Cognitive decline following incident and preexisting diabetes mellitus in a population sample

Interactive effect of diabetes mellitus and subclinical MRI markers of cerebrovascular disease on cognitive decline and incident dementia: a memory-clinic study

BACKGROUND

Cognitive impairment is an increasingly recognized comorbidity of diabetes, yet the mechanisms underlying this association remain poorly understood. This knowledge gap has contributed to conflicting findings regarding the impact of diabetes on long-term cognitive outcomes in older adults. The presence of cerebrovascular disease (CeVD) may potentially modify this relationship. However, interactive effect between diabetes and subclinical MRI markers of CeVD on cognitive trajectories and incident dementia remains unexplored.

METHODS

A total of 654 participants underwent brain MRI at baseline, from whom 614 with at least one follow-up were selected for longitudinal analysis. Cognitive tests were performed annually up to 5 years. CeVD markers of interest were lacunes, white matter hyperintensities (WMHs), cerebral microbleeds (CMBs), cortical microinfarcts (CMIs), intracranial stenosis (ICS), and cortical infarcts. Blood-based Alzheimer biomarkers, including p-tau181 and p-tau181/Aβ42 ratio, were used as indicators of Alzheimer pathology.

RESULTS

At baseline, diabetes was associated with lower cognitive performance and higher burden of CeVD, but not p-tau181 or p-tau181/Aβ42 ratio. Longitudinally, we found an interactive effect of diabetes and WMHs, rather than an independent effect of diabetes, on cognitive decline and dementia risk. Subgroup analyses showed association of diabetes with cognitive outcomes was stronger in participants with high WMHs load but non-significant in those with low WMHs load. Moreover, these associations remained unchanged after adjusting for blood-based Alzheimer biomarkers.

CONCLUSIONS

The effect of diabetes on cognitive decline is contingent upon the presence of WMHs and independent of Alzheimer's pathology. This finding raises the possibility of utilizing WMHs as an imaging biomarker to identify diabetic subgroup at greater risk of developing cognitive impairment. Furthermore, therapeutic interventions targeting WMHs may prevent cognitive deterioration in older adults with diabetes.

Trends in Cognitive Function Before and After Diabetes Onset: The China Health and Retirement Longitudinal Study

BACKGROUND AND OBJECTIVES

Individuals with prevalent diabetes were known to have a higher risk of dementia and lower cognitive function. However, trends of cognitive function before diabetes and in the short term after new-onset diabetes remain unclear.

METHODS

This study included participants without baseline diabetes from the China Health and Retirement Longitudinal Study. Cognitive tests were conducted at baseline (wave 1) and at least one time from wave 2 (2013) to wave 4 (2018). Cognitive function was assessed using a global cognition score which was the summary measure of 4 cognitive tests. A linear mixed model was constructed to fit the trends in cognitive function before and after diabetes onset and the trends among nondiabetes. The threshold of statistical significance was p < 0.05.

RESULTS

During the 7-year follow-up, 1,207 (9.7% of 12,422, 59.1 ± 8.6 years, 39.9% male participants) participants developed new-onset diabetes. The cognitive function of both the without diabetes group and the diabetes group declined annually during the follow-up. The annual decline rate of the diabetes group before diabetes onset was similar to that of the without diabetes group during the whole follow-up period. After diabetes onset, participants experienced statistically significant faster cognitive declines in global cognition (-0.023 SD/year; 95% CI -0.043 to -0.004; p = 0.019) and visuospatial abilities test (-0.036 SD/year; -0.061 to -0.011; p = 0.004), but not in tests of episodic memory (-0.018 SD/year; -0.041 to 0.004; p = 0.116), attention and calculation (-0.017 SD/year; -0.037 to 0.003; p = 0.090), or orientation (0.001 SD/year; -0.018 to 0.020; p = 0.894), compared with the cognitive slope before diabetes. In subgroup analysis, compared with those who developed diabetes between 45-54 years, those developing diabetes older (55-64 years, p for interaction = 0.701; 65-74 years, p for interaction = 0.996) did not demonstrate different rates of global cognitive decline after diabetes.

DISCUSSION

Individuals experienced faster rate of cognitive decline in a few years after diabetes onset, but not during the prediabetes period. Age did not modify the effect of diabetes on postdiabetes cognitive decline. Efforts in eliminating the adverse impacts on cognition should be started on diagnosis of diabetes.

