Duke Twins Study of Memory in Aging in the NAS-NRC Twin Registry

Preventing cognitive decline by reducing BP target (PCOT): A randomized, pragmatic, multi-health systems clinical trial

BACKGROUND

Growing evidence suggests that intensive lowering of systolic blood pressure (BP) may prevent mild cognitive impairment (MCI) and dementia. However, current guidelines provide inconsistent recommendations regarding optimal BP targets, citing safety concerns of excessive BP lowering in the diverse population of older adults. We are conducting a pragmatic trial to determine if an implementation strategy to reduce systolic BP to <130 and diastolic BP to <80 mmHg will safely slow cognitive decline in older adults with hypertension when compared to patients receiving usual care.

METHODS

The Preventing Cognitive Decline by Reducing BP Target Trial (PCOT) is an embedded randomized pragmatic clinical trial in 4000 patients from two diverse health-systems who are age ≥ 70 years with BP >130/80 mmHg. Participants are randomized to the intervention arm or usual care using a permuted block randomization within each health system. The intervention is a combination of team-based care with clinical decision support to lower home BP to <130/80 mmHg. The primary outcome is cognitive decline as determined by the change in the modified Telephone Interview for Cognitive Status (TICS-m) scores from baseline. As a secondary outcome, patients who decline ≥3 points on the TICS-m will complete additional cognitive assessments and this information will be reviewed by an expert panel to determine if they meet criteria for MCI or dementia.

CONCLUSION

The PCOT trial will address the effectiveness and safety of hypertension treatment in two large health systems to lower BP targets to reduce risk of cognitive decline in real-world settings.

Remember This: Age Moderation of Genetic and Environmental Contributions to Verbal Episodic Memory from Midlife through Late Adulthood

It is well documented that memory is heritable and that older adults tend to have poorer memory performance than younger adults. However, whether the magnitudes of genetic and environmental contributions to late-life verbal episodic memory ability differ from those at earlier ages remains unresolved. Twins from 12 studies participating in the Interplay of Genes and Environment in Multiple Studies (IGEMS) consortium constituted the analytic sample. Verbal episodic memory was assessed with immediate word list recall (N = 35,204 individuals; 21,792 twin pairs) and prose recall (N = 3,805 individuals; 2,028 twin pairs), with scores harmonized across studies. Average test performance was lower in successively older age groups for both measures. Twin models found significant age moderation for both measures, with total inter-individual variance increasing significantly with age, although it was not possible definitively to attribute the increase specifically to either genetic or environmental sources. Pooled results across all 12 studies were compared to results where we successively dropped each study (leave-one-out) to assure results were not due to an outlier. We conclude the models indicated an overall increase in variance for verbal episodic memory that was driven by a combination of increases in the genetic and nonshared environmental parameters that were not independently statistically significant. In contrast to reported results for other cognitive domains, differences in environmental exposures are comparatively important for verbal episodic memory, especially word list learning.

Traumatic brain injury and dementia risk in male veteran older twins-Controlling for genetic and early life non-genetic factors

INTRODUCTION

This study leveraged the twin study design, which controls for shared genetic and early life exposures, to investigate the association between traumatic brain injury (TBI) and dementia.

METHODS

Members of the National Academy of Sciences-National Research Council's Twins Registry of World War II male veterans were assigned a cognitive outcome based on a multi-step assessment protocol. History of TBI was obtained via interviews.

RESULTS

Among 8302 individuals, risk of non-Alzheimer's disease (non-AD) dementia was higher in those with TBI (hazard ratio [HR] = 2.00, 95% confidence interval [CI], 0.97-4.12), than for AD (HR = 1.23, 95% CI, 0.76-2.00). To add more control of genetic and shared environmental factors, we analyzed 100 twin pairs discordant for both TBI and dementia onset, and found TBI-associated risk for non-AD dementia increased further (McNemar odds ratio = 2.70; 95% CI, 1.27-6.25).

