Diabetes as a risk factor for dementia and mild cognitive impairment: a meta-analysis of longitudinal studies

Metabolic Risk Factors of Sporadic Alzheimer's Disease: Implications in the Pathology, Pathogenesis and Treatment

Alzheimer's disease (AD), the major cause of dementia among the elderly world-wide, manifests in familial and sporadic forms, and the latter variety accounts for the majority of the patients affected by this disease. The etiopathogenesis of sporadic AD is complex and uncertain. The autopsy studies of AD brain have provided limited understanding of the antemortem pathogenesis of the disease. Experimental AD research with transgenic animal or various cell based models has so far failed to explain the complex and varied spectrum of AD dementia. The review, therefore, emphasizes the importance of AD related risk factors, especially those with metabolic implications, identified from various epidemiological studies, in providing clues to the pathogenesis of this complex disorder. Several metabolic risk factors of AD like hypercholesterolemia, hyperhomocysteinemia and type 2 diabetes have been studied extensively both in epidemiology and experimental research, while much less is known about the role of adipokines, pro-inflammatory cytokines and vitamin D in this context. Moreover, the results from many of these studies have shown a degree of variability which has hindered our understanding of the role of AD related risk factors in the disease progression. The review also encompasses the recent recommendations regarding clinical and neuropathological diagnosis of AD and brings out the inherent uncertainty and ambiguity in this area which may have a distinct impact on the outcome of various population-based studies on AD-related risk factors.

Impact of cigarette smoke extract and hyperglycemic conditions on blood-brain barrier endothelial cells

Background

Diabetes and tobacco smoking are significant public health concerns which have been shown to independently impact the blood–brain barrier (BBB). Since smoking is a risk factor for diabetes and shares some of the common pathological pathways leading to metabolic abnormalities, it is hypothesized that their combination would produce additive or synergistic BBB dysfunction. Therefore, the objective of this study was to assess this hypothesis and evaluate the magnitude of these effects in vitro using hCMEC/D3 cells; a well-established human BBB endothelial cell line.

Methods

Monolayers of hCMEC/D3 cells were exposed to hyperglycemic conditions (HG; 35 mM) or 5% soluble cigarette smoke extracts (CSE, model of mainstream smoke exposure) for 12–24 h. Cells were then harvested for subsequent biochemical analyses. Transendothelial electrical resistance (TEER) and paracellular permeability to florescent dextrans were used to assess monolayer integrity. Analysis of released factors and cytokines was carried out by ELISA. Western blot (WB) analysis/immunofluorescence of relevant molecular targets was carried out. P-gp efflux activity was measured using rhodamine 123.

Results

Immunofluorescence and WB data showed a significant ZO-1 down-regulation by HG and/or CSE over 24 h exposure. CSE in presence of HG produced a synergistic increase in release of vascular endothelial growth factor that was accompanied by decreased TEER and augmented permeability to labeled dextrans in a size-dependent manner. Moreover, CSE increased the expression of GLUT-1 and SGLT-1 in isolated membrane fractions of hCMEC/D3 cells. The effect was amplified by HG. Both, HG and CSE elicited the membrane upregulation of P-glycoprotein (P-gp) expression which however, was not paralleled by a comparable efflux activity. Interestingly, concomitant exposure to HG and CSE evoked a marked upregulation of PECAM-1 and other pro-inflammatory markers including IL-6 and -8, when compared to each condition alone. Moreover, exposure to all tested conditions amplified (to a different degree) cellular oxidative stress response denoted by increased Nrf2 nuclear translocation.

Conclusion

Overall, our results have clearly shown an additive pattern in the release of angiogenic and inflammatory factors following concomitant exposure to HG and CSE. This suggests the involvement of common key modulators in BBB impairment by both CS and HG possibly through the activation of oxidative stress responses.

Glycemia, Diabetes Status, and Cognition in Hispanic Adults Aged 55-64 Years

OBJECTIVES

To examine the association of glycemia and diabetes status with cognition among 600 Hispanics aged 55 to 64 years from Northern Manhattan.

METHODS

Diabetes was ascertained by history or hemoglobin A1c. Normal glucose tolerance and prediabetes were ascertained with hemoglobin A1c. Memory was assessed with the Selective Reminding Test. Executive abilities were assessed using the Color Trails 1 and 2 and verbal fluency test. The cross-sectional association of glycemia and diabetes status with cognitive performance was examined using linear regression.

RESULTS

Participants had a mean age of 59.2 (2.9) years, 76.7% were women, and more than 65% had prediabetes or diabetes. HbA1C (β = -0.97, p < .001) and diabetes (β = -2.06, p = .001) were related with lower Selective Reminding Test total recall after adjustment for demographics, education, and vascular risk factors. Prediabetes was associated with worse performance in Color Trail 2 (β = -6.45 p = .022) after full adjustment.

CONCLUSIONS

Higher glycemia and diabetes are related to worse memory and executive abilities in late middle age, whereas prediabetes is related only to worse executive abilities. Longitudinal follow-up is needed to understand the order and progression of these deficits.

HHEX_23 AA Genotype Exacerbates Effect of Diabetes on Dementia and Alzheimer Disease: A Population-Based Longitudinal Study

BACKGROUND

Research has suggested that variations within the IDE/HHEX gene region may underlie the association of type 2 diabetes with Alzheimer disease (AD). We sought to explore whether IDE genes play a role in the association of diabetes with dementia, AD, and structural brain changes using data from two community-based cohorts of older adults and a subsample with structural MRI.

METHODS AND FINDINGS

The first cohort, which included dementia-free adults aged ≥75 y (n = 970) at baseline, was followed for 9 y to detect incident dementia (n = 358) and AD (n = 271) cases. The second cohort (for replication), which included 2,060 dementia-free participants aged ≥60 y at baseline, was followed for 6 y to identify incident dementia (n = 166) and AD (n = 121) cases. A subsample (n = 338) of dementia-free participants from the second cohort underwent MRI. HHEX_23 and IDE_9 were genotyped, and diabetes (here including type 2 diabetes and prediabetes) was assessed. In the first cohort, diabetes led to an adjusted hazard ratio (HR) of 1.73 (95% CI 1.19-2.32) and 1.66 (95% CI 1.06-2.40) for dementia and AD, respectively, among all participants. Compared to people carrying the GG genotype without diabetes, AA genotype carriers with diabetes had an adjusted HR of 5.54 (95% CI 2.40-7.18) and 4.81 (95% CI 1.88-8.50) for dementia and AD, respectively. There was a significant interaction between HHEX_23-AA and diabetes on dementia (HR 4.79, 95% CI 1.63-8.90, p = 0.013) and AD (HR 3.55, 95% CI 1.45-9.91, p = 0.025) compared to the GG genotype without diabetes. In the second cohort, the HRs were 1.68 (95% CI 1.04-2.99) and 1.64 (1.02-2.33) for the diabetes-AD and dementia-AD associations, respectively, and 4.06 (95% CI 1.06-7.58, p = 0.039) and 3.29 (95% CI 1.02-8.33, p = 0.044) for the interactions, respectively. MRI data showed that HHEX_23-AA carriers with diabetes had significant structural brain changes compared to HHEX_23-GG carriers without diabetes. No joint effects of IDE_9 and diabetes on dementia were shown. As a limitation, the sample sizes were small for certain subgroups.

CONCLUSIONS

A variant in the HHEX_23 gene interacts with diabetes to be associated with a substantially increased risk of dementia and AD, and with structural brain changes among dementia-free elderly people.

Severe diabetic retinal disease and dementia risk in type 2 diabetes

BACKGROUND

Persons with type 2 diabetes are at an increased risk of dementia compared to those without, but the etiology of this increased risk is unclear.

OBJECTIVE

Cerebral microvascular disease may mediate the link between diabetes and dementia. Given the anatomical and physiological similarities between cerebral and retinal microvessels, we examined the longitudinal association between diabetic retinal disease and dementia in patients with type 2 diabetes.

METHODS

Longitudinal cohort study of 29,961 patients with type 2 diabetes aged ≥60 years. Electronic medical records were used to collect diagnoses and treatment of severe diabetic retinal disease (i.e., diabetic proliferative retinopathy and macular edema) between 1996-1998 and dementia diagnoses for the next ten years (1998-2008). The association between diabetic retinal disease and dementia was evaluated by Cox proportional hazard models adjusted for sociodemographics, as well as diabetes-specific (e.g., diabetes duration, pharmacotherapy, HbA1c, hypoglycemia, hyperglycemia) and vascular (e.g., vascular disease, smoking, body mass index) factors.

RESULTS

2,008 (6.8%) patients had severe diabetic retinal disease at baseline and 5,173 (17.3%) participants were diagnosed with dementia during follow-up. Those with diabetic retinal disease had a 42% increased risk of incident dementia (demographics adjusted Hazards Ratio (HR) = 1.42, 95% Confidence Interval (CI) 1.27, 1.58); further adjustment for diabetes-specific (HR 1.29; 95% CI 1.14, 1.45) and vascular-related disease conditions (HR 1.35; 95% CI 1.21, 1.52) attenuated the relation slightly.

CONCLUSION

Diabetic patients with severe diabetic retinal disease have an increased risk of dementia. This may reflect a causal link between microvascular disease and dementia.

Cognitive Function and Control of Type 2 Diabetes Mellitus in Young Adults

Background:

Type 2 diabetes mellitus (T2DM) has been associated with impairment of cognitive function. Studies show a strong negative correlation between the levels of glycosylated hemoglobin and cognitive function in adult patients above the mean age of 60 years. In healthy adults, age-related cognitive impairment is mostly reported after the age of 60 years, hence the decline in cognitive function can be a part of normal aging without diabetes. Since the majority of patients with diabetes are between the ages of 40 and 59 years, it is crucial to ascertain whether the levels of glycosylated hemoglobin negatively correlate with the levels of cognitive function scores in adult patients of age 60 years or younger, similar to the way it correlates in patients older than 60 years of age, or not.

Aims:

We observed the relationship between the levels of glycosylated hemoglobin and the levels of cognitive function in patients of age 60 years or younger with T2DM.

Materials and Methods:

Eighty-two patients with T2DM underwent cognitive assessment testing by using a Modified Mini-Mental State Examination (3MS), and their cognitive function scores were correlated with their glycosylated hemoglobin levels, durations of diabetes, and levels of education.

Results:

Cognitive impairment was observed in 19.5% of the studied patients. We found a weakly negative relationship between the glycosylated hemoglobin level and cognitive function score (r = -0.292), a moderately negative relationship between the duration of diabetes and cognitive function score (r = -0.303), and a weakly positive relationship between the level of education and cognitive function score (r = 0.277).

Conclusion:

Cognitive impairment affects one-fifth of the patients of age 60 years or younger with T2DM. It is weakly negatively related to the glycosylated hemoglobin level, moderately negatively related to the duration of diabetes, and weakly positively related to the level of education.

[Differential characteristics of type 2 diabetes in the elderly. Role of dipeptidyl peptidase 4 inhibitors]

The prevalence of type 2 diabetes mellitus increases with age, reaching rates around 30% in those over 75 years. The type 2 diabetes mellitus in the elderly has different pathophysiological and clinical characteristics from those of the younger diabetic patient. Some differential aspects in this population are the lower life expectancy and the frequent comorbidity, frailty and associated disability. Avoiding hypoglycemia is a therapeutic priority, given their increased risk of severe hypoglycemia. It is a situation in which the benefits of intensive glycemic control are virtually non-existent, thus prevention of side effects of treatments becomes a priority. Therefore, the goals of glycemic control should be less stringent than in the general population (glycated hemoglobin>7%), and the drugs of choice should be those with a low risk of side effects (especially hypoglycemia) and well tolerated. Dipeptidyl peptidase 4 inhibitors (iDPP4) are particularly useful in this age group, either as a second drug added to metformin monotherapy, or as first line when metformin is contraindicated or not tolerated. In this article the evidence available on the efficacy and tolerance of different pharmacological options available in population over 70 years is reviewed.

Cognitive Impairment in Diabetes: Rationale and Design Protocol of the Cog-ID Study

Background

Cognitive impairment frequently co-occurs with type 2 diabetes but is often undiagnosed. Cognitive impairment affects self-management leading to treatment-related complications.

Objective

The aim of this study is to develop a stepped diagnostic procedure, consisting of a screening test complemented by an evaluation by a general practitioner (GP), to detect undiagnosed cognitive impairment in older people with type 2 diabetes.

Methods

The accuracy of two self-administered cognitive tests, the “Test Your Memory” (TYM) and “Self-Administered Gerocognitive Examination” (SAGE) alone, and in combination with an evaluation by a GP will be assessed. A diagnosis of mild cognitive impairment (MCI) or dementia at a memory clinic will serve as reference standard. This cognitive impairment in diabetes (Cog-ID) study will include 513 people from primary care facilities aged ≥70 with type 2 diabetes. The participants will first fill out the TYM and SAGE tests, followed by a standardized GP evaluation for cognitive impairment, including a mini mental state examination (MMSE). Subsequently, participants suspected of cognitive impairment (on either test or the GP assessment) and a random sample of 15% (65/435) of participants without suspected cognitive impairment will be referred to the memory clinic. At the memory clinic, a medical examination, neuropsychological examination, and magnetic resonance imaging (MRI) of the brain will be performed. Participants will also fill out questionnaires assessing health status and depressive symptoms at baseline and after 6 and 24 months.

Results

This research obtained funding and ethical approval. Enrolment started in August, 2012, and all study-related activities will be completed in September, 2016.

Conclusions

With the results from this study, physicians will be able to detect cognitive impairment affecting type 2 diabetes patients through case-finding, and can use tailored care to reduce associated complications. Additionally, the results may stimulate discussions about cognitive impairment and whether early recognition is desirable.

