTS

(1) review the relation of neuropathologic indices to clinical diagnoses and cognition proximate to death; (2) examine the relation of risk factors to clinical outcomes; (3) examine the relation of risk factors to measures of neuropathology; and (4) summarize additional study findings. We then discuss and contextualize the study findings.

National Institute on Aging-Alzheimer's Association guidelines for the neuropathologic assessment of Alzheimer's disease

A consensus panel from the United States and Europe was convened recently to update and revise the 1997 consensus guidelines for the neuropathologic evaluation of Alzheimer's disease (AD) and other diseases of brain that are common in the elderly. The new guidelines recognize the pre-clinical stage of AD, enhance the assessment of AD to include amyloid accumulation as well as neurofibrillary change and neuritic plaques, establish protocols for the neuropathologic assessment of Lewy body disease, vascular brain injury, hippocampal sclerosis, and TDP-43 inclusions, and recommend standard approaches for the workup of cases and their clinico-pathologic correlation.

Terminal decline in motor function

The study aim was to test the hypothesis that motor function undergoes accelerated decline proximate to death. As part of a longitudinal clinical-pathologic study, 124 older Roman Catholic nuns, priests, and monks completed at least 7 annual clinical evaluations, died, and underwent brain autopsy and uniform neuropathologic examination. Each evaluation included administration of 11 motor tests and 19 cognitive tests from which global measures of motor and cognitive function were derived. The global motor measure (baseline M = 0.82, SD = 0.21) declined a mean 0.024 unit per year (95% confidence interval [CI]: -0.032, -0.016) until a mean of 2.46 years (95% CI: -2.870, -2.108) before death when rate of decline increased nearly fivefold to -0.117 unit per year (95% CI: -0.140, -0.097). The global cognitive measure (baseline M = 0.07, SD = 0.45) declined a mean of 0.027-unit per year (95% CI: -0.041, -0.014) until a mean of 2.76 years (95% CI: -3.157, -2.372) before death when rate of decline increased more than 13-fold to -0.371 unit per year (95% CI: -0.443, -0.306). Onset of terminal motor decline was highly correlated with onset of terminal cognitive decline (r = .94, 95% CI: 0.81, 0.99), but rates of motor and cognitive change were not strongly correlated (preterminal r = .20, 95% CI: -0.05, 0.38; terminal r = .34, 95% CI: 0.03, 0.62). Higher level of plaques and tangles was associated with earlier onset of terminal decline in motor function, but no pathologic measures were associated with rate of preterminal or terminal motor decline. The results demonstrate that motor and cognitive functions both undergo a period of accelerated decline in the last few years of life.

Leukocyte CCR2 expression is associated with mini-mental state examination score in older adults

INTRODUCTION

Circulating inflammatory markers may play an important role in cognitive impairment at older ages. Mice deficient for the chemokine (C-C motif) receptor 2 (CCR2) develop an accelerated Alzheimer-like pathology. CCR2 is also important in neurogenesis. To identify human gene transcripts most closely associated with Mini-Mental State Examination (MMSE) scores, we undertook a genome-wide and inflammation specific transcriptome screen in circulating leukocytes from a population-based sample.

METHODS

We measured in vivo transcript levels by microarray analysis in 691 subjects (mean age 72.6 years) in the InCHIANTI study (Invecchiare in Chianti, aging in the Chianti area). We assessed expression associations with MMSE performance at RNA collection and prior 9-year change in MMSE score in linear regression models.

RESULTS

In genome-wide analysis, raised CCR2 expression was cross-sectionally the most strongly associated transcript with lower MMSE score (beta=-0.16, p=5.1×10(-6), false discovery rate (FDR; q=0.077). Amongst inflammatory transcripts, only CCR2 expression was associated with both MMSE score and accelerated decline in score over the preceding 9 years (beta=-0.16, p=5.1×10(-6), q=0.003; and beta=-0.13, p=5.5×10(-5), q=0.03, respectively). CCR2 expression was also positively associated with apolipoprotein E (ApoE) e4 Alzheimer disease risk haplotype.