DISCUSSION

These findings suggest that non-AD mechanisms may underlie the association between TBI and dementia, potentially providing insight into inconsistent results from prior studies.

Genome-wide screen to identify genetic loci associated with cognitive decline in late-life depression

OBJECTIVE

This study sought to conduct a comprehensive search for genetic risk of cognitive decline in the context of geriatric depression.

DESIGN

A genome-wide association study (GWAS) analysis in the Neurocognitive Outcomes of Depression in the Elderly (NCODE) study.

SETTING

Longitudinal, naturalistic follow-up study.

PARTICIPANTS

Older depressed adults, both outpatients and inpatients, receiving care at an academic medical center.

MEASUREMENTS

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropsychological battery was administered to the study participants at baseline and a minimum of twice within a subsequent 3-year period in order to measure cognitive decline. A GWAS analysis was conducted to identify genetic variation that is associated with baseline and change in the CERAD Total Score (CERAD-TS) in NCODE.

RESULTS

The GWAS of baseline CERAD-TS revealed a significant association with an intergenic single-nucleotide polymorphism (SNP) on chromosome 6, rs17662598, that surpassed adjustment for multiple testing (p = 3.7 × 10-7; false discovery rate q = 0.0371). For each additional G allele, average baseline CERAD-TS decreased by 8.656 points. The most significant SNP that lies within a gene was rs11666579 in SLC27A1 (p = 1.1 × 10-5). Each additional copy of the G allele was associated with an average decrease of baseline CERAD-TS of 4.829 points. SLC27A1 is involved with processing docosahexaenoic acid (DHA), an endogenous neuroprotective compound in the brain. Decreased levels of DHA have been associated with the development of Alzheimer's disease. The most significant SNP associated with CERAD-TS decline over time was rs73240021 in GRXCR1 (p = 1.1 × 10-6), a gene previously linked with deafness. However, none of the associations within genes survived adjustment for multiple testing.

CONCLUSIONS

Our GWAS of cognitive function and decline among individuals with late-life depression (LLD) has identified promising candidate genes that, upon replication in other cohorts of LLD, may be potential biomarkers for cognitive decline and suggests DHA supplementation as a possible therapy of interest.

The NAS-NRC Twin Registry and Duke Twins Study of Memory in Aging: An Update

The National Academy of Sciences-National Research Council (NAS-NRC) Twin Registry is one of the oldest, national population-based twin registries in the USA. It comprises 15,924 White male twin pairs born in the years 1917-1927 (N = 31.848), both of whom served in the armed forces, chiefly during World War II. This article updates activities in this registry since the most recent report in Twin Research and Human Genetics (Page, 2006). Records-based data include information from enlistment charts and Veterans Administration data linkages. There have been three major epidemiologic questionnaires and an education and earnings survey. Separate data collection efforts with the NAS-NRC registry include the National Heart, Lung, and Blood Institute (NHLBI) subsample, the Duke Twins Study of Memory in Aging and a clinically based study of Parkinson's disease. Progress has been made on consolidating the various data holdings of the NAS-NRC Twin Registry. Data that had been available through the National Academy of Sciences are now freely available through National Archive of Computerized Data on Aging (NACDA).

Epigenetic assimilation in the aging human brain

Background

Epigenetic drift progressively increases variation in DNA modification profiles of aging cells, but the finale of such divergence remains elusive. In this study, we explored the dynamics of DNA modification and transcription in the later stages of human life.

Results

We find that brain tissues of older individuals (>75 years) become more similar to each other, both epigenetically and transcriptionally, compared with younger individuals. Inter-individual epigenetic assimilation is concurrent with increasing similarity between the cerebral cortex and the cerebellum, which points to potential brain cell dedifferentiation. DNA modification analysis of twins affected with Alzheimer’s disease reveals a potential for accelerated epigenetic assimilation in neurodegenerative disease. We also observe loss of boundaries and merging of neighboring DNA modification and transcriptomic domains over time.

