Diabetes, cognitive impairment, and dementia

Association between low cognitive performance and diabetes-related health indicators across racial and ethnic groups in adults with diabetes

AIM

To examine the associations between low cognitive performance (LCP) and diabetes-related health indicators (including body mass index [BMI], HbA1c, systolic blood pressure [SBP], low-density lipoprotein [LDL] and self-reported poor physical health) and whether these associations vary across racial/ethnic subgroups.

METHODS

We identified adults aged 60 years or older with self-reported diabetes from the 2011-2014 National Health and Nutrition Examination Survey. Individuals with cognitive test scores in the lowest quartile were defined as having LCP. We used regression models to measure the associations of LCP with diabetes-related biometrics (BMI, HbA1c, SBP and LDL); and self-reported poor physical health. Moreover, we explored potential variations in these associations across racial/ethnic subgroups.

RESULTS

Of 873 (261 with LCP) adults with diabetes, LCP was associated with higher HbA1c, SBP and LDL (adjusted difference: 0.41%, 5.01 mmHg and 5.08 mg/dL, respectively; P < .05), and greater odds of reporting poor physical health (adjusted odds ratio: 1.59, P < .05). The association between LCP and HbA1c was consistent across racial/ethnic groups, and notably pronounced in Hispanic and Other. BMI worsened with LCP, except for non-Hispanic Black. Excluding the Other group, elevated SBP was observed in people with LCP, with Hispanic showing the most significant association. LDL levels were elevated with LCP for Hispanic and Other. Physical health worsened with LCP for both non-Hispanic Black and Hispanic.

CONCLUSIONS

We quantified the association between LCP and diabetes-related health indicators. These associations were more pronounced in Hispanic and Other racial/ethnic groups.

The Relationship Between Multimorbidity and Types of Chronic Diseases and Self-Rated Memory

This study explores the impact of multimorbidity and types of chronic diseases on self-rated memory in older adults in the United States. Data were drawn from the 2011 wave of the National Health and Aging Trends Study (NHATS, N = 6,481). Logistic regressions were used to examine the associations between multimorbidity and types of chronic diseases and fair/poor self-rated memory. Compared to respondents with no or one chronic disease, respondents with multimorbidity showed 35% higher odds of reporting fair/poor self-rated memory. Also, stroke, osteoporosis, and arthritis were identified as increasing the odds of reporting fair/poor self-rated memory by 41%, 20%, and 30%, respectively. Demonstrating the importance of both multimorbidity and types of chronic diseases in self-reporting of memory, our findings suggest the need to educate older adults with multimorbidity and certain types of diseases regarding negative self-rated memory and its consequences.

Diffusion Tensor Imaging Reveals Altered Topological Efficiency of Structural Networks in Type-2 Diabetes Patients With and Without Mild Cognitive Impairment

BACKGROUND

Some patients with type 2 diabetes mellitus (T2DM) progress towards mild cognitive impairment (MCI), while some patients can always maintain normal cognitive function. Network topologic alterations at global and nodal levels between T2DM individuals with and without cognitive impairment may underlie the difference.

PURPOSE

To investigate the topological alterations of the whole-brain white matter (WM) structural connectome in T2DM patients with and without MCI and characterize its relationship with disease severity.

STUDY TYPE

Cross-sectional and prospective study.

SUBJECTS

Forty-four (63.6% females) T2DM patients, 22 with mild cognitive impairment (DM-MCI) and 22 with normal cognition (DM-NC), and 34 (58.8% females) healthy controls (HC).

FIELD STRENGTH/SEQUENCE

3 T/diffusion tensor imaging.

ASSESSMENT

Graph theoretical analysis was used to investigate the topological organization of the structural networks. The global topological properties and nodal efficiency were investigated and compared. Relationship between network metrics and clinical measurements was characterized.

STATISTICAL TESTS

Student's t-test, chi-square test, ANOVA, partial correlation analyses, and multiple comparisons correction.