CONCLUSIONS

We show for the first time that CCR2 expression is associated with lower MMSE scores in an older human population. Laboratory models of Ccr2-mediated β-amyloid removal and regulation of neurogenesis affecting cognitive function may be applicable in humans. CCR2-mediated pathways may provide a possible focus for intervention to potentiate protective reactions to Alzheimer pathology in older people, including for people with an adverse ApoE haplotype.

Impairment in associative memory in healthy aging is distinct from that in other types of episodic memory

There is evidence that age related changes in episodic memory are heterogeneous and result from diverse pathologies. To test this, we examined performance of healthy high-functioning younger (N=41, ages 18-60 y) and older (N=58, ages 61-83 y) individuals in tests of associative memory, logical memory and memory in executive and object-recognition domains. We compared their relationships to each other and to other cognitive functions, including, psychomotor speed and verbal and spatial working memory. Older individuals showed significantly greater reduction in an index of the ability to learn new associations (NAL) than for memory in executive and object-recognition domains. Age-related reduction in NAL and in logical memory was of similar severity, but the two measures showed only moderate correlation when age and other cognitive functions were controlled for. NAL shows an age-related pattern of change distinct from memory in executive and object-recognition domains and from logical (item) memory. We propose that in healthy well-functioning individuals, NAL taps processes which support binding of newly learned association in context of accumulating information, a key function of the hippocampus. NAL may thus serve as a selective marker of complex, hippocampus-based, cognitive functions in studies of normal cognitive aging and of its possible relationship to early dementia.

Mechanisms of age-related cognitive change and targets for intervention: social interactions and stress

BACKGROUND

The effects of biological and physical factors on cognitive aging are widely studied. Less is known about the role of psychosocial factors such as stress and social relationships for cognitive functioning.

METHODS

Speakers in Session IV of the Summit focused on possible mechanisms linking social interactions and stressful experiences to cognitive changes with aging.

RESULTS

Elevated cortisol, repetitive thinking, negative emotions, neuroticism, chronic stress, and early life adversity were negatively associated with memory and other cognitive dimensions in later life. In contrast, supportive social relationships were found to be positively related to cognitive functioning. Some evidence was provided for multidirectional, causal relationships involving stress and negative affect as both antecedents and consequences of cognitive decline.

CONCLUSIONS

The findings contribute to understanding the potential underlying causal processes linking psychosocial factors and cognitive aging with a developmental focus on the etiology of declines and onset of cognitive impairments. This work provides an important foundation for future research to identify modifiable factors and to design interventions to minimize cognitive declines and optimize cognitive health in adulthood.

Increased fragmentation of rest-activity patterns is associated with a characteristic pattern of cognitive impairment in older individuals

STUDY OBJECTIVES

Aging is accompanied by changes in cognitive function, and changes in rest-activity patterns. Previous work has demonstrated associations between global rest-activity measures and cognitive performance on a number of tasks. Recently, we demonstrated that aging is associated with changes in the minute-to-minute fragmentation of rest-activity patterns in addition to changes in amounts of rest and activity. Given the body of experimental evidence linking sleep fragmentation with decrements in cognitive function in animals and humans, we hypothesized that increased fragmentation of rest-activity patterns would be associated with decreased cognitive function in older individuals.

DESIGN

Cross-sectional.

PARTICIPANTS

700 community-dwelling individuals from the Rush Memory and Aging Project.

MEASUREMENTS AND RESULTS

We obtained up to 11 days of actigraphic recordings in subjects' home environments and quantified the fragmentation of rest and activity using a recently developed state transition metric. We tested the associations between this metric and performance in 5 cognitive domains. Greater fragmentation of both rest and activity were associated with lower levels of cognitive performance, and this association was independent of total amounts of rest or activity. There was a characteristic pattern of cognitive deficits associated with rest and activity fragmentation, with preferential involvement of perceptual speed, semantic memory, working memory, and visuospatial abilities, and relative sparing of episodic memory.