Conclusions

Age-dependent epigenetic divergence, paradoxically, changes to convergence in the later stages of life. The newly described phenomena of epigenetic assimilation and tissue dedifferentiation may help us better understand the molecular mechanisms of aging and the origins of diseases for which age is a risk factor.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-016-0946-8) contains supplementary material, which is available to authorized users.

Mediation Effect of Oral Hygiene on the Relationship Between Cognitive Function and Oral Health in Older Adults

Poor oral health is a common problem among older adults in general and particularly among those with cognitive impairment. The current study was conducted to (a) explore direct and indirect relationships between cognitive function and oral health outcomes and (b) test the mediating effect of oral hygiene on the relationship between cognitive function and oral health. The current study used data from 327 community-dwelling older adults in West Virginia who completed an oral health evaluation, comprehensive cognitive assessment, and questionnaire about oral hygiene. Structure equation modeling was used to test for mediation. Results showed that more severe cognitive impairment was related to poorer oral health outcomes and less frequent tooth brushing and flossing. Tooth brushing serves as a mediator between cognitive impairment and oral health outcome. The current study suggests regular tooth brushing is a promising intervention to maintain oral health among individuals with cognitive impairment. [Journal of Gerontological Nursing, 42(5), 30-37.].

Dental care utilization among older adults with cognitive impairment in the USA

AIM

We examined the relationship between cognitive impairment and dental care utilization among older adults in the USA.

METHODS

A total of 329 older adults aged 70 years and older in West Virginia, USA, were included in the present analyses. We carried out multivariate ordinal regression analyses.

RESULTS

Individuals with dementia were less likely to visit a dentist regularly, and more time had passed since their last dental visit compared with individuals with normal cognitive function. However, the pattern of dental care utilization for those with cognitive impairment, not dementia did not differ from individuals with normal cognition. A perceived greater social network and having dental insurance were associated with increased dental care utilization.

CONCLUSIONS

Less dental care utilization might contribute to the oral health problems often observed among individuals with dementia. Efforts to increase the use of dental care should include cost-effective options for dental insurance. In addition, educating formal and informal caregivers on the importance of dental care might be beneficial, as these individuals are in the best position to facilitate dental care for individuals with dementia.

Cohort Profile: The National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry)

The National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry) is a comprehensive registry of White male twin pairs born in the USA between 1917 and 1927, both of the twins having served in the military. The purpose was medical research and ultimately improved clinical care. The cohort was assembled in the early 1960s with identification of approximately 16,000 twin pairs, review of service records, a brief mailed questionnaire assessing zygosity, and a health survey largely comparable to questionnaires used at that time with Scandinavian twin registries. Subsequent large-scale data collection occurred in 1974, 1985 and 1998, repeating the health survey and including information on education, employment history and earnings. Self-reported data have been supplemented with mortality, disability and medical data through record linkage. Potential collaborators should access the study website [http://www.iom.edu/Activities/Veterans/TwinsStudy.aspx] or e-mail the Medical Follow-up Agency at [Twins@nas.edu]. Questionnaire data are being prepared for future archiving with the National Archive of Computerized Data on Aging (NACDA) at the Inter-University Consortium for Political and Social Research (ICPSR), University of Michigan, MI.

Functional limitations in older adults who have cognitive impairment without dementia

OBJECTIVE

To characterize the prevalence of functional limitations among older adults with cognitive impairment without dementia (CIND).

METHODS

Secondary data analysis was performed using the Aging, Demographics, and Memory Study data set. A total of 856 individuals aged ≥ 71 years were assigned to 3 diagnostic cognitive categories. A questionnaire was completed by a proxy informant regarding functional limitations for 744 of the 856 respondents.

RESULTS

Of the 744 patients, 263 (13.9%) had dementia, 201 (21.3%) had CIND, and 280 (64.8%) had normal cognition. Informants reported ≥1 instrumental activities of daily living (ADLs) limitation in 45% of the patients with CIND compared to 13% of the patients with normal cognition and 85% of the patients with dementia (P < .001). The ADL impairments among individuals with CIND were primarily attributed to physical health problems (n = 41; 40%).