Vascular contributions to cognitive impairment and dementia including Alzheimer's disease

Scientific evidence continues to demonstrate the linkage of vascular contributions to cognitive impairment and dementia such as Alzheimer's disease. In December, 2013, the Alzheimer's Association, with scientific input from the National Institute of Neurological Disorders and Stroke and the National Heart, Lung and Blood Institute from the National Institutes of Health, convened scientific experts to discuss the research gaps in our understanding of how vascular factors contribute to Alzheimer's disease and related dementia. This manuscript summarizes the meeting and the resultant discussion, including an outline of next steps needed to move this area of research forward.

Plasma metabolomic profiling of patients with diabetes-associated cognitive decline

Diabetes related cognitive dysfunction (DACD), one of the chronic complications of diabetes, seriously affect the quality of life in patients and increase family burden. Although the initial stage of DACD can lead to metabolic alterations or potential pathological changes, DACD is difficult to diagnose accurately. Moreover, the details of the molecular mechanism of DACD remain somewhat elusive. To understand the pathophysiological changes that underpin the development and progression of DACD, we carried out a global analysis of metabolic alterations in response to DACD. The metabolic alterations associated with DACD were first investigated in humans, using plasma metabonomics based on high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry and multivariate statistical analysis. The related pathway of each metabolite of interest was searched in database online. The network diagrams were established KEGGSOAP software package. Receiver operating characteristic (ROC) analysis was used to evaluate diagnostic accuracy of metabolites. This is the first report of reliable biomarkers of DACD, which were identified using an integrated strategy. The identified biomarkers give new insights into the pathophysiological changes and molecular mechanisms of DACD. The disorders of sphingolipids metabolism, bile acids metabolism, and uric acid metabolism pathway were found in T2DM and DACD. On the other hand, differentially expressed plasma metabolites offer unique metabolic signatures for T2DM and DACD patients. These are potential biomarkers for disease monitoring and personalized medication complementary to the existing clinical modalities.

Matching Diabetes and Alcoholism: Oxidative Stress, Inflammation, and Neurogenesis Are Commonly Involved

Diabetes and alcohol misuse are two of the major challenges in health systems worldwide. These two diseases finally affect several organs and systems including the central nervous system. Hippocampus is one of the most relevant structures due to neurogenesis and memory-related processing among other functions. The present review focuses on the common profile of diabetes and ethanol exposure in terms of oxidative stress and proinflammatory and prosurvival recruiting transcription factors affecting hippocampal neurogenesis. Some aspects around antioxidant strategies are also included. As a global conclusion, the present review points out some common hits on both diseases giving support to the relations between alcohol intake and diabetes.

Risk of dementia in patients hospitalised with type 1 and type 2 diabetes in England, 1998-2011: a retrospective national record linkage cohort study

AIMS/HYPOTHESIS

Type 2 diabetes increases the risk of subsequent dementia. Our objective was to determine whether a similar risk of subsequent dementia is associated with type 1 diabetes in a large defined population.

METHODS

This retrospective cohort study examined national administrative record-linked statistical data on hospital care and mortality in England, 1998-2011. Cohorts of people admitted to hospital when aged 30 or over were constructed: 343,062 people with type 1 diabetes; 1,855,141 people with type 2 diabetes; and a reference cohort. Results were expressed as rate ratios (RR) comparing each diabetes cohort with the control cohort.

RESULTS

The overall RR for dementia in people admitted to hospital with type 1 diabetes was 1.65 (95% CI 1.61, 1.68), and for people admitted to hospital with type 2 diabetes was 1.37 (1.35, 1.38). Young age at admission for diabetes appeared to confer a greater rate of subsequent dementia; the RR for dementia in people admitted to hospital with type 1 diabetes aged 30-39 years was 7.10 (4.65, 10.6), which reduced to 4.40 (3.55, 5.40) in those aged 40-49 at admission, and further reduced with increasing age to 1.16 (1.11, 1.20) in those aged 80 or over at admission. A similar pattern was seen with type 2 diabetes.

CONCLUSIONS/INTERPRETATION

Type 1 diabetes, as well as type 2 diabetes, may be associated with an elevated risk of subsequent dementia. The risk of dementia varies with age at admission to hospital with diabetes, and appears to be much greater in the young.

Diabetes in older people: new insights and remaining challenges

Diabetes in ageing communities imposes a substantial personal and public health burden by virtue of its high prevalence, its capacity to cause disabling vascular complications, the emergence of new non-vascular complications, and the effects of frailty. In this Review, we examine the current state of knowledge about diabetes in older people (aged ≥ 75 years) and discuss how recognition of the effect of frailty and disability is beginning to lead to new management approaches. A multidimensional and multidisciplinary assessment process is essential to obtain information on medical, psychosocial, and functional capabilities, and also on how impairments of these functions could limit activities. Major aims of diabetes care include maintenance of independence, functional status, and quality of life by reduction of symptom and medicine burden, and active identification of risks. Linking of therapeutic targets to individual functional status is mandatory and very tight glucose control is often not necessary. Hypoglycaemia remains an important avoidable iatrogenic event. Quality diabetes care in older people remains an important challenge for health professionals.

Lifestyle and health-related risk factors and risk of cognitive aging among older veterans

Lifestyle and health-related factors are critical components of the risk for cognitive aging among veterans. Because dementia has a prolonged prodromal phase, understanding effects across the life course could help focus the timing and duration of prevention targets. This perspective may be especially relevant for veterans and health behaviors. Military service may promote development and maintenance of healthy lifestyle behaviors, but the period directly after active duty has ended could be an important transition stage and opportunity to address some important risk factors. Targeting multiple pathways in one intervention may maximize efficiency and benefits for veterans. A recent review of modifiable risk factors for Alzheimer's disease estimated that a 25% reduction of a combination of seven modifiable risk factors including diabetes, hypertension, obesity, depression, physical inactivity, smoking, and education/cognitive inactivity could prevent up to 3 million cases worldwide and 492,000 cases in the United States. Lifestyle interventions to address cardiovascular health in veterans may serve as useful models with both physical and cognitive activity components, dietary intervention, and vascular risk factor management. Although the evidence is accumulating for lifestyle and health-related risk factors as well as military risk factors, more studies are needed to characterize these factors in veterans and to examine the potential interactions between them.

Link between type 2 diabetes and Alzheimer's disease: from epidemiology to mechanism and treatment

The aim of this paper is to provide a comprehensive review of the epidemiological evidence linking type 2 diabetes mellitus and its related conditions, including obesity, hyperinsulinemia, and metabolic syndrome, to Alzheimer’s disease (AD). Several mechanisms could help to explain this proposed link; however, our focus is on insulin resistance and deficiency. Studies have shown that insulin resistance and deficiency can interact with amyloid-β protein and tau protein phosphorylation, each leading to the onset and development of AD. Based on those epidemiological data and basic research, it was recently proposed that AD can be considered as “type 3 diabetes”. Special attention has been paid to determining whether antidiabetic agents might be effective in treating AD. There has been much research both experimental and clinical on this topic. We mainly discuss the clinical trials on insulin, metformin, thiazolidinediones, glucagon-like peptide-1 receptor agonists, and dipeptidyl peptidase-4 inhibitors in the treatment of AD. Although the results of these trials seem to be contradictory, this approach is also full of promise. It is worth mentioning that the therapeutic effects of these drugs are influenced by the apolipoprotein E (APOE)-ε4 genotype. Patients without the APOE-ε4 allele showed better treatment effects than those with this allele.

Cognitive function in patients with diabetes mellitus: guidance for daily care

Diabetes mellitus is associated with an increase in the risk of dementia and the proportion of patients who convert from mild cognitive impairment (MCI) to dementia. In addition to MCI and dementia, the stages of diabetes-associated cognitive dysfunction include subtle cognitive changes that are unlikely to affect activities of daily life or diabetes self-management. These diabetes-associated cognitive decrements have structural brain correlates detectable with brain MRI, but usually show little progression over time. Although cognitive decrements do not generally represent a pre-dementia stage in patients below the age of 60-65 years, in older individuals these subtle cognitive changes might represent the earliest stages of a dementia process. Acknowledgment of diabetes-associated cognitive decrements can help to improve understanding of patients' symptoms and guide management. Future challenges are to establish the importance of screening for cognitive impairment in people with diabetes, to identify those at increased risk of accelerated cognitive decline at an early stage, and to develop effective treatments.

Diabetes and cognition

Dementia is a major cause of disability and death among older adults. Those with type 2 diabetes (T2D) are 50-100% more likely to develop dementia than those without T2D, but it is unknown whether this association reflects a causal relationship. Proposed mechanisms through which T2D could cause dementia include the effects of insulin dysregulation and chronic hyperglycemia on features of Alzheimer's disease and macrovascular and microvascular disorders in the brain. More research is needed to elucidate the link between T2D and dementia and identify strategies to maintain cognitive function among people with T2D.

Is there a "metabolic-mood syndrome"? A review of the relationship between obesity and mood disorders

Obesity and mood disorders are highly prevalent and co-morbid. Epidemiological studies have highlighted the public health relevance of this association, insofar as both conditions and its co-occurrence are associated with a staggering illness-associated burden. Accumulating evidence indicates that obesity and mood disorders are intrinsically linked and share a series of clinical, neurobiological, genetic and environmental factors. The relationship of these conditions has been described as convergent and bidirectional; and some authors have attempted to describe a specific subtype of mood disorders characterized by a higher incidence of obesity and metabolic problems. However, the nature of this association remains poorly understood. There are significant inconsistencies in the studies evaluating metabolic and mood disorders; and, as a result, several questions persist about the validity and the generalizability of the findings. An important limitation in this area of research is the noteworthy phenotypic and pathophysiological heterogeneity of metabolic and mood disorders. Although clinically useful, categorical classifications in both conditions have limited heuristic value and its use hinders a more comprehensive understanding of the association between metabolic and mood disorders. A recent trend in psychiatry is to move toward a domain specific approach, wherein psychopathology constructs are agnostic to DSM-defined diagnostic categories and, instead, there is an effort to categorize domains based on pathogenic substrates, as proposed by the National Institute of Mental Health (NIMH) Research Domain Criteria Project (RDoC). Moreover, the substrates subserving psychopathology seems to be unspecific and extend into other medical illnesses that share in common brain consequences, which includes metabolic disorders. Overall, accumulating evidence indicates that there is a consistent association of multiple abnormalities in neuropsychological constructs, as well as correspondent brain abnormalities, with broad-based metabolic dysfunction, suggesting, therefore, that the existence of a "metabolic-mood syndrome" is possible. Nonetheless, empirical evidence is necessary to support and develop this concept. Future research should focus on dimensional constructs and employ integrative, multidisciplinary and multimodal approaches.

Glucose regulation, cognition, and brain MRI in type 2 diabetes: a systematic review

Type 2 diabetes is associated with cognitive dysfunction and structural brain changes. Abnormalities in glucose regulation are involved in several complications related to type 2 diabetes, but their role in these cerebral complications is unclear. We systematically reviewed studies of the association between glucose regulation (glycaemia, hypoglycaemic events, insulin concentration, insulin resistance, and glucose-lowering treatment) and cognitive function and brain abnormalities on MRI in people with type 2 diabetes. The 86 papers included showed that glycaemia, particularly high HbA1c concentration and glucose variability, are negatively associated with cognitive function in people with type 2 diabetes without dementia. However, the strength of this association is weak, and HbA1c generally accounted for less than 10% of the variance in cognition. Importantly, few studies have measured long-term cerebral outcomes, such as dementia and structural brain changes on MRI, and the effect of glucose-lowering treatment on these outcomes. More randomised controlled trials are needed to establish the effect of glucose-lowering treatment on long-term cognitive function in people with type 2 diabetes.

Diabetes Mellitus, Cognitive Impairment, and Traditional Chinese Medicine

Diabetes mellitus (DM) is a metabolic disorder affecting a large number of people worldwide. Numerous studies have demonstrated that DM can cause damage to multiple systems, leading to complications such as heart disease, cancer, and cerebrovascular disorders. Numerous epidemiological studies have shown that DM is closely associated with dementia and cognition dysfunction, with recent research focusing on the role of DM-mediated cerebrovascular damage in dementia. Despite the therapeutic benefits of antidiabetic agents for the treatment of DM-mediated cognitive dysfunction, most of these pharmaceutical agents are associated with various undesirable side-effects and their long-term benefits are therefore in doubt. Early evidence exists to support the use of traditional Chinese medicine (TCM) interventions, which tend to have minimal toxicity and side-effects. More importantly, these TCM interventions appear to offer significant effects in reducing DM-related complications beyond blood glucose control. However, more research is needed to further validate these claims and to explore their relevant mechanisms of action. The aims of this paper are (1) to provide an updated overview on the association between DM and cognitive dysfunction and (2) to review the scientific evidence underpinning the use of TCM interventions for the treatment and prevention of DM-induced cognitive dysfunction and dementia.

Stability in Cognitive Function Over 18 Years: Prevalence and Predictors among Older Mexican Americans

PURPOSE

Numerous studies have examined the association of physical, behavioral and social factors with cognitive decline in older adults. Less attention has been placed on factors associated with long-term maintenance of intact cognition even into very old age. A greater understanding of those factors can inform the development of activities for maintaining cognitive strength.

METHODS

Using a sample from the Hispanic Established Populations for Epidemiologic Study of the Elderly, a population-based study of non-institutionalized Mexican Americans aged 65 and older from five Southwestern states (N = 2767), latent class mixture models were developed to identify subgroups of cognitive change over time.

RESULTS

Three distinct trajectories of cognitive change were identified and characterized as stable, slow decline and rapid decline. Compared to the rapid decline group, a higher proportion of the stable cognition group were women, had high school education, were married and attended church one or more times per week. Regular church attendance had a significant positive impact in the stable group (β = 0.64, p <0.01), the slow decline group (β = 0.84, p <0.001) and the rapid decline group (β = 2.50, p <0.001). Activity limitations had a consistently negative association with cognition in the stable, slow decline and rapid decline groups (β = -0.37, p <0.001; β = -0.85, p <0.001; and β = -1.58, p <0.001 respectively).

CONCLUSION

Substantial heterogeneity exists in rates of cognitive decline among older Mexican Americans. Interventions targeting cognitive maintenance may benefit from increased focus on factors associated with continued social engagement.

Diabetes in midlife and cognitive change over 20 years: a cohort study

BACKGROUND

Type 2 diabetes is associated with dementia risk, but evidence is limited for possible associations of diabetes and prediabetes with cognitive decline.

OBJECTIVE

To determine whether diabetes in midlife is associated with 20-year cognitive decline and to characterize long-term cognitive decline across clinical categories of hemoglobin A1c (HbA1c) levels.

DESIGN

Prospective cohort study.

SETTING

The community-based ARIC (Atherosclerosis Risk in Communities) study.

PARTICIPANTS

13,351 black and white adults aged 48 to 67 years at baseline (1990 to 1992).

MEASUREMENTS

Diabetes was defined by self-reported physician diagnosis or medication use or HbA1c level of 6.5% or greater. Undiagnosed diabetes, prediabetes, and glucose control in persons with diagnosed diabetes were defined by clinical categories of HbA1c level. Delayed word recall, digit symbol substitution, and word fluency tests were used to assess cognitive performance and were summarized with a global Z score.

RESULTS

Diabetes in midlife was associated with a 19% greater cognitive decline over 20 years (adjusted global Z-score difference, -0.15 [;95% CI, -0.22 to -0.08];) compared with no diabetes. Cognitive decline was significantly greater among persons with prediabetes (HbA1c level of 5.7% to 6.4%) than among those with an HbA1c level less than 5.7%. Participants with poorly controlled diabetes (HbA1c level ≥ 7.0%) had greater decline than those whose diabetes was controlled (adjusted global Z-score difference, -0.16; P = 0.071). Longer-duration diabetes was also associated with greater late-life cognitive decline (P for trend < 0.001). Rates of decline did not differ significantly between white and black persons (P for interaction = 0.44).

LIMITATION

Single HbA1c measurement at baseline, 1 test per cognitive domain, and potential geographic confounding of race comparisons.

CONCLUSION

Diabetes prevention and glucose control in midlife may protect against late-life cognitive decline.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Alleles that increase risk for type 2 diabetes mellitus are not associated with increased risk for Alzheimer's disease

Although epidemiological studies suggest that type 2 diabetes mellitus (T2DM) increases the risk of late-onset Alzheimer's disease (LOAD), the biological basis of this relationship is not well understood. The aim of this study was to examine the genetic comorbidity between the 2 disorders and to investigate whether genetic liability to T2DM, estimated by a genotype risk scores based on T2DM associated loci, is associated with increased risk of LOAD. This study was performed in 2 stages. In stage 1, we combined genotypes for the top 15 T2DM-associated polymorphisms drawn from approximately 3000 individuals (1349 cases and 1351 control subjects) with extracted and/or imputed data from 6 genome-wide studies (>10,000 individuals; 4507 cases, 2183 controls, 4989 population controls) to form a genotype risk score and examined if this was associated with increased LOAD risk in a combined meta-analysis. In stage 2, we investigated the association of LOAD with an expanded T2DM score made of 45 well-established variants drawn from the 6 genome-wide studies. Results were combined in a meta-analysis. Both stage 1 and stage 2 T2DM risk scores were not associated with LOAD risk (odds ratio = 0.988; 95% confidence interval, 0.972-1.004; p = 0.144 and odds ratio = 0.993; 95% confidence interval, 0.983-1.003; p = 0.149 per allele, respectively). Contrary to expectation, genotype risk scores based on established T2DM candidates were not associated with increased risk of LOAD. The observed epidemiological associations between T2DM and LOAD could therefore be a consequence of secondary disease processes, pleiotropic mechanisms, and/or common environmental risk factors. Future work should focus on well-characterized longitudinal cohorts with extensive phenotypic and genetic data relevant to both LOAD and T2DM.

Insulin reverses the high-fat diet-induced increase in brain Aβ and improves memory in an animal model of Alzheimer disease

Defects in insulin production and signaling are suspected to share a key role in diabetes and Alzheimer disease (AD), two age-related pathologies. In this study, we investigated the interrelation between AD and diabetes using a high-fat diet (HFD) in a mouse model of genetically induced AD-like neuropathology (3xTg-AD). We first observed that cerebral expression of human AD transgenes led to peripheral glucose intolerance, associated with pancreatic human Aβ accumulation. High-fat diet enhanced glucose intolerance, brain soluble Aβ, and memory impairment in 3xTg-AD mice. Strikingly, a single insulin injection reversed the deleterious effects of HFD on memory and soluble Aβ levels, partly through changes in Aβ production and/or clearance. Our results are consistent with the development of a vicious cycle between AD and diabetes, potentiating both peripheral metabolic disorders and AD neuropathology. The capacity of insulin to rapidly break the deleterious effects of this cycle on soluble Aβ concentrations and memory has important therapeutic implications.

Type 2 diabetes and cognitive decline over 14 years in middle-aged African Americans and whites: the ARIC Brain MRI Study

BACKGROUND

Diabetes predicts late-life dementia, but the association with rate of cognitive decline is inconsistent and has rarely been examined in non-white populations, despite the high prevalence of diabetes in African Americans. We evaluated the effect of diabetes on cognitive decline in middle-aged African Americans and whites.

METHODS

Atherosclerosis Risk in Communities (ARIC) Brain MRI Study participants (n = 1,886, mean age = 60, 49% African American) underwent assessments of verbal memory, processing speed, and verbal fluency four times over 14 years. Using race-stratified mixed linear effects models, we examined cognitive change for participants with prevalent (baseline) diabetes and incident (diagnosed after baseline) diabetes versus those without diabetes.

RESULTS

African Americans had more advanced diabetes, as indicated by fasting blood glucose levels, anti-diabetes medication use, and cardiovascular risk profiles. African Americans with prevalent diabetes experienced 41% greater annual decline in processing speed scores (p = 0.048) and 50% greater annual decline in verbal fluency scores (p = 0.042) than those without diabetes; incident diabetes was not associated with cognitive decline. Among whites, diabetes was not associated with cognitive decline.

CONCLUSIONS

Prevalent diabetes was associated with greater cognitive decline in middle-aged African Americans, possibly reflecting adverse effects of longer duration and more advanced diabetes.

Short-lived diabetes in the young-adult ZDF rat does not exacerbate neuronal Ca(2+) biomarkers of aging

Results from clinical studies provide evidence that cognitive changes relatively late in life may be traced to antecedent conditions including diabetes, obesity, a sedentary lifestyle, and an atherogenic diet. As such, several traits of Type 2 diabetes (T2DM) could be considered pathogenic factors of aging, contributing to age-dependent cognitive decline and our susceptibility to Alzheimer's disease. It appears that both the duration of metabolic condition and the age of the individual, together can contribute to the potential impact on peripheral as well as brain health. Because of robust evidence that in animal models of aging, Ca(2+) dysregulation alters neuronal health, synaptic plasticity, and learning and memory processes, we tested the hypothesis that peripheral metabolic dysregulation could exacerbate Ca(2+) dysfunction in hippocampal CA1 neurons. Using intracellular/ extracellular electrophysiological and Ca(2+) imaging techniques, we show that Ca(2+)levels at rest or during synaptic stimulation, the Ca(2+)-dependent afterhyperpolarization, baseline field potentials, and short-term synaptic plasticity were not significantly altered in young-adult male Zucker diabetic fatty rats compare to their lean counterparts. Our observations suggest that early phases of T2DM characterized by high levels of glucose and insulin may be too transient to alter hippocampal CA1 physiology in this animal model of diabetes. These results are supported by clinical data showing that longer T2DM duration can have greater negative impact on cognitive functions. This article is part of a Special Issue entitled SI: Brain and Memory.

Brain structural changes and their correlation with vascular disease in type 2 diabetes mellitus patients: a voxel-based morphometric study

Voxel-based morphometry has been used in the study of alterations in brain structure in type 1 diabetes mellitus patients. These changes are associated with clinical indices. The age at onset, pathogenesis, and treatment of type 1 diabetes mellitus are different from those for type 2 diabetes mellitus. Thus, type 1 and type 2 diabetes mellitus may have different impacts on brain structure. Only a few studies of the alterations in brain structure in type 2 diabetes mellitus patients using voxel-based morphometry have been conducted, with inconsistent results. We detected subtle changes in the brain structure of 23 cases of type 2 diabetes mellitus, and demonstrated that there was no significant difference between the total volume of gray and white matter of the brain of type 2 diabetes mellitus patients and that in controls. Regional atrophy of gray matter mainly occurred in the right temporal and left occipital cortex, while regional atrophy of white matter involved the right temporal lobe and the right cerebellar hemisphere. The ankle-brachial index in patients with type 2 diabetes mellitus strongly correlated with the volume of brain regions in the default mode network. The ankle-brachial index, followed by the level of glycosylated hemoglobin, most strongly correlated with the volume of gray matter in the right temporal lobe. These data suggest that voxel-based morphometry could detect small structural changes in patients with type 2 diabetes mellitus. Early macrovascular atherosclerosis may play a crucial role in subtle brain atrophy in type 2 diabetes mellitus patients, with chronic hyperglycemia playing a lesser role.

Spontaneous brain activity in type 2 diabetics revealed by amplitude of low-frequency fluctuations and its association with diabetic vascular disease: a resting-state FMRI study

Purpose

To investigate correlations between altered spontaneous brain activity, diabetic vascular disease, and cognitive function for patients with type 2 diabetes mellitus (T2DM) using resting-state functional magnetic resonance imaging (rs-fMRI).

Methods

Rs-fMRI was performed for T2DM patients (n = 26) and age-, gender-, and education-matched non-diabetic control subjects (n = 26). Amplitude of low frequency fluctuations (ALFF) were computed from fMRI signals to measure spontaneous neuronal activity. Differences in the ALFF patterns between patients and controls, as well as their correlations with clinical variables, were evaluated.

Results

Compared with healthy controls, T2DM patients exhibited significantly decreased ALFF values mainly in the frontal and parietal lobes, the bilateral thalumi, the posterior lobe of the cerebellum, and increased ALFF values mainly in the visual cortices. Furthermore, lower ALFF values in the left subcallosal gyrus correlated with lower ankle-brachial index values (r = 0.481, p = 0.020), while lower ALFF values in the bilateral medial prefrontal gyri correlated with higher urinary albumin-creatinine ratio (r = −0.418, p = 0.047). In addition, most of the regions with increased ALFF values in the visual cortices were found to negatively correlate with MoCA scores.

Conclusions

These results confirm that ALFF are altered in many brain regions in T2DM patients, and this is associated with the presence of diabetic vascular disease and poor cognitive performance. These findings may provide additional insight into the neurophysiological mechanisms that mediate T2DM-related cognitive dysfunction, and may also serve as a reference for future research.

General anesthetic and the risk of dementia in elderly patients: current insights

In this review, we aim to provide clinical insights into the relationship between surgery, general anesthesia (GA), and dementia, particularly Alzheimer’s disease (AD). The pathogenesis of AD is complex, involving specific disease-linked proteins (amyloid-beta [Aβ] and tau), inflammation, and neurotransmitter dysregulation. Many points in this complex pathogenesis can potentially be influenced by both surgery and anesthetics. It has been demonstrated in some in vitro, animal, and human studies that some anesthetics are associated with increased aggregation and oligomerization of Aβ peptide and enhanced accumulation and hyperphosphorylation of tau protein. Two neurocognitive syndromes that have been studied in relation to surgery and anesthesia are postoperative delirium and postoperative cognitive dysfunction, both of which occur more commonly in older adults after surgery and anesthesia. Neither the route of anesthesia nor the type of anesthetic appears to be significantly associated with the development of postoperative delirium or postoperative cognitive dysfunction. A meta-analysis of case-control studies found no association between prior exposure to surgery utilizing GA and incident AD (pooled odds ratio =1.05, P=0.43). The few cohort studies on this topic have shown varying associations between surgery, GA, and AD, with one showing an increased risk, and another demonstrating a decreased risk. A recent randomized trial has shown that patients who received sevoflurane during spinal surgery were more likely to have progression of preexisting mild cognitive impairment compared to controls and to patients who received propofol or epidural anesthesia. Given the inconsistent evidence on the association between surgery, anesthetic type, and AD, well-designed and adequately powered studies with longer follow-up periods are required to establish a clear causal association between surgery, GA, and AD.

Potential for primary prevention of Alzheimer's disease: an analysis of population-based data

BACKGROUND

Recent estimates suggesting that over half of Alzheimer's disease burden worldwide might be attributed to potentially modifiable risk factors do not take into account risk-factor non-independence. We aimed to provide specific estimates of preventive potential by accounting for the association between risk factors.

METHODS

Using relative risks from existing meta-analyses, we estimated the population-attributable risk (PAR) of Alzheimer's disease worldwide and in the USA, Europe, and the UK for seven potentially modifiable risk factors that have consistent evidence of an association with the disease (diabetes, midlife hypertension, midlife obesity, physical inactivity, depression, smoking, and low educational attainment). The combined PAR associated with the risk factors was calculated using data from the Health Survey for England 2006 to estimate and adjust for the association between risk factors. The potential of risk factor reduction was assessed by examining the combined effect of relative reductions of 10% and 20% per decade for each of the seven risk factors on projections for Alzheimer's disease cases to 2050.

FINDINGS

Worldwide, the highest estimated PAR was for low educational attainment (19·1%, 95% CI 12·3-25·6). The highest estimated PAR was for physical inactivity in the USA (21·0%, 95% CI 5·8-36·6), Europe (20·3%, 5·6-35·6), and the UK (21·8%, 6·1-37·7). Assuming independence, the combined worldwide PAR for the seven risk factors was 49·4% (95% CI 25·7-68·4), which equates to 16·8 million attributable cases (95% CI 8·7-23·2 million) of 33·9 million cases. However, after adjustment for the association between the risk factors, the estimate reduced to 28·2% (95% CI 14·2-41·5), which equates to 9·6 million attributable cases (95% CI 4·8-14·1 million) of 33·9 million cases. Combined PAR estimates were about 30% for the USA, Europe, and the UK. Assuming a causal relation and intervention at the correct age for prevention, relative reductions of 10% per decade in the prevalence of each of the seven risk factors could reduce the prevalence of Alzheimer's disease in 2050 by 8·3% worldwide.

INTERPRETATION

After accounting for non-independence between risk factors, around a third of Alzheimer's diseases cases worldwide might be attributable to potentially modifiable risk factors. Alzheimer's disease incidence might be reduced through improved access to education and use of effective methods targeted at reducing the prevalence of vascular risk factors (eg, physical inactivity, smoking, midlife hypertension, midlife obesity, and diabetes) and depression.

FUNDING

National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care for Cambridgeshire and Peterborough.

Diabetes and dementia in older people: a Best Clinical Practice Statement by a multidisciplinary National Expert Working Group

Both dementia and diabetes mellitus are long-term disabling conditions and each may be a co-morbidity of the other. Type 2 diabetes is associated with a 1.5- to 2-fold higher risk of dementia. Diabetes also may occur for the first time in many individuals with mental ill health, including cognitive impairment and dementia, and this may complicate management and lead to difficulties in self-care. Case finding is often poor for cognitive impairment in medical settings and for diabetes in mental health settings and this needs to be addressed in the development of care pathways for both conditions. Many other deficiencies in quality care (both for dementia and diabetes) currently exist, but we hope that this Best Clinical Practice Statement will provide a platform for further work in this area. We have outlined the key steps in an integrated care pathway for both elements of this clinical relationship, produced guidance on identifying each condition, dealt with the potentially hazardous issue of hypoglycaemia, and have outlined important competencies required of healthcare workers in both medical/diabetes and mental health settings to enhance clinical care.

Cortical source multivariate EEG synchronization analysis on amnestic mild cognitive impairment in type 2 diabetes

Is synchronization altered in amnestic mild cognitive impairment (aMCI) and normal cognitive functions subjects in type 2 diabetes mellitus (T2DM)? Resting eye-closed EEG data were recorded in 8 aMCI subjects and 11 age-matched controls in T2DM. Three multivariate synchronization algorithms (S-estimator (S), synchronization index (SI), and global synchronization index (GSI)) were used to measure the synchronization in five ROIs of sLORETA sources for seven bands. Results showed that aMCI group had lower synchronization values than control groups in parietal delta and beta2 bands, temporal delta and beta2 bands, and occipital theta and beta2 bands significantly. Temporal (r = 0.629; P = 0.004) and occipital (r = 0.648; P = 0.003) theta S values were significantly positive correlated with Boston Name Testing. In sum, each of methods reflected that the cortical source synchronization was significantly different between aMCI and control group, and these difference correlated with cognitive functions.

Diabetes and the brain: oxidative stress, inflammation, and autophagy

Diabetes mellitus is a common metabolic disorder associated with chronic complications including a state of mild to moderate cognitive impairment, in particular psychomotor slowing and reduced mental flexibility, not attributable to other causes, and shares many symptoms that are best described as accelerated brain ageing. A common theory for aging and for the pathogenesis of this cerebral dysfunctioning in diabetes relates cell death to oxidative stress in strong association to inflammation, and in fact nuclear factor κB (NFκB), a master regulator of inflammation and also a sensor of oxidative stress, has a strategic position at the crossroad between oxidative stress and inflammation. Moreover, metabolic inflammation is, in turn, related to the induction of various intracellular stresses such as mitochondrial oxidative stress, endoplasmic reticulum (ER) stress, and autophagy defect. In parallel, blockade of autophagy can relate to proinflammatory signaling via oxidative stress pathway and NFκB-mediated inflammation.

Lixisenatide treatment for older patients with type 2 diabetes mellitus uncontrolled on oral antidiabetics: meta-analysis of five randomized controlled trials

AIM

Evaluate the efficacy and safety of lixisenatide, a once-daily prandial glucagon-like peptide-1 receptor agonist, in older patients with type 2 diabetes mellitus (T2DM) insufficiently controlled on oral antidiabetics (OADs).

METHODS

A meta-analysis was conducted on data from older patients (≥65 years) from five of the GetGoal trials, in which patients with T2DM were treated with lixisenatide 20 µg once daily or placebo, as an add-on to OADs. The primary endpoint in all trials was change from baseline at week 24 in glycated hemoglobin (HbA1c). Other endpoints included changes in post-prandial plasma glucose (PPG), fasting plasma glucose (FPG) and weight. Composite and safety endpoints were also analyzed.

RESULTS

A total of 501 patients aged ≥65 years were included in this meta-analysis: 304 received lixisenatide plus OADs and 197 received placebo as add-on to OADs. Lixisenatide as an add-on to OADs significantly reduced HbA1c, PPG, FPG and weight, with placebo-corrected treatment effects at week 24 of -0.54% (p<0.0001), -126 mg/dL (p<0.0001), -13 mg/dL (p=0.0005) and -0.90 kg (p=0.0021), respectively. Patients receiving lixisenatide plus OADs were significantly more likely to achieve composite (HbA1c levels<7%, HbA1c levels<7% and no symptomatic hypoglycemia, and HbA1c levels<7%, no weight gain and no symptomatic hypoglycemia) and safety endpoints than those receiving placebo plus OADs. Symptomatic hypoglycemia was experienced by 8.55% and 3.55% of patients in the lixisenatide plus OADs and placebo plus OADs groups, respectively (p=0.0276), although no serious hypoglycemic episodes were reported.

CONCLUSIONS

Lixisenatide plus OADs improved glycemic control in older patients inadequately controlled on OADs compared with placebo plus OADs. Lixisenatide is well tailored to the pathophysiology of T2DM in older patients.

Brain changes underlying cognitive dysfunction in diabetes: what can we learn from MRI?

Diabetes is associated with cognitive dysfunction and an increased risk of dementia. This article addresses findings with brain MRI that may underlie cognitive dysfunction in diabetes. Studies in adults with type 1 diabetes show regional reductions in brain volume. In those with a diabetes onset in childhood, these volume reductions are likely to reflect the sum of changes that occur during brain development and changes that occur later in life due to exposure to diabetes-related factors. Type 2 diabetes is associated with global brain atrophy and an increased burden of small-vessel disease. These brain changes occur in the context of aging and often also in relation to an adverse vascular risk factor profile. Advanced imaging techniques detect microstructural lesions in the cerebral gray and white matter of patients with diabetes that affect structural and functional connectivity. Challenges are to further unravel the etiology of these cerebral complications by integrating findings from different imaging modalities and detailed clinical phenotyping and by linking structural MRI abnormalities to histology. A better understanding of the underlying mechanisms is necessary to establish interventions that will improve long-term cognitive outcomes for patients with type 1 and type 2 diabetes.

Diabetes, dysglycemia and cognitive dysfunction

Evidence from the last decade supports the hypothesis that diabetes may be viewed as a disease of accelerated cognitive ageing. It is a risk factor for the development of dementia, for an accelerated rate of cognitive decline and for cognitive dysfunction. Thus, 'diabetes-related cognitive dysfunction' may be viewed as another long-term complication of diabetes. This article will review the evidence supporting this hypothesis and will elaborate on the implications for patient care, as well as discuss potential treatment options and their limitation. The final section reviews possible mechanistic explanations.

Diabetes mellitus and disturbances in brain connectivity: a bidirectional relationship?

Diabetes mellitus (DM) is associated with deficits across multiple cognitive domains. The observed impairments in cognitive function are hypothesized to be subserved by alterations in brain structure and function. Several lines of evidence indicate that alterations in glial integrity and function, as well as abnormal synchrony within brain circuits and associated networks, are observed in adults with DM. Microangiopathy and alterations in insulin homeostasis appear to be principal effector systems, although a unitary explanation subsuming the complex etiopathology of white matter in DM is unavailable. A contemporary model of disease pathophysiology for several mental disorders, including but not limited to mood disorders, posits abnormalities in the synchronization of cellular systems in circuits. The observation that similar abnormalities occur in diabetic populations provides the basis for hypothesizing the convergence of pathoetiological factors. Herein, we propose that abnormal structure, function and chemical composition as well as synchrony within and between circuits is an accompaniment of DM and is shared in common with several mental disorders.

Type 2 diabetes as a risk factor for cognitive impairment: current insights

Type 2 diabetes mellitus (T2DM) is a risk factor for cognitive dysfunction and dementia in the elderly. T2DM has been thought to be associated with vascular diseases, eventually leading to vascular dementia, but recent studies have established that T2DM is also associated with Alzheimer's disease (AD). With the increase in the number of elderly individuals with T2DM, the number of diabetic patients with cognitive dysfunction has been increasing. T2DM may accelerate AD-associated pathologies through insulin resistance. Vascular pathologies may also be associated with cognitive dysfunction and dementia in T2DM subjects. Several other mechanisms also seem to be involved in T2DM-related cognitive dysfunction. More investigations to clarify the association of T2DM with cognitive impairment are warranted. These investigations may help to increase our understanding of AD and open a new door to the development of therapeutics. Recent pharmaceutical advancement in T2DM treatment has resulted in the availability of a wide range of antidiabetics. Some evidence has suggested that antidiabetic therapies help to prevent cognitive dysfunction. At present, however, the optimal level of blood glucose control and the best combination of medications to achieve it in terms of cognitive preservation have not been established. More investigation is warranted. Cognitive dysfunction is an emerging new complication of T2DM that requires further study.

Physical activity, weight status, diabetes and dementia: a 34-year follow-up of the population study of women in Gothenburg

BACKGROUND

There is evidence of a synergistic interaction between obesity and sedentary lifestyle with respect to diabetes. Although diabetes is a known risk factor for dementia, it is unclear if both diseases have common aetiologies.

METHODS

A community-based sample of 1,448 Swedish women, aged 38-60 years and free of diabetes and dementia in 1968, was followed by means of up to 5 examinations spread over 34 years. 9.6% of all women developed diabetes and 11.4% developed dementia (over 40,000 person-years of follow-up for each disease). Cox proportional hazard regression was used to assess the influence of selected risk factors on both diseases, and the relation between diabetes and dementia.

RESULTS

Comparing risk factors for incident diabetes and dementia, both diseases showed a synergistic association with obesity combined with a low level of leisure time physical activity [hazard ratio (HR) for interaction = 2.7, 95% confidence interval (CI) = 1.2-6.3 for diabetes and HR = 3.3, 95% CI = 1.1-9.9 for dementia]. Development of diabetes doubled the risk for subsequent dementia (HR = 2.2, 95% CI = 1.1-4.4), which was slightly reduced upon adjustment for common risk factors.

CONCLUSIONS

Shared risk factors suggest a similar aetiology for diabetes and dementia and partially explain the association between diseases.

Small vessel disease and memory loss: what the clinician needs to know to preserve patients' brain health

Small vessel disease (SVD) in the brain manifests in the periventricular and deep white matter and radiographically is described as "leukoaraiosis". It is increasingly recognized as a cause of morbidity from middle age onward and this clinical relevance has paralleled advances in the field of neuroradiology. Overall, SVD is a heterogenous group of vascular disorders that may be asymptomatic, or a harbinger of many conditions that jeopardize brain health. Management and prevention focuses on blood pressure control, lifestyle modification, and symptomatic treatment.

Diabetes and the brain: issues and unmet needs

Diabetes mellitus (DM) is associated with an increased risk of mild cognitive impairment, dementia and stroke. The association between DM and dementia appears to be stronger for vascular cognitive impairment than for Alzheimer’s disease, suggesting cerebrovascular disease may be an important factor in cognitive impairment in DM. Although the exact mechanisms by which DM affects the brain remain unclear, changes to brain vasculature, disturbances of cerebral insulin signaling, insulin resistance, glucose toxicity, oxidative stress, accumulation of advanced glycation end products, hypoglycemic episodes, and alterations in amyloid metabolism may all be involved. Cognitive impairment and dementia associated with DM may also be mediated via vascular risk factors, in particular brain ischemia, the occurrence of which can have an additive or synergistic effect with concomitant neurodegenerative processes. To date, no drug has been approved for the treatment of vascular dementia and there are no specific pharmacological treatments for preventing or reducing cognitive decline in patients with DM. Most focus has been on tighter management of vascular risk factors, although evidence of reduced cognitive decline through reducing blood pressure, lipid-lowering or tighter glycemic control is inconclusive. Tailored, multimodal therapies may be required to reduce the risk of cognitive dysfunction and decline in patients with DM. The use of pleiotropic drugs with multimodal mechanisms of action (e.g., cerebrolysin, Actovegin) may have a role in the treatment of cognitive dysfunction and their use may warrant further investigation in diabetic populations.

Alzheimer's disease and type 2 diabetes: multiple mechanisms contribute to interactions

Obesity, metabolic syndrome, and type 2 diabetes (T2D) are related disorders with widespread deleterious effects throughout the body. One important target of damage is the brain. Persons with metabolic disorders are at significantly increased risk for cognitive decline and the development of vascular dementia and Alzheimer's disease. Our review of available evidence from epidemiologic, clinical, and basic research suggests that neural dysfunction from T2D-related disease results from several underlying mechanisms, including metabolic, inflammatory, vascular, and oxidative changes. The relationships between T2D and neural dysfunction are regulated by several modifiers. We emphasize 2 such modifiers, the genetic risk factor apolipoprotein E and an age-related endocrine change, low testosterone. Both factors are independent risk factors for Alzheimer's disease that may also cooperatively regulate pathologic interactions between T2D and dementia. Continued elucidation of the links between metabolic disorders and neural dysfunction promises to foster the development of effective therapeutic strategies.