Effects of intensive glucose lowering on brain structure and function in people with type 2 diabetes (ACCORD MIND): a randomised open-label substudy

The negative effects of obesity and poor glycemic control on cognitive function: a proposed model for possible mechanisms

Obesity has reached epidemic proportions and is a contributor to many adverse health outcomes, including increased risk for dementia and adverse structural and functional brain changes. Milder forms of cognitive impairment in multiple domains can also be found in obese individuals of all ages that are believed to stem from brain abnormalities long prior to onset of neurologic conditions such as dementia. However, the mechanisms for adverse brain changes and subsequent cognitive dysfunction in obesity are complex and poorly understood. This paper proposes a possible etiologic model for obesity associated cognitive impairment with emphasis on the role of poor glycemic control and conditions like type 2 diabetes mellitus. Clinical implications associated with treatment of obesity in persons with cognitive deficits in addition to the cognitive promoting effects of weight loss surgery are also discussed.

Diabetes. Cognitive decline and T2DM--a disconnect in the evidence?

Type 2 diabetes mellitus is associated with an increased risk of cognitive decline and dementia. Observational data suggest that hyperglycaemia, hypertension and dyslipidaemia might be involved in the causal pathway underlying this link, but data from the ACCORD MIND investigators challenge these findings. Why are the findings of observational and intervention studies so disconnected?

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.

Cardiorespiratory fitness and cognitive function in middle age: the CARDIA study

OBJECTIVE

To investigate whether greater cardiorespiratory fitness (CRF) is associated with better cognitive function 25 years later.

METHODS

We studied 2,747 participants in the community-based Coronary Artery Risk Development in Young Adults Study of black and white men and women aged 18 to 30 years at recruitment in 1985-1986 (baseline year 0). Symptom-limited maximal treadmill test durations at years 0 and 20 provided measures of CRF. Cognitive tests at year 25 measured verbal memory (Rey Auditory Verbal Learning Test [RAVLT]), psychomotor speed (Digit Symbol Substitution Test [DSST]), and executive function (Stroop Test).

RESULTS

Per minute of baseline CRF, the RAVLT was 0.12 words recalled higher (standard error [SE] = 0.03, p < 0.0001), the DSST was 0.92 digits higher (SE = 0.13, p < 0.0001), and the Stroop Test score was 0.52 lower (better performance, SE = 0.11, p < 0.0001), after accounting for race, sex, age, education, and clinical center. Compared with the lowest quartile of CRF, each cognitive test was 21% to 34% of an SD better in the highest CRF quartile. Further adjustment for lifestyle and clinical measures attenuated coefficients for RAVLT and DSST slightly, while the coefficient predicting the Stroop Test lost more than half its value (p = 0.07). Analysis in the subset of 1,957 participants who also completed the year-20 treadmill test showed that 20-year change in CRF was positively associated only with DSST (p < 0.001).

CONCLUSIONS

Better verbal memory and faster psychomotor speed at ages 43 to 55 years were clearly associated with better CRF 25 years earlier.

Update on cognitive decline and dementia in elderly patients with diabetes

AIM

This article is an update of the relationship between type 2 diabetes (T2D), cognitive dysfunction and dementia in older people.

METHODS AND RESULTS

The number of older patients consulting for diabetes who also exhibit cognitive difficulties is consistently growing because of the increased longevity of the population as a whole and, according to a number of studies, the increased risk of cognitive impairment and dementia in older diabetic patients. Many studies have demonstrated a link between poor glucose control and deteriorated cognitive function in diabetic patients. A history of severe hypoglycaemic episodes has also been associated with a greater risk of late-in-life cognitive deficits and dementia in patients with T2D. Several processes are thought to promote cognitive decline and dementia in diabetics. Based on both clinical and non-clinical findings, the factors most likely to alter brain function and structure are cerebrovascular complications of diabetes, alterations in glucose and insulin, and recurrent hypoglycaemia. Together with other diabetes complications, cognitive deficits contribute to functional impairment, increased frequency of depression-related symptoms, greater incidence of recurrent hypoglycaemia, poorer adherence to treatment and, finally, poorer prognosis, as evidenced by recent longitudinal studies.

CONCLUSION

Clinical guidelines have recently been devised for older diabetic patients, particularly those with cognitive deficits and a reduced capacity to self-manage. In the most vulnerable patients, specific treatment strategies have been proposed for glycaemic control to limit metabolic decompensation and avoid the risk of hypoglycaemia. Educational measures, provided mainly to maintain patient autonomy and avoid hospital admission, have also been adapted according to patients' cognitive and functional status.

Outcome markers for clinical trials in cerebral amyloid angiopathy

Efforts are underway for early-phase trials of candidate treatments for cerebral amyloid angiopathy, an untreatable cause of haemorrhagic stroke and vascular cognitive impairment. A major barrier to these trials is the absence of consensus on measurement of treatment effectiveness. A range of potential outcome markers for cerebral amyloid angiopathy can be measured against the ideal criteria of being clinically meaningful, closely representative of biological progression, efficient for small or short trials, reliably measurable, and cost effective. In practice, outcomes tend either to have high clinical salience but low statistical efficiency, and thus more applicability for late-phase studies, or greater statistical efficiency but more limited clinical meaning. The most statistically efficient markers might be those that are potentially reversible with treatment, although their clinical significance remains unproven. Many of the candidate outcomes for cerebral amyloid angiopathy trials are probably applicable also to other small-vessel brain diseases.

The impact of glucose disorders on cognition and brain volumes in the elderly: the Sydney Memory and Ageing Study

Type 2 diabetes predicts accelerated cognitive decline and brain atrophy. We hypothesized that impaired fasting glucose (IFG) and incident glucose disorders have detrimental effects on global cognition and brain volume. We further hypothesized that metabolic and inflammatory derangements accompanying hyperglycaemia contribute to change in brain structure and function. This was a longitudinal study of a community-dwelling elderly cohort with neuropsychological testing (n = 880) and brain volumes by magnetic resonance imaging (n = 312) measured at baseline and 2 years. Primary outcomes were global cognition and total brain volume. Secondary outcomes were cognitive domains (processing speed, memory, language, visuospatial and executive function) and brain volumes (hippocampal, parahippocampal, precuneus and frontal lobe). Participants were categorised as normal, impaired fasting glucose at both assessments (stable IFG), baseline diabetes or incident glucose disorders (incident diabetes or IFG at 2 years). Measures included inflammatory cytokines and oxidative metabolites. Covariates were age, sex, education, non-English speaking background, smoking, blood pressure, lipid-lowering or antihypertensive medications, mood score, apolipoprotein E genotype and baseline cognition or brain volume. Participants with incident glucose disorders had greater decline in global cognition and visuospatial function compared to normal, similar to that observed in baseline diabetes. Homocysteine was independently associated with the observed effect of diabetes on executive function. Apolipoprotein E genotype did not influence the observed effects of diabetes on cognition. Incident glucose disorders and diabetes were also associated with greater 2-year decline in total brain volume, compared to normal (40.0 ± 4.2 vs. 46.7 ± 5.7 mm(3) vs. 18.1 ± 6.2, respectively, p < 0.005). Stable IFG did not show greater decline in global cognition or brain volumes compared to normal. Incident glucose disorders, like diabetes, are associated with accelerated decline in global cognition and brain volumes in non-demented elderly, whereas stable IFG is not. Preventing deterioration in glucose metabolism in the elderly may help preserve brain structure and function.

Influence of cognitive impairment on the management of ischaemic stroke

BACKGROUND

Because of ageing of the population, it is more and more frequent to treat ischaemic stroke patients with pre-stroke cognitive impairment (PSCI). Currently, there is no specific recommendation on ischaemic stroke management in these patients, both at the acute stage and in secondary prevention. However, these patients are less likely to receive treatments proven effective in randomised controlled trials, even in the absence of contra-indication.

OBJECTIVE

To review the literature to assess efficacy and safety of validated therapies for acute ischaemic stroke and secondary prevention in PSCI patients.

RESULTS

Most randomised trials did not take into account the pre-stroke cognitive status. The few observational studies conducted at the acute stage or in secondary prevention, did not provide any information that the benefit could be either lost or replaced by harm in the presence of PSCI.

CONCLUSIONS

There is no reason not to treat ischaemic stroke patients with PSCI according to the currently available recommendations for acute management and secondary prevention. Further observational studies are needed and pre-stroke cognition should be taken into account in future stroke trials.

Cognitive function and brain structure in persons with type 2 diabetes mellitus after intensive lowering of blood pressure and lipid levels: a randomized clinical trial

IMPORTANCE

Persons with type 2 diabetes mellitus (T2DM) are at increased risk for decline in cognitive function, reduced brain volume, and increased white matter lesions in the brain. Poor control of blood pressure (BP) and lipid levels are risk factors for T2DM-related cognitive decline, but the effect of intensive treatment on brain function and structure is unknown.

OBJECTIVE

To examine whether intensive therapy for hypertension and combination therapy with a statin plus a fibrate reduces the risk of decline in cognitive function and total brain volume (TBV) in patients with T2DM.

DESIGN, SETTING, AND PARTICIPANTS

A North American multicenter clinical trial including 2977 participants without baseline clinical evidence of cognitive impairment or dementia and with hemoglobin A1c (HbA1c) levels less than 7.5% randomized to a systolic BP goal of less than 120 vs less than 140 mm Hg (n = 1439) or to a fibrate vs placebo in patients with low-density lipoprotein cholesterol levels less than 100 mg/dL (n = 1538). Participants were recruited from August 1, 2003, through October 31, 2005, with the final follow-up visit by June 30, 2009.

MAIN OUTCOME MEASURES

Cognition was assessed at baseline and 20 and 40 months. A subset of 503 participants underwent baseline and 40-month brain magnetic resonance imaging to assess for change in TBV and other structural measures of brain health.

RESULTS

Baseline mean HbA1c level was 8.3%; mean age, 62 years; and mean duration of T2DM, 10 years. At 40 months, no differences in cognitive function were found in the intensive BP-lowering trial or in the fibrate trial. At 40 months, TBV had declined more in the intensive vs standard BP-lowering group (difference, -4.4 [95% CI, -7.8 to -1.1] cm(3); P = .01). Fibrate therapy had no effect on TBV compared with placebo.

CONCLUSIONS AND RELEVANCE

In participants with long-standing T2DM and at high risk for cardiovascular events, intensive BP control and fibrate therapy in the presence of controlled low-density lipoprotein cholesterol levels did not produce a measurable effect on cognitive decline at 40 months of follow-up. Intensive BP control was associated with greater decline in TBV at 40 months relative to standard therapy. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00000620.

Midlife type 2 diabetes and poor glycaemic control as risk factors for cognitive decline in early old age: a post-hoc analysis of the Whitehall II cohort study

BACKGROUND

Type 2 diabetes increases the risk for dementia, but whether it affects cognition before old age is unclear. We investigated whether duration of diabetes in late midlife and poor glycaemic control were associated with accelerated cognitive decline.

METHODS

5653 participants from the Whitehall II cohort study (median age 54.4 years [IQR 50.3-60.3] at first cognitive assessment), were classified into four groups: normoglycaemia, prediabetes, newly diagnosed diabetes, and known diabetes. Tests of memory, reasoning, phonemic and semantic fluency, and a global score that combined all cognitive tests, were assessed three times over 10 years (1997-99, 2002-04, and 2007-09). Mean HbA1c was used to assess glycaemic control during follow-up. Analyses were adjusted for sociodemographic characteristics, health-related behaviours, and chronic diseases.

FINDINGS

Compared with normoglycaemic participants, those with known diabetes had a 45% faster decline in memory (10 year difference in decline -0.13 SD, 95% CI -0.26 to -0.00; p=0.046), a 29% faster decline in reasoning (-0.10 SD, -0.19 to -0.01; p=0.026), and a 24% faster decline in the global cognitive score (-0.11 SD, -0.21 to -0.02; p=0.014). Participants with prediabetes or newly diagnosed diabetes had similar rates of decline to those with normoglycaemia. Poorer glycaemic control in participants with known diabetes was associated with a significantly faster decline in memory (-0.12 [-0.22 to -0.01]; p=0.034) and a decline in reasoning that approached significance (-0.07 [-0.15 to 0.00]; p=0.052).

INTERPRETATION

The risk of accelerated cognitive decline in middle-aged patients with type 2 diabetes is dependent on both disease duration and glycaemic control.

FUNDING

US National Institutes of Health, UK Medical Research Council.

Dementia and cognitive decline in type 2 diabetes and prediabetic stages: towards targeted interventions

Type 2 diabetes is associated with dementia, and also with more slight cognitive decrements. In this Review we discuss trajectories from normal cognition to dementia in people with type 2 diabetes, and explore opportunities for treatment. Slight diabetes-associated cognitive decrements and dementia affect different age groups and show a different evolution. These cognitive entities should therefore not be regarded as a continuum, although their effects might be additive. Vascular damage is a key underlying process in both entities. Glucose-mediated processes and other metabolic disturbances might also have a role. No treatment has been established, but management of vascular risk factors and optimisation of glycaemic control could have therapeutic benefit. We identify possible opportunities for intervention to improve cognitive outcomes in people with type 2 diabetes, and suggest how treatment can be tailored to individual risk profiles and comorbidities.

The older patient with diabetes: a practical approach

Type 2 diabetes mellitus is very prevalent among persons aged 60-80 years old. This population is expected to increase in number and is characterized by the presence of comorbidities, long standing diabetes, frailty, high rate of cognitive impairment and limited life expectancy. These characteristics have a significant impact on diabetes and treatment among the elderly, much as diabetes predisposes to these conditions. In this article we will describe mechanisms that may lead to insulin resistance and diabetes among the elderly and also how these conditions contribute to the development of frailty and cognitive impairment. Hypoglycemia and it's consequences are important considerations when planning the treatment of diabetes. Treatment options in light of new goals and the danger of hypoglycemia will be detailed.

Severe hypoglycemia and cognitive decline in older people with type 2 diabetes: the Edinburgh type 2 diabetes study

OBJECTIVE

People with type 2 diabetes are at increased risk of age-related cognitive decline and dementia. Hypoglycemia is a candidate risk factor, but the direction of association between episodes of severe hypoglycemia and cognitive decline in type 2 diabetes remains uncertain.

RESEARCH DESIGN AND METHODS

In the Edinburgh Type 2 Diabetes Study, cognitive function was assessed in 831 adults with type 2 diabetes (aged 60-75 years) at baseline and after 4 years. Scores on seven neuropsychological tests were combined into a standardized general ability factor g. Self-reported history of severe hypoglycemia at baseline (history of hypoglycemia) and at follow-up (incident hypoglycemia) was recorded.

RESULTS

A history of hypoglycemia was reported by 9.3% of subjects, and 10.2% reported incident hypoglycemia. Incident hypoglycemia was associated with poorer cognitive ability at baseline (age- and sex-adjusted odds ratio for lowest tertile of g 2.04 [95% CI 1.25-3.31], P = 0.004). Both history of hypoglycemia and incident hypoglycemia were also associated with greater cognitive decline during follow-up (mean follow-up g adjusted for age, sex, and baseline g -0.25 vs. 0.03 [P = 0.02] and -0.28 vs. 0.04 [P = 0.01], respectively), including after addition of vascular risk factors and cardiovascular and microvascular disease to the models (-0.23 vs. 0.03 [P = 0.04] and -0.21 vs. 0.05 [P = 0.03], respectively).

CONCLUSIONS

The relationship between cognitive impairment and hypoglycemia appeared complex, with severe hypoglycemia associated with both poorer initial cognitive ability and accelerated cognitive decline.

Higher RBC EPA + DHA corresponds with larger total brain and hippocampal volumes: WHIMS-MRI study

OBJECTIVE

To test whether red blood cell (RBC) levels of marine omega-3 fatty acids measured in the Women's Health Initiative Memory Study were related to MRI brain volumes measured 8 years later.

METHODS

RBC eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and MRI brain volumes were assessed in 1,111 postmenopausal women from the Women's Health Initiative Memory Study. The endpoints were total brain volume and anatomical regions. Linear mixed models included multiple imputations of fatty acids and were adjusted for hormone therapy, time since randomization, demographics, intracranial volume, and cardiovascular disease risk factors.

RESULTS

In fully adjusted models, a 1 SD greater RBC EPA + DHA (omega-3 index) level was correlated with 2.1 cm(3) larger brain volume (p = 0.048). DHA was marginally correlated (p = 0.063) with total brain volume while EPA was less so (p = 0.11). There were no correlations between ischemic lesion volumes and EPA, DHA, or EPA + DHA. A 1 SD greater omega-3 index was correlated with greater hippocampal volume (50 mm(3), p = 0.036) in fully adjusted models. Comparing the fourth quartile vs the first quartile of the omega-3 index confirmed greater hippocampal volume (159 mm(3), p = 0.034).

CONCLUSION

A higher omega-3 index was correlated with larger total normal brain volume and hippocampal volume in postmenopausal women measured 8 years later. While normal aging results in overall brain atrophy, lower omega-3 index may signal increased risk of hippocampal atrophy. Future studies should examine whether maintaining higher RBC EPA + DHA levels slows the rate of hippocampal or overall brain atrophy.

Change in brain and lesion volumes after CEE therapies: the WHIMS-MRI studies

OBJECTIVES

To determine whether smaller brain volumes in older women who had completed Women's Health Initiative (WHI)-assigned conjugated equine estrogen-based hormone therapy (HT), reported by WHI Memory Study (WHIMS)-MRI, correspond to a continuing increased rate of atrophy an average of 6.1 to 7.7 years later in WHIMS-MRI2.

METHODS

A total of 1,230 WHI participants were contacted: 797 (64.8%) consented, and 729 (59%) were rescanned an average of 4.7 years after the initial MRI scan. Mean annual rates of change in total brain volume, the primary outcome, and rates of change in ischemic lesion volumes, the secondary outcome, were compared between treatment groups using mixed-effect models with adjustment for trial, clinical site, age, intracranial volumes, and time between MRI measures.

RESULTS

Total brain volume decreased an average of 3.22 cm(3)/y in the active arm and 3.07 cm(3)/y in the placebo arm (p = 0.53). Total ischemic lesion volumes increased in both arms at a rate of 0.12 cm(3)/y (p = 0.88).

CONCLUSIONS

Conjugated equine estrogen-based postmenopausal HT, previously assigned at WHI baseline, did not affect rates of decline in brain volumes or increases in brain lesion volumes during the 4.7 years between the initial and follow-up WHIMS-MRI studies. Smaller frontal lobe volumes were observed as persistent group differences among women assigned to active HT compared with placebo. Women with a history of cardiovascular disease treated with active HT, compared with placebo, had higher rates of accumulation in white matter lesion volume and total brain lesion volume. Further study may elucidate mechanisms that explain these findings.

Brain alterations and clinical symptoms of dementia in diabetes: aβ/tau-dependent and independent mechanisms

Emerging evidence suggests that diabetes affects cognitive function and increases the incidence of dementia. However, the mechanisms by which diabetes modifies cognitive function still remains unclear. Morphologically, diabetes is associated with neuronal loss in the frontal and temporal lobes including the hippocampus, and aberrant functional connectivity of the posterior cingulate cortex and medial frontal/temporal gyrus. Clinically, diabetic patients show decreased executive function, information processing, planning, visuospatial construction, and visual memory. Therefore, in comparison with the characteristics of AD brain structure and cognition, diabetes seems to affect cognitive function through not only simple AD pathological feature-dependent mechanisms but also independent mechanisms. As an Aβ/tau-independent mechanism, diabetes compromises cerebrovascular function, increases subcortical infarction, and might alter the blood-brain barrier. Diabetes also affects glucose metabolism, insulin signaling, and mitochondrial function in the brain. Diabetes also modifies metabolism of Aβ and tau and causes Aβ/tau-dependent pathological changes. Moreover, there is evidence that suggests an interaction between Aβ/tau-dependent and independent mechanisms. Therefore, diabetes modifies cognitive function through Aβ/tau-dependent and independent mechanisms. Interaction between these two mechanisms forms a vicious cycle.

Diabetes mellitus and dementia

Growing epidemiologic evidence has suggested that people with diabetes mellitus are at an increased risk for the development of dementia. However, the results for the subtypes of dementia are inconsistent. This review examines the risk of dementia in people with diabetes mellitus, and discusses the possible mechanism underpinning this association. Diabetes mellitus is associated with a 1.5- to 2.5-fold greater risk of dementia among community-dwelling elderly people. Notably, diabetes mellitus is a significant risk factor for not only vascular dementia, but also Alzheimer's disease. The mechanisms underpinning the association are unclear, but it may be multifactorial in nature, involving factors such as cardiovascular risk factors, glucose toxicity, changes in insulin metabolism and inflammation. The optimal management of these risk factors in early life may be important to prevent late-life dementia. Furthermore, novel therapeutic strategies will be needed to prevent or reduce the development of dementia in people with diabetes mellitus.

Central nervous system imaging in diabetic cerebrovascular diseases and white matter hyperintensities

Diabetes mellitus is an important vascular risk factor for cerebrovascular disease. This occurs through pathophysiologic changes to the microcirculation as arteriolosclerosis and to the macrocirculation as large artery atherosclerosis. Imaging techniques can provide detailed visualization of the cerebrovasculature using CT (computed tomography) angiography and MR (magnetic resonance) angiography. Newer techniques focused on advanced parenchymal imaging include CT perfusion, quantitative MRI, and diffusion tensor imaging; each identifies brain lesion burden due to diabetes mellitus. These imaging approaches have provided insights into the diabetes mellitus brain and cerebral circulation pathophysiology. Imaging has taught us that diabetics develop cerebral atrophy, silent infarcts, and white matter disease more rapidly than other patient populations. Longitudinal studies are needed to quantify the rate and extent of such structural brain and blood vessel changes and how they relate to cognitive decline. Diabetes prevention and treatment strategies will then be possible to slow the development of such changes.

Diabetes cognitive impairments and the effect of traditional chinese herbs

The problem of cognitive impairment resulting from diabetes is gaining more acceptance and attention. Both type 1 and type 2 diabetes mellitus have been proved to be associated with reduced performance on numerous domains of cognitive function. Although the exact mechanisms of cognitive impairments in diabetes have not been completely understood, hyperglycemia and insulin resistance seem to play significant roles. And other possible risk factors such as hypoglycemia, insulin deficiency, vascular risk factors, hyperactive HPA axis, depression, and altered neurotransmitters will also be examined. In the meanwhile, this review analyzed the role of the active ingredient of Chinese herbal medicine in the treatment of diabetes cognitive impairments.

Physical disability in the elderly with diabetes: epidemiology and mechanisms

Diabetes mellitus is a common chronic condition worldwide, especially in the elderly population. Several epidemiologic studies in the last 2 years have consistently associated diabetes with physical disability, a condition that may profoundly affect the quality of life of older people. Although in older people with diabetes, the pathogenesis of functional limitation and disability has not been completely elucidated, it is certainly complex and involves multiple potential pathways. In this narrative review, we described the most recent epidemiologic and clinical evidence supporting the association between diabetes and impaired physical function in older persons focusing on emerging biological mechanisms explaining the excess risk of disability associated with diabetes.

Albuminuria and cognitive decline in people with diabetes and normal renal function

BACKGROUND AND OBJECTIVES

Diabetes mellitus is associated with increased risk of cognitive impairment. This study examines whether microvascular disease, as measured by albuminuria and decline in estimated GFR (eGFR), is associated with cognitive decline during 3.3 years of follow-up in individuals with diabetes with a normal baseline eGFR (approximately 90 ml/min per 1.73 m(2)).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Participants were from the Action to Control Cardiovascular Risk in Diabetes Memory in Diabetes study (N=2977; mean age 62.5 ± 5.8 years; recruitment from August 2003 to December 2005, followed through June 2009), which examined the association of intensive versus standard glucose control on cognitive function. Participants underwent three neuropsychologic tests at baseline, 20 months, and 40 months. Tests included information processing speed, verbal memory, and executive function. Mixed-effects models were used to assess the association of albuminuria and eGFR on the percentage decline in each test.

RESULTS

Participants with albuminuria at baseline and follow-up (persistent albuminuria) (-5.8% [95% confidence interval (CI), -7.3 to -4.2]) and participants with albuminuria at follow-up but none at baseline (progressive albuminuria) (-4.1% [95% CI, -5.6 to -2.7]) had greater percentage declines on information processing speed than participants without albuminuria at baseline and at follow-up (no albuminuria) (-2.6% [95% CI, -3.4 to -1.9]) (P=0.001 and P=0.10, respectively). There were borderline percentage changes in the test of verbal memory (4.8% [95% CI, 2.4 to 7.1] and 4.7% [95% CI, 2.5 to 7.0] versus 7.1% [95% CI, 6.0 to 8.3]; P=0.11 and P=0.08, respectively). On logistic regression analysis, persistent albuminuria (odds ratio, 1.37 [95% CI, 1.09 to 1.72]) and progressive albuminuria (odds ratio, 1.25 [95% CI, 1.02 to 1.56]) were associated with a ≥ 5% decline in information processing speed scores but not with verbal memory or executive function performance. A 1 ml/min per 1.73 m(2) per year eGFR decline had a borderline association with decline in tests of cognitive function.

CONCLUSIONS

Persistent albuminuria and progressive albuminuria are associated with a decline in cognitive function in relatively young individuals with diabetes with unimpaired eGFR. These findings do not rule out the possibility of other processes causing cognitive decline.

Risk score for prediction of 10 year dementia risk in individuals with type 2 diabetes: a cohort study

BACKGROUND

Although patients with type 2 diabetes are twice as likely to develop dementia as those without this disease, prediction of who has the highest future risk is difficult. We therefore created and validated a practical summary risk score that can be used to provide an estimate of the 10 year dementia risk for individuals with type 2 diabetes.

METHODS

Using data from two longitudinal cohorts of patients with type 2 diabetes (aged ≥60 years) with 10 years of follow-up, we created (n=29,961) and validated (n=2413) the risk score. We built our prediction model by evaluating 45 candidate predictors using Cox proportional hazard models and developed a point system for the risk score based on the size of the predictor's β coefficient. Model prediction was tested by discrimination and calibration methods. Dementia risk per sum score was calculated with Kaplan-Meier estimates.

FINDINGS

Microvascular disease, diabetic foot, cerebrovascular disease, cardiovascular disease, acute metabolic events, depression, age, and education were most strongly predictive of dementia and constituted the risk score (C statistic 0·736 for creation cohort and 0·746 for validation cohort). The dementia risk was 5·3% (95% CI 4·2-6·3) for the lowest score (-1) and 73·3% (64·8-81·8) for the highest (12-19) sum scores.

INTERPRETATION

To the best of our knowledge, this is the first risk score for the prediction of 10 year dementia risk in patients with type 2 diabetes mellitus. The risk score can be used to increase vigilance for cognitive deterioration and for selection of high-risk patients for participation in clinical trials.

FUNDING

Kaiser Permanente Community Benefit, National Institute of Health, Utrecht University, ZonMw, and Fulbright.

Effects of randomization to intensive glucose control on adverse events, cardiovascular disease, and mortality in older versus younger adults in the ACCORD Trial

OBJECTIVE

We explore the effect of randomized treatment, comparing intensive to standard glucose-lowering strategies on major cardiovascular outcomes, death, and severe adverse events in older versus younger participants in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial.

RESEARCH DESIGN AND METHODS

Participants with type 2 diabetes (n = 10,251) with a mean age of 62 years, a median duration of diabetes of 10 years, and a median A1C of 8.1% (65 mmol/mol) were randomized to treatment strategies targeting either A1C <6.0% (42 mmol/mol) or 7.0-7.9% (53-63 mmol/mol) and followed for a mean of 3.7 years. Outcomes were analyzed within subgroups defined by baseline age (<65 vs. ≥65 years).

RESULTS

Older and younger ACCORD participants achieved similar intensive-arm A1C levels and between-arm A1C differences. Within the older subgroup, similar hazards of the cardiovascular primary outcome and total mortality were observed in the two arms. While there was no intervention effect on cardiovascular mortality in the older subgroup, there was an increased risk in the intensive arm for the younger subgroup (older hazard ratio [HR] = 0.97; younger HR = 1.71; P = 0.03). Regardless of intervention arm, the older subgroup experienced higher annualized rates of severe hypoglycemia (4.45% intensive and 1.36% standard) than the younger subgroup (2.45% intensive and 0.80% standard).

CONCLUSIONS

Intensive glucose lowering increased the risk of cardiovascular disease and total mortality in younger participants, whereas it had a neutral effect in older participants. The intensive to standard relative risk of severe hypoglycemia was similar in both age subgroups, with higher absolute rates in older participants within both treatment arms.

Vascular risk factors and cognitive disorders

Delaying the onset of dementia by just a few years could have a major impact on the prevalence of the disease at the population level. Vascular risk factors are modifiable and may offer an important opportunity for preventive approaches. Several studies have shown that diabetes, hypertension, obesity, and smoking are associated with an increased risk of cognitive decline and dementia, but other groups have not observed such a relation. Positive associations were observed mainly in studies where risk factors were assessed in midlife, suggesting that age is an important modulator in the relation between vascular risk factors and cognition. The population attributable risk of dementia is particularly high for hypertension. Associations of vascular risk factors with cognitive decline and dementia are probably mediated largely by cerebrovascular disease, including both stroke and covert vascular brain injury, which can have additive or synergistic effects with coexisting neurodegenerative lesions. To date, randomized trials have not convincingly demonstrated that treating vascular risk factors is associated with a reduction in cognitive decline or dementia risk. Of eight randomized trials testing the effect of antihypertensive agents on dementia risk, only one was positive, and another in a subgroup of individuals with recurrent stroke. In most trials, cognition and dementia were secondary outcomes, follow-up was short and treatment was initiated at an older age. No effect on cognitive decline or dementia could be demonstrated for statins and intensive glycemic control. Future areas of investigation could include differential class effects of antihypertensive drugs on cognitive outcomes and identification of high risk individuals as target population for clinical trials initiated in midlife.

The influence of subclinical cardiovascular disease and related risk factors on cognition in type 2 diabetes mellitus: The DHS-Mind study

We hypothesized that measures of coronary artery calcified plaque (CAC) collected at baseline from the Diabetes Heart Study (DHS) would explain associations between cognition and diabetes collected at follow-up approximately 7 years later. The DHS is a sibling study of cardiovascular disease (CVD) in a cohort with a high prevalence of type 2 diabetes (~80%). Associations between baseline CAC and cognitive performance were tested using generalized estimating equations and mixed effects models to adjust for familial relationships. Diabetes status was associated (p<0.05) with poorer performance on tests of verbal memory, processing speed, and semantic fluency adjusting for age, sex, education, and hypertension status. As hypothesized, including CAC in the statistical model attenuated this association. Additionally, CAC and fasting glucose predicted performance in tasks not associated with diabetes status in this study (Stroop Task, Phonemic Fluency). These results confirm work attributing the heterogeneity of cognitive outcomes in type 2 diabetes to subclinical risk factors that combine to affect different aspects of brain function. Importantly, these results imply that risk factor intervention should begin before comorbidities, particularly CVD, become clinically apparent.

Dysglycaemia, vasculopenia, and the chronic consequences of diabetes

High glucose concentrations are independent risk factors for many serious disorders. Glucose lowering can reduce or prevent many of these disorders. The mechanisms that cause glucose-linked tissue damage are unclear; however, the sequence of tissue changes that lead to one of these consequences (ie, retinopathy) have been understood for decades because the retina can be easily inspected and changes in its vascular supply can easily be assessed. The possibility that the long-term harms of raised glucose concentrations are mediated through reduced capillary perfusion (ie, vasculopenia) is suggested by strong epidemiological links between capillary abnormalities in the retina and most of the complications of diabetes, a delay between the therapeutic effect of glucose lowering in the retina and in other tissues, laboratory evidence that atherosclerosis is promoted by abnormalities in the capillary-rich vasa vasorum of conductance vessels, and similarities in capillary abnormalities in the retina and the kidney of people with diabetes. These findings also suggest that the retina might be a window through which the effect of raised glucose concentrations on a wide range of tissues can be seen. If continuing research lends support to this theory, treatments that counteract the effect of glucose on capillaries such as those in the retina might ultimately also reduce other serious consequences of dysglycaemia.

Effect of thiazolidinediones and insulin on cognitive outcomes in ACCORD-MIND

OBJECTIVE

To examine the relationship of cognitive performance to exposure to insulin (INS) and thiazolidinediones (TZD) in the ACCORD-MIND cohort.

METHODS

Participants (55-80years) with type 2 diabetes (T2D), hemoglobin A1c (HbA1c) >7.5% (>58mmol/mol), and a high risk of cardiovascular events were randomly assigned to receive intensive control targeting HbA1c to <6.0% (42mmol/mol) or a standard strategy targeting HbA1c to 7.0%-7.9% (53-63mmol/mol). The Digit Symbol Substitution Test (DSST) was assessed at baseline and at 20 and 40months. Exposure to INS was calculated as average daily dose/kg of body weight; exposure to rosiglitazone (ROS) was calculated as days of ROS prescription in the intervals preceding the 20- and 40-month DSSTs.

RESULTS

At baseline, INS use was associated with reduced DSST performance, but not after controlling for comorbidities and lab values. There was no relationship between use of a TZD and DSST performance on at baseline. ROS but not INS exposure was associated with greater decline in DSST performance over 40months in subjects randomized to the intensive but not the standard group.

CONCLUSIONS

Exposure to a TZD may increase cognitive decline in some patients with T2D. However, these results may be confounded by unexplained differences between participants.

Sugar for the brain: the role of glucose in physiological and pathological brain function

The mammalian brain depends upon glucose as its main source of energy, and tight regulation of glucose metabolism is critical for brain physiology. Consistent with its critical role for physiological brain function, disruption of normal glucose metabolism as well as its interdependence with cell death pathways forms the pathophysiological basis for many brain disorders. Here, we review recent advances in understanding how glucose metabolism sustains basic brain physiology. We synthesize these findings to form a comprehensive picture of the cooperation required between different systems and cell types, and the specific breakdowns in this cooperation that lead to disease.

Vascularization pattern after ischemic stroke is different in control versus diabetic rats: relevance to stroke recovery

BACKGROUND AND PURPOSE

Pre-existing diabetes mellitus worsens brain functionality in ischemic stroke. We have previously shown that type 2 diabetic rats exhibit enhanced dysfunctional cerebral neovascularization and when these rats are subjected to cerebral ischemic reperfusion injury develop hemorrhagic transformation and greater neurological deficits. However, our knowledge of vascular and functional plasticity during the recovery phase of diabetic stroke is limited. This study tested the hypothesis that vascular repair is impaired in the poststroke period in diabetes mellitus, and this is associated with poor sensorimotor and cognitive function. We further hypothesized that glycemic control prevents impaired vascularization and improves functional outcome in diabetes mellitus.

METHODS

Vascularization was assessed in the ipsilateral and contralateral hemispheres in control, diabetes mellitus and diabetes mellitus plus metformin groups 14 days after ischemic reperfusion injury, as well as in respective sham controls. Three-dimensional reconstruction of the fluorescein isothiocyanate (FITC)-stained vasculature was achieved by confocal microscopy, and stereological parameters, including vascular volume and surface area, were measured. Astrogliosis was determined by glial fibrillary acidic protein staining. The relative rates of sensorimotor recovery, cognitive decline, and spontaneous activity were assessed.

RESULTS

Vascular density in the peri-infarct area was significantly reduced in diabetes mellitus, whereas there was reparative neovascularization in control rats. Astroglial swelling and reactivity were more pronounced in diabetic stroke compared with control stroke. Diabetes mellitus blunted sensorimotor recovery and also exacerbated anxiety-like symptoms and cognitive deficits. Glycemic control started after stroke partially prevented these changes.

CONCLUSIONS

Diabetes mellitus impairs poststroke reparative neovascularization and impedes the recovery. Glycemic control after stroke can improve neurovascular repair and improve functional outcome.

Cardiovascular Risk Profile and Cognitive Function in Young, Middle-Aged, and Elderly Subjects

Background and Purpose—

Cognitive decline occurs earlier than previously realized and is already evident at the age of 45. Because cardiovascular risk factors are established risk factors for cognitive decline in old age, we investigated whether cardiovascular risk factors are also associated with cognitive decline in young and middle-aged groups.

Methods—

The cross-sectional study included 3778 participants aged 35 to 82 years (mean age, 54 years) and free of cardiovascular disease and stroke. Cognitive function was measured with the Ruff Figural Fluency Test (RFFT; worst score, 0; best score, 175 points) and the Visual Association Test (VAT; worst score, 0; best score, 12 points). Overall cardiovascular risk was assessed with the Framingham Risk Score (FRS) for general cardiovascular disease (best score, −5; worst score, 33 points).

Results—

Mean RFFT score (SD) was 70 (26) points, median VAT score (interquartile range) was 10 (9–11) points, and mean FRS (SD) was 10 (6) points. Using linear regression analysis adjusting for educational level, RFFT was negatively associated with FRS. RFFT score decreased by 1.54 points (95% confidence interval, −1.66 to −1.44; P <0.001) per point increase in FRS. This negative association was not only limited to older age groups, but also found in the young (35–44 years). The main influencing components of the FRS were age ( P <0.001), diabetes mellitus ( P =0.001), and smoking ( P <0.001). Similar results were found for VAT score as outcome measure.

Conclusions—

In this large population–based cohort, a worse overall cardiovascular risk profile was associated with poorer cognitive function. This association was already present in young adults aged 35 to 44 years.

Relationship between markers of insulin resistance, markers of adiposity, HbA1c, and cognitive functions in a middle-aged population-based sample: the MONA LISA study

OBJECTIVE

To determine the relationship between markers of insulin resistance (fasting insulin and homeostasis model assessment of insulin resistance), markers of adiposity (BMI, waist circumference, and body fat), HbA1c, and cognitive performances in a middle-aged population-based sample free of diabetes.

RESEARCH DESIGN AND METHODS

Our study sample consisted of 1,172 people aged 35-64 years (49% women), free of diabetes, and recruited between 2005 and 2007 in the MONA LISA survey. Cognitive functions (memory, attention, and processing speed) were evaluated by neuropsychological tests: word-list learning test, digit symbol substitution test (DSST), word fluency test, and Stroop Test. Multiple logistic regressions were used to estimate the relationship between cognitive performance and metabolic markers. We serially adjusted for age, sex, education, and occupational status (model A), additionally for income, smoking, alcohol consumption, sedentarity, and psychotropic substance use (model B), and finally, included variables linked to the metabolic syndrome (hypertension, dyslipidemia, vascular disease, and C-reactive protein) and depression (model C).

RESULTS

Elevated markers of adiposity were associated with poor cognitive performance in tests evaluating processing speed. The probability of being in the lowest quartile of each test was nearly doubled for participants in the upper quartile of BMI, compared with those in the lowest one [BMI, adjusted odds ratio (OR) 2.18, P = 0.003 (DSST), and OR 2.09, P = 0.005 (Stroop Test)]. High HbA1c was associated with poor cognitive performance in DSST (adjusted OR 1.75, P = 0.037). Waist circumference was linked to poor cognitive performance in men but not in women.

CONCLUSIONS

Poor cognitive performance is associated with adiposity and hyperglycemia in healthy middle-aged people.

Management of type 2 diabetes in older people

The prevalence of diabetes is increasing due to aging of the population and increasing obesity. In the developed world, there is an epidemiologic shift from diabetes being a disease of middle age to being a disease of older people due to increased life expectancy. In old age, diabetes is associated with high comorbidity burden and increased prevalence of geriatric syndromes in addition to the traditional vascular complications. Therefore, comprehensive geriatric assessment should be performed on initial diagnosis of diabetes. Due to the heterogeneous nature of older people with diabetes and variations in their functional status, comorbidities, and life expectancy, therapeutic interventions, and glycemic targets should be individualized taking into consideration patients' preferences and putting quality of life at the heart of their care plans.

Hypoglycemia and diabetes: a report of a workgroup of the American Diabetes Association and the Endocrine Society

OBJECTIVE

To review the evidence about the impact of hypoglycemia on patients with diabetes that has become available since the past reviews of this subject by the American Diabetes Association and The Endocrine Society and to provide guidance about how this new information should be incorporated into clinical practice.

PARTICIPANTS

Five members of the American Diabetes Association and five members of The Endocrine Society with expertise in different aspects of hypoglycemia were invited by the Chair, who is a member of both, to participate in a planning conference call and a 2-day meeting that was also attended by staff from both organizations. Subsequent communications took place via e-mail and phone calls. The writing group consisted of those invitees who participated in the writing of the manuscript. The workgroup meeting was supported by educational grants to the American Diabetes Association from Lilly USA, LLC and Novo Nordisk and sponsorship to the American Diabetes Association from Sanofi. The sponsors had no input into the development of or content of the report.

EVIDENCE

The writing group considered data from recent clinical trials and other studies to update the prior workgroup report. Unpublished data were not used. Expert opinion was used to develop some conclusions.

CONSENSUS PROCESS

Consensus was achieved by group discussion during conference calls and face-to-face meetings, as well as by iterative revisions of the written document. The document was reviewed and approved by the American Diabetes Association's Professional Practice Committee in October 2012 and approved by the Executive Committee of the Board of Directors in November 2012 and was reviewed and approved by The Endocrine Society's Clinical Affairs Core Committee in October 2012 and by Council in November 2012.

CONCLUSIONS

The workgroup reconfirmed the previous definitions of hypoglycemia in diabetes, reviewed the implications of hypoglycemia on both short- and long-term outcomes, considered the implications of hypoglycemia on treatment outcomes, presented strategies to prevent hypoglycemia, and identified knowledge gaps that should be addressed by future research. In addition, tools for patients to report hypoglycemia at each visit and for clinicians to document counseling are provided.

Hypoglycemia and diabetes: a report of a workgroup of the American Diabetes Association and the Endocrine Society

OBJECTIVE

To review the evidence about the impact of hypoglycemia on patients with diabetes that has become available since the past reviews of this subject by the American Diabetes Association and The Endocrine Society and to provide guidance about how this new information should be incorporated into clinical practice.

PARTICIPANTS

Five members of the American Diabetes Association and five members of The Endocrine Society with expertise in different aspects of hypoglycemia were invited by the Chair, who is a member of both, to participate in a planning conference call and a 2-day meeting that was also attended by staff from both organizations. Subsequent communications took place via e-mail and phone calls. The writing group consisted of those invitees who participated in the writing of the manuscript. The workgroup meeting was supported by educational grants to the American Diabetes Association from Lilly USA, LLC and Novo Nordisk and sponsorship to the American Diabetes Association from Sanofi. The sponsors had no input into the development of or content of the report.

EVIDENCE

The writing group considered data from recent clinical trials and other studies to update the prior workgroup report. Unpublished data were not used. Expert opinion was used to develop some conclusions.

CONSENSUS PROCESS

Consensus was achieved by group discussion during conference calls and face-to-face meetings, as well as by iterative revisions of the written document. The document was reviewed and approved by the American Diabetes Association's Professional Practice Committee in October 2012 and approved by the Executive Committee of the Board of Directors in November 2012 and was reviewed and approved by The Endocrine Society's Clinical Affairs Core Committee in October 2012 and by Council in November 2012.

CONCLUSIONS

The workgroup reconfirmed the previous definitions of hypoglycemia in diabetes, reviewed the implications of hypoglycemia on both short- and long-term outcomes, considered the implications of hypoglycemia on treatment outcomes, presented strategies to prevent hypoglycemia, and identified knowledge gaps that should be addressed by future research. In addition, tools for patients to report hypoglycemia at each visit and for clinicians to document counseling are provided.

Influence of type 2 diabetes on brain volumes and changes in brain volumes: results from the Women's Health Initiative Magnetic Resonance Imaging studies

OBJECTIVE

To study how type 2 diabetes adversely affects brain volumes, changes in volume, and cognitive function.

RESEARCH DESIGN AND METHODS

Regional brain volumes and ischemic lesion volumes in 1,366 women, aged 72-89 years, were measured with structural brain magnetic resonance imaging (MRI). Repeat scans were collected an average of 4.7 years later in 698 women. Cross-sectional differences and changes with time between women with and without diabetes were compared. Relationships that cognitive function test scores had with these measures and diabetes were examined.

RESULTS

The 145 women with diabetes (10.6%) at the first MRI had smaller total brain volumes (0.6% less; P = 0.05) and smaller gray matter volumes (1.5% less; P = 0.01) but not white matter volumes, both overall and within major lobes. They also had larger ischemic lesion volumes (21.8% greater; P = 0.02), both overall and in gray matter (27.5% greater; P = 0.06), in white matter (18.8% greater; P = 0.02), and across major lobes. Overall, women with diabetes had slightly (nonsignificant) greater loss of total brain volumes (3.02 cc; P = 0.11) and significant increases in total ischemic lesion volumes (9.7% more; P = 0.05) with time relative to those without diabetes. Diabetes was associated with lower scores in global cognitive function and its subdomains. These relative deficits were only partially accounted for by brain volumes and risk factors for cognitive deficits.

CONCLUSIONS

Diabetes is associated with smaller brain volumes in gray but not white matter and increasing ischemic lesion volumes throughout the brain. These markers are associated with but do not fully account for diabetes-related deficits in cognitive function.

Diabetes, glucose control, and 9-year cognitive decline among older adults without dementia

OBJECTIVES

To determine if prevalent and incident diabetes mellitus (DM) increase risk of cognitive decline and if, among elderly adults with DM, poor glucose control is related to worse cognitive performance. DESIGN Prospective cohort study.

SETTING

Health, Aging, and Body Composition Study at 2 community clinics.

PARTICIPANTS

A total of 3069 elderly adults (mean age, 74.2 years; 42% black; 52% female).

MAIN OUTCOME MEASURES

Participants completed the Modified Mini-Mental State Examination (3MS) and Digit Symbol Substitution Test (DSST) at baseline and selected intervals over 10 years. Diabetes mellitus status was determined at baseline and during follow-up visits. Glycosylated hemoglobin A1c level was measured at years 1 (baseline), 4, 6, and 10 from fasting whole blood.

RESULTS

At baseline, 717 participants (23.4%) had prevalent DM and 2352 (76.6%) were without DM, 159 of whom developed incident DM during follow-up. Participants with prevalent DM had lower baseline test scores than participants without DM (3MS: 88.8 vs 90.9; DSST: 32.5 vs 36.3, respectively; t = 6.09; P = .001 for both tests). Results from mixed-effects models showed a similar pattern for 9-year decline (3MS: -6.0- vs -4.5-point decline; t = 2.66; P = .008; DSST: -7.9- vs -5.7-point decline; t = 3.69; P = .001, respectively). Participants with incident DM tended to have baseline and 9-year decline scores between the other 2 groups but were not statistically different from the group without DM. Multivariate adjustment for demographics and medical comorbidities produced similar results. Among participants with prevalent DM, glycosylated hemoglobin A1c level was associated with lower average mean cognitive scores (3MS: F = 8.2; P for overall = .003; DSST: F = 3.4; P for overall = .04), even after multivariate adjustment.

CONCLUSION

Among well-functioning older adults, DM and poor glucose control among those with DM are associated with worse cognitive function and greater decline. This suggests that severity of DM may contribute to accelerated cognitive aging.

Type 2 diabetes and cognitive impairment: linking mechanisms

This manuscript provides a brief review of current concepts in the mechanisms potentially linking type-2-diabetes (T2D) with cognitive impairment. Existing epidemiologic studies, imaging studies, autopsy studies, and clinical trials provide insights into the mechanisms linking T2D and cognitive impairment. There seems to be little dispute that T2D can cause cerebrovascular disease and thus cause vascular cognitive impairment (VCI). Whether T2D can cause late onset Alzheimer's disease (LOAD) remains to be elucidated. Many epidemiologic studies show an association between T2D and cognitive impairment, but the association with VCI seems to be stronger compared to LOAD, suggesting that cerebrovascular disease may be the main mechanism linking T2D and cognitive impairment. Imaging studies show an association between T2D and imaging markers of LOAD, but these observations could still be explained by cerebrovascular mechanisms. Autopsy studies are few and conflicting, with some suggesting a predominantly cerebrovascular mechanism, and others providing support for a neurodegenerative mechanism. Thus far, the evidence from clinical trials is mixed in supporting a causal association between T2D and cognitive impairment, and most clinical trials that can answer this question are yet to be reported or finished. Given the epidemic of T2D in the world, it is important to elucidate whether the association between T2D and cognitive impairment, particularly LOAD, is causal, and if so, what the mechanisms are.

Continuous glucose monitoring and cognitive performance in type 2 diabetes

BACKGROUND

Type 2 diabetes is associated with reductions in cognitive function that are associated with glycated hemoglobin (HbA1c) levels, but there is no information on whether cognition is related to postmeal glucose spikes. We explored the relationship of cognition to glucose levels measured by a continuous glucose monitoring system (CGMS) both before and after a weight loss diet.

SUBJECTS AND METHODS

Forty-four white subjects with type 2 diabetes (59.0 ± 6.2 years old; body mass index, 32.8 ± 4.2 kg/m(2); HbA1c, 6.9 ± 1.0%) completed an 8-week energy-restricted (approximately 6-7 MJ, 30% deficit) diet. Cognitive functioning (short-term memory, working memory, speed of processing [inspection time], psychomotor speed, and executive function) was assessed during four practice sessions, baseline, and Week 8. Parallel glucose levels were attained using the CGMS in 27 subjects. Outcomes were assessed by fasting blood glucose (FBG), postprandial peak glucose (G(max)), time spent >12 mmol/L (T > 12), and 24-h area under the glucose curve (AUC(24)).

RESULTS

Despite a fall in FBG of 0.65 mmol/L after 8 weeks, digits backward results correlated with FBG at both Week 0 and Week 8 (r = -0.43, P < 0.01 and r = -0.32, P < 0.01, respectively). Digits forward results correlated with FBG (r = -0.39, P < 0.01), G(max) (r = -0.46, P < 0.05), and AUC(24) (r = -0.50, P < 0.01) at Week 0 and FBG (r = -0.59, P < 0.001), G(max) (r = 0.37, P = 0.01), AUC(24) (r = -0.41, P < 0.01), and percentage weight loss (r = 0.31, P < 0.01) at Week 8. Cognitive function was not altered by weight loss, gender, baseline lipid levels, or premorbid intelligence levels (National Adult Reading Test).

CONCLUSIONS

FBG, G(max,) and AUC(24) were related to cognitive function and an energy-restricted diet for 8 weeks did not alter this relationship.

Diabetes and the elderly brain: sweet memories?

Type 2 diabetes is common in older people and is associated with higher risk of both vascular dementia and Alzheimer's disease. This review examines the evidence for increased risk of dementia and mild cognitive impairment in patients with diabetes and the role of potential confounders. The relationship of diabetes and impaired fasting glucose with brain structure is also reviewed, focusing on longitudinal studies in older people. The pathophysiology underlying cognitive change in type 2 diabetes is examined with reference to vascular disease, hypoglycaemia, inflammation and insulin levels. Implications for clinical care in older people with diabetes are discussed, with a recommendation for cognitive evaluation as a routine part of end-organ, diabetes complication review.