CONCLUSIONS

The fragmentation of periods of rest and activity is a clinically important characteristic of rest-activity patterns that correlates with cognitive performance in older individuals.

Correlation of Alzheimer disease neuropathologic changes with cognitive status: a review of the literature

Clinicopathologic correlation studies are critically important for the field of Alzheimer disease (AD) research. Studies on human subjects with autopsy confirmation entail numerous potential biases that affect both their general applicability and the validity of the correlations. Many sources of data variability can weaken the apparent correlation between cognitive status and AD neuropathologic changes. Indeed, most persons in advanced old age have significant non-AD brain lesions that may alter cognition independently of AD. Worldwide research efforts have evaluated thousands of human subjects to assess the causes of cognitive impairment in the elderly, and these studies have been interpreted in different ways. We review the literature focusing on the correlation of AD neuropathologic changes (i.e. β-amyloid plaques and neurofibrillary tangles) with cognitive impairment. We discuss the various patterns of brain changes that have been observed in elderly individuals to provide a perspective for understanding AD clinicopathologic correlation and conclude that evidence from many independent research centers strongly supports the existence of a specific disease, as defined by the presence of Aβ plaques and neurofibrillary tangles. Although Aβ plaques may play a key role in AD pathogenesis, the severity of cognitive impairment correlates best with the burden of neocortical neurofibrillary tangles.

Terminal dedifferentiation of cognitive abilities

OBJECTIVE

To test the cognitive dedifferentiation hypothesis that cognitive abilities become increasingly correlated in late life.

METHODS

Participants are 174 older persons without dementia at the beginning of a longitudinal clinical-pathologic cohort study. At annual intervals for 6 to 15 years prior to death, they completed a battery of cognitive performance tests from which previously established composite measures of episodic memory, semantic memory, working memory, and perceptual speed were derived. At death, there was a uniform neuropathologic assessment and levels of diffuse plaques, neuritic plaques, and neurofibrillary tangles were summarized in a composite measure. Change in the 4 cognitive outcomes was analyzed simultaneously in a mixed-effects model that allowed rate of decline to accelerate at a variable point before death.

RESULTS

On average, cognitive decline before the terminal period was relatively gradual, and rates of change in different cognitive domains were moderately correlated, ranging from 0.25 (episodic memory-working memory) to 0.46 (episodic memory-semantic memory). By contrast, cognition declined rapidly during the terminal period, and rates of change in different cognitive functions were strongly correlated, ranging from 0.83 (working memory-perceptual speed) to 0.89 (episodic memory-semantic memory, semantic memory-working memory). Higher level of plaques and tangles on postmortem examination was associated with faster preterminal decline and earlier onset of terminal decline but not with rate of terminal decline or correlations between rates of change in different cognitive functions.

CONCLUSION

In the last years of life, covariation among cognitive abilities sharply increases consistent with the cognitive dedifferentiation hypothesis.

Appraisal of cognition in preclinical Alzheimer's disease: a conceptual review

Biomarker evidence and clinical observations support the hypothesis that there is a diagnosable condition termed preclinical Alzheimer's disease (AD). Recently, a workgroup convened under the auspices of the National Institute on Aging and the Alzheimer's Association proposed a framework for defining preclinical AD. The definition was based on the presence of biomarkers that are indicative of the AD pathophysiological process. In the context of abnormal AD biomarkers, the workgroup postulated that 'subtle cognitive changes' occurred as well. Based on studies of genetically at-risk individuals and those destined to become demented, who were observed while still cognitively normal, low performance on learning and memory functions may be the earliest cognitive manifestations of preclinical AD, at the group level at least. It is not clear whether subtle cognitive decline can be detected reliably on an individual basis. Preclinical AD cognitive changes could be diagnosed by traditional neuropsychological testing, computerized testing, assessments of subjective memory loss, assessments of levels of participation in cognitively stimulating activities and direct measurement of activity using recently developed monitoring technology. Confounding effects of normal aging, test-retest variability, variations in educational attainment, as well as the presence of other brain diseases make diagnosing cognitive decline due to preclinical AD challenging.