Vascular cognitive impairment - Past, present, and future challenges

Vascular cognitive impairment (VCI) is a lifelong process encompassing a broad spectrum of cognitive disorders, ranging from subtle or mild deficits to prodromal and fully developed dementia, originating from cerebrovascular lesions such as large and small vessel disease. Genetic predisposition and environmental exposure to risk factors such as unhealthy lifestyles, hypertension, cardiovascular disease, and metabolic disorders will synergistically interact, yielding biochemical and structural brain changes, ultimately culminating in VCI. However, little is known about the pathological processes underlying VCI and the temporal dynamics between risk factors and disease mechanisms (biochemical and structural brain changes). This narrative review aims to provide an evidence-based summary of the link between individual vascular risk/disorders and cognitive dysfunction and the potential structural and biochemical pathophysiological processes. We also discuss some key challenges for future research on VCI. There is a need to shift from individual risk factors/disorders to comorbid vascular burden, identifying and integrating imaging and fluid biomarkers, implementing a life-course approach, considering possible neuroprotective influences of positive life exposures, and addressing biological sex at birth and gender differences. Finally, this review highlights the need for future researchers to leverage and integrate multidimensional data to advance our understanding of the mechanisms and pathophysiology of VCI.

Relationship between Cognitive Impairment and Depressive Symptoms with Somatosensory Functions in Diabetic and Non-Diabetic Older Adults and Its Impact on Quality of Life

Aging is an inevitable process that impacts the peripheral and central nervous systems and is considered one of the strongest risk factors for neurodegenerative diseases. In addition, when it also presents with diabetes mellitus, the risk of neurological damage may be further increased. This current study aimed to explore the relationships between peripheral sensory system decline and cognitive functions, the symptoms of depression, and quality of life (QoL) as metrics of central nervous system impairment in institutionalized older adults. A total of 95 individuals participated in this case-control study, which included diabetics and non-diabetics. The superficial sensory pathway was assessed in terms of thermal sensation, nociception, and non-discriminative touch, and the deep sensory pathway was evaluated by assessing vibration and light touch-pressure sensations. To assess function at the intellectual level, the Mini-Mental State Examination (MMSE) and Trail Making Test (TMT) cognitive functional tests were used, while the symptoms of depression and QoL were explored by employing the Yesavage Geriatric Depression Scale and EuroQol 5D questionnaire (EQ-5D), respectively. In the overall population analyses, altered thermal sensation was significantly associated with cognitive impairment (CI; p < 0.05). In turn, bivariate analyses and a binary logistic regression showed that the symptoms of depression and QoL were significantly related to altered vibratory sensation when assessed using a medical tuning fork (p < 0.05). In the group of diabetic patients, those with CI also had significantly lower thermal sensation (p < 0.05) and non-discriminative touch sensation, although this was only a trend (p = 0.055). Diabetics with depression had a significantly worse non-discriminative touch (p < 0.05) and vibratory sensation when tested with a tuning fork (p < 0.05). In addition, poorer QoL was associated with reduced sensitivity to heat (p < 0.05), light touch pressure (p < 0.05), and vibrations when assessed either with a tuning fork (p < 0.05) or a biothesiometer (p < 0.05). In contrast, no relationships were found between sensory functions and cognitive assessments in non-diabetic patients. These findings indicate that superficial sensitivity damage was related to CI, while deep sensation alterations were related to depression and poor QoL, with diabetes apparently further strengthening these relationships.

Trajectories of Cognition and Daily Functioning Before and After Incident Diabetes

OBJECTIVE

The temporal pattern of cognitive and functional change before and after incident diabetes remains unknown.

RESEARCH DESIGN AND METHODS

Data from wave 2 to wave 9 (2004-2018) of the English Longitudinal Study of Ageing were used. Global cognition (assessed by orientation, memory, and executive function) and daily functioning (calculated as the sum of impaired basic and instrumental activities of daily living) were measured in each wave. Incident diabetes was defined as glycated hemoglobin A1c ≥6.5% (47.5 mmol/mol), self-reported doctor diagnosis of diabetes, or glucose-lowering medication use during follow-up.

RESULTS

Among the 6,342 participants (mean age 65.0 years, 57.8% women) included, 576 participants (9.1%) with incident diabetes were identified during a median follow-up of 13.3 years. The annual rates of change in global cognition (β = -0.035 SD/year; 95% CI -0.054 to -0.015), orientation (-0.031 SD/year; -0.060 to -0.002), memory (-0.016 SD/year; -0.029 to -0.003), and executive function (-0.027 SD/year; -0.042 to -0.013) were accelerated after diabetes diagnosis compared with before the event. The postdiabetes annual changes in daily functioning (0.093 points/year; 95% CI 0.056-0.131) were also accelerated compared with the prediabetes diagnosis. However, the rate of cognitive and functional decline before the diabetes diagnosis in participants with future incident diabetes was similar to the rate in participants without diabetes. Also, no significant acute change was observed during its onset.

CONCLUSIONS

Incident diabetes is associated with accelerated cognitive and functional decline after, but not before, the event. We suggest careful monitoring for cognitive and physical dysfunction after a diabetes diagnosis.

