Severity of memory impairment in the elderly: Association with health care resource use and functional limitations in the United States

Metformin, Cognitive Function, and Changes in the Gut Microbiome

The decline in cognitive function and the prevalence of neurodegenerative disorders are among the most serious threats to health in old age. The prevalence of dementia has reached 50 million people worldwide and has become a major public health problem. The causes of age-related cognitive impairment are multiple, complex, and difficult to determine. However, type 2 diabetes (T2D) is linked to an enhanced risk of cognitive impairment and dementia. Human studies have shown that patients with T2D exhibit dysbiosis of the gut microbiota. This dysbiosis may contribute to the development of insulin resistance and increased plasma lipopolysaccharide concentrations. Metformin medication mimics some of the benefits of calorie restriction and physical activity, such as greater insulin sensitivity and decreased cholesterol levels, and hence may also have a positive impact on aging in humans. According to recent human investigations, metformin might partially restore gut dysbiosis related to T2D. Likewise, some studies showed that metformin reduced the risk of dementia and improved cognition, although not all studies are concordant. Therefore, this review focused on those human studies describing the effects of metformin on the gut microbiome (specifically the changes in taxonomy, function, and circulating metabolomics), the changes in cognitive function, and their possible bidirectional implications.

Assessing cognitive decline in the aging brain: lessons from rodent and human studies

As life expectancy continues to increase worldwide, age-related dysfunction will largely impact our societies in the future. Aging is well established to promote the deterioration of cognitive function and is the primary risk factor for the development of prevalent neurological disorders. Even in the absence of dementia, age-related cognitive decline impacts specific types of memories and brain structures in humans and animal models. Despite this, preclinical and clinical studies that investigate age-related changes in brain physiology often use largely different methods, which hinders the translational potential of findings. This review seeks to integrate what is known about age-related changes in the brain with analogue cognitive tests used in humans and rodent studies, ranging from "pen and paper" tests to virtual-reality-based paradigms. Finally, we draw parallels between the behavior paradigms used in research compared to the enrollment into clinical trials that aim to study age-related cognitive decline.

The Role of Cognitive Self-Report Measure Type in Predicting Cognitive Decline Among Older Adults: A Systematic Review

Many types of items are used to measure self-reported cognition, resulting in heterogeneity across studies. Certain cognitive self-report measure types may be more predictive of future decline. Therefore, the purpose of this systematic review was to compare whether specific types of cognitive self-report measures better predict risk for cognitive decline over time when measures are directly compared within the same study. The PRISMA criteria guided the review. Eligibility criteria included: longitudinal studies, outcome of cognitive decline, at least 2 different cognitive self-report measures, and no cognitive impairment at baseline. Nineteen studies were included in the final review. A narrative synthesis of results was completed, resulting in 3 thematic groups of comparisons across self-reported measure types. Self-reported memory decline with worry and peer perceptions of memory were associated with the highest risk for cognitive decline. Future longitudinal investigations of self-reported cognitive problems should focus on using measures that may be most sensitive to predicting cognitive decline risk.

Hearing Sensitivity, Cardiovascular Risk, and Neurocognitive Function: The Hispanic Community Health Study/Study of Latinos (HCHS/SOL)

Question

Is hearing impairment associated with cardiovascular disease risk and cognitive function among Hispanic or Latino participants?

Findings

In this cohort study of 9623 Hispanic/Latino adults, hearing impairment was associated with poorer cognitive performance on all tasks, and cardiovascular disease risk did not attenuate these relationships. Rather, hearing impairment modified the associations between cardiovascular disease risk and learning and memory; only among individuals with hearing impairment, being identified as having excessively high glucose was associated with poorer learning and memory relative to participants considered healthy individuals.

Meaning

Hearing impairment may exacerbate the associations between high glucose and poorer cognition, particularly for learning and memory among Hispanic or Latino persons.

Importance

Both cardiovascular disease risk and hearing impairment are associated with cognitive dysfunction. However, the combined influence of the 2 risk factors on cognition is not well characterized.

Objective

To examine associations between hearing impairment, cardiovascular disease risk, and cognitive function.

Design, Setting, and Participants

This population-based, prospective cohort, multisite cross-sectional analysis of baseline data collected between 2008 and 2011 as part of the Hispanic Community Health Study/Study of Latinos included 9623 Hispanic or Latino adults aged 45 to 74 years in New York, Chicago, Miami, and San Diego.

Exposures

Hearing impairment of at least mild severity was defined as the pure tone average of 500, 1000, 2000, and 4000 Hz greater than 25 dB hearing level (dB HL) in the better ear. Our measure of cardiovascular disease risk was a latent class variable derived from body mass index, ankle-brachial index, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, fasting blood glucose, and the Framingham Cardiovascular Risk score.

Main Outcomes and Measures

Results on Brief-Spanish English Verbal Learning Test (episodic learning and memory), and Word Fluency (verbal fluency), and Digit Symbol Subtest (processing speed/executive functioning), and a cognitive composite of the mentioned tests (overall cognition).

Results

Participants (N = 9180) were 54.4% female and age 56.5 years on average. Hearing impairment was associated with poorer performance on all cognitive measures (global cognition: unstandardized β, −0.11; 95% CI, −0.16 to 0.07). Cardiovascular grouping (healthy, typical, high cardiovascular disease risk, and hyperglycemia) did not attenuate the associations between hearing impairment and cognition (global cognition: unstandardized β, −0.11; 95% CI, −0.15 to −0.06). However, cardiovascular grouping interacted with hearing impairment such that hyperglycemia in the context of hearing impairment exacerbated poor performance on learning and memory tasks (F₃ = 3.70 and F₃ = 2.92, respectively).

Conclusions and Relevance

The findings of this cohort study suggest that hearing impairment increases the likelihood that individuals with excessively high glucose perform poorly on learning and memory tasks. Further research is needed to specify the mechanisms by which cardiovascular disease risk and hearing impairment are collectively associated with cognition.

Memory and Personality Development in Adulthood: Evidence From Four Longitudinal Studies

OBJECTIVES

Personality traits have been related to concurrent memory performance. Most studies, however, have focused on personality as a predictor of memory; comparatively less is known about whether memory is related to personality development across adulthood. Using 4 samples, the present study tests whether memory level and change are related to personality change in adulthood.

METHOD

Participants were drawn from 2 waves of the Wisconsin Longitudinal Study Graduates (WLSG; N = 3,232, mean age = 64.28, SD = 0.65) and Wisconsin Longitudinal Study Siblings (WLSS; N = 1,570, mean age = 63.52, SD = 6.69) samples, the Midlife in the United States (MIDUS; N = 1,901, mean age = 55.43, SD = 10.98), and the Health and Retirement Study (HRS; N = 6,038, mean age = 65.47, SD = 8.28). Immediate and delayed recall and the 5 major personality traits were assessed at baseline and follow-up.

RESULTS

There was heterogeneity in the associations across samples. A meta-analysis of latent change in the four samples indicated that lower baseline memory performance was related to an increase in neuroticism (B = -0.002; 95% CI = -0.004, -0.0008) and a decrease in agreeableness (B = 0.004; 95% CI = 0.002, 0.007) and conscientiousness (B = 0.005; 95% CI = 0.0008, 0.010). In addition, declines in memory were related to steeper declines in extraversion (B = 0.06; 95% CI = 0.003, 0.11), openness (B = 0.04; 95% CI = 0.007, 0.069), and conscientiousness (B = 0.05; 95% CI = 0.019, 0.09).

DISCUSSION

The present study indicates that poor memory and declines in memory over time are related to maladaptive personality change. These associations, however, were small and inconsistent across samples.

Association between Intake of Energy and Macronutrients and Memory Impairment Severity in US Older Adults, National Health and Nutrition Examination Survey 2011-2014

Without a cure, dementia affects about 50 million people worldwide. Understanding the effects of dietary habits, a key lifestyle behavior, on memory impairment is critical to inform early behavioral modification to delay further memory loss and progression to dementia. We examined the associations of total energy intake and energy intake from macronutrients with memory impairment among older US adults using data from the nationally representative National Health and Nutrition Examination Survey study 2011-2014. A total of 3623 participants aged ≥60 years were analyzed. Comparing to those with low total energy intake, individuals with high intake were more likely to have severe memory impairment (OR: 1.52, 95% CI: 1.15 to 2.02; ptrend = 0.005). Specifically, higher energy intake from carbohydrate (OR: 1.59, 95% CI: 1.12 to 2.26) and sugar (OR: 1.54, 95% CI: 1.11 to 2.16) were both significantly associated with the presence of memory impairment. Additionally, higher energy intake from fat, carbohydrate and sugar were significantly associated with more server memory impairment (fat: ptrend = 0.04; carbohydrate: ptrend = 0.03; sugar: ptrend = 0.02). High energy intake, either total or from carbohydrates, fat or sugar, is associated with memory impairment severity in the older US population. No such association was found in energy intake from protein.

Differences in the Associations Between Memory Complaints and Depressive Symptoms Among Black and White Older Adults

OBJECTIVE

To test whether race (specifically Black or White) moderates the relationship between memory complaints and depressive symptoms in cognitively normal older adults, and if these relationships vary by memory complaint characteristics.

METHODS

Data from Black (n = 551) and White (n = 1,158) cognitively intact participants (Mage = 77.1, SD = 7.5; 76.6% female) in the Minority Aging Research Study and the Rush Memory and Aging Project were used. Participants completed annual clinical evaluations, including the Center for Epidemiologic Studies Depression scale and two memory complaint questions, over periods of up to 18 years. Ordinal mixed effects models were used to examine within-person relationships between memory complaints and depressive symptoms over time, as well as whether race moderated these associations.

RESULTS

Reports of greater memory change over time were associated with more depressive symptoms for both Black and White older adults. However, reports of greater frequency of memory problems were related to depressive symptoms for Black older adults only.

CONCLUSION

Findings suggest differential associations between memory complaints and depressive symptoms in cognitively normal Black and White older adults and call for future research to examine the influence of race and related factors on memory complaints and depressive symptoms.

The CBP KIX domain regulates long-term memory and circadian activity

Background

CREB-dependent transcription necessary for long-term memory is driven by interactions with CREB-binding protein (CBP), a multi-domain protein that binds numerous transcription factors potentially affecting expression of thousands of genes. Identifying specific domain functions for multi-domain proteins is essential to understand processes such as cognitive function and circadian clocks. We investigated the function of the CBP KIX domain in hippocampal memory and gene expression using CBP^KIX/KIX mice with mutations that prevent phospho-CREB (Ser133) binding.

Results

We found that CBP^KIX/KIX mice were impaired in long-term memory, but not learning acquisition or short-term memory for the Morris water maze. Using an unbiased analysis of gene expression in the dorsal hippocampus after training in the Morris water maze or contextual fear conditioning, we discovered dysregulation of CREB, CLOCK, and BMAL1 target genes and downregulation of circadian genes in CBP^KIX/KIX mice. Given our finding that the CBP KIX domain was important for transcription of circadian genes, we profiled circadian activity and phase resetting in CBP^KIX/KIX mice. CBP^KIX/KIX mice exhibited delayed activity peaks after light offset and longer free-running periods in constant dark. Interestingly, CBP^KIX/KIX mice displayed phase delays and advances in response to photic stimulation comparable to wildtype littermates. Thus, this work delineates site-specific regulation of the circadian clock by a multi-domain protein.

Conclusions

These studies provide insight into the significance of the CBP KIX domain by defining targets of CBP transcriptional co-activation in memory and the role of the CBP KIX domain in vivo on circadian rhythms.

Graphical abstract

Acute Healthcare Utilization of a Multidisciplinary Neurocognitive Dementia Patient Cohort

Background and Purpose

Upon referral from the primary care provider (PCP), dementia is diagnosed either by a neuropsychological evaluation (NPE) or at a multidisciplinary neurocognitive clinic (MNC). Following the NPE, patients continue receiving care from their PCP. In contrast, patients at the MNC are followed by a multidisciplinary care team that provides expertise across specialties in dementia care and education for the patient, family members, and care providers. The purpose of the study was to determine the utilization of acute healthcare services during the 2 years following a diagnosis of dementia in patients from the MNC and NPE.

Methods

A retrospective review was performed of 581 electronic medical records from January 2010 through December 2014 for 2 cohorts of patients diagnosed with dementia 1) by a neuropsychologist or 2) in a MNC. Acute-care hospital admissions, emergency room (ER) visits, and nonroutine PCP visits were identified. Categorical demographics and utilization variables were summarized by frequency. Chi-square analysis was used to analyze demographic characteristics and overall utilization between MNCs and NPE. Utilization in comparison with various demographic characteristics was analyzed using Spearman correlation coefficients and negative binomial regressions.

Results

Patients evaluated in the MNC were older, more severely impaired, and lived alone more often compared with NPE patients, but there was no increase in hospital admissions and ER visits. Patients who underwent NPE were 1.58 times more likely to have a nonroutine PCP office visit than patients evaluated in the MNC (p=0.0093).

Conclusions

Performing follow-up in multidisciplinary clinics provides patients with more education and may help to reduce the utilization of healthcare services.

Muscle weakness and functional limitations in an ethnically diverse sample of older adults

Objectives: Muscle weakness is often linked to functional limitations in older adults. However, certain demographic characteristics, such as ethnicity, may differentially impact the association between weakness and functional limitations. This investigation sought to (1) identify sex- and ethnically-specific muscle weakness thresholds associated with functional limitations among older adults, and (2) determine the odds of functional limitations for each ethnicity by sex after identifying older adults below the weakness thresholds.Design: Persons aged ≥60 years from the 2011-2012 to 2013-2014 waves of the National Health and Nutrition Examination Survey identifying as non-Hispanic white, non-Hispanic black, Hispanic, or non-Hispanic Asian were included. Handgrip strength was normalized to each participant's body weight (normalized grip strength (NGS)). Participants responded to 19-items asking them about their ability to perform certain activities of daily living, instrumental activities of daily living, leisure and social activities, lower extremity mobility functions, and general physical activities. Receiver operating characteristic curves identified the optimal NGS thresholds associated with functional limitations. Covariate-adjusted multiple logistic regression models were performed to determine the odds of functional limitations for weak vs. not-weak participants.Results: Of the 3,027 participants, the highest NGS thresholds for functional limitations were in non-Hispanic Asian males (0.41; p < 0.001) and Hispanic females (0.36; p < 0.001); whereas, the lowest NGS thresholds were in Hispanic males (0.25; p < 0.001) and non-Hispanic black females (0.23; p < 0.001). Weak non-Hispanic Asian males (odds ratio (OR): 10.42; 95% confidence interval (CI): 10.24, 10.61) and females (OR: 11.95; CI: 11.71, 12.19) had the highest odds for functional limitations compared to their non-weak counterparts.Conclusion: Preserving muscle strength, especially for certain older adult populations, may help reduce the odds of developing functional limitations. Interventions designed to increase muscle strength to preserve or improve function should consider the role of ethnicity when designing such interventions and identifying at risk populations.

Utilization of Medications With Cognitive Impairment Side Effects and the Implications for Older Adults' Cognitive Function

Objectives: Many medications have cognitive impairment, memory loss, amnesia, or dementia as side effects ("cognitive side effects" hereafter), but little is known about trends in the prevalence of these medications or their implications for population-level cognitive impairment. Method: We use data from the National Health and Nutrition Examination Survey (1999-2016) to describe trends in the use of medications with cognitive side effects among adults aged 60+ (N = 16,937) and their implications for cognitive functioning (measured using word learning and recall, animal fluency, and digit symbol substitution assessments). Results: Between 1999 to 2000 and 2015 to 2016, the prevalence of older adults taking one, two, and at least three medications with cognitive side effects increased by 10.2%, 57.3%, and 298.7%, respectively. Compared to non-users, respondents who simultaneously used three or more medications with cognitive side effects scored 0.22 to 0.27 standard deviations lower in word learning and recall (p = .02), digit symbol substitution (p < .01), and the average standardized score of the three assessments (p < .001). Limitation: Dosage of medications associated with cognitive side effects was not measured. Discussion: Concurrent use of medications with cognitive side effects among older adults has increased dramatically over the past two decades. The use of such medications is associated with cognitive impairment and may explain for disparities in cognitive function across subgroups. These findings highlight the need for cognitive screenings among patients who consume medications with cognitive side effects. They also highlight the synergic effects of polypharmacy and potential drug-drug interactions that result in cognitive deficits.

Mimicking Age-Associated Gadd45γ Dysregulation Results in Memory Impairments in Young Adult Mice

Age-related memory loss is observed across multiple mammalian species and preferentially affects hippocampus-dependent memory. Memory impairments are characterized by accelerated decay of spatial memories. Nevertheless, the molecular mechanisms underlying these deficits are still largely unknown. Here, we investigated the expression and function of the growth arrest DNA damage (Gadd45) family during aging and cognition, respectively. We report that aging impairs the expression of Gadd45γ in the hippocampus of cognitively impaired male mice. Mimicking this decrease in young adult male mice led to age-like memory deficits in hippocampus-dependent memory tasks. Gadd45γ reduction impaired the activity of key components of the mitogen-activated protein kinase (MAPK) pathway (p38 and JNK) in mouse hippocampal cultures. Furthermore, we found that activation of downstream targets, such as ATF-2, c-Jun, and CREB (cAMP response element-binding protein), was disrupted. Finally, we showed that Gadd45γ is required for induction of key early- and late-response genes that have been associated with aging. Together, these findings indicate that Gadd45γ expression regulates cognitive abilities and synapse-to-nucleus communication and suggest Gadd45γ dysfunction as a potential mechanism contributing to age-related cognitive impairments.SIGNIFICANCE STATEMENT A high percentage of subjects experience age-related memory loss that burdens daily performance. Although many advances have been made, the precise changes in the brain governing these deficits are unclear. Identifying molecular processes that are required for cognition and are altered during old age is crucial to develop preventive or therapeutic strategies. Here, we show that baseline and learning-induced expression of the growth arrest DNA damage (Gadd45) γ is selectively impaired in the hippocampus of aged mice with cognitive deficits. Next, we show that modeling this impairment in young adult mice with normal cognitive performance disrupts long- and short-term memories in an age-like manner. Finally, we demonstrate that Gadd45γ regulates synapse-to-nucleus communication processes that are needed for plasticity-associated gene expression.

The treatment of cognitive dysfunction in dementia: a multiple treatments meta-analysis

OBJECTIVE

No cure is currently available for dementia; however, various treatments and interventions have been reported to be effective. The factors influencing the efficacy of dementia treatment have not been comprehensively evaluated. This study evaluated the factors influencing treatment effects on cognitive dysfunction in dementia by comparing the results obtained from a meta-analysis based on meta-regression.

METHODS

We searched for articles, clinical trials, and meta-analyses on the efficacy of pharmacotherapy or psychosocial treatment for dementia published between 2000 and 2016 in the MEDLINE/PubMed, Cochrane Library, SCOPUS, and Airiti Library databases.

RESULTS

The 235 selected studies involved 44,854 patients with dementia (mainly vascular dementia, Alzheimer disease, and mild cognitive impairment). A preliminary random effects meta-analysis yielded a positive overall effect. The pooled standardized mean difference of the treatment effects on cognitive dysfunction was 0.439 (95% confidence interval 0.374, 0.504). The results of meta-regression showed that in young patients (β = - 0.036, p value < 0.001) with vascular dementia (β = 0.603, p value < 0.001), the efficacies of treatment 2 (symptomatic treatment for vascular dementia with piracetam, nimodipine, aniracetam, flunarizine, vinpocetine, hyperbaric oxygen, oxiracetam, or EGB761) and treatment 5 (treatment with other alternative therapies including acupuncture, premarin, statin, butylphthalide soft capsules, donepezil, huperzine A, and lithium treatment) were higher than those of other existing treatments for cognitive dysfunction (β = 0.308 and 0.321, p values = 0.010 and < 0.001, respectively).

CONCLUSION

The most effective intervention for dementia available is symptomatic treatment for vascular dementia. Antipsychotic treatment for dementia alleviates cognitive dysfunction less effectively than does symptomatic treatment. Alternative therapies are also effective at present. Further research on causes and very early diagnosis of Alzheimer disease is warranted.

Sleep and other correlates of high-level health in older adults

A large sample (N = 1139) of adults ≥75 years from the 2011-2014 NHANES cohorts was used to examine predictors of high-level health. Analyses were done with SAS to control for sample weights and allow results to be reported as population parameters. The majority of participants described their health as high-level (73.6%). Logistic regression found a longer sleep duration, minority status, decreased income, multiple medications, low physical activity, and late stage memory impairment were significant predictors of low-level health (p < .05) while sex, education level, marital status, body mass index, and depression symptoms were not. The assessment of sleep should be expanded to cover dimensions such as sleep quality and sleep disorders to help maintain wellness in older adults. This study supports that the majority of older adults have high-level health and identifies several modifiable factors to maintain wellness.