Preclinical cognitive trajectories differ for Alzheimer's disease and vascular dementia

We investigated differences between Alzheimer's disease (AD) and vascular dementia (VaD) from the appearance of the first cognitive symptoms, focusing on both time of onset and rate of accelerated decline for different cognitive functions before dementia diagnosis. Data from a longitudinal population-based study were used, including 914 participants (mean age = 82.0 years, SD = 5.0) tested with a cognitive battery (word recall and recognition, Block Design, category fluency, clock reading) on up to four occasions spanning 10 years. We fit a series of linear mixed effects models with a change point to the cognitive data, contrasting each dementia group to a control group. Significant age-related decline was observed for all five cognitive tasks. Relative to time of diagnosis, the preclinical AD persons deviated from the normal aging curve earlier (up to 9 years) compared to the preclinical VaD persons (up to 6 years). However, once the preclinical VaD persons started to decline, they deteriorated at a faster rate than the preclinical AD persons. The results have important implications for identifying the two dementia disorders at an early stage and for selecting cognitive tasks to evaluate treatment effects for persons at risk of developing AD and VaD.

Cerebral microinfarcts: the invisible lesions

The association between small but still visible lacunar infarcts and cognitive decline has been established by population-based radiological and pathological studies. Microscopic examination of brain sections shows even smaller but substantially more numerous microinfarcts, the focus of this Review. These lesions often result from small vessel pathologies such as arteriolosclerosis or cerebral amyloid angiopathy. They typically go undetected in clinical-radiological correlation studies that rely on conventional structural MRI, although the largest acute microinfarcts can be detected by diffusion-weighted imaging. In view of their high numbers and widespread distribution, microinfarcts could directly disrupt important cognitive networks and thus account for some of the neurological dysfunction associated with lesions visible on conventional MRI such as lacunar infarcts and white matter hyperintensities. Standardised neuropathological assessment criteria and the development of non-invasive means of detection during life would be major steps towards understanding the causes and consequences of otherwise macroscopically invisible microinfarcts.

Timing of onset of cognitive decline: results from Whitehall II prospective cohort study

OBJECTIVES

To estimate 10 year decline in cognitive function from longitudinal data in a middle aged cohort and to examine whether age cohorts can be compared with cross sectional data to infer the effect of age on cognitive decline.

DESIGN

Prospective cohort study. At study inception in 1985-8, there were 10,308 participants, representing a recruitment rate of 73%.

SETTING

Civil service departments in London, United Kingdom.

PARTICIPANTS

5198 men and 2192 women, aged 45-70 at the beginning of cognitive testing in 1997-9.

MAIN OUTCOME MEASURE

Tests of memory, reasoning, vocabulary, and phonemic and semantic fluency, assessed three times over 10 years.

RESULTS

All cognitive scores, except vocabulary, declined in all five age categories (age 45-49, 50-54, 55-59, 60-64, and 65-70 at baseline), with evidence of faster decline in older people. In men, the 10 year decline, shown as change/range of test × 100, in reasoning was -3.6% (95% confidence interval -4.1% to -3.0%) in those aged 45-49 at baseline and -9.6% (-10.6% to -8.6%) in those aged 65-70. In women, the corresponding decline was -3.6% (-4.6% to -2.7%) and -7.4% (-9.1% to -5.7%). Comparisons of longitudinal and cross sectional effects of age suggest that the latter overestimate decline in women because of cohort differences in education. For example, in women aged 45-49 the longitudinal analysis showed reasoning to have declined by -3.6% (-4.5% to -2.8%) but the cross sectional effects suggested a decline of -11.4% (-14.0% to -8.9%).

CONCLUSIONS

Cognitive decline is already evident in middle age (age 45-49).