RESULTS

The global topological organization of WM networks was significantly disrupted in T2DM patients with cognitive impairment (reduced global and local efficiency and increased shortest path length) but not in those with normal cognition, compared with controls. The DM-MCI group had significantly decreased network efficiency compared with the DM-NC group. Compared with controls, decreased nodal efficiency was detected in three regions in DM-NC group. More regions with decreased nodal efficiency were found in the DM-MCI group. Altered global network properties and nodal efficiency of some regions were correlated with diabetic duration, HbA1c levels, and cognitive assessment scores.

DATA CONCLUSION

The more disrupted WM connections and weaker organized network are found in DM-MCI patients relative to DM-NC patients and controls. Network analyses provide information for the neuropathology of cognitive decline in T2DM patients. Altered nodal efficiency may act as potential markers for early detection of T2DM-related MCI.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 2.

Intrinsic Aerobic Capacity Affects Hippocampal pAkt and HSP72 Response to an Acute High Fat Diet and Heat Treatment in Rats

BACKGROUND

Aerobic capacity is associated with metabolic, cardiovascular, and neurological health. Low-capacity runner (LCR) rats display low aerobic capacity, metabolic dysfuction, and spatial memory deficits. A heat treatment (HT) can improve metabolic dysfunction in LCR peripheral organs after high fat diet (HFD). Little is known about metabolic changes in the brains of these rats following HT.

OBJECTIVE

Our objective was to examine the extent to which high or low aerobic capacity impacts Akt (a protein marker of metabolism) and heat shock protein 72 (HSP72, a marker of heat shock response) after HFD and HT in hippocampus.

METHODS

We measured phosphorylated Akt (pAkt) in the striatum and hippocampus, and HSP72 in the hippocampus, of HFD-fed and chow-fed LCR and high-capacity runner (HCR) rats with and without HT.

RESULTS

pAkt was lower in the hippocampus of chow-fed LCR than HCR rats. HFD resulted in greater pAkt in LCR but not HCR rats, but HT resulted in lower pAkt in the LCR HFD group. HSP72 was greater in both HCR and LCR rat hippocampus after HT. The HFD blunted this effect in LCR compared to HCR hippocampus.

CONCLUSION

The abnormal phosphorylation of Akt and diminished HSP response in the hippocampus of young adult LCR rats might indicate early vulnerability to metabolic challenges in this key brain region associated with learning and memory.

Effect of Garcinia mangostana pericarp extract on glial NF-κB levels and expression of serum inflammation markers in an obese-type 2 diabetes mellitus animal model

Type 2 diabetes mellitus (T2DM) is an age-related disease associated with cerebral inflammation and Alzheimer's disease. Garcinia mangostana pericarp (GMP) possesses antihyperglycemic, antidiabetic and anti-inflammatory effects. The aim of the present study was to evaluate the effect of GMP extract on cerebral inflammation in Wistar rats with T2DM by examining the expression levels of glial nuclear factor-κB (NF-κB), interleukin (IL)-6, tumor necrosis factor-α (TNF-α) and superoxide dismutase (SOD). A total of 36 8-10-week-old male Wistar rats were randomly divided into six groups and provided a standard diet (normal control; C1), high-fat diet (HFD) with 200 g/kg GMP extract BW/day (GMP control; C2), HFD with streptozotocin-nicotinamide (diabetic control; C3), and HFD with 100 (M1), 200 (M2) or 400 g/kg body weight (BW)/day (M3) GMP extract for Wistar rats with diabetes. GMP extract was administered for 8 weeks after induction of T2DM was confirmed. Glial NF-κB activity was assessed by immunohistochemical staining, and by measuring IL-6 levels, TNF-α levels and SOD activity in the serum using ELISA. BW significantly increased following HFD treatment. After 7 weeks, the BW remained significantly higher compared with the normal control and GMP extract-treated groups, but decreased continuously in the T2DM groups. Glial NF-κB immunoreaction in the hippocampal region was significantly higher in the diabetic Wistar rats compared with the normal control Wistar rats, and 200 g/kg BW/day GMP significantly reduced its activity. The T2DM Wistar rats showed significantly higher expression levels of serum IL-6 and TNF-α and lower activity of SOD compared with the normal control Wistar rats. Meanwhile, rats in GMP groups M1, M2 and M3 exhibited significant reductions in the levels of IL-6 and TNF-α expression, and increases in SOD activity. GMP extract treatment effectively reduced hippocampal NF-κB, IL-6 and TNF-α levels and increased antioxidant SOD activity. These results suggest that GMP extract prevents cerebral inflammation in T2DM Wistar rats.