Lifestyle and Cognitive Decline in Community-Dwelling Stroke Survivors

Background: Patients with stroke are at a higher risk of cognitive impairment and Alzheimer’s disease dementia. Objective: To quantify the role of lifestyle pre-stroke, post-stroke, and changes in lifestyle before and after stroke with cognitive decline in community-dwelling stroke survivors. Methods: Utilizing data from the Chicago Health and Aging Project, a population-based cohort study, we studied 1,078 individuals with stroke (662 incident and 416 prevalent) who underwent cognitive testing during the study period. A healthy lifestyle score was defined by scoring four behaviors: non-smoking, exercising, being cognitively active, and having a high-quality diet. The global cognitive score was derived from a comprehensive battery of 4 standardized tests. Results: The mean age at incident stroke was 78.2 years, and 60.1% were women. A healthy lifestyle pre-incident stroke was associated with a slower rate of cognitive decline after stroke. Participants with 3–4 healthy lifestyle factors pre-incident stroke had a slower cognitive decline after stroke by 0.046 units/year (95% CI 0.010, 0.083), or 47.7% slower, than participants with 0–1 healthy lifestyle factor. Lifestyle score post-prevalent stroke was not associated with cognitive decline. Changes in lifestyle behaviors from pre- to post-incident stroke were related to cognitive decline after stroke. Individuals who deteriorated their lifestyle quality after stroke had a faster cognitive decline by 0.051 units/year (β –0.051, 95% CI –0.090, –0.012) than participants with no change in lifestyle score. Conclusion: A healthy lifestyle pre-stroke was associated with a slower rate of cognitive decline in stroke survivors, highlighting the importance of primary prevention. After the stroke, changes in lifestyle behaviors may influence the cognitive abilities of older adults as they age.

Diabetes-Specific Dementia: A Structured Literature Review of Cognitive Assessment Methods

Diabetes mellitus is a known risk factor for the development of multiple subtypes of dementia and mild cognitive impairment. Recent research identifies a cause-specific diabetes-related dementia with a unique set of characteristics. Currently, there is no standard cognitive assessment battery recommended to specifically assess dementia that is a direct consequence of chronic diabetes, and some evaluations have been used for decades with minimal revisions, regardless of appropriateness. We performed a systematic review of the dementia/cognition evaluation methods most commonly used in the literature for assessing diabetic patients and identified which cognitive domains are typically assessed in this setting, and whether cognitive changes were more reflective of a vascular pathology, Alzheimer's pathology, or something else entirely. Search results yielded 1089 articles. After screening for appropriateness, a total of 11 full-text articles were assessed. In general, subjects in the reviewed studies were assessed using a variety of testing methods, examining different combinations of cognitive domains. A standard, clear definition of which cognitive domains are the most important to assess in diabetic patients is needed in order to determine what combination of assessment tools are most pertinent. Given the growing subset of the US population, careful reconsideration of cognitive assessment methods is needed to create self-care plans that take into account a specific collection of cognitive challenges for those with diabetes.

Cardiovascular and metabolic morbidity following spinal cord injury

BACKGROUND CONTEXT

Individuals living with a spinal cord injury (SCI) are at heightened risk for a number of chronic health conditions such as secondary comorbidities that may develop or be influenced by the injury, the presence of impairment, and/or the process of aging.

PURPOSE

The objective of this study was to compare the incidence of and adjusted hazards for cardiovascular and metabolic (cardiometabolic) morbidities among adults following SCI compared to adults without SCIs.

STUDY DESIGN/SETTING

Longitudinal cohort from a nationwide insurance claims database.

PATIENT SAMPLE

Privately-insured beneficiaries were included if they had an ICD-9-CM diagnostic code for traumatic SCI (n=9,081). Adults without SCI were also included (n=1,474,232).

OUTCOME MEASURES AND METHODS

Incidence estimates of common cardiometabolic morbidities were compared at 4-years of enrollment. Survival models were used to quantify unadjusted and adjusted hazard ratios for incident cardiometabolic morbidities.

RESULTS

Adults living with traumatic SCIs had a higher 5-year incidence of any cardiometabolic morbidities (56.2% vs. 36.4%) as compared to adults without SCI, and differences were to a clinically meaningful extent. Survival models demonstrated that adults with SCI had a greater hazard for any cardiometabolic morbidity (Hazard Ratio [HR]: 1.67; 95%CI: 1.58, 1.76) and all cardiometabolic disorders; this ranged from HR: 1.45 (1.32, 1.59) for non-alcoholic fatty liver disease to HR: 3.55 (3.36, 3.76) for heart failure.