CONCLUSIONS

Many individuals with CIND have impairment in a range of complex and basic daily activities, largely due to physical health problems.

High throughput DNA sequencing to detect differences in the subgingival plaque microbiome in elderly subjects with and without dementia

Background

To investigate the potential association between oral health and cognitive function, a pilot study was conducted to evaluate high throughput DNA sequencing of the V3 region of the 16S ribosomal RNA gene for determining the relative abundance of bacterial taxa in subgingival plaque from older adults with or without dementia.

Methods

Subgingival plaque samples were obtained from ten individuals at least 70 years old who participated in a study to assess oral health and cognitive function. DNA was isolated from the samples and a gene segment from the V3 portion of the 16S bacterial ribosomal RNA gene was amplified and sequenced using an Illumina HiSeq1000 DNA sequencer. Bacterial populations found in the subgingival plaque were identified and assessed with respect to the cognitive status and oral health of the participants who provided the samples.

Results

More than two million high quality DNA sequences were obtained from each sample. Individuals differed greatly in the mix of phylotypes, but different sites from different subgingival depths in the same subject were usually similar. No consistent differences were observed in this small sample between subjects separated by levels of oral health, sex, or age; however a consistently higher level of Fusobacteriaceae and a generally lower level of Prevotellaceae was seen in subjects without dementia, although the difference did not reach statistical significance, possibly because of the small sample size.

Conclusions

The results from this pilot study provide suggestive evidence that alterations in the subgingival microbiome are associated with changes in cognitive function, and provide support for an expanded analysis of the role of the oral microbiome in dementia.

Caring for individuals with dementia and cognitive impairment, not dementia: findings from the aging, demographics, and memory study

OBJECTIVES

To compare the characteristics and outcomes of caregivers of adults with dementia with those of caregivers of adults with cognitive impairment, not dementia (CIND).

DESIGN

Cross-sectional.

SETTING

In-home assessment for cognitive impairment and self-administered caregiving questionnaire.

PARTICIPANTS

One hundred sixty-nine primary family caregivers of participants in the Aging, Demographics, and Memory Study (ADAMS). ADAMS participants were aged 71 and older drawn from the nationally representative Health and Retirement Study.

MEASUREMENTS

Neuropsychological testing, neurological examination, clinical assessment, and medical history were used to assign a diagnosis of normal cognition, CIND, or dementia. Caregiving measures included caregiving time, functional limitations, depressive symptoms, physical and emotional strain, caregiving rewards, caregiver health, and demographic characteristics.

RESULTS

Dementia caregivers spent approximately 9 hours per day providing care, compared with 4 hours per day for CIND caregivers (P=.001). Forty-four percent of dementia caregivers exhibited depressive symptoms, compared with 26.5% of CIND caregivers (P=.03). Physical and emotional strains were similar in both groups of caregivers. Regardless of the strains, nearly all caregivers reported some benefits from providing care. Behavioral problems (P=.01) and difficulty with instrumental activities of daily living (P=.01) in persons with CIND partially explained emotional strain experienced by CIND caregivers. For those with dementia, behavioral problems predicted caregiver emotional strain (P<.001) and depressive symptoms (P=.01).

CONCLUSION

Although support services are available to dementia caregivers, CIND caregivers also expend considerable time and experience strains. The real caregiver burden of cognitive impairment in the U.S. population may therefore be greatly underestimated if people who have reached the diagnostic threshold for dementia are focused on exclusively.