Brain microstructural abnormalities in type 2 diabetes mellitus: A systematic review of diffusion tensor imaging studies

Type 2 diabetes mellitus (T2DM) is associated with deficits in the structure and function of the brain. Diffusion tensor imaging (DTI) is a highly sensitive method for characterizing cerebral tissue microstructure. Using PRISMA guidelines, we identified 29 studies which have demonstrated widespread brain microstructural impairment and topological network disorganization in patients with T2DM. Most consistently reported structures with microstructural abnormalities were frontal, temporal, and parietal lobes in the lobar cluster; corpus callosum, cingulum, uncinate fasciculus, corona radiata, and internal and external capsules in the white matter cluster; thalamus in the subcortical cluster; and cerebellum. Microstructural abnormalities were correlated with pathological derangements in the endocrine profile as well as deficits in cognitive performance in the domains of memory, information-processing speed, executive function, and attention. Altogether, the findings suggest that the detrimental effects of T2DM on cognitive functions might be due to microstructural disruptions in the central neural structures.

Investigation of glucose fluctuations by approaches of multi-scale analysis

Glucose variability provides detailed information on glucose control and fluctuation. The aim of this study is to investigate the glucose variability by multi-scale analysis approach on 72-h glucose series captured by continuous glucose monitoring system (CGMS), gaining insights into the variability and complexity of the glucose time series data. Ninety-eight type 2 DM patients participated in this study, and 72-h glucose series from each subject were recorded by CGMS. Subjects were divided into two subgroups according to the mean amplitude of glycemic excursions (MAGE) value threshold at 3.9 based on Chinese standard. In this study, we applied two types of multiple scales analysis methods on glucose time series: ensemble empirical mode decomposition (EEMD) and refined composite multi-scale entropy (RCMSE). With EEMD, glucose series was decomposed into several intrinsic mode function (IMF), and glucose variability was examined on multiple time scales with periods ranging from 0.5 to 12 h. With RCMSE, complexity of the structure of glucose series was quantified at each time scale ranging from 5 to 30 min. Subgroup with higher MAGE value (>3.9) presented higher glycemic baseline and variability. There were significant differences in glycemic variability on IMFs3-5 between subgroups with MAGE>3.9 and MAGE < = 3.9 (p<0.001), but no significant differences in variability on IMFs1-2. The complexity of glucose series quantified by RCMSE showed statistically difference on each time scale from 5 to 30 min between subgroups (p<0.05). Glucose series from subjects with higher MAGE value represented higher variability but lower complexity on multiple time scales. Compared with traditional matrices measuring the glucose variability, approaches of EEMD and RCMSE can quantify the dynamic glycemic fluctuation in multiple time scales and provide us more detailed information on glycemic variability and complexity.

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

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

Adenosine monophosphate-activated protein kinase activation mediates the leptin-induced attenuation of cognitive impairment in a streptozotocin-induced rat model

Several lines of evidence have shown that the incidence of cognitive impairment in diabetic patients is significantly higher than that in healthy individuals, but the exact pathogenesis has not been fully elucidated. Furthermore, it has been suggested that leptin may have a therapeutic effect in cognitive dysfunction. The aim of the present study was to observe the effect of leptin on cognitive dysfunction in streptozotocin (STZ)-induced diabetic rats, and to explore whether adenosine monophosphate-activated protein kinase (AMPK) activation was involved in any potential therapeutic effect of leptin. Compared with control rats, STZ rats exhibited decreased levels of AMPK and a poor performance in the Morris water maze, while these changes were reversed by leptin. Furthermore, Compound C, an AMPK antagonist, significantly attenuated the leptin-induced cognitive function improvement in the STZ rats. In conclusion, these results suggest that AMPK activation may play a critical role in the leptin-induced attenuation of STZ-induced cognitive impairment.

