Effect of the treatment of Type II diabetes mellitus on the development of cognitive impairment and dementia

The Impact of Common Epidemiological Factors on Gray and White Matter Volumes in Magnetic Resonance Imaging-Is Prevention of Brain Degeneration Possible?

Introduction: The aim of the study was to evaluate the impact of multiple risk factors (age, diabetes, hypertension, hyperlipidemia, BMI, smoking, alcohol) on the gray and white matter volumes as well as on the burden of white matter hyperintensities (WMH).

Material and Methods: The study group consisted of 554 subjects (age range: 50–69 yrs, F/M: 367/187) recruited from the larger cohort of the Polish fraction of the Prospective Urban Rural Epidemiological (PURE) study. The participants answered questionnaires about their lifestyle, underwent physical and psychological examination (MoCA test), laboratory blood tests followed by brain MRI. Volumetric measurements of the total gray matter (GMvol), total white matter (WMvol) and WHM (WMHvol) normalized to the total intracranial volume were performed using the Computational Anatomy Toolbox 12 (CAT12) and Statistical Parametric Maps 12 (SPM12) based on 3D T1-weighted sequence. The influence of risk factors was assessed using multiple regression analysis before and after correction for multiple comparisons.

Results: Older age was associated with lower GMvol and WMvol, and higher WMHvol (p < 0.001). Smaller GMvol volume was associated with higher WMHvol (p < 0.001). Higher WMHvol was associated with hypertension (p = 0.01) and less significantly with hyperlipidemia (only before correction p = 0.03). Diabetes, abnormal BMI, smoking and alcohol intake did not have any significant impact on GMvol, WMvol or WMHvol (p > 0.05). MoCA score was not influenced by any of the factors.

Conclusions: Gray matter loss is strongly associated with the accumulation of WMH which seems to be potentially preventable by maintaining normal blood pressure and cholesterol levels.

Sodium nitroprusside prevents the detrimental effects of glucose on the neurovascular unit and behaviour in zebrafish

Diabetes is associated with dysfunction of the neurovascular unit, although the mechanisms of this are incompletely understood and currently no treatment exists to prevent these negative effects. We previously found that the nitric oxide (NO) donor sodium nitroprusside (SNP) prevents the detrimental effect of glucose on neurovascular coupling in zebrafish. We therefore sought to establish the wider effects of glucose exposure on both the neurovascular unit and on behaviour in zebrafish, and the ability of SNP to prevent these. We incubated 4-days post-fertilisation (dpf) zebrafish embryos in 20 mM glucose or mannitol for 5 days until 9 dpf, with or without 0.1 mM SNP co-treatment for 24 h (8-9 dpf), and quantified vascular NO reactivity, vascular mural cell number, expression of a klf2a reporter, glial fibrillary acidic protein (GFAP) and transient receptor potential cation channel subfamily V member 4 (TRPV4), as well as spontaneous neuronal activation at 9 dpf, all in the optic tectum. We also assessed the effect on light/dark preference and locomotory characteristics during free-swimming studies. We find that glucose exposure significantly reduced NO reactivity, klf2a reporter expression, vascular mural cell number and TRPV4 expression, while significantly increasing spontaneous neuronal activation and GFAP expression (all in the optic tectum). Furthermore, when we examined larval behaviour, we found that glucose exposure significantly altered light/dark preference and high and low speed locomotion while in light. Co-treatment with SNP reversed all these molecular and behavioural effects of glucose exposure. Our findings comprehensively describe the negative effects of glucose exposure on the vascular anatomy, molecular phenotype and function of the optic tectum, and on whole-organism behaviour. We also show that SNP or other NO donors may represent a therapeutic strategy to ameliorate the complications of diabetes on the neurovascular unit.This article has an associated First Person interview with the first author of the paper.

Accumulating Data to Optimally Predict Obesity Treatment (ADOPT) Core Measures: Psychosocial Domain

BACKGROUND

Within the Accumulating Data to Optimally Predict obesity Treatment (ADOPT) Core Measures Project, the psychosocial domain addresses how psychosocial processes underlie the influence of obesity treatment strategies on weight loss and weight maintenance. The subgroup for the psychosocial domain identified an initial list of high-priority constructs and measures that ranged from relatively stable characteristics about the person (cognitive function, personality) to dynamic characteristics that may change over time (motivation, affect).

OBJECTIVES

This paper describes (a) how the psychosocial domain fits into the broader model of weight loss and weight maintenance as conceptualized by ADOPT; (b) the guiding principles used to select constructs and measures for recommendation; (c) the high-priority constructs recommended for inclusion; (d) domain-specific issues for advancing the science; and (e) recommendations for future research.

SIGNIFICANCE

The inclusion of similar measures across trials will help to better identify how psychosocial factors mediate and moderate the weight loss and weight maintenance process, facilitate research into dynamic interactions with factors in the other ADOPT domains, and ultimately improve the design and delivery of effective interventions.

Strategies for dementia prevention: latest evidence and implications

Dementia is a common and debilitating syndrome with enormous impact on individuals and societies. Preventing disease onset or progression would translate to public health and societal benefits. In this review, we discuss the latest evidence on interventions that may show promise for the prevention of cognitive decline. We appraise existing evidence primarily drawn from randomized controlled trials, systematic reviews, and meta-analyses, but also highlight observational studies in humans and relevant work in model organisms. Overall, there is currently limited evidence to support a cause-effect relationship between any preventive strategy and the development or progression of dementia. However, studies to date suggest that a multifactorial intervention comprising regular exercise and healthy diet, along with the amelioration of vascular risk factors, psychosocial stress, and major depressive episodes may be most promising for the prevention of cognitive decline. We discuss the challenges, future directions, and implications of this line of research.

Effect of the treatment of Type 2 diabetes mellitus on the development of cognitive impairment and dementia

BACKGROUND

Prevention of cognitive impairment and dementia is an important public health goal. Epidemiological evidence shows a relationship between cognitive impairment and Type 2 diabetes mellitus. The risk of dementia increases with duration of disease. This updated systematic review investigated the effect on cognitive function of the type of treatment and level of metabolic control in people with Type 2 diabetes.

OBJECTIVES

To assess the effects of different strategies for managing Type 2 diabetes mellitus on cognitive function and the incidence of dementia.

SEARCH METHODS

We searched ALOIS (the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group (CDCIG)), the Cochrane Library, MEDLINE, Embase, PsycINFO, CINAHL and LILACS on 15 October 2016. ALOIS contains records from all major health care databases, (CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, LILACS), as well as from many trials' registers and grey literature sources.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) which compared two or more different treatments for Type 2 diabetes mellitus and in which cognitive function was measured at baseline and after treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the quality of the included RCTs. We pooled data for comparable trials and estimated the effects of treatment by using risk ratios (RRs) and mean differences (MDs), according to the nature of the outcome. We assessed the quality of the evidence using GRADE methods.

MAIN RESULTS

We identified seven eligible studies but only four provided data we could include in efficacy analyses. Two of these studies compared intensive versus standard glycaemic control and two compared different pharmacological treatments. All studies were at unclear risk of bias in at least two domains and one large study was at high risk of performance and detection bias.(a) Two studies with 13,934 participants at high cardiovascular risk provided efficacy data on intensive versus standard glycaemic control. A third study with 1791 participants provided additional data on hypoglycaemic episodes and mortality. There is probably no difference between treatment groups in the number of participants who decline by at least 3 points on the Mini-Mental State Examination (MMSE) over five years (RR 0.98, 95% CI 0.88 to 1.08; 1 study; n = 11,140; moderate-quality evidence); and there may also be little or no difference in the incidence of dementia (RR 1.27, 95% CI 0.87 to 1.85; 1 study; n = 11,140; low-quality evidence). From another study, there was probably little or no difference in MMSE score after 40 months (MD -0.01, 95% CI -0.18 to 0.16; 1 study; n = 2794; moderate quality evidence). Participants exposed to the intensive glycaemic control strategy probably experience more episodes of severe hypoglycaemia than those who have standard treatment (RR 2.18, 95% CI 1.52 to 3.14; 2 studies; n = 12,827; moderate-quality evidence). The evidence from these trials suggests that the intensity of glycaemic control may have little or no effect on all-cause mortality (RR 0.99, 95% CI 0.87 to 1.13; 3 studies; n = 15,888; low-quality evidence).(b) One study with 156 participants compared glibenclamide (glyburide) with repaglinide. There may be a small advantage of glibenclamide on global cognitive function measured with the MMSE after 12 months (MD -0.90, 95% CI -1.68 to -0.12; low-quality evidence). No data were reported on the incidence of dementia, hypoglycaemic events or all-cause mortality.(c) One study with 145 participants compared rosiglitazone plus metformin to glibenclamide (glyburide) plus metformin over 24 weeks. It reported only on cognitive subdomains and not on global cognitive function, incidence of MCI or dementia, hypoglycaemic events or all causes of mortality.

AUTHORS' CONCLUSIONS

We found no good evidence that any specific treatment or treatment strategy for Type 2 diabetes can prevent or delay cognitive impairment. The best available evidence related to the comparison of intensive with standard glycaemic control strategies. Here there was moderate-quality evidence that the strategies do not differ in their effect on global cognitive functioning over 40 to 60 months.

Obesity and brain illness: from cognitive and psychological evidences to obesity paradox

Recent findings showed that obesity represents an additional risk factor to developing brain illness such as cognitive impairments and psychopathological disorders. However, some benefits of overweight in the elderly have been identified and an "obesity paradox" has been shown. Currently, it is still unknown how obesity and brain functioning could be linked, and the process by which body fat independently injures cognitive abilities and psychological well-being remains unclear. To establish the independent role of obesity on cognitive abilities and mental health, clarifying the role played by several factors and understanding their interaction is essential. In this review, we discuss the relationship between obesity and brain illness and underline the role played by confounders and other covariates to determine this link.

Potentials of incretin-based therapies in dementia and stroke in type 2 diabetes mellitus

Patients with type 2 diabetes mellitus are at risk for accelerated cognitive decline and dementia. Furthermore, their risk of stroke is increased and their outcome after stroke is worse than in those without diabetes. Incretin-based therapies are a class of antidiabetic agents that are of interest in relation to these cerebral complications of diabetes. Two classes of incretin-based therapies are currently available: the glucagon-like-peptide-1 agonists and the dipeptidyl peptidase-4 -inhibitors. Independent of their glucose-lowering effects, incretin-based therapies might also have direct or indirect beneficial effects on the brain. In the present review, we discuss the potential of incretin-based therapies in relation to dementia, in particular Alzheimer's disease, and stroke in patients with type 2 diabetes. Experimental studies on Alzheimer's disease have found beneficial effects of incretin-based therapies on cognition, synaptic plasticity and metabolism of amyloid-β and microtubule-associated protein tau. Preclinical studies on incretin-based therapies in stroke have shown an improved functional outcome, a reduction of infarct volume as well as neuroprotective and neurotrophic properties. Both with regard to the treatment of Alzheimer's disease, and with regard to prevention and treatment of stroke, randomized controlled trials in patients with or without diabetes are underway. In conclusion, experimental studies show promising results of incretin-based therapies at improving the outcome of Alzheimer's disease and stroke through glucose-independent pleiotropic effects on the brain. If these findings would indeed be confirmed in large clinical randomized controlled trials, this would have substantial impact.

Treatment of Vascular Cognitive Impairment

OPINION STATEMENT

Cerebrovascular disease (CVD) is an important cause of cognitive dysfunction and dementia. The term vascular cognitive impairment (VCI) is used to describe the entire spectrum of cognitive dysfunction-ranging from mild impairment to dementia-attributable to all forms of cerebrovascular disease. Accurate assessment and management of vascular risk factors are a top priority in the treatment of VCI, particularly early in the disease when prevention strategies may prove to be more effective. There are limited treatment options to improve cognition and function in VCI. Several acetylcholinesterase inhibitors and the NMDA receptor antagonist memantine have been studied in large, well-designed trials. These agents are safe and provide modest cognitive benefits in vascular dementia (VaD) but have demonstrated inconsistent efficacy on functional measures. Other therapies, such as aspirin, calcium channel blockers, and vitamin supplementation, have less evidence to support their use in improving cognition in VCI. Although primary prevention trials suggest that treatment of hypertension, adherence to a Mediterranean diet, physical activity, and smoking cessation may reduce the risk of cognitive decline, there is limited evidence regarding these interventions in helping improve cognition in VCI. The pathophysiology and treatment of cerebral autosomal dominant arteriopathy with subcortical infarcts (CADASIL), cerebral amyloid angiopathy (CAA), and subcortical white matter disease (SWMD) deserves special consideration.

Intensive glycaemic control and cognitive decline in patients with type 2 diabetes: a meta-analysis

The aim of this meta-analysis was to compare the effect of intensive vs standard glycaemic control on cognitive decline in type 2 diabetic patients. A systematic search of PubMed and ALOIS was conducted from inception up to October 30, 2014. Randomised controlled trials (RCTs) of type 2 diabetic patients comparing the rate of change in cognitive function among participants assigned to intensive vs standard glycaemic control were included. An inverse-variance-weighted random effects model was used to calculate standardised mean differences (SMDs) and 95% CIs. A total of 24 297 patients from five RCTs were included in the meta-analysis. Follow-up ranged from 3.3 to 6.2 years. The result from the pooled analysis showed that intensive glycaemic control was not associated with a slower rate of cognitive decline in patients with type 2 diabetes, compared with standard glycaemic control (SMD=0.02; 95% CI=-0.03 to 0.08) although there was some heterogeneity across individual studies (I(2)=68%, P for heterogeneity=0.01). There are few diabetes control trials including cognitive endpoints and a small number of trials comparing intensive and standard treatment strategies. Currently, intensive glycaemic control should not be recommended for prevention of cognitive decline in patients with type 2 diabetes because there is no evidence of its effectiveness. Moreover, the use of intensive diabetes treatment results in an increase of risk of hypoglycaemia, which is linked to a greater risk of poor cognition.

Modifiable risk factors for Alzheimer disease and subjective memory impairment across age groups

Introduction

Previous research has identified modifiable risk factors for Alzheimer's disease (AD) in older adults. Research is limited on the potential link between these risk factors and subjective memory impairment (SMI), which may precede AD and other dementias. Examination of these potential relationships may help identify those at risk for AD at a stage when interventions may delay or prevent further memory problems. The objective of this study was to determine whether risk factors for AD are associated with SMI among different age groups.

Method

Trained interviewers conducted daily telephone surveys (Gallup-Healthways) of a representative community sample of 18,614 U.S. respondents, including 4,425 younger (age 18 to 39 years), 6,365 middle-aged (40 to 59 years), and 7,824 older (60 to 99 years) adults. The surveyors collected data on demographics, lifestyles, and medical information. Less education, smoking, hypertension, diabetes, less exercise, obesity and depression, and interactions among them, were examined for associations with SMI. Weighted logistic regressions and chi-square tests were used to calculate odds ratios and confidence intervals for SMI with each risk factor and pairwise interactions across age groups.

Results

Depression, less education, less exercise, and hypertension were significantly associated with SMI in all three age groups. Several interactions between risk factors were significant in younger and middle-aged adults and influenced their associations with SMI. Frequency of SMI increased with age and number of risk factors. Odds of having SMI increased significantly with just having one risk factor.

Conclusions

These results indicate that modifiable risk factors for AD are also associated with SMI, suggesting that these relationships occur in a broad range of ages and may be targeted to mitigate further memory problems. Whether modifying these risk factors reduces SMI and the eventual incidence of AD and other dementias later in life remains to be determined.

Effects of hypertension and diabetes on sentence comprehension in aging

OBJECTIVES

To assess the impact of hypertension and diabetes mellitus on sentence comprehension in older adults.

METHOD

Two hundred and ninety-five adults aged 55 to 84 (52% men) participated in this study. Self-report mail survey combined with medical evaluations were used to determine eligibility. Multiple sources were used to determine whether hypertension and diabetes were present or absent and controlled or uncontrolled. Sentence comprehension was evaluated with two tasks: embedded sentences (ES) and sentences with multiple negatives (MN). Outcome measures were percent accuracy and mean reaction time of correct responses on each task.

RESULTS

Regression models adjusted for age, gender, and education showed that the presence of hypertension impaired comprehension on the multiple negatives task (p < .01), whereas the presence of diabetes impaired the comprehension of embedded sentences (p < .05). Uncontrolled diabetes significantly impaired accurate comprehension of sentences with multiple negatives (p < .05). No significant patterns were found for reaction time.

DISCUSSION

The presence of hypertension and diabetes adversely affected sentence comprehension, but the relative contribution of each was different. These findings support the researchers' earlier speculations on the neurobiological mechanisms underlying the effects of hypertension and diabetes on language and cognition in aging. Uncontrolled disease status demonstrated more complicated age-related effects on sentence processing, highlighting the clinical importance for cognitive aging of identifying and managing vascular risk factors.

Reduction of Long-Term Care Dependence After an 8-Year Primary Care Prevention Program for Stroke and Dementia: The INVADE Trial

BACKGROUND

Stroke and dementia are the major causes for long-term care (LTC) dependence in old age. This intervention trial compared a multidomain prevention program for stroke and dementia with usual medical care in reducing the need for LTC.

METHODS AND RESULTS

The Intervention Project on Cerebrovascular Disease and Dementia in the District of Ebersberg (INVADE) was a general practice-based 8-year trial in 2 defined catchment areas in Upper Bavaria, Germany. All 11 317 insurants of a statutory health insurance plan who were ≥55 years of age and lived in the intervention district were offered the opportunity to participate in a prevention program; 3908 enrolled. The 13 301 insurants in the reference district received usual medical care. The intervention consisted of the systematic identification and evidence-based treatment of vascular risk factors. The primary clinical end point was incidence of LTC dependence according to external assessment by a special medical service in the framework of the statutory German LTC insurance. Age- and sex-specific incidence rates from the reference district were used to calculate the expected number of cases of LTC dependence under usual medical care. The expected number was compared with the observed number of cases in the intervention district. Analysis was by intention to treat. During the 5 years after completion of the recruitment period, significantly fewer incident cases of LTC dependence arose in the intervention district than expected (χ(2)=13.25; P<0.001). In women, the incidence was reduced by 10% (P<0.01). In men, the incidence was reduced by 9.6% (P<0.05).

CONCLUSIONS

Our results support the feasibility and effectiveness of a primary care prevention program for stroke and dementia to reduce the risk of developing LTC dependence.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01107548. (J Am Heart Assoc. 2012;1:e000786 doi: 10.1161/JAHA.112.000786.).

Mild cognitive impairment and dementia: the importance of modifiable risk factors

BACKGROUND

Mild cognitive impairment (MCI), a common condition among the elderly, is defined as a deterioration of memory, attention, and cognitive function that exceeds what would be expected for the individual's age and level of education, yet does not interfere significantly with the activities of daily living. MCI may be a precursor of dementia; the rate of transition from MCI to dementia is 10% to 20% per year. The role of somatic diseases and modifiable risk factors in MCI and dementia needs further study.

METHODS

We analyzed pertinent original articles and reviews published 1990 up to December 2010 that were retrieved by a selective search in PubMed and the Cochrane Library.

RESULTS

MCI and dementia are associated with many somatic disorders and modifiable risk factors. MCI has biologically plausible associations with hypertension, diabetes mellitus, and hyperlipidemia, although the interventional trials performed to date have yielded negative results. Recently, chronic renal failure has also been recognized as a risk factor. Insufficient evidence supports a putative benefit on MCI from the substitution of vitamin B12, vitamin D, or testosterone (when these substances are deficient), the treatment of hyperhomocysteinemia or subclinical thyroid dysfunction, or hormone replacement therapy after menopause. Epidemiological data suggest that a Mediterranean diet, physical activity, and moderate alcohol consumption protect against MCI, while cigarette smoking promotes it and should be stopped.

CONCLUSION

Modifiable risk factors for MCI should be sought (at the very latest) in persons who already have MCI, as their optimal treatment may improve these patients' cognitive performance or keep the existing deficits from progressing.

The projected effect of risk factor reduction on Alzheimer's disease prevalence

At present, about 33·9 million people worldwide have Alzheimer's disease (AD), and prevalence is expected to triple over the next 40 years. The aim of this Review was to summarise the evidence regarding seven potentially modifiable risk factors for AD: diabetes, midlife hypertension, midlife obesity, smoking, depression, cognitive inactivity or low educational attainment, and physical inactivity. Additionally, we projected the effect of risk factor reduction on AD prevalence by calculating population attributable risks (the percent of cases attributable to a given factor) and the number of AD cases that might be prevented by risk factor reductions of 10% and 25% worldwide and in the USA. Together, up to half of AD cases worldwide (17·2 million) and in the USA (2·9 million) are potentially attributable to these factors. A 10-25% reduction in all seven risk factors could potentially prevent as many as 1·1-3·0 million AD cases worldwide and 184,000-492,000 cases in the USA.

Integrating health into cognitive aging: toward a preventive cognitive neuroscience of aging

OBJECTIVES

We argue that age is a descriptive, and not explanatory, variable and consequently cannot account for the cognitive changes that often occur with aging. Once age is removed from consideration, other truly causal explanations for "cognitive aging" must be identified. We argue that health and disease represent an important class of explanatory variables for age-related cognitive changes.

METHODS/RESULTS

We make this argument first by reviewing the prevalence of risk factors, disability, and subclinical and frank disease in the elderly population. We emphasize that the complexity of health effects rivals that of age on cognition while noting that most studies of cognitive aging rarely consider this complexity fully. We then consider in more detail the "vascular hypothesis," which proposes that vascular diseases (e.g., stroke, heart disease) and their risk factors (e.g., hypertension) can explain aspects of cognitive decline in aging through their impact on circulatory and brain functions. Clinical implications of this hypothesis suggest that treatment of vascular risk factors might well reduce the incidence or severity of dementia syndromes.

DISCUSSION

We conclude with a brief summary of approaches to further integrate aspects of health and disease into the study of "cognitive aging."

Latest Advances on Interventions that May Prevent, Delay or Ameliorate Dementia

OBJECTIVES

IN THIS PAPER WE AIM TO: (1) identify and review midlife risk factors that may contribute to the development of dementia and that may be amenable to intervention; (2) review advances made in our understanding of the most common cause of dementia, Alzheimer's disease (AD), where current pharmacological studies have aimed to modify the disease course; and (3) explore other interventions that may slow cognitive decline in those with AD.

METHODS

A review of the literature was conducted to look for interventions that may modify the risk of incident dementia or that may modify symptom progression in those with diagnosed dementia.

RESULTS

(1) Midlife risks identified as amenable to intervention include blood pressure, diabetes, elevated cholesterol, poor psychosocial and lifestyle factors. (2) The leading drugs in development can be grouped by their principal target: anti-amyloid, anti-tau and mitochondrial stability. However to date, there have been no successes in late stage Phase III trials of putative disease-modifying drugs for AD. (3) Once the diagnosis of dementia has been made there is little that can slow the rate of decline. Possible exceptions include the use of exercise and antihypertensive medication with some nootropic medication showing promise in small trials.

CONCLUSION

(1) It is clear that there are several risk factors in midlife that may lead to a greater likelihood of developing dementia. However, there is no simple intervention to modify these risks. It seems sensible to conclude from the data that avoiding high blood pressure, controlling cholesterol and diabetes as well as maintaining a healthy diet and lifestyle may lower the risk of developing dementia. (2) The need for better outcome measures in clinical trials is evident and may, in part, explain the numerous failures in late-stage clinical trials of disease-modifying drugs. Improved diagnostic test batteries to reduce population heterogeneity in early intervention studies will be required for robust clinical trials in the future. (3) Current research indicates that there is little that can delay decline; however, future trials may wish to focus on nootropics.

Cerebrovascular risk factors and preclinical memory decline in healthy APOE ε4 homozygotes

OBJECTIVE

To characterize the effects of cerebrovascular (CV) risk factors on preclinical memory decline in cognitively normal individuals at 3 levels of genetic risk for Alzheimer disease (AD) based on APOE genotype.

METHODS

We performed longitudinal neuropsychological testing on an APOE ε4 enriched cohort, ages 21-97. The long-term memory (LTM) score of the Auditory Verbal Learning Test (AVLT) was the primary outcome measure. Any of 4 CV risk factors (CVany), including hypercholesterolemia (CHOL), prior cigarette use (CIG), diabetes mellitus (DM), and hypertension (HTN), was treated as a dichotomized variable. We estimated the longitudinal effect of age using statistical models that simultaneously modeled the cross-sectional and longitudinal effects of age on AVLT LTM by APOE genotype, CVany, and the interaction between the two.

RESULTS

A total of 74 APOE ε4 homozygotes (HMZ), 239 ε4 heterozygotes (HTZ), and 494 ε4 noncarriers were included. APOE ε4 carrier status showed a significant quadratic effect with age-related LTM decline in all models as previously reported. CVany was associated with further longitudinal AVLT LTM decline in APOE ε4 carriers (p=0.02), but had no effect in noncarriers. When ε4 HTZ and HMZ were considered separately, there was a striking effect in HMZ (p<0.001) but not in HTZ. In exploratory analyses, significant deleterious effects were found for CIG (p=0.001), DM (p=0.03), and HTN (p=0.05) in APOE ε4 carriers only that remained significant only for CIG after correction for multiple comparisons.

CONCLUSION

CV risk factors influence age-related memory decline in APOE ε4 HMZ.

Treatment of cardiovascular risk factors to prevent cognitive decline and dementia: a systematic review

BACKGROUND

Over the last decade, evidence has accumulated that vascular risk factors increase the risk of Alzheimer disease (AD). So far, few randomized controlled trials have focused on lowering the vascular risk profile to prevent or postpone cognitive decline or dementia.

OBJECTIVE

To systematically perform a review of randomized controlled trials (RCTs) evaluating drug treatment effects for cardiovascular risk factors on the incidence of dementia or cognitive decline.

SELECTION CRITERIA

RCTs studying the effect of treating hypertension, dyslipidemia, hyperhomocysteinemia, obesity, or diabetes mellitus (DM) on cognitive decline or dementia, with a minimum follow-up of 1 year in elderly populations.

OUTCOME MEASURE

Cognitive decline or incident dementia.

MAIN RESULTS

In the identified studies, dementia was never the primary outcome. Statins (2 studies) and intensified control of type II DM (1 study) appear to have no effect on prevention of cognitive decline. Studies on treatment of obesity are lacking, and the results of lowering homocysteine (6 studies) are inconclusive. There is some evidence of a preventive effect of antihypertensive medication (6 studies), but results are inconsistent.

CONCLUSION

The evidence of a preventive treatment effect aimed at vascular risk factors on cognitive decline and dementia in later life is scarce and mostly based on secondary outcome parameters. Several important sources of bias such as differential dropout may importantly affect interpretation of trial results.

Testing covariates of Type 2 diabetes-cognition associations in older adults: moderating or mediating effects?

OBJECTIVE

The general goal of this study was to advance our understanding of Type 2 diabetes (T2D)-cognition relationships in older adults by linking and testing comprehensive sets of potential moderators, potential mediators, and multiple cognitive outcomes.

METHOD

We identified in the literature 13 health-related (but T2D-distal) potential covariates, representing four informal domains (i.e., biological vitality, personal affect, subjective health, lifestyle activities). Cross-sectional data from the Victoria Longitudinal Study (age range = 53-90 years; n = 41 T2D and n = 458 control participants) were used. We first examined whether any of the 13 potential covariates influenced T2D-cognition associations, as measured by a comprehensive neuropsychological battery (15 measures). Next, using standard regression-based moderator and mediator analyses, we systematically tested whether the identified covariates would significantly alter observed T2D-cognition relationships.

RESULTS

Six potential covariates were found to be sensitive to T2D associations with performance on seven cognitive measures. Three factors (systolic blood pressure, gait-balance composite, subjective health) were significant mediators. Each mediated multiple cognitive outcomes, especially measures of neurocognitive speed, executive functioning, and episodic memory.

CONCLUSIONS

Our findings offer a relatively comprehensive perspective of T2D-related cognitive deficits, comorbidities, and modulating influences. The implications for future research reach across several fields of study and application. These include (1) neuropsychological research on neural and biological bases of T2D-related cognitive decline, (2) clinical research on intervention and treatment strategies, and (3) larger-scale longitudinal studies examining the potential multilateral and dynamic relationships among T2D status, related comorbidities, and cognitive outcomes.

Cardiovascular risk factors, cerebrovascular disease burden, and healthy brain aging

Cardiovascular risk factors have been associated with 2 common manifestation of unhealthy brain in older people, cognitive impairment and depression. The evidence for these effects is almost entirely observational, but links hypertension, smoking, hypercholesterolemia, diabetes mellitus, and hyperhomocysteinemia with cognitive impairment and depression. Unfortunately randomized trials evaluating interventions for these risk factors on the outcomes of cognition or mood have either been inconclusive or negative. However, as there are considerable other health benefits from targeting cardiovascular risk factors, these interventions should be more widely adopted, which would also probably result in positive outcomes for the brain.

Short-term longitudinal trends in cognitive performance in older adults with type 2 diabetes

Type 2 diabetes is associated with cognitive deficits, although inconsistently across neuropsychological domains. We examined 3-year longitudinal data from the Victoria Longitudinal Study, comparing diabetes (n = 28) and control (n = 272) older adults on a comprehensive neuropsychological battery. Assessing potential change and stability, we found that (a) baseline diabetes group deficits in semantic speed and speed-intensive executive function were preserved, (b) new average deficits for reaction time and nonspeeded executive function appeared, and (c) no differential short-term change was observed. It is clinically and theoretically important to examine sequential change in multiple domains over time.

The effects of cardiovascular risk factors on cognitive compromise

As life expectancy in the United States continues to increase, the projected numbers of elderly people who will develop dementia will grow rapidly. This paper reviews four well-established cardiovascular risk factors (type 2 diabetes, hypertension, cholesterol, and inflammation), for which there is longitudinal epidemiological evidence of increased risk of dementia, Alzheimer's disease, mild cognitive impairment, and cognitive decline. These risk factors are of special interest because of their potential modif lability, which may affect the course of cognitive compromise. Diabetes is the cardiovascular risk factor (CvRF) most consistently associated with cognition. Hypertension in midlife is consistently associated with cognition, but its associations with late-life hypertension are less clear. Total cholesterol is not consistently associated with cognition, interleukin-6 and C-reactive protein are inflammatory markers relatively consistently associated with cognition. Composites of the CvRFs increase the risk for dementia in a dose-dependent fashion, suggesting a cumulative effect of these factors on neuronal stress. In the relatively few studies that have reported interactions of risk factors, they potentiate each other. The effect of each of these risk factors varies according to apolipoprotein E genotype, it may be that the effect of these risk factors varies according to the presence of the others, and these complex relationships underlie the biological mechanisms of cognitive compromise. This may be crucial for understanding the effects on cognition of druqs and other approaches, such as lifestyle chanqe, for treatinq these risk factors.

The prevention of dementia

OBJECTIVE

Dementia is prevalent in older adults and the population is ageing. Many factors have been associated with dementia and anything that may aid the prevention of dementia is of importance.

METHOD

The literature in this area was evaluated and information relating to the various factors that may impact upon the prevention of dementia is presented below.

RESULTS

Factors that have been associated with a possible increased risk of developing dementia include high blood pressure, (at least in midlife), high body mass index, smoking and possibly diabetes although the evidence is mixed. There is currently no clear evidence with regard to cholesterol and metabolic syndrome although both may be implicated. Having education and maintaining a Mediterranean diet, including vegetable, fruit and fish intake, have been linked to a lower incidence of dementia as has low to moderate alcohol intake. Although care must be taken with the latter given the different characteristics of the studies reporting on alcohol and dementia.

CONCLUSION

It may be that risk and protective factors vary with age, however, in the absence of prophylactic treatment it seems likely that the maintenance of a healthy lifestyle may represent the best option with regard to the prevention of dementia.

Increased glucose levels are associated with episodic memory in nondiabetic women

OBJECTIVE

Patients with type 2 diabetes have an increased risk of a reduction in cognitive function. We investigated the hypothesis that plasma glucose is associated with a reduction in episodic and/or semantic memory already in nondiabetic subjects.

RESEARCH DESIGN AND METHODS

We linked two large population-based datasets in Sweden: the Betula study, in which a random sample from the population aged 35-85 years was investigated for cognitive function, including episodic and semantic memory; and the Västerbotten Intervention Program, a health survey with subjects aged 40, 50, and 60 years, that includes measuring of fasting and 2-h plasma glucose, along with other risk factors for diabetes and cardiovascular disease. We identified 411 (179 men and 232 women, mean age 50.6 +/- 8.0 years) nondiabetic subjects, free from dementia, who had participated in the two surveys within 6 months.

RESULTS

Women had better episodic (score 7.37 +/- 1.42) and semantic memory (score 16.05 +/- 2.76) than men (score 6.59 +/- 1.29 and 15.15 +/- 2.92, respectively, P < 0.001 for both). In an adjusted multivariate model, fasting plasma glucose (fPG) and 2-h plasma glucose (2hPG) were significantly negatively associated with episodic memory (fPG: B -0.198, SE 0.068, beta -0.209, P = 0.004; and 2hPG: B -0.061, SE 0.031, beta -0.148, P = 0.048, respectively) in women but not in men. The association was not found in relation to semantic memory.

CONCLUSIONS

We conclude that an increase in plasma glucose is associated with impairment in episodic memory in women. This could be explained by a negative effect on the hippocampus caused by raised plasma glucose levels.

What are the benefits of cognitive enhancers for Alzheimer's Disease: use of Population Impact Measures

Background

The study aims to quantify the population impact of prescribing cholinesterase inhibitors to slow the cognitive decline in Alzheimer's disease (AD), and to compare with the benefit of treating hypertension to prevent the onset of AD.

Methods

Literature review to ascertain the prevalence of AD, benefits of interventions, analysis of local and national surveys to measure the current use of interventions in the relevant population and application of the relevant findings to calculate Population Impact Measures. The Number of Events Prevented in a Population (NEPP) by the intervention over a defined time period is calculated for a UK urban population in one Local Authority (population size 217,000).

Results

Treatment of all eligible patients with mild to moderate AD with Cholinesterase Inhibitors would prevent cognitive deterioration (measured by ADAS – cog scale) in 123.6 (95% Confidence Intervals (CI) 82.3, 169.1), 16.4 (95% CI 2.1, 31.2) would show a mild improvement (4 points or more on the ADAS – cog scale) and 2.6 (95% CI 0.2, 5.8) would show an improvement of 7 points or more over a period of 6 months. This would require the treatment of 406 patients with Cholinesterase Inhibitors.

Increasing from the current treatment rate of 46% of eligible patients to 'best practice' level would prevent cognitive deterioration in 66.8 (95% CI 44.0, 92.6), 8.99 (95% CI 1.2, 16.8) and 1.4 (95% CI 0.11, 3.2) would improve by 4 and 7 points respectively on the ADAS – cog scale over 6 months. This would require the treatment of an extra 187 patients with Cholinesterase Inhibitors beyond current practice, at an additional annual direct drug cost of £187,000.

Improving the treatment of hypertension from current practice by 20% could prevent 8.2 (95% CI 2.3, 16.8) incident cases of AD in the next year. This would require the treatment of an extra 2711 patients with antihypertensive drugs.

Conclusion

Population Impact Measures are a new method to allow a demonstration of the magnitude of the benefit for the whole population following interventions. The use of drugs to slow cognitive decline, or to prevent AD by treating hypertension, can thus be assessed in a prioritisation exercise in competition with alternative use of resources.

Hyperinsulinemia and cognitive decline in a middle-aged cohort

OBJECTIVE

Determining modifiable risks factors for cognitive decline and dementia are a public health priority as we seek to prevent dementia. Type 2 diabetes and related disorders such as hyperinsulinemia increase with aging and are increasing in the U.S. population. Our objective was to determine whether hyperinsulinemia is associated with cognitive decline among middle-aged adults without type 2 diabetes, dementia, or stroke in the Atherosclerosis Risk in Communities (ARIC) cohort.

RESEARCH DESIGN AND METHODS

Middle-aged adults (aged 45-64 years at baseline) in the ARIC cohort had fasting insulin and glucose assessed between 1987 and 1989. Subjects with dementia, type 2 diabetes, or stroke at baseline were excluded from analysis. Three tests of cognitive function available at baseline and 6 years later were delayed word recall (DWR), digit symbol subtest (DSS), and first letter word fluency (WF). Cross-sectional comparisons and linear regression models were computed for cognitive tests at baseline and change in cognitive test scores to determine whether cognitive function was associated with two measures of insulin resistance, fasting insulin and homeostasis model assessment (HOMA). Linear regression models controlled for age, sex, race, marital status, education level, smoking status, alcohol use, depression, hypertension, and hyperlipidemia.

RESULTS

In unadjusted and adjusted analyses, hyperinsulinemia based on fasting insulin and HOMA at baseline was associated with significantly lower baseline DWR, DSS, and WF scores and a greater decline over 6 years in DWR and WF.

CONCLUSIONS

Insulin resistance is a potentially modifiable midlife risk factor for cognitive decline and dementia.

Improving metabolic control leads to better working memory in adults with type 2 diabetes

OBJECTIVE

The goals of this study were to determine whether improvements in metabolic control can ameliorate the cognitive dysfunction associated with type 2 diabetes and evaluate the possibility that such improvements are mediated by changes in circulating insulin or insulin resistance.

RESEARCH DESIGN AND METHODS

This randomized double-blind trial enrolled 145 subjects at 18 centers in the U.S. Older adults with type 2 diabetes receiving metformin monotherapy received add-on therapy with either rosiglitazone, a thiazolidinedione insulin sensitizer, or glyburide. Cognitive function was assessed at baseline and week 24 using the Digit Symbol Substitution Test, the Rey Auditory Verbal Learning Test, and the Cambridge Neuropsychological Test Automated Battery.

RESULTS

Pretreatment fasting plasma glucose (FPG) in both groups was similar, and after 24 weeks both treatment groups showed similar significant reductions in FPG (2.1-2.3 mmol/l). Working memory improved with both rosiglitazone (P < 0.001) and glyburide (P = 0.017). Improvement (25-31% reduction in errors) was most evident on the Paired Associates Learning Test and was significantly correlated (r = 0.30) with improved glycemic control as measured by FPG.

CONCLUSIONS

Similar and statistically significant cognitive improvement was observed with both rosiglitazone and glyburide therapy, and the magnitude of this effect was correlated with the degree to which FPG improved. These results suggest that a cognitive benefit is achievable with pharmacological interventions targeting glycemic control.