Operationalizing diagnostic criteria for Alzheimer's disease and other age-related cognitive impairment-Part 2

This article focuses on the effects of operational differences in case ascertainment on estimates of prevalence and incidence of cognitive impairment and/or dementia of the Alzheimer type. Experience and insights are discussed by investigators from the Framingham Heart Study, the East Boston Senior Health Project, the Chicago Health and Aging Project, the Mayo Clinic Study of Aging, the Baltimore Longitudinal Study of Aging, and the Aging, Demographics, and Memory Study. There is a general consensus that the single most important factor determining prevalence estimates of Alzheimer's disease (AD) is the severity of cognitive impairment used as a threshold to define cases. Studies that require a level of cognitive impairment in which persons are unable to provide self-care will have much lower estimates than the studies aimed at identifying persons in the earliest stages of AD. There are limited autopsy data from the aforementioned epidemiological studies to address accuracy in the diagnosis of etiological subtype, namely the specification of AD alone or in combination with other types of pathology. However, other community-based cohort studies show that many persons with mild cognitive impairment and also some persons without dementia or mild cognitive impairment meet pathological criteria for AD, thereby suggesting that the number of persons who would benefit from an effective secondary prevention intervention is probably higher than the published prevalence estimates. Improved accuracy in the clinical diagnosis of AD is anticipated with the addition of molecular and structural biomarkers in the next generation of epidemiological studies.

Cognitive performance and informant reports in the diagnosis of cognitive impairment and dementia in African Americans and whites

BACKGROUND

The diagnosis of cognitive impairment and dementia must reflect an increasingly diverse and aging United States population. This study compared direct testing and informant reports of cognition with clinical diagnoses of cognitive impairment and dementia between African Americans and whites.

METHODS

Participants in the Aging, Demographics, and Memory Study completed in-person dementia evaluations, and were assigned clinical diagnoses (by a consensus panel of dementia experts) of normal; cognitive impairment, not demented (CIND); and dementia. The Consortium to Establish a Registry for Alzheimer's Disease (CERAD) total score and the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) were used to assess cognitive performance and reported cognitive decline.

RESULTS

A higher CERAD total score was associated with lower odds of CIND and dementia, at comparable ratios between African Americans and whites. Higher IQCODE scores were associated with increased odds of dementia in both African Americans and whites. Higher IQCODE scores were associated with increased odds of CIND among whites, but not among African Americans.

CONCLUSIONS

Cultural differences may influence informant reports of prevalent CIND and dementia. Our findings also highlight the need for more comparative research to establish the cultural validity of measures used to diagnose these conditions.

Genetic aspects of behavioral neurotoxicology

Considerable progress has been made over the past couple of decades concerning the molecular bases of neurobehavioral function and dysfunction. The field of neurobehavioral genetics is becoming mature. Genetic factors contributing to neurologic diseases such as Alzheimer's disease have been found and evidence for genetic factors contributing to other diseases such as schizophrenia and autism are likely. This genetic approach can also benefit the field of behavioral neurotoxicology. It is clear that there is substantial heterogeneity of response with behavioral impairments resulting from neurotoxicants. Many factors contribute to differential sensitivity, but it is likely that genetic variability plays a prominent role. Important discoveries concerning genetics and behavioral neurotoxicity are being made on a broad front from work with invertebrate and piscine mutant models to classic mouse knockout models and human epidemiologic studies of polymorphisms. Discovering genetic factors of susceptibility to neurobehavioral toxicity not only helps identify those at special risk, it also advances our understanding of the mechanisms by which toxicants impair neurobehavioral function in the larger population. This symposium organized by Edward Levin and Annette Kirshner, brought together researchers from the laboratories of Michael Aschner, Douglas Ruden, Ulrike Heberlein, Edward Levin and Kathleen Welsh-Bohmer conducting studies with Caenorhabditis elegans, Drosophila, fish, rodents and humans studies to determine the role of genetic factors in susceptibility to behavioral impairment from neurotoxic exposure.

A biometric latent curve analysis of memory decline in older men of the NAS-NRC twin registry

Previous research has shown cognitive abilities to have different biometric patterns of age-changes. We examined the variation in episodic memory (word recall task) for over 6,000 twin pairs who were initially aged 59-75, and were subsequently re-assessed up to three more times over 12 years. In cross-sectional analyses, variation in the number of words recalled independent of age was explained largely by non-shared influences (65-72%), with clear additive genetic influences (12-32%), and marginal shared family influences (1-18%). The longitudinal phenotypic analysis of the word recall task showed systematic linear declines over age, but several nonlinear models with more dramatic changes at later ages, improved the overall fit. A two-part spline model for the longitudinal twin data with an optimal turning point at age 74 led to: (a) a separation of non-shared environmental influences and transient measurement error (~50%); (b) strong additive genetic components of this latent curve (~44% at age 60) with increases (over 50%) up to age 74, but with no additional genetic variation after age 74; (c) the smaller influences of shared family environment (~15% at age 74) were constant over all ages; (d) non-shared effects play an important role over most of the life-span but diminish after age 74.

Midlife activity predicts risk of dementia in older male twin pairs

BACKGROUND

This was a prospective study of dementia to elucidate mechanisms of disease risk factors amenable to modification and specifically to determine whether midlife cognitive and physical leisure activities are associated with delayed onset or reduced risk of dementia within older male twin pairs.

METHODS

The co-twin control design used prospectively collected exposure information to predict risk of dementia 20 to 40 years later. The subjects were community-dwelling and nursing home residents living throughout the continental United States. We studied 147 male twin-pairs who were discordant for dementia or age of dementia onset and were members of the National Academy of Sciences-National Research Council Twin Registry of World War II veterans and participants in the Duke Twins Study of Memory in Aging. The main outcome measure was diagnosed dementia by using a two-stage screen and full clinical evaluation. Conditional odds ratios were estimated for the association between midlife leisure activities and late-life dementia.

RESULTS

Greater midlife cognitive activity was associated with a 26% risk reduction for dementia onset. Protective effects were most robust in monozygotic twin pairs, where genetic and early-life influences were most tightly controlled, and for activities that were often cognitive and social in nature. Cognitive activity was particularly protective among monozygotic twin pairs carrying the apolipoprotein E epsilon4 allele, with a 30% risk reduction. Midlife physical activity did not modify dementia risk.

CONCLUSIONS

Participation in a range of cognitively and socially engaging activities in midlife reduced risk for dementia and AD in twins discordant for onset, particularly among twin pairs at elevated genetic risk, and might be indicative of an enriched environment.

Consortium to Establish a Registry for Alzheimer's Disease (CERAD): the first twenty years

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD) was funded by the National Institute on Aging in 1986 to develop standardized, validated measures for the assessment of Alzheimer's disease (AD). The present report describes the measures that CERAD developed during its first decade and their continued use in their original and translated forms. These measures include clinical, neuropsychological, neuropathologic, and behavioral assessments of AD and also assessment of family history and parkinsonism in AD. An approach to evaluating neuroimages did not meet the standards desired. Further evaluations that could not be completed because of lack of funding (but where some materials are available) include evaluation of very severe AD and of service use and need by patient and caregiver. The information that was developed in the U.S. and abroad permits standardized assessment of AD in clinical practice, facilitates epidemiologic studies, and provides information valuable for individual and public health planning. CERAD materials and data remain available for those wishing to use them.

Job demands and dementia risk among male twin pairs

BACKGROUND

Job characteristics may influence dementia risk, but some types of job complexity remain to be examined. Twin studies provide a useful methodology to examine job differences between pairs who share many environmental and genetic influences.

METHODS

Members of the NAS-NRC Twins Registry of World War II Veterans received a clinical evaluation for dementia and had job ratings from the Dictionary of Occupational Titles.

RESULTS

Cotwin-control models (n = 220 pairs) indicated lower dementia risk with greater job demands of reasoning, mathematics, language, and vocational training, with comparable results in case-control models (n=425 cases). These effects were significant among twin pairs discordant for 6 or more years, but not among those discordant between 3-5 years. Results were similar for Alzheimer's disease, and main effects were not further explained by zygosity or apolipoprotein E genotype.

CONCLUSIONS

Jobs that utilize data, academic skills, and extensive vocational training may protect against dementia; however, in twin pairs these effects only emerged among individuals who remained free of dementia several years after onset in their sibling.