Benzodiazepine & nonbenzodiazepine prescriptions for Taiwanese elderly with type 2 diabetes contributes to cognitive dysfunction

BACKGROUND

This study examined the relationship of cognitive function and benzodiazepine/nonbenzodiazepine hypnotics (BZD/nonBZD) and other risk factors in a national sample of Taiwan's elderly diabetic patients.

METHODS

Data were drawn from the "2005 Taiwan National Health Interview Survey (NHIS)", a population-based study of a national sample of adults aged 65 years and older. A total of 653 participants were included in this study. The Mini-Mental State Examination (MMSE) was used to evaluate patient's cognitive function for which the cut-off score is education-adjusted.

RESULTS

There were 130 participants left in the diabetic group and 523 participants in the control group. The average age was 74.2 and 73.3 respectively. The rate of cognitive dysfunction in DM and non DM participants was 11.5% (15/130) and 8.4% (44/523). Compared with those without diabetes in multivariate logistic regression, the odds ratio of cognitive impairment was 1.87-fold higher for diabetic patients (95% CI 1.04-3.61) after adjusting for sociodemographic characteristics, comorbidities, and BZD/nonBZD. Other factors were not significant. We performed an additional logistic analysis for which the odds ratio of cognitive impairment in diabetic patients with BZD/nonBZD was significantly increased to 2.41 (95% CI 1.08-5.40) than for patients without diabetes and BZD/nonBZD.

CONCLUSION

In our research, cognitive dysfunction was associated with diabetes. BZD/nonBZD may have conferred additional risk of cognitive impairment in our elderly diabetic patients. We should consider examining the mental function of DM patients regularly and try our best to avoid potentially inappropriate medications (PIMs).

EFFECT OF TYPE 2 DIABETES MELLITUS ON BRAIN METABOLITES BY USING PROTON MAGNETIC RESONANCE SPECTROSCOPY-A SYSTEMATIC REVIEW

Cerebral metabolism will be affected in T2DM either by chronic hyperglycemia or by chronic hypoxia. Proton magnetic resonance spectroscopy (¹H-MRS) of the brain provides detailed information about the structure, dynamics, reaction state and chemical environment of molecules. It also measures the levels of brain metabolites such as myo-inositol (mI), N acetyl aspartate (NAA), creatine (Cr), choline (Cho), glutamate (Glu), glutamine (Gln) and gamma amino butyric acid (GABA). Several studies suggest that people with type 2 diabetes mellitus (T2DM) are at an increased risk of cognitive impairment in comparison with the general population. The altered metabolites may cause cognitive dysfunction in T2DM. This review article concludes that in T2DM, metabolite levels were altered in different regions of brain.

Leptin deficiency is involved in the cognitive impairment of streptozocin-induced diabetic rats undergoing cardiopulmonary bypass

Several lines of evidence have demonstrated that leptin is probably involved in the cognitive impairment which induced by a single injection of streptozocin (STZ). However, there is little literature reporting the relationship between cognitive impairment and cardiopulmonary bypass (CPB). This study aimed to investigate the role of leptin in the cognitive impairment of STZ-induced diabetic rats undergoing CPB. Wistar rats received 2 h of CPB exposure 1 month after a single intraperitoneal injection of 60 mg/kg of STZ or the vehicle. Behavioral results of rats in Morris water maze were recorded. After that, rat hippocampi were harvested for measuring leptin, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). Besides, we observed intracerebroventricular injection of leptin on the cognitive impairment of diabetic-rats undergoing CPB and measured behavioral performance and hippocampal TNF-α and IL-1β levels. Rats undergoing CPB significantly aggravates STZ-induced an increase of the latency to the platform and a decrease of the proportion of time spent in the target quadrant of rats in Morris water maze test. Additionally, the expression of leptin significantly decreased, while TNF-α and IL-1β levels significantly increased. Moreover, intracerebroventricular injection of leptin has a therapeutic effect for cognitive impairment of diabetic rats undergoing CPB. Leptin deficiency in hippocampus is probably involved in the cognitive impairment of streptozocin-induced diabetic rats undergoing cardiopulmonary bypass.

