Intensive multifactorial treatment and cognitive functioning in screen-detected type 2 diabetes--the ADDITION-Netherlands study: a cluster-randomized trial

Systematic evaluation and meta-analysis of the effects of major dietary patterns on cognitive function in healthy adults

PURPOSE

Evidence shows diet promotes brain health. Combining foods and nutrients may have beneficial synergistic effects, but the effects on cognitive function interventions are inconsistent. So, a meta-analysis of RCTs was conducted to examine the specific effects on cognitive function.

METHODS

We searched four databases from creation to April 2023. Eligible randomized controlled trials were identified. A random-effects meta-analysis was used to combine standardized mean differences (SMD) (95% confidence intervals [CI]), and homogeneity tests for a variance were calculated.

RESULTS

A total of 19 studies involving 12,119 participants were included in this systematic review. The dietary intervention group had a positive effect on overall cognitive functioning compared to the control group (SMD = 0.14, 95% CI [0.08, 0.20], P < 0.00001). The dietary intervention improved executive function, processing speed and language skills (SMD = -0.10, 95% CI [-0.17,-0.04], P = 0.002, I2 = 0%), (SMD = -0.16, 95% CI [-0.23,-0.09], P < 0.00001, I2 = 0%), (SMD = 0.10, 95% CI [0.01, 0.20], P = 0.03, I2 = 0%). The dietary intervention had no effect on delayed memory and spatial ability (SMD = 0.04, 95% CI [-0.02, 0.09], P = 0.20, I2 = 0%), (SMD = 0.08, 95% CI [-0.01, 0.16], P = 0.08, I2 = 0%).

CONCLUSION

The Mediterranean diet, a diet with restricted caloric intake, a diet incorporating aerobic exercise, a low-carbohydrate diet, and a healthy lifestyle diet (increased intake of fruits and vegetables, and weight and blood pressure management) appear to have positive effects on cognitively healthy adults, as reflected in their overall cognitive, processing speed, executive, and language functions.

PROSPERO REGISTRATION NUMBER

CRD42023414704.

Intensified Multifactorial Intervention in Patients with Type 2 Diabetes Mellitus

In the management of diabetes mellitus, one of the most important goals is to prevent its micro- and macrovascular complications, and to that end, multifactorial intervention is widely recommended. Intensified multifactorial intervention with pharmacotherapy for associated risk factors, alongside lifestyle modification, was first shown to be efficacious in patients with microalbuminuria (Steno-2 study), then in those with less advanced microvascular complications (the Anglo-Danish-Dutch Study of Intensive Treatment In People with Screen Detected Diabetes in Primary Care [ADDITION]-Europe and the Japan Diabetes Optimal Treatment study for 3 major risk factors of cardiovascular diseases [J-DOIT3]), and in those with advanced microvascular complications (the Nephropathy In Diabetes-Type 2 [NID-2] study and Diabetic Nephropathy Remission and Regression Team Trial in Japan [DNETT-Japan]). Thus far, multifactorial intervention led to a reduction in cardiovascular and renal events, albeit not necessarily significant. It should be noted that not only baseline characteristics but also the control status of the risk factors and event rates during intervention among the patients widely varied from one trial to the next. Further evidence is needed for the efficacy of multifactorial intervention in a longer duration and in younger or elderly patients. Moreover, now that new classes of antidiabetic drugs are available, it should be addressed whether strict and safe glycemic control, alongside control of other risk factors, could lead to further risk reductions in micro- and macrovascular complications, thereby decreasing all-cause mortality in patients with type 2 diabetes mellitus.

Multi-Domain Interventions for Dementia Prevention - A Systematic Review

OBJECTIVES

There is a growing incidence of cognitive decline and dementia associated with the ageing population. Lifestyle factors such as diet, physical activity, and cognitive activities may individually or collectively be undertaken to increase one's odds of preventing cognitive decline and future dementia. This study will examine whether clinical trials using multidomain lifestyle intervention can significantly decrease the risk of cognitive decline and therefore dementia.

DESIGN, SETTING AND PARTICIPANTS

This systematic literature review of multidomain lifestyle interventions for the prevention of cognitive decline and dementia followed the PRISMA guidelines. Clinical trials involving multidomain intervention (i.e., diet and physical activity, or without cognitive training) in older adults (≥ 49 years old) at higher risk of dementia were identified through 5 electronic databases (EMBASE, MEDLINE, CINAHL, Cochrane, and Scopus). A comprehensive search was performed to identify and retrieve publications until 15 November 2022. Trials were published in English.

RESULTS

The included studies (n=15) assessed change in cognition in response to a multidomain lifestyle intervention. However, the cognitive outcome measures used in these studies were heterogeneous. Despite this heterogeneity, two thirds of the studies showed improvement in cognition following a multidomain intervention (n=10 with a total of 9,439 participants). However, five studies reported no improvement in cognition following the multidomain intervention. The most common form of dietary intervention included higher amount of fruit and vegetable intake; whole-grain cereal products instead of refined; low fat options in milk and meat products; and limiting sucrose intake to less than 50 g/day. Most clinical trial studies were powered to examining the effects of multidomain interventions in cognition but were not designed to test the contribution of individual domains (i.e., dietary changes, increased physical activity, or increased cognitive stimulation alone).

CONCLUSION

This systematic review aimed to determine the effect of multimodal lifestyle interventions on cognitive outcomes in older adults at risk of dementia. We found that participants with conditions that may increase the risk of dementia, (e.g., hypertension, cardiovascular fragility) do benefit from multi-modal lifestyle changes including diet, physical activity, and cognitive training. Two thirds of studies using multidomain lifestyle interventions showed improvements in cognitive function. Trials with a focus on cognitive training, dietary improvement, and physical activity may prevent or delay cognitive decline in older adults including those at risk of developing dementia. Future studies should consider longer follow-up periods and adequate power to be able to examine the effects of each lifestyle component in the context of multimodal interventions.

Cross-sectional association of metrics derived from continuous glucose monitoring with cognitive performance in older adults with type 2 diabetes

AIM

To examine the association between continuous glucose monitoring (CGM)-derived metrics and cognitive performance in older adults with type 2 diabetes (T2D).

MATERIALS AND METHODS

A total of 100 outpatients with T2D aged 70 years or older were analysed. Participants underwent CGM for 14 days. As CGM-derived metrics, mean sensor glucose (SG), glucose coefficient of variation (CV), time in range (TIR; 70-180 mg/dl), time above range (TAR; > 180 mg/dl) and time below range (TBR; < 70 mg/dl), were calculated. Participants underwent cognitive tests, including the Japanese version of the Montreal Cognitive Assessment (MoCA-J), a delayed word-recall test from the Alzheimer's Disease Assessment Scale-cognitive subscale, a digit symbol substitution test, a letter word fluency test, a trail-making test (TMT) and digit span test (DSP).

RESULTS

In multiple regression analyses adjusted for confounders, a higher mean SG was associated with a lower performance in MoCA-J and TMT part B (TMT-B) (P < .05). A higher TAR was associated with a lower performance in TMT-B and DSP-backward (P < .05). By contrast, a higher TIR was associated with better function in TMT-B and DSP-backward (P < .05). Furthermore, CV and TBR were not associated with any cognitive function.

CONCLUSION

Hyperglycaemia metrics and TIR derived from CGM are associated with cognitive functions, especially with executive function and working memory, in older adults with T2D.

New Horizons-Cognitive Dysfunction Associated With Type 2 Diabetes

The prevalence of type 2 diabetes (T2D) and cognitive dysfunction increases with age. As society ages, clinicians will be increasingly tasked with managing older people who have both T2D and cognitive dysfunction. T2D is associated with an increased risk of cognitive dysfunction and hence there is increasing interest in whether T2D is a causal factor in the pathogenesis of cognitive decline and dementia. Recent advances in the use of sensitive measures of in vivo brain dysfunction in life-course studies can help understand potential mechanistic pathways and also help guide recommendations for clinical practice. In this article we will describe new horizons in the understanding of cognitive dysfunction associated with T2D. Coming from a clinical perspective, we discuss potential mechanisms and pathways linking the 2 conditions and the contribution of multimodal neuroimaging and study designs to advancing understanding in the field. We also highlight the important issues on the horizon that will need addressing in clinical identification, management, and risk reduction for people with coexistent T2D and cognitive dysfunction.

Females with type 2 diabetes are at higher risk for accelerated cognitive decline than males: CAROLINA-COGNITION study

BACKGROUND AND AIM

Cognitive dysfunction is increasingly recognized as an important comorbidity of type 2 diabetes (T2D). We aimed to establish if the risk of accelerated cognitive decline (ACD) is higher in females with T2D than males.

METHODS AND RESULTS

3163 participants (38% female) with T2D from the cognition substudy of CAROLINA® (NCT01243424) were included (mean age 64.4 ± 9.2 years; T2D duration 7.6 ± 6.1 years). The cognitive outcome was occurrence of ACD at end of follow-up, defined as a regression based index score ≤16th percentile on either the Mini-Mental State Examination (MMSE) or a composite measure of attention and executive functioning (Trail Making and Verbal Fluency Test). Potential confounders, were taken into account at an individual patient level. Logistic regression analysis was used to investigate ACD risk by sex. We assessed potential mediators for sex differences in ACD using Causal Mediation Analysis (CMA). After a median follow-up duration of 6.1 ± 0.7 years, 361 (30.0%) females compared to 494 (25.2%) males exhibited ACD (OR 1.27 [95%CI 1.08-1.49], p = .003). Depressive symptoms, which were more common in females (24.3% vs 12.5%), mediated between sex and ACD (mediation effect 20.3%, p = 0.03). There were no other significant mediators.

CONCLUSION

Females with T2D had a higher risk of ACD compared to males. This was partly explained by depressive symptoms. After evaluation of vascular and diabetes-related risk factors, complications and treatment, a major share of the higher risk of ACD in females remained unexplained. Our results highlight the need for further research on causes of sex-specific ACD in T2D.

Trials and Treatments for Vascular Brain Health: Risk Factor Modification and Cognitive Outcomes

There is robust evidence linking vascular health to brain health, cognition, and dementia. In this article, we present evidence from trials of vascular risk factor treatment on cognitive outcomes. We summarize findings from randomized controlled trials of antihypertensives, lipid-lowering medications, diabetes treatments (including antidiabetic drugs versus placebo, and intensive versus standard glycemic control), and multidomain interventions (that target several domains simultaneously such as control of vascular and metabolic factors, nutrition, physical activity, and cognitive stimulation etc). We report that evidence on the efficacy of vascular risk reduction interventions is promising, but not yet conclusive, and several methodological limitations hamper interpretation. Evidence mainly comes from high-income countries and, as cognition and dementia have not been the primary outcomes of many trials, evaluation of cognitive changes have often been limited. As the cognitive aging process occurs over decades, it is unclear whether treatment during the late-life window is optimal for dementia prevention, yet older individuals have been the target of most trials thus far. Further, many trials have not been powered to explore interactions with modifiers such as age, race, and apolipoprotein E, even though sub-analyses from some trials indicate that the success of interventions differs depending on patient characteristics. Due to the complex multifactorial etiology of dementia, and variations in risk factors between individuals, multidomain interventions targeting several risk factors and mechanisms are likely to be needed and the long-term sustainability of preventive interventions will require personalized approaches that could be facilitated by digital health tools. This is especially relevant during the coronavirus disease 2019 (COVID-19) pandemic, where intervention strategies will need to be adapted to the new normal, when face-to-face engagement with participants is limited and public health measures may create changes in lifestyle that affect individuals’ vascular risk profiles and subsequent risk of cognitive decline.

Association of Type 2 Diabetes, According to the Number of Risk Factors Within Target Range, With Structural Brain Abnormalities, Cognitive Performance, and Risk of Dementia

OBJECTIVE

Type 2 diabetes is associated with increased risks of cognitive dysfunction and brain abnormalities. The extent to which risk factor modification can mitigate these risks is unclear. We investigated the associations between incident dementia, cognitive performance, and brain abnormalities among individuals with type 2 diabetes, according to the number of risk factors on target, compared with control subjects without diabetes.

RESEARCH DESIGN AND METHODS

Prospective data were from UK Biobank of 87,856 individuals (n = 10,663 diabetes, n = 77,193 control subjects; baseline 2006-2010), with dementia follow-up until February 2018. Individuals with diabetes were categorized according to the number of seven selected risk factors within the guideline-recommended target range (nonsmoking; guideline-recommended levels of glycated hemoglobin, blood pressure, BMI, albuminuria, physical activity, and diet). Outcomes were incident dementia, domain-specific cognitive performance, white matter hyperintensities, and total brain volume.

RESULTS

After a mean follow-up of 9.0 years, 147 individuals (1.4%) with diabetes and 412 control subjects (0.5%) had incident dementia. Among individuals with diabetes, excess dementia risk decreased stepwise for a higher number of risk factors on target. Compared with control subjects (incidence rate per 1,000 person-years 0.62 [95% CI 0.56; 0.68]), individuals with diabetes who had five to seven risk factors on target had no significant excess dementia risk (absolute rate difference per 1,000 person-years 0.20 [-0.11; 0.52]; hazard ratio 1.32 [0.89; 1.95]). Similarly, differences in processing speed, executive function, and brain volumes were progressively smaller for a higher number of risk factors on target. These results were replicated in the Maastricht Study.

CONCLUSIONS

Among individuals with diabetes, excess dementia risk, lower cognitive performance, and brain abnormalities decreased stepwise for a higher number of risk factors on target.

Glycated haemoglobin (HbA1c ), diabetes and neuropsychological performance in community-dwelling older adults

AIMS

Given that diabetes is associated with cognitive impairment and dementia in later life, we aimed to investigate the relationship between glycated haemoglobin (HbA_1c ), diabetes and domain-specific neuropsychological performance in older adults.

METHODS

Cross-sectional cohort study using data from the Trinity-Ulster-Department of Agriculture (TUDA) study. Participants underwent detailed cognitive and neuropsychological assessment using the Mini-Mental State Examination (MMSE), Frontal Assessment Battery (FAB) and Repeatable Assessment for Neuropsychological Status (RBANS). Linear regression was used to assess associations between HbA_1c , diabetes status and neuropsychological performance, with adjustment for important clinical covariates.

RESULTS

Of 4938 older adults (74.1 ± 8.3 years; 66.9% female), 16.3% (n = 803) had diabetes (HbA_1c  ≥ 6.5%; 48 mmol/mol), with prediabetes (HbA_1c  ≥ 5.7%-6.4%; 39-47 mmol/mol) present in 28.3% (n = 1395). Increasing HbA_1c concentration was associated with poorer overall performance on the FAB [β: -0.01 (-0.02, -0.00); p = 0.04 per % increase] and RBANS [β = -0.66 (-1.19, -0.13); p = 0.02 per % increase]. Increasing HbA_1c was also associated with poorer performance on immediate memory, visuo-spatial, language and attention RBANS domains. Diabetes was associated poorer performance on neuropsychological tests of immediate memory, language, visual-spatial and attention.

CONCLUSIONS

Both increasing HbA_1c and the presence of diabetes were associated with poorer cognitive and domain-specific performance in older adults. HbA_1c , and not just diabetes status per se, may represent an important target in the promotion of optimal brain health in older adults.

The Multi-Domain Intervention Trial in Older Adults With Diabetes Mellitus for Prevention of Dementia in Japan: Study Protocol for a Multi-Center, Randomized, 18-Month Controlled Trial

Background: The Japan-Multi-domain Intervention Trial for Prevention of Dementia in Older Adults with Diabetes (J-MIND-Diabetes) is an 18-month, multi-centered, open-labeled, randomized controlled trial designed to identify whether multi-domain intervention targeting modifiable risk factors for dementia could prevent the progression of cognitive decline among older adults with type 2 diabetes mellitus (T2DM). This manuscript describes the study protocol for the J-MIND-Diabetes trial. Materials and Methods: Subjects of this trial will comprise a total of 300 T2DM outpatients aged 70-85 years with mild cognitive impairment. Subjects will be centrally randomized into intervention and control groups at a 1:1 allocation ratio using the stratified permuted-block randomization methods. The intervention group will participate in multi-domain intervention programs aimed at: (1) management of metabolic and vascular risk factors; (2) physical exercise and self-monitoring of physical activity; (3) nutritional guidance; and (4) social participation. The control group will receive usual T2DM care and general instructions on dementia prevention. The primary and secondary outcomes will be assessed at baseline, at 6- and 18-month follow-up. The primary outcome is change from baseline at 18 months in a global composite score combining several neuropsychological domains, including global cognitive function, memory, attention, executive function, processing speed and language. Secondary outcomes include: (1) cognitive changes in neuropsychological tests; (2) changes in geriatrics assessments; (3) metabolic control and diabetic complications; (4) changes in blood and urinary markers. Discussion: This trial will be the first trial to demonstrate the effectiveness of multi-domain intervention in preventing cognitive decline in older adults with T2DM at increased risk of dementia in Japan. Trial Registration: UMIN000035911; Registered on the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) 18 February 2019. (https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000040908).

DL-3-n-butylphthalide ameliorates diabetes-associated cognitive decline by enhancing PI3K/Akt signaling and suppressing oxidative stress

DL-3-n-Butylphthalide (DL-NBP), a small molecular compound extracted from the seeds of Apium graveolens Linn (Chinese celery), has been shown to exert neuroprotective effects due to its anti-inflammatory, anti-oxidative and anti-apoptotic activities. DL-NBP not only protects against ischemic cerebral injury, but also ameliorates vascular cognitive impairment in dementia patients including AD and PD. In the current study, we investigated whether and how DL-NBP exerted a neuroprotective effect against diabetes-associated cognitive decline (DACD) in db/db mice, a model of type-2 diabetes. db/db mice were orally administered DL-NBP (20, 60, 120 mg· kg-1· d-1) for 8 weeks. Then the mice were subjected to behavioral test, their brain tissue was collected for morphological and biochemical analyses. We showed that oral administration of DL-NBP significantly ameliorated the cognitive decline with improved learning and memory function in Morris water maze testing. Furthermore, DL-NBP administration attenuated diabetes-induced morphological alterations and increased neuronal survival and restored the levels of synaptic protein PSD95, synaptophysin and synapsin-1 as well as dendritic density in the hippocampus, especially at a dose of 60 mg/kg. Moreover, we revealed that DL-NBP administration suppressed oxidative stress by upregulating Nrf2/HO-1 signaling, and increased brain-derived neurotrophic factor (BDNF) expression by activating PI3K/Akt/CREB signaling in the hippocampus. These beneficial effects of DL-NBP were observed in high glucose-treated PC12 cells. Our results suggest that DL-NBP may be a potential pharmacologic agent for the treatment of DACD.

Impact of Intensive Glucose Control on Brain Health: Meta-Analysis of Cumulative Data from 16,584 Patients with Type 2 Diabetes Mellitus

INTRODUCTION

Despite growing evidence that type 2 diabetes is associated with dementia, the question of whether intensive glucose control can prevent or arrest cognitive decline remains unanswered. In the analysis reported here, we explored the effect of intensive glucose control versus standard care on brain health, including structural abnormalities of the brain (atrophy, white matter hyperintensities, lacunar infarction, and cerebral microbleeds), cognitive dysfunction, and risk of dementia.

METHODS

We searched the PubMed and Embase databases, the Web of Science website, and the Clinicaltrial.gov registry for studies published in English prior to July 2020. Only studies with a randomized controlled trial (RCT) design were considered. We analyzed structural abnormalities of the brain (atrophy, white matter hyperintensities, lacunar infarction, and cerebral microbleeds), cognitive function (cognitive impairment, executive function, memory, attention, and information-processing speed), and dementia (Alzheimer's disease, vascular dementia, and mixed dementia).

RESULTS

Six studies (5 different RCTs) with 16,584 participants were included in this meta-analysis. One study that compared structural changes between groups receiving intensive versus conventional glucose control measures reported non-significant results. The results of the five studies, comprising four cohorts, indicated a significantly poorer decline in cognitive function in the intensive glucose control group (β - 0.03, 95% confidence interval [CI] - 0.05 to - 0.02) than in the conventional glucose control group. Further subgroup analysis showed a significant difference in the change in cognitive performance in composite cognitive function (β - 0.03, 95% CI - 0.05 to - 0.01) and memory (β  - 0.13, 95% CI - 0.25 to - 0.02). One trial evaluated the prevalence of cognitive impairment and dementia between groups receiving intensive and conventional glucose control, respectively, and the differences were insignificant.

CONCLUSION

This meta-analysis suggests that intensive glucose control in patients with type 2 diabetes can slow down cognitive decline, especially the decline in composite cognition and memory function. However, further studies are necessary to confirm the impact of strict glucose control on structural abnormalities in the brain and the risk of dementia.

Long-term Change in Physiological Markers and Cognitive Performance in Type 2 Diabetes: The Look AHEAD Study

CONTEXT

The effects of physiological improvements on cognitive function among persons with type 2 diabetes mellitus (T2DM) are not fully understood.

OBJECTIVE

To determine whether improvements in physiological markers (body weight, blood sugar control, and physical activity) during intensive lifestyle intervention (ILI) are associated with enhancements in cognitive function in older adults with T2DM.

DESIGN

Multisite randomized controlled trial.

SETTING

Academic research centers.

PATIENTS OR OTHER PARTICIPANTS

Participants were aged 45-76 years, with T2DM.

INTERVENTION

The Action for Health in Diabetes (Look AHEAD) study, a randomized, controlled clinical trial of ILI.

MAIN OUTCOME MEASURE

Two to 3 cognitive assessments were collected from 1089 participants, the first and last occurring a mean (standard deviation) of 8.6 (1.0) and 11.5 (0.7) years after enrollment.

RESULTS

Greater improvement in blood sugar control was associated with better cognitive scores (fasting glucose and Rey Auditory Verbal Learning Test [AVLT]: P = 0.0148; fasting glucose and Digit Symbol Coding (DSC): P = 0.0360; HbA1C and DSC: P = 0.0477); but weight loss had mixed associations with cognitive scores (greater body mass index [BMI] reduction and worse AVLT overall: P = 0.0053; and greater BMI reduction and better DSC scores among those overweight but not obese at baseline: P = 0.010). Associations were strongest among those who were overweight (not obese) at baseline, and among those with a history of cardiovascular disease (CVD) at baseline.

CONCLUSIONS

Improvements in glycemic control, but not necessarily weight status, during ILI may be associated with better subsequent cognitive performance. These associations may differ by adiposity and CVD history.

Effect of poor glycemic control in cognitive performance in the elderly with type 2 diabetes mellitus: The Mexican Health and Aging Study

Background

Cognitive impairment is twice more frequent in elderly with type 2 diabetes mellitus (DM). This study was conducted to determine the association between glycemic control and cognitive performance among community-dwelling elderly persons in Mexico.

Methods

Cross-sectional study conducted in individuals aged 60 years or elderly participating in the 2012 Mexican Health and Aging Study. Type 2 DM participants were classified in 3 groups according to their glycated hemoglobin levels (Hb_A1c): < 7% (intensive control), 7–7.9% (standard control) or ≥ 8% (poor control), and cognitive performance: low (CCCE ≤44 points), intermediate (44.1–59.52 points), or high (≥59.53 points). Multinomial logistic regression models were constructed to determine this association.

Results

Two hundred sixteen community-dwelling adults aged 60 and older with type 2 diabetes were selected. Subjects in the low cognitive performance group were older (69.7 ± 6.6 vs 65.86 ± 5.18 years, p < .001) and had a lower educational level (2.5 ± 2.6 vs 7.44 ± 4.15 years, p < .000) when compared to the high cognitive performance participants. Hb_A1c ≥ 8% was associated with having low (Odds Ratio (OR) 3.17, 95% CI 1.17–8.60, p = .024), and intermediate (OR 3.23, 95% CI 1.27–8.20, p = .014) cognitive performance; this trend was not found for Hb_A1c 7.0–7.9% group.

The multinomial regression analysis showed that the presence of Hb_A1c ≥ 8% (poor glycemic control) was associated with low (OR 3.17, 95% CI = 1.17–8.60, p = .024), and intermediate (OR 3.23, 95% CI = 1.27–8.20, p = .014) cognitive performance. After adjusting for confounding variables.

Conclusions

Glycemic control with a Hb_A1c ≥ 8% was associated with worse cognitive performance.

The ER stress-autophagy axis: implications for cognitive dysfunction in diabetes mellitus

Unfolded protein response (UPR) often coordinates with autophagy to maintain cellular proteostasis. Disturbance of proteostasis correlates with diseases including diabetes and neurological complications. In a recent article in Clinical Science, Kong et al. highlighted the critical role of endoplasmic reticulum (ER) stress-autophagy axis in maintaining cognitive functions and provided pharmacological evidence with respect to cognitive improvements in a diabetic mouse model. These novel findings present new insights into the pathological mechanisms and therapeutic implications with the ER stress modulators in diabetes-related cognitive dysfunction.

Type 2 diabetes and cognitive dysfunction-towards effective management of both comorbidities

Type 2 diabetes and cognitive dysfunction are highly prevalent disorders worldwide. Although type 2 diabetes is associated with an increased risk of dementia, awareness of the link between the two conditions is poor, and few recommendations are available to guide clinicians about how to approach cognitive dysfunction in people with diabetes. Clinical guidelines in diabetes have only recently begun to emphasise the importance of cognitive impairment in diabetes and its management. This Series paper aims to synthesise knowledge about the link between diabetes and cognitive dysfunction, issues pertaining to screening and diagnosis of cognitive impairment and dementia in those with type 2 diabetes, management of diabetes in people with cognitive dysfunction (accounting for age and frailty), and emerging therapies for prevention. A conceptual framework for approaching screening and diagnosis is included, and future research directions to guide the field forward are suggested.

Pathways of Prevention: A Scoping Review of Dietary and Exercise Interventions for Neurocognition

Alzheimer's disease and related dementias (ADRD) represent an increasingly urgent public health concern, with an increasing number of baby boomers now at risk. Due to a lack of efficacious therapies among symptomatic older adults, an increasing emphasis has been placed on preventive measures that can curb or even prevent ADRD development among middle-aged adults. Lifestyle modification using aerobic exercise and dietary modification represents one of the primary treatment modalities used to mitigate ADRD risk, with an increasing number of trials demonstrating that exercise and dietary change, individually and together, improve neurocognitive performance among middle-aged and older adults. Despite several optimistic findings, examination of treatment changes across lifestyle interventions reveals a variable pattern of improvements, with large individual differences across trials. The present review attempts to synthesize available literature linking lifestyle modification to neurocognitive changes, outline putative mechanisms of treatment improvement, and discuss discrepant trial findings. In addition, previous mechanistic assumptions linking lifestyle to neurocognition are discussed, with a focus on potential solutions to improve our understanding of individual neurocognitive differences in response to lifestyle modification. Specific recommendations include integration of contemporary causal inference approaches for analyzing parallel mechanistic pathways and treatment-exposure interactions. Methodological recommendations include trial multiphase optimization strategy (MOST) design approaches that leverage individual differences for improved treatment outcomes.

Autophagy Activation is Associated with Neuroprotection in Diabetes-associated Cognitive Decline

Autophagy is a lysosome-dependent cellular catabolic mechanism that mediates the turnover of dysfunctional organelles and aggregated proteins. It has a neuroprotective role on neurodegenerative diseases. Here, we hypothesized that autophagy may also have a neuroprotective role in diabetes-associated cognitive decline (DACD). In current study, we found that db/db mice display cognitive decline with inferior learning and memory function. The accumulation of β-amyloid1-42 (Aβ1-42), which is a characteristic of Alzheimer's disease (AD), was markedly higher in the prefrontal cortex (PFC), cornu ammon1 (CA1), and dentate gyrus (DG) areas of the hippocampus in db/db mice. Moreover, BDNF and microtubule associated protein 2 (MAP2) levels were lower in the hippocampus of db/db mice. However, there was no noticeable differences in the level of apoptosis in the hippocampus between control (CON) mice and db/db mice. Markers of autophagy in the hippocampus were elevated in db/db mice. The expression levels of ATG5, ATG7, and LC3B were higher, and the level of P62 was lower. An autophagy inhibitor, 3-MA, and ATG7 siRNA significantly reversed the activation of autophagy in vitro, which was accompanied with a higher level of apoptosis. Taken together, our current study suggests that diabetes is associated with cognitive decline, and activation of autophagy has a neuroprotective role in DACD.

High-Normal Adolescent Fasting Plasma Glucose Is Associated With Poorer Midlife Brain Health: Bogalusa Heart Study

CONTEXT

It is unclear how adolescent glycemic status relates to brain health in adulthood.

OBJECTIVE

To assess the association between adolescent fasting plasma glucose (FPG) and MRI-based brain measures in midlife.

DESIGN

Between 1973 and 1992, the Bogalusa Heart Study (BHS) collected FPG from children, 3 to 18 years old, and followed up between 1992 and 2018. Cognitive tests and brain MRI were collected in 2013 to 2016 and 2018.

SETTING

Observational longitudinal cohort study.

PARTICIPANTS

Of 1298 contacted BHS participants, 74 completed screening, and 50 completed MRI.

MAIN OUTCOME MEASURES

Mean FPG per participant at ages <20, 20 to 40, and over 40 years old; brain white matter hyperintensity (WMH) volume, gray matter volume, and functional MRI (fMRI) activation to a Stroop task; tests of logical and working memory, executive function, and semantic fluency.

RESULTS

At MRI, participants were middle aged (51.3 ± 4.4 years) and predominantly female (74%) and white (74%). Mean FPG was impaired for zero, two, and nine participants in pre-20, 20 to 40, and over-40 periods. The pre-20 mean FPG above the pre-20 median value (i.e., above 83.5 mg/dL) was associated with greater WMH volume [mean difference: 0.029% of total cranial volume, CI: (0.0059, 0.052), P = 0.015] and less fMRI activation [-1.41 units (-2.78, -0.05), P = 0.043] on midlife MRI compared with below-median mean FPG. In controlling for over-40 mean FPG status did not substantially modify the associations. Cognitive scores did not differ by pre-20 mean FPG.

CONCLUSIONS

High-normal adolescent FPG may be associated with preclinical brain changes in midlife.

Interventions involving a major dietary component improve cognitive function in cognitively healthy adults: a systematic review and meta-analysis

Accumulating evidence suggests a role for diet in promoting brain health. The purpose of this systematic review was to (1) quantitatively assess whether interventions with a major dietary component can enhance cognition in cognitively healthy adults and (2) identify responsive domains of cognition to inform the design of future dietary trials. Electronic databases were systematically searched to find eligible randomized controlled trials that assessed the effect of interventions with a major dietary component on cognitive function or incident dementia in adults without known cognitive impairment. Standardized mean differences (SMDs) (95% confidence interval [CI]) were combined using a random-effects meta-analysis, and tests of homogeneity of variance were calculated. Two trials reported dementia outcomes and were qualitatively described. Fifteen trials encompassing 6480 participants were eligible for meta-analysis. Compared to control, intervention improved performance on measures of global cognition (SMD = 0.14, 95% CI 0.01-0.27, P = .05, I² 76%), executive function (SMD = 0.11, 95% CI 0.04-0.18, P = .003, I² 0%), and processing speed (SMD = 0.12, 95% CI 0.05-0.19, P = .001, I² 0%). There was no effect of intervention on delayed memory (SMD = 0.04, 95% CI -0.02 to 0.09, P = .18, I² 4%). Significant heterogeneity and funnel plot asymmetry were detected for global cognition, but removal of studies with high risk of bias did not change the pooled findings. Current evidence is limited but indicates that diverse interventions improve nonmemory cognitive functions during normal cognitive aging. Measures of executive function and processing speed should be considered as feasible end points in future dietary intervention trials.

Commentary on: "Effects of Regular Physical Activity on the Cognitive Performance of Type 2 Diabetic Patients: A Systematic Review" by Podolski et al. (Metab Syndr Relat Disord 2017;15:481-493)

Type 2 diabetes mellitus (T2DM) imparts an increased risk for cognitive decline, specifically executive function, which is important to maintain for diabetes self-management. There is evidence to suggest that exercise improves cognition in healthy older adults; however, the literature in adults with T2DM is lacking. This commentary is in complement to Podolski et al.'s systematic review evaluating the effects of physical activity on cognitive function in adults with T2DM. We have included eight additional studies and further highlight their conclusions on the heterogeneity of the literature thus far. Three current issues with the literature are as follows: (1) variability in interventions (e.g., aerobic, resistance, lifestyle, and yoga), (2) variability in cognitive outcome measures, and (3) lack of detailed description of the population studied, for example, baseline glycated hemoglobin (A1C) values. Overall, making it difficult to compare these studies and draw final conclusions. Thus, the efficacy for exercise to improve cognition in adults with T2DM is not yet well understood. Potential ways to mitigate these limitations could be for future studies that (1) use robust methodology whenever possible, that is, randomized controlled trials, (2) to follow current guideline-derived exercise recommendations for adults with T2DM, and (3) utilize cognitive outcome measures that are consistent across studies. The hope is that these consistencies in turn will help to determine the efficacy of exercise on cognitive function in adults with T2DM and therefore, allow national organizations to develop recommendations and guidelines for healthcare practitioners to follow.

HbA1c, diabetes and cognitive decline: the English Longitudinal Study of Ageing

AIMS/HYPOTHESIS

The aim of the study was to evaluate longitudinal associations between HbA_1c levels, diabetes status and subsequent cognitive decline over a 10 year follow-up period.

METHODS

Data from wave 2 (2004-2005) to wave 7 (2014-2015) of the English Longitudinal Study of Ageing (ELSA) were analysed. Cognitive function was assessed at baseline (wave 2) and reassessed every 2 years at waves 3-7. Linear mixed models were used to evaluate longitudinal associations.

RESULTS

The study comprised 5189 participants (55.1% women, mean age 65.6 ± 9.4 years) with baseline HbA_1c levels ranging from 15.9 to 126.3 mmol/mol (3.6-13.7%). The mean follow-up duration was 8.1 ± 2.8 years and the mean number of cognitive assessments was 4.9 ± 1.5. A 1 mmol/mol increment in HbA_1c was significantly associated with an increased rate of decline in global cognitive z scores (-0.0009 SD/year, 95% CI -0.0014, -0.0003), memory z scores (-0.0005 SD/year, 95% CI -0.0009, -0.0001) and executive function z scores (-0.0008 SD/year, 95% CI -0.0013, -0.0004) after adjustment for baseline age, sex, total cholesterol, HDL-cholesterol, triacylglycerol, high-sensitivity C-reactive protein, BMI, education, marital status, depressive symptoms, current smoking, alcohol consumption, hypertension, CHD, stroke, chronic lung disease and cancer. Compared with participants with normoglycaemia, the multivariable-adjusted rate of global cognitive decline associated with prediabetes and diabetes was increased by -0.012 SD/year (95% CI -0.022, -0.002) and -0.031 SD/year (95% CI -0.046, -0.015), respectively (p for trend <0.001). Similarly, memory, executive function and orientation z scores showed an increased rate of cognitive decline with diabetes.

CONCLUSIONS/INTERPRETATION

Significant longitudinal associations between HbA_1c levels, diabetes status and long-term cognitive decline were observed in this study. Future studies are required to determine the effects of maintaining optimal glucose control on the rate of cognitive decline in people with diabetes.

Interaction Between Midlife Blood Glucose and APOE Genotype Predicts Later Alzheimer's Disease Pathology

Elevated blood glucose and the apolipoprotein (APOE) ɛ4 allele have both been associated with increased dementia risk; however, the neuropathological mechanisms underlying these associations remain unclear. We examined the impact of APOE genotype and midlife blood glucose on post-mortem vascular and Alzheimer's disease (AD) neuropathology. Ninety-four participants from the Framingham Heart Study without diagnosed diabetes underwent health examination at midlife and brain autopsy at death. Histopathological measures of vascular and AD neuropathology were obtained and analyzed. Results demonstrated that, among APOE ɛ4 carriers, elevated blood glucose was associated with more severe AD pathology. There was no such relationship with vascular pathology. In a relatively healthy sample with low vascular risk burden, midlife elevated blood glucose was associated with greater AD pathology among APOE ɛ4 carriers. A better understanding of interactive effects of APOE genotype and vascular risk on neuropathology has implications for identification of individuals at risk for decline and long-term preventive treatment.

Rationale and design of the CAROLINA® - cognition substudy: a randomised controlled trial on cognitive outcomes of linagliptin versus glimepiride in patients with type 2 diabetes mellitus

Background

Type 2 diabetes mellitus is associated with cognitive dysfunction and an increased risk of dementia. Linagliptin is a glucose-lowering agent of the dipeptidyl peptidase-IV (DPP-IV) inhibitor class that is of particular interest for the prevention of accelerated cognitive decline, because it may potentially benefit the brain through pleiotropic effects, beyond glucose lowering. This paper presents the design of a study that aims to establish if linagliptin is superior to the sulfonylurea glimepiride in the prevention of accelerated cognitive decline in patients with type 2 diabetes mellitus.

Methods

The cognition substudy is an integral part of the ongoing event-driven, randomised, double blind CARdiOvascular safety of LINAgliptin (CAROLINA®) trial, which evaluates the effect of treatment with linagliptin versus glimepiride on cardiovascular outcomes. CAROLINA® includes patients with type 2 diabetes mellitus with sub-optimal glycaemic control at elevated cardiovascular risk. The substudy will evaluate patients randomised and treated who have a baseline Mini Mental State Examination (MMSE) score ≥ 24, documented years of formal education with at least one valid cognitive assessment at baseline and during follow-up. The primary cognitive outcome is the occurrence of accelerated cognitive decline at the end of follow-up. The two treatment groups will be compared by using a logistic regression. Accelerated cognitive decline is defined as a rate of cognitive decline that falls at or below the 16th percentile of decline for the whole cohort on either the MMSE or a combined score of the trail making and verbal fluency test. Potential confounders are taken into account at an individual patient level, using a regression based index.

Discussion

Between December 2010 and December 2012, 6042 patients were randomised and treated with either linagliptin (5 mg) or glimepiride (1-4 mg) once daily in CAROLINA®. Cognitive tests were conducted in nearly 4500 participants at baseline and are scheduled for two subsequent assessments, after 160 weeks of follow-up and end of follow-up. This substudy of the ongoing CAROLINA® trial will establish if linagliptin is superior to glimepiride in the prevention of accelerated cognitive decline in patients with type 2 diabetes mellitus. Final results are expected in 2019.

Trial registration

ClinicalTrials.gov Identifier: NCT 01243424.

Electronic supplementary material

The online version of this article (10.1186/s12883-018-1014-7) contains supplementary material, which is available to authorized users.

Cognitive performance of older adults in a specialized diabetes clinic

BACKGROUND

Diabetes mellitus is a risk factor for cognitive changes, but assessment for cognitive disorders in this population is performed infrequently. The present study examined the frequency of cognitive disorders and patterns of deficit in patients enrolled in a specialized clinic for diabetes.

METHODS

A cross-sectional study was conducted to assess cognition in Mount Sinai Diabetes Center patients. Thirty eligible subjects aged ≥50 years were assessed and compared with non-diabetic cognitively normal control subjects, as well as non-diabetic subjects with mild cognitive impairment (MCI). The main outcome(s) and measure(s) were obtained through cognitive assessment and diagnosis using the Alzheimer's Disease Centers' uniform data set.

RESULTS

Forty percent of subjects were newly diagnosed with a cognitive disorder: 10% were diagnosed with dementia and 30% with MCI. Diabetic subjects performed worse on the Mini-Mental State Examination (27.2 vs 28.4; P = 0.0132), list generation (9.5 vs 12.2; P = 0.0190), Trail Making Test, Parts A (70.1 vs 43.0; P < 0.0001) and B (197.2 vs 123.6; P < 0.0001), and the Digit Symbol test (12.7 vs 40.1; P < 0.0001) than cognitively normal individuals. Compared with subjects with MCI (amnestic type), diabetic subjects performed better on tasks of immediate and delayed recall (11.2 vs 7.3 [P = 0.0048] and 8.4 vs. 4.1 [P = 0.0003], respectively).

CONCLUSIONS

Undiagnosed cognitive disorders are common and underappreciated in patients being treated in a specialized diabetes clinic. It may be important to make cognitive assessment a standard part of patient assessments.

Brain functional alterations in Type 2 Diabetes - A systematic review of fMRI studies

Type 2 Diabetes (T2DM) is emerging as a major global health issue. T2DM can adversely affect cognition and increase dementia risk. This systematic review aimed to examine the functional brain changes that may underlie cognitive dysfunction in adults with T2DM. Studies were restricted to those which used functional magnetic resonance imaging (fMRI). Nineteen independent studies were identified, mostly comprised of middle aged or older adults. Resting-state studies demonstrated that compared to controls, connectivity of the Default Mode Network (DMN) was reduced and the majority of task-based studies identified reduced activation in T2DM patients in regions relevant to task performance. Abnormalities of low frequency spontaneous brain activity were observed, particularly in visual regions. As most studies demonstrated that alterations in fMRI were related to poorer neuropsychological task performance, these results indicate that functional brain abnormalities in T2DM have consequences for cognition.

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.

Cognitive disorders in diabetic patients

This chapter gives an overview of the literature on cognitive dysfunction in adults with type 1 or type 2 diabetes. First, methods to evaluate cognitive functioning and the pattern and severity of cognitive dysfunction in relation to diabetes will be discussed. The reader will note that diabetes is associated with worse cognitive functioning and an increased dementia risk. Next, diabetes-associated abnormalities on brain MRI, including reductions in brain volume - i.e., cerebral atrophy - and vascular lesions, will be addressed. At the group level there are clear relations between these imaging abnormalities and cognitive dysfunction, but at the level of the individual patient these relations are often less clear. Subsequently, risk factors for cognitive performance will be discussed. Evidently, these risk factors are related to diabetes type and the age of the patients involved. For type 1 diabetes, an early age at diabetes onset is the most consistent risk factor, whereas in type 2 diabetes, vascular risk factors and vascular comorbidities are consistent indicators of increased risk. The final section of the chapter addresses possible preventive and treatment measures and implications for daily care.

A Narrative Review of Diabetes Intervention Studies to Explore Diabetes Care Opportunities for Pharmacists

Background. We conducted a review of current diabetes intervention studies in type 2 diabetes and identified opportunities for pharmacists to deliver quality diabetes care. Methods. A search on randomised controlled trials (RCT) on diabetes management by healthcare professionals including pharmacists published between 2010 and 2015 was conducted. Results and Discussion. Diabetes management includes multifactorial intervention which includes seven factors as outlined in diabetes guidelines, namely, glycaemic, cholesterol and blood pressure control, medication, lifestyle, education, and cardiovascular risk factors. Most studies do not provide evidence that the intervention methods used included all seven factors with exception of three RCT which indicated HbA1c (glycated hemoglobin) reduction range of 0.5% to 1.8%. The varied HbA1C reduction suggests a lack of standardised and consistent approach to diabetes care. Furthermore, the duration of most studies was from one month to two years; therefore long term outcomes could not be established. Conclusion. Although pharmacists' contribution towards improving clinical outcomes of diabetes patients was well documented, the methods used to deliver structured, consistent evidence-based care were not clearly stipulated. Therefore, approaches to achieving long term continuity of care are uncertain. An intervention strategy that encompass all seven evidence-based factors will be useful.

Memory and executive functions in persons with type 2 diabetes: a meta-analysis

Literature suggests that persons with type 2 diabetes mellitus (T2DM) are at risk for cognitive impairment, hence dementia. Common domains reported to be affected in those with T2DM are memory and executive functions. The extent of influence of T2DM on these domains has varied among studies. A systematic review and meta-analysis was carried out to understand whether sub-domains contributed to the variations observed in published research. We searched 'PubMed', 'ScienceDirect', 'SciVerseHub', 'Psychinfo', 'Proquest' 'Ebsco' and 'J-gate Plus' databases for published studies on cognition and T2DM among persons aged 50 years and older. Memory, executive functions and processing speed domain and sub-domain scores were extracted; effect sizes (Cohen's d) were calculated and analysed. Eight hundred seventeen articles were found. After various levels of filtering, 15 articles met the inclusion criteria for quantitative analyses. The analyses indicated that in comparison to controls, persons with T2DM showed decrements in episodic memory (d = -0.51), logical memory (d = -0.24), sub-domain of executive functions which included phonemic fluency (d = -0.35) and cognitive flexibility (d = 0.52), and speed of processing (d = -0.22). We found no difference in the sub-domains of verbal short-term memory and working memory. The meta-analysis revealed a detrimental effect of T2DM on cognitive sub-domains, namely, episodic memory and cognitive flexibility. There was a trend for the logical memory, phonemic fluency and processing speed to be affected. The analysis indicates that T2DM is a detrimental factor on certain cognitive sub-domains, rendering the person vulnerable to subsequent dementia. Copyright © 2016 John Wiley & Sons, Ltd.

Does Intensive Glucose Control Prevent Cognitive Decline in Diabetes? A Meta-Analysis

Diabetes mellitus is associated with cognitive decline and impaired performance in cognitive function tests among type 1 and type 2 diabetics. Even though the use of tight glucose control has been limited by a reported higher mortality, few reports have assessed the impact of treatment intensity on cognitive function. We conducted a meta-analysis to evaluate if an intensive glucose control in diabetes improves cognitive function, in comparison to standard therapy. We included 7 studies that included type 1 or type 2 diabetics and used standardized tests to evaluate various cognitive function domains. Standardized mean differences (SMDs) were calculated for each domain. We found that type 1 diabetics get no cognitive benefit from a tight glucose control, whereas type 2 diabetics get some benefit on processing speed and executive domains but had worse performances in the memory and attention domains, along with a higher incidence of mortality when using intensive glucose control regimes.

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.

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

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

Glycemia and cognitive function in metabolic syndrome and coronary heart disease

OBJECTIVE

Higher hemoglobin A1c (HbA1c) is associated with lower cognitive function in type 2 diabetes. To determine whether associations persist at lower levels of dysglycemia in patients who have established cardiovascular disease, cognitive performance was assessed in the Targeting INflammation Using SALsalate in CardioVascular Disease (TINSAL-CVD) trial.

METHODS

The age-adjusted relationships between HbA1c and cognitive performance measured by the Mini-Mental State Examination, Digit Symbol Substitution Test, Rey Auditory Verbal Learning Test, Trail Making Test, and Categorical Verbal Fluency were assessed in 226 men with metabolic syndrome and established stable coronary artery disease.

RESULTS

Of the participants, 61.5% had normoglycemia, 20.8% had impaired fasting glucose, and 17.7% had type 2 diabetes. HbA1c was associated with cognitive function tests of Digit Symbol Substitution Test, Rey Auditory Verbal Learning Test, Trail Making Test, and Categorical Verbal Fluency (all P < .02), but not the Mini-Mental State Examination. In an age-adjusted model, a 1% (11 mmol/mol) higher HbA1c value was associated with a 5.9 lower Digit Symbol Substitution Test score (95% confidence interval [CI], -9.58 to -2.21; P < .0001); a 2.44 lower Rey Auditory Verbal Learning Test score (95% CI, -4.00 to -0.87; P < .0001); a 15.6 higher Trail Making Test score (95% CI, 5.73 to 25.6; P < .0001); and a 3.71 lower Categorical Verbal Fluency score (95% CI, -6.41 to -1.01; P < .02). In a multivariate model adjusting for age, education, and cardiovascular covariates, HbA1c remained associated with cognitive function tests of Rey Auditory Verbal Learning Test (R(2) = 0.27, P < .0001), Trail Making Test (R(2) = 0.18, P < .0001), and Categorical Verbal Fluency (R(2) = 0.20, P < .0001), although association with the Digit Symbol Substitution Test was reduced.

CONCLUSIONS

Higher HbA1c is associated with lower cognitive function performance scores across multiple domain tests in men with metabolic syndrome and coronary artery disease. Future studies may demonstrate whether glucose lowering within the normative range improves cognitive health.

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

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

Diabetes 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.

Magnitude of cognitive dysfunction in adults with type 2 diabetes: a meta-analysis of six cognitive domains and the most frequently reported neuropsychological tests within domains

The objectives were to conduct a meta-analysis in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards to determine effect sizes (Cohen's d) for cognitive dysfunction in adults with type 2 diabetes, relative to nondiabetic controls, and to obtain effect sizes for the most commonly reported neuropsychological tests within domains. Twenty-four studies, totaling 26,137 patients (n = 3351 with diabetes), met study inclusion criteria. Small to moderate effect sizes were obtained for five of six domains: motor function (3 studies, n = 2374; d = -0.36), executive function (12 studies, n = 1784; d = -0.33), processing speed (16 studies, n = 3076; d = -0.33), verbal memory (15 studies, n = 4,608; d = -0.28), and visual memory (6 studies, n = 1754; d = -0.26). Effect size was smallest for attention/concentration (14 studies, n = 23,143; d = -0.19). The following tests demonstrated the most notable performance decrements in diabetes samples: Grooved Pegboard (dominant hand) (d = -0.60), Rey Auditory Verbal Learning Test (immediate) (d = -0.40), Trails B (d = -0.39), Rey-Osterreith Complex Figure (delayed) (d = -0.38), Trails A (d = -0.34), and Stroop Part I (d = -0.28). This study provides effect sizes to power future epidemiological and clinical diabetes research studies examining cognitive function and to help inform the selection of neuropsychological tests.

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.

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.

Mild depressive symptoms do not influence cognitive functioning in patients with type 2 diabetes

Type 2 diabetes (T2DM) is associated both with cognitive decrements and depressive symptoms. Since depression in itself has been associated with cognitive decrements we aimed to investigate the influence of depressive symptoms on the relation between T2DM and cognitive functioning. Data were derived from three independent studies on cognitive functioning in patients with T2DM (n=366) and controls without diabetes (n=204), two with longitudinal and one with only cross-sectional assessments. Depressive symptoms were measured with self-report inventories (CES-D or BDI-II). The composite z-score of the domains memory, information-processing speed, and attention and executive function was the primary cognitive outcome measure. Mixed linear regression analyses were used in a stepped approach to compare cognitive functioning between (1) patients with T2DM and controls (cross-sectionally and longitudinally), (2) participants with and without depressive symptoms, separately for patients and controls, and (3) patients and controls after adjustment for depressive symptoms. In addition the mediating effect of depressive symptoms was assessed with a bootstrapping technique. Depressive symptoms were present in 11% of the patients with T2DM and in 7% of controls (p=0.15). Cognitive performance in patients with T2DM was worse than in controls (overall difference composite z-score -0.13). However, T2DM was not associated with accelerated cognitive decline over three years of follow-up relative to controls. Controls with depressive symptoms performed worse than those without depressive symptoms, although not statistically significant. Performance in patients with T2DM with and without depressive symptoms was similar. Adjustment for depressive symptoms and estimation of the mediating effect showed that the difference between patients and controls was not mediated by depressive symptoms. In conclusion, the modest cognitive decrements that are associated with T2DM are not due to the presence of mild depressive symptoms.