CONCLUSIONS

Adults with SCIs have a significantly higher incidence of and risk for common cardiometabolic morbidities, as compared to adults without SCIs. Efforts are needed to facilitate the development of improved clinical screening algorithms and early interventions to reduce risk of cardiometabolic disease onset/progression in this vulnerable population.

Predictors of cognitive decline in a multi-racial sample of midlife women: A longitudinal study

Objective: Hypertension, diabetes, depressive symptoms, and smoking are predictors of cognitive decline in late life. It is unknown if these risk factors are associated with cognition during midlife or if the associations between these risk factors and cognition vary by race. This longitudinal study examined (a) risk factors for decline in episodic memory, processing speed, and working memory in midlife women and (b) if the associations between risk factors and cognitive decline were moderated by race. Method: Participants (aged 42-52) were European American (n = 1,000), African American (n = 516), and Asian American (n = 437) women from the Study of Women's Health Across the Nation. Two-level hierarchical linear models tested risk factors, race, and their interactions as predictors of cognitive change over time. Results: African Americans had poorer baseline episodic memory, processing speed, and working memory and greater episodic memory decline compared to European Americans. Asian Americans had poorer episodic memory and working memory, but better processing speed than European Americans. Depressive symptoms were associated with poorer episodic memory and processing speed at baseline; further, diabetes was associated with poorer processing speed at baseline. Greater depressive symptoms were associated with poorer episodic memory at baseline for African Americans but not European Americans. Conclusions: Our study results highlight racial disparities in cognition during midlife. Depressive symptoms may be particularly detrimental to the cognitive health of African Americans. Clinical and public health interventions for healthy cognitive aging should be tailored to the unique risks of racial groups. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Stressful Life Events and Racial Disparities in Cognition Among Middle-Aged and Older Adults

BACKGROUND

It is well-documented that African Americans have elevated risk for cognitive impairment and dementia in late life, but reasons for the racial disparities remain unknown. Stress processes have been linked to premature age-related morbidity, including Alzheimer's and related dementias (ADRD), and plausibly contribute to social disparities in cognitive aging.

OBJECTIVE

We examined the relationship between stressful life events and cognitive decline among African American and White participants enrolled in the Wisconsin Registry for Alzheimer's Prevention (WRAP).

METHODS

Linear mixed models including demographic, literacy, and health-related covariates were used to estimate (1) relationships between a life event index score and decline in cognitive test performance in two domains of executive function (Speed & Flexibility, Working Memory) and one domain of episodic memory (Verbal Learning & Memory) among 1,241 WRAP enrollees, stratified by race, and (2) contributions of stressful life events to racial differences in cognition within the full sample.

RESULTS

African Americans (N = 50) reported more stressful life events than Whites (N = 1,191). Higher stress scores associated with poorer Speed & Flexibility performance in both groups, though not with declines across time, and partially explained racial differentials in this domain. Among African Americans only, stressor exposure also associated with age-related decline in Verbal Learning & Memory. Stressor-cognition relationships were independent of literacy and health-related variables.

CONCLUSIONS

Greater lifetime stress predicted poorer later-life cognition, and, in a small sample of African Americans, faster declines in a key domain of episodic memory. These preliminary findings suggest that future work in large minority aging cohorts should explore stress as an important source of modifiable, socially-rooted risk for impairment and ADRD in African Americans, who are disproportionately exposed to adverse experiences across the life course.

The Relation of Diabetes to Memory Function

PURPOSE OF REVIEW

Research has consistently shown that type 2 diabetes (T2D) is associated with increased risk of all-cause dementia. Because one of the most common clinical presentations of early stage dementia is memory impairment, we examined the relationship of T2D with memory function, using the recently published scientific literature.

RECENT FINDINGS

We conducted a structured review to identify studies of "T2D and memory" published since 2015. After review of the 129 articles retrieved, we identified 14 studies meeting the inclusion and exclusion criteria. Among the eight studies with a single assessment of memory function in time (mostly cross-sectional), six found an association of T2D with lower memory function, but mostly in select subgroups of persons. Separately, six studies included repeated measures of memory (longitudinal design). Four out of six longitudinal studies found that T2D was related with a faster decline in memory, while two did not. Among the four studies showing a relation with memory decline, two had sample sizes of 9000-10,000 persons. Further, three longitudinal studies controlled for hypertension and stroke as covariates, and results suggested that common vascular risk factors and diseases do not account for the relation. While mechanistic studies clearly support a role for cerebrovascular disease in the relation of T2D with cognition, emerging data suggest that insulin resistance in the brain itself may also play a role. Most, but not all, recently published studies suggest that T2D is associated with a lower level and faster decline in memory function. This association does not appear to be fully accounted for by common vascular processes. More research will clarify the mechanisms linking T2D to memory and dementia.

Psychological Morbidity and Chronic Disease Among Adults With Traumatic Spinal Cord Injuries: A Longitudinal Cohort Study of Privately Insured Beneficiaries

OBJECTIVE

To compare the longitudinal incidence of psychological morbidities and multimorbidity and estimates of chronic diseases among adults with spinal cord injuries (SCIs) as compared with adults without SCIs.

METHODS

Privately insured beneficiaries who had medical coverage at any time between January 1, 2001, and December 31, 2017 were included if they had an International Classification of Diseases, Ninth Revision, Clinical Modification diagnostic code for a traumatic SCI (n=6,847).

RESULTS

Adults with SCIs (n=6847) had a higher incidence of adjustment reaction (7.2% [n=493] vs 5.0% [n=42,862]), anxiety disorders (19.3% [n=1,322] vs 14.1% [n=120,872]), depressive disorders (29.3% [n=2,006] vs 9.3% [n=79,724]), alcohol dependence (2.4% [n=164] vs 1.0% [n=8,573]), drug dependence (2.3% [n=158] vs 0.8% [n=6,858]), psychogenic pain (1.0% [n=69] vs 0.2% [n=1,715]), dementia (6.5% [n=445] vs 1.5% [n=12,859]), insomnia (10.9% [n=746] vs 7.2% [n=61,722]), and psychological multimorbidity (37.4% [n=2,561] vs 23.9% [n=204,882]) as compared with adults without SCIs (n=857,245). The adjusted hazard ratios (HRs) of each psychological outcome were significantly higher for individuals with SCI and ranged from 1.18 (95% CI, 1.08-1.29) for anxiety disorders to 3.32 (95% CI, 1.93-5.71) for psychogenic pain. Adults with SCIs also had a significantly higher prevalence of all chronic diseases and chronic disease multimorbidity (51.1% vs 14.1%), except human immunodeficiency virus infection/AIDS. After propensity matching for age, education, race, sex, and chronic diseases (n=5884 matched pairs), there was still a significantly higher incidence of most psychological disorders and psychological multimorbidity among adults with SCIs.

CONCLUSION

Adults with traumatic SCIs experienced an increased incidence of psychological morbidities and multimorbidity as compared with adults without SCIs. Clinical efforts are needed to improve mental health screening and targeted interventions to reduce the risk for psychological disease onset in the traumatic SCI population.

Chronic disease profiles of subjective memory complaints: a latent class analysis of older people in a rural Malaysian community

Background: Subjective memory complaints (SMC) are common in the elderly and have been suggested as the first subtle sign of decline which can predict dementia. Cognitive decline is thought to be related to inflammatory processes similarly found in other chronic diseases and conditions such as stroke, heart disease and arthritis. This study aimed to examine the association of SMC with chronic diseases and the profile of these health conditions reported by a group of older adults.Methods: Data from a cross-sectional survey conducted from August 2013 and March 2014 was drawn from 6179 individuals aged 56 years and above. Multivariable logistic regression analyses were used to examine SMC's relationship with individual chronic diseases (asthma, kidney disease, heart disease, stroke, arthritis, hypertension and diabetes) and multimorbidity. Latent class analysis (LCA) was used to identify the profile of health conditions. The effect of SMC was estimated in a multinomial logistic regression as part of the latent class model.Results: SMC was statistically significant in its association with asthma, stroke, heart disease, arthritis and multimorbidity in the fully controlled multivariable logistic regression models. Three health profiles were identified: low comorbidity (n = 4136, low rates in all health conditions), arthritis group (n = 860) and diabetes and hypertension group (n = 1183). SMC was associated with arthritis group (OR = 2.04, 95% CI = 1.51-2.75) and diabetes and hypertension group (OR = 1.22, 95% CI = 1.03-1.46).Conclusion: Adapting a combination of analytical approaches allows a better understanding in the assessment of SMC's relationship with chronic diseases and the patterns of distribution of these health conditions.

Disparities in diabetes-related multiple chronic conditions and mortality: The influence of race

AIMS

The aims of this study are to confirm disparities in diabetes mortality rates based on race, determine if race predicts combinations of diabetes and multiple chronic conditions (MCC) that are leading causes of death (LCD), and determine if combinations of diabetes plus MCC mediate the relationship between race and mortality.

METHODS

We performed a retrospective cohort study of 443,932 Medicare beneficiaries in the State of Michigan with type 2 diabetes mellitus and MCC. We applied Cox proportional hazards regression to determine predictors of mortality. We applied multinomial logistic regression to determine predictors of MCC combinations.

RESULTS

We found that race influences mortality in Medicare beneficiaries with Type 2 diabetes mellitus and MCC. Prior to adjusting for MCC combinations, we observed that Blacks and American Indian/Alaska Natives have increased risk of mortality compared to Whites, while there is no difference in mortality between Hispanics and Whites. Regarding MCC combinations, Black/African American beneficiaries experience increased odds for most MCC combinations while Asian/Pacific Islanders and Hispanics experience lower odds for MCC combinations, compared to Whites. When adjusting for MCC, mortality disparities observed between Whites, Black/African Americans, and American Indians/Alaska Natives persist.

CONCLUSIONS

Compared to Whites, Black/African Americans in our cohort had increased odds of most MCC combinations, and an increased risk of mortality that persisted even after adjusting for MCC combinations.

Comprehensive transcriptomic analysis indicates brain regional specific alterations in type 2 diabetes

Type 2 diabetes (T2D) can result in a number of comorbidities involving various organs including heart, eye, kidney and even the brain. However, little is known about the molecular basis of T2D associated brain disorders. In this study, we performed a comprehensive transcriptomic analysis in a total of 304 T2D samples and 608 matched control samples from thirteen distinct brain regions. We observed prominent difference among transcriptomic profiles of diverse brain regions in T2D. The most striking change was found in caudate with thousands of T2D-associated genes identified, followed by hippocampus, while nearly no transcriptomic change was observed in other brain regions. Functional analysis of T2D-associated genes revealed impaired synaptic functions and an association with neurodegenerative diseases. Co-expression analysis of caudate transcriptomic profiles unveiled a core regional specific module that was disorganized in T2D. Sub-modules consisting of regional markers were enriched in T2D risk single nucleotide polymorphisms (SNPs) and implied a causal link with T2D. Hub genes of this module include NSF and ADD2, the former of which has been associated with T2D and neurogenerative diseases. Thus, our work provides useful information for further studies in T2D associated brain disorders.

Short height and poor education increase the risk of dementia in Nigerian type 2 diabetic women

Introduction

There is urgent need to investigate type 2 diabetes and dementia crosstalk in sub-Saharan African countries with special attention to women who have higher vulnerability. Nigeria which has the highest number of diabetics on the African continent is a good location for the investigation.

Methods

Biophysical parameters, occupation, education, burden of diabetes mellitus, cardiovascular health, and cognition were evaluated in 102 type 2 diabetics and 99 controls.

Results

Short physical stature and lower level of education were hallmarks of diabetes in females. Two dementia scales (Mini–Mental State Examination and six-item Cognitive Impairment Test) showed cognitive impairment status, with the six-item Cognitive Impairment Test scale being more specific and sensitive. Both scales showed correlations with age, education, weight, height, and disease onset, whereas fasten blood glucose was negatively correlated with height and their blood pressure was normal.

Discussion

Height, an easy-to-measure parameter in Nigeria, may reveal increased risk of dementia in poorly educated female Nigerian diabetics, thus helping to improve preventive and therapeutic interventions.

Brain MRI findings related to Alzheimer's disease in older African American adults

Although a substantial body of research has identified brain MRI measures as important markers of Alzheimer's disease (AD) risk, progression, and treatment response, most of that research has been performed in non-Hispanic white American populations, leading to questions about the utility of the brain MRI measures among individuals of other races or ethnicities. African American individuals in particular are under-represented in AD research, and may exhibit differences in prevalence of AD risk factors, prevalence of AD, incidence of AD, the clinical course of cognitive decline, and AD neuropathology, each of which could influence the utility of brain MRI markers. Unfortunately, while current evidence suggests that African Americans exhibit poorer brain health late in life based on brain MRI measurements, several other aspects of brain MRI markers in this population are unclear, including trajectories of brain MRI markers leading up to old age, relationships between traditional brain health risk factors and brain MRI findings, and the status of brain MRI markers as correlates of cognitive impairment. This unclear state of affairs highlights the urgency of future research in which large numbers of older African American adults contribute longitudinal brain MRI measurements concurrent with clinical, cognitive, and molecular biomarker measurements, ideally in the context of AD preventive or therapeutic trials.

Cognitive decline is related to high blood glucose levels in older Chinese adults with the ApoE ε3/ε3 genotype

Background

Few studies have investigated the effects of blood glucose (BG) on cognitive function in community-dwelling elderly individuals carrying the apolipoprotein E (APOE) ε3 allele.

Objective

To explore the effect of high BG levels on cognitive function in APOE ε3-carrying, non-demented, community-dwelling older adults, as compared to their counterparts carrying the APOE ε4 or APOE ε2 alleles.

Methods

Within the China Longitudinal Ageing Study, we recruited 282 elderly adults without dementia. Data collected included demographic information; psychological measures; laboratory test results, including BG and plasma lipid levels; and APOE genotypes. We divided the participants into APOE ε2(ε2/ε2, ε2/ε3), ε3(ε3/ε3), and ε4(ε3/ε4, ε4/ε4) groups. Partial correlation analyses and multivariate linear regression analyses were utilized to compare the cognitive function and laboratory data between the APOE groups. White matter hyperintensity (WMH) was measured on magnetic resonance images in 77 participants.

Results

With adjustment for age, sex, education, and diabetes, higher BG in non-demented community-dwelling older adults was associated with cognitive decline in immediate memory and executive function. In the APOE ε3 group, elevated BG was associated with cognitive decline in immediate memory, executive function, and perceptual reasoning. In the APOE ε4 group, higher BG was also correlated with a decline in abstract reasoning. There was a trend for association between higher BG and more severe WMHs.

Conclusion

Worse cognitive function was correlated withApoEε3/ε3 genotype carriers with higher BG in community-dwelling older adults.

Type 2 diabetes mellitus, brain atrophy and cognitive decline in older people: a longitudinal study

AIMS/HYPOTHESIS

The aims of the study were to examine whether type 2 diabetes mellitus is associated with greater brain atrophy and cognitive decline, and whether brain atrophy mediates associations between type 2 diabetes and cognitive decline.

METHODS

Participants without dementia aged 55-90 years from the Cognition and Diabetes in Older Tasmanians (CDOT) study underwent brain MRI (ventricular and total brain volume) and neuropsychological measures (global function and seven cognitive domains) at three time points over 4.6 years. Mixed models were used to examine longitudinal associations of type 2 diabetes with cognitive and MRI measures, adjusting for covariates. A test of mediation was used to determine whether brain atrophy explained associations between type 2 diabetes and cognitive decline.

RESULTS

A total of 705 participants (diabetes: n = 348, mean age 68.2 years [SD 7.0]; no diabetes: n = 357, mean age 72.5 years [SD 7.1]) were available at baseline. Adjusting for age, sex, education and vascular risk factors, there were significant diabetes × time interactions for verbal memory (β -0.06; 95% CI -0.09, -0.02) and verbal fluency (β -0.03; 95% CI -0.06, -0.00). Although people with diabetes had lower brain (β -14.273; 95% CI -21.197, -6.580) and greater ventricular (β 2.672; 95% CI 0.152, 5.193) volumes at baseline, there were no significant diabetes × time interactions (p > 0.05) or evidence of mediation of the diabetes-cognition relationship by brain atrophy.

CONCLUSIONS/INTERPRETATION

In older community-dwelling people, type 2 diabetes is associated with decline in verbal memory and fluency over ~5 years. The effect of diabetes on brain atrophy may begin earlier (midlife).

Locus Coeruleus Degeneration Induces Forebrain Vascular Pathology in a Transgenic Rat Model of Alzheimer's Disease

Noradrenergic locus coeruleus (LC) neuron loss is a significant feature of mild cognitive impairment and Alzheimer's disease (AD). The LC is the primary source of norepinephrine in the forebrain, where it modulates attention and memory in vulnerable cognitive regions such as prefrontal cortex (PFC) and hippocampus. Furthermore, LC-mediated norepinephrine signaling is thought to play a role in blood-brain barrier (BBB) maintenance and neurovascular coupling, suggesting that LC degeneration may impact the high comorbidity of cerebrovascular disease and AD. However, the extent to which LC projection system degeneration influences vascular pathology is not fully understood. To address this question in vivo, we stereotactically lesioned LC projection neurons innervating the PFC of six-month-old Tg344-19 AD rats using the noradrenergic immunotoxin, dopamine-β-hydroxylase IgG-saporin (DBH-sap), or an untargeted control IgG-saporin (IgG-sap). DBH-sap-lesioned animals performed significantly worse than IgG-sap animals on the Barnes maze task in measures of both spatial and working memory. DBH-sap-lesioned rats also displayed increased amyloid and inflammation pathology compared to IgG-sap controls. However, we also discovered prominent parenchymal albumin extravasation with DBH-sap lesions indicative of BBB breakdown. Moreover, microvessel wall-to-lumen ratios were increased in the PFC of DBH-sap compared to IgG-sap rats, suggesting that LC deafferentation results in vascular remodeling. Finally, we noted an early emergence of amyloid angiopathy in the DBH-sap-lesioned Tg344-19 AD rats. Taken together, these data indicate that LC projection system degeneration is a nexus lesion that compromises both vascular and neuronal function in cognitive brain areas during the prodromal stages of AD.

Associations of literacy with diabetes indicators in older adults

BACKGROUND

Literacy, the ability to access, understand and utilise information and concepts from diverse sources in ways that promote good outcomes is key to successful ageing. Domain-specific health and financial literacy are particularly relevant to older adults as they face increasingly complex health and financial demands including those related to chronic conditions like type 2 diabetes. We therefore investigated the associations of literacy, including health and financial literacy, with diabetes indicators (ie, haemoglobin A1c and blood glucose) in a community-based cohort study of ageing.

METHODS

Participants were 908 non-demented older adults (age ~81 years;75% women) from the Rush Memory and Aging Project. Literacy was measured using questions designed to assess comprehension of health and financial information and concepts and yielded a total score and domain-specific health and financial literacy scores. Non-fasting haemoglobin A1c and blood glucose samples were collected, participants were queried about diabetes status and medications for diabetes were visually inspected and coded. Participants also underwent a cognitive assessment, medical history and depressive symptom screening.

RESULTS

In separate multivariable linear regression models, total (p values <0.03) and health (p values <0.009) literacy were inversely associated with haemoglobin A1c and blood glucose levels after adjusting for age, sex, education, hypertension, global cognitive functioning and depressive symptoms. Financial literacy was inversely associated with haemoglobin A1c levels in adjusted models (p=0.04). Sensitivity analyses conducted among individuals without diabetes revealed similar results.

CONCLUSION

Lower literacy levels are associated with higher diabetes indicators, particularly haemoglobin A1c which is suggestive of longer-term glycaemic instability.

The chicken or the egg? Does glycaemic control predict cognitive function or the other way around?

The association between type 2 diabetes and cognitive dysfunction is well established. Prevention of the development of type 2 diabetes and its complications, as well as cognitive dysfunction and dementia, are leading goals in these fields. Deciphering the causality direction of the interplay between type 2 diabetes and cognitive dysfunction, and understanding the timeline of disease progression, are crucial for developing efficient prevention strategies. The prevailing perception is that type 2 diabetes leads to cognitive dysfunction and dementia. There is substantial evidence showing that accelerated cognitive decline in type 2 diabetes starts in midlife (mean age 40-60 years) and that it may even begin at the prediabetes stage. However, in this issue of Diabetologia, Altschul et al (doi: https://doi.org/10.1007/s00125-018-4645-8 ) show evidence for the reverse causality hypothesis, i.e. that lower cognitive function precedes poor glycaemic control. They found that cognitive function at early adolescence (age 11 years) predicts both HbA1c levels and cognitive function at age 70 years. Moreover, they found that lower cognitive function at age 70 is associated with an increase in HbA1c from age 70 to 79 years. Based on these findings, future studies should explore whether developing prevention strategies that target young adolescents with lower cognitive function will result in prevention of type 2 diabetes, breaking the vicious cycle of type 2 diabetes and cognitive dysfunction.

Changes of glucose levels precede dementia in African-Americans with diabetes but not in Caucasians

INTRODUCTION

Changes in glucose levels may represent a powerful metabolic indicator of dementia in African-Americans with diabetes. It is unclear whether these changes also occur in Caucasians.

METHODS

A secondary data analysis using electronic medical records from 5228 African-Americans and Caucasians aged ≥65 years was carried out. Mixed effects models with repeated serum glucose measurements were used to compare changes in glucose levels between African-Americans and Caucasian patients with and without incident dementia.

RESULTS

African-Americans and Caucasians with diabetes had significantly different changes in glucose levels by dementia status (P < .0001). African-Americans experienced a significant decline in glucose levels before the dementia diagnosis (estimated glucose decline 1.3421 mg/dL per year, P < .0001) than those who did not develop dementia. Caucasians with and without dementia showed stable glucose levels over time (P = .3071).

DISCUSSION

Significant changes in glucose levels precede dementia in African-American patients with diabetes but not in Caucasians.

Neuropathologic features of TOMM40 '523 variant on late-life cognitive decline

INTRODUCTION

The study investigated the role of neuropathologies in the relationship between TOMM40 '523 genotype and late-life cognitive decline.

METHODS

Participants were community-dwelling older persons who had annual cognitive assessments and brain autopsies after death. Genotyping used DNA from peripheral blood or postmortem brain tissue. Linear mixed models assessed the extent to which the association of '523 genotype with cognitive decline is attributable to neuropathologies.

RESULTS

Relative to ε3/ε3 homozygotes with '523-S/VL or '523-VL/VL genotype, both '523-L carriers and ε3/ε3 homozygotes with '523-S/S genotype had faster cognitive decline. The association of '523-L with cognitive decline was attenuated and no longer significant after controlling for Alzheimer's and other neuropathologies. By contrast, the association of '523-S/S was unchanged.

DISCUSSION

There are two distinct TOMM40 '523 signals in relation to late-life cognitive decline. One signal primarily acts through AD and other common neuropathologies, whereas the other operates through a different mechanism.