Brain diabetic neurodegeneration segregates with low intrinsic aerobic capacity

OBJECTIVES

Diabetes leads to cognitive impairment and is associated with age-related neurodegenerative diseases including Alzheimer's disease (AD). Thus, understanding diabetes-induced alterations in brain function is important for developing early interventions for neurodegeneration. Low-capacity runner (LCR) rats are obese and manifest metabolic risk factors resembling human "impaired glucose tolerance" or metabolic syndrome. We examined hippocampal function in aged LCR rats compared to their high-capacity runner (HCR) rat counterparts.

METHODS

Hippocampal function was examined using proton magnetic resonance spectroscopy and imaging, unbiased stereology analysis, and a Y maze. Changes in the mitochondrial respiratory chain function and levels of hyperphosphorylated tau and mitochondrial transcriptional regulators were examined.

RESULTS

The levels of glutamate, myo-inositol, taurine, and choline-containing compounds were significantly increased in the aged LCR rats. We observed a significant loss of hippocampal neurons and impaired cognitive function in aged LCR rats. Respiratory chain function and activity were significantly decreased in the aged LCR rats. Hyperphosphorylated tau was accumulated within mitochondria and peroxisome proliferator-activated receptor-gamma coactivator 1α, the NAD(+)-dependent protein deacetylase sirtuin 1, and mitochondrial transcription factor A were downregulated in the aged LCR rat hippocampus.

INTERPRETATION

These data provide evidence of a neurodegenerative process in the hippocampus of aged LCR rats, consistent with those seen in aged-related dementing illnesses such as AD in humans. The metabolic and mitochondrial abnormalities observed in LCR rat hippocampus are similar to well-described mechanisms that lead to diabetic neuropathy and may provide an important link between cognitive and metabolic dysfunction.

Multi-scale glycemic variability: a link to gray matter atrophy and cognitive decline in type 2 diabetes

OBJECTIVE

Type 2 diabetes mellitus (DM) accelerates brain aging and cognitive decline. Complex interactions between hyperglycemia, glycemic variability and brain aging remain unresolved. This study investigated the relationship between glycemic variability at multiple time scales, brain volumes and cognition in type 2 DM.

RESEARCH DESIGN AND METHODS

Forty-three older adults with and 26 without type 2 DM completed 72-hour continuous glucose monitoring, cognitive tests and anatomical MRI. We described a new analysis of continuous glucose monitoring, termed Multi-Scale glycemic variability (Multi-Scale GV), to examine glycemic variability at multiple time scales. Specifically, Ensemble Empirical Mode Decomposition was used to identify five unique ultradian glycemic variability cycles (GVC1-5) that modulate serum glucose with periods ranging from 0.5-12 hrs.

RESULTS

Type 2 DM subjects demonstrated greater variability in GVC3-5 (period 2.0-12 hrs) than controls (P<0.0001), during the day as well as during the night. Multi-Scale GV was related to conventional markers of glycemic variability (e.g. standard deviation and mean glycemic excursions), but demonstrated greater sensitivity and specificity to conventional markers, and was associated with worse long-term glycemic control (e.g. fasting glucose and HbA1c). Across all subjects, those with greater glycemic variability within higher frequency cycles (GVC1-3; 0.5-2.0 hrs) had less gray matter within the limbic system and temporo-parietal lobes (e.g. cingulum, insular, hippocampus), and exhibited worse cognitive performance. Specifically within those with type 2 DM, greater glycemic variability in GVC2-3 was associated with worse learning and memory scores. Greater variability in GVC5 was associated with longer DM duration and more depression. These relationships were independent of HbA1c and hypoglycemic episodes.

CONCLUSIONS

Type 2 DM is associated with dysregulation of glycemic variability over multiple scales of time. These time-scale-dependent glycemic fluctuations might contribute to brain atrophy and cognitive outcomes within this vulnerable population.

Diabetes mellitus and risk of dementia: A meta-analysis of prospective observational studies

AIMS/INTRODUCTION

The aim of the present study was to investigate the association between diabetes and the risk of all type dementia (ATD), Alzheimer's disease (AD) and vascular dementia (VaD).

MATERIALS AND METHODS

Prospective observational studies describing the incidence of ATD, AD and VaD in patients with diabetes mellitus were extracted from PubMed, EMBASE and other databases up to January 2012. Pooled relative risk (RR) estimates and 95% confidence intervals (CIs) were calculated using the random-effects model. Subgroup analyses and sensitivity analysis were also carried out.

RESULTS

A total of 28 studies contributed to the analysis. Pooled RR of developing ATD (n = 20) was 1.73 (1.65-1.82, I (2) = 71.2%), AD (n = 20) was 1.56 (1.41-1.73, I (2) = 9.8%) and VaD (n = 13) was 2.27 (1.94-2.66, I (2) = 0%) in patients with diabetes mellitus. Higher and medium quality studies did not show any significant difference for pooled RR for ATD, AD or VaD. Sensitivity analyses showed robustness of pooled RR among ATD, AD and VaD, showing no single study had a major impact on pooled RR.

CONCLUSIONS

The results showed a 73% increased risk of ATD, 56% increase of AD and 127% increase of VaD in diabetes patients.

A systematic review of the association of diabetic retinopathy and cognitive impairment in people with Type 2 diabetes

A systematic review of studies reporting data on the relationship between diabetic eye disease and cognitive impairment in Type 2 diabetes was conducted. The increase in cognitive impairment has mirrored the global increase in diabetes. The aim of the systematic review was to determine the level of association between diabetic retinopathy and cognitive impairment. Item selection, data extraction and critical appraisal were undertaken using standard procedures and independently verified by two researchers. 3 out of 10 potentially relevant studies were included. All studies showed a level of association between diabetic retinopathy and cognitive impairment, suggesting a near threefold increased risk of cognitive impairment in patients with diabetic retinopathy compared to those without. An association of cognitive impairment and severity of diabetic retinopathy was found in males. Diabetic retinopathy was more strongly linked to impairment in the cognitive domains of verbal learning and recent memory. An increased risk of cognitive impairment in patients with diabetic retinopathy was found in the reviewed studies. However, the relationship of severity of diabetic retinopathy and cognitive impairment has not been established. Further studies with standardized measurements for cognitive impairment and diabetic retinopathy are required to delineate this relationship and the role of other factors in this relationship.

R D Lawrence Lecture 2010. The brain as a target organ in Type 2 diabetes: exploring the links with cognitive impairment and dementia

Type 2 diabetes is associated with cognitive impairment and dementia, but the precise underlying mechanisms remain unresolved. Very high blood glucose concentrations are associated with mood changes and poor memory function, possibly by causing alterations in cerebral blood flow or osmotic changes in neurones, and correction of acute hyperglycaemia appears beneficial. Chronic hyperglycaemia may cause structural changes in the brain, such as cerebral microvascular disease, and there are strong associations between the presence of retinal microvascular abnormalities and cognitive function. Functional insulin deficiency in the brain may also be a factor, but trials with rosiglitazone in people with diabetes and other trials in people with Alzheimer's disease have shown no specific benefit of insulin sensitization. There is an association between hypoglycaemia and cognitive impairment in people with Type 2 diabetes; part of that association may simply be a consequence of the fact that people with cognitive impairment find it more difficult to manage their diabetes and so are more prone to hypoglycaemia. The potential for hypoglycaemia to cause harm to the brain has been debated for many years, and the issue remains unresolved. An ongoing prospective study of risk factors for cognitive impairment in people with Type 2 diabetes (Edinburgh Type 2 Diabetes Study) should improve our understanding of the aetiology of cognitive impairment and inform the design of future intervention trials.

Accelerated progression from mild cognitive impairment to dementia in people with diabetes

OBJECTIVE

The effect of diabetes on mild cognitive impairment (MCI) and its conversion to dementia remains controversial. We sought to examine whether diabetes and pre-diabetes are associated with MCI and accelerate the progression from MCI to dementia.

RESEARCH DESIGN AND METHODS

In the Kungsholmen Project, 963 cognitively intact participants and 302 subjects with MCI (120 with amnestic MCI [aMCI] and 182 with other cognitive impairment no dementia [oCIND]) age ≥ 75 years were identified at baseline. The two cohorts were followed for 9 years to detect the incident MCI and dementia following international criteria. Diabetes was ascertained based on a medical examination, hypoglycemic medication use, and random blood glucose level ≥ 11.0 mmol/l. Pre-diabetes was defined as random blood glucose level of 7.8-11.0 mmol/l in diabetes-free participants. Data were analyzed using standard and time-dependent Cox proportional-hazards models.

RESULTS

During the follow-up period, in the cognitively intact cohort, 182 people developed MCI (42 aMCI and 140 oCIND), and 212 developed dementia. In the MCI cohort, 155 subjects progressed to dementia, the multi-adjusted hazard ratio (95% CI) of dementia was 2.87 (1.30-6.34) for diabetes, and 4.96 (2.27-10.84) for pre-diabetes. In a Kaplan-Meier survival analysis, diabetes and pre-diabetes accelerated the progression from MCI to dementia by 3.18 years. Diabetes and pre-diabetes were neither cross-sectionally nor longitudinally associated with MCI.

CONCLUSIONS

Diabetes and pre-diabetes substantially accelerate the progression from MCI to dementia, and anticipate dementia occurrence by more than 3 years in people with MCI. The association of diabetes with the development of MCI is less evident in old people.

Association between cognitive function and social support with glycemic control in adults with diabetes mellitus

OBJECTIVES

To examine whether cognitive impairment in adults with diabetes mellitus is associated with worse glycemic control and to assess whether level of social support for diabetes mellitus care modifies this relationship.

DESIGN

Cross-sectional analysis.

SETTING

The 2003 Health and Retirement Study (HRS) Mail Survey on Diabetes and the 2004 wave of the HRS.

PARTICIPANTS

Adults aged 50 and older with diabetes mellitus in the United States (N=1,097, mean age 69.2).

MEASUREMENTS

Glycosylated hemoglobin (HbA1c) level; cognitive function, measured with the 35-point HRS cognitive scale (HRS-cog); sociodemographic variables; duration of diabetes mellitus; depressed mood; social support for diabetes mellitus care; self-reported knowledge of diabetes mellitus; treatments for diabetes mellitus; components of the Total Illness Burden Index related to diabetes mellitus; and functional limitations.

RESULTS

In an ordered logistic regression model for the three ordinal levels of HbA1c (<7.0, 7.0-7.9, >or=8.0 mg/dL), respondents with HRS-cog scores in the lowest quartile had significantly higher HbA1c levels than those in the highest cognitive quartile (adjusted odds ratio=1.80, 95% confidence interval=1.11-2.92). A high level of social support for diabetes mellitus care modified this association; for respondents in the lowest cognitive quartile, those with high levels of support had significantly lower odds of having higher HbA1c than those with low levels of support (1.11 vs 2.87, P=.02).

CONCLUSION

Although cognitive impairment was associated with worse glycemic control, higher levels of social support for diabetes mellitus care ameliorated this negative relationship. Identifying the level of social support available to cognitively impaired adults with diabetes mellitus may help to target interventions for better glycemic control.

The role of metabolic derangements and glucocorticoid excess in the aetiology of cognitive impairment in type 2 diabetes. Implications for future therapeutic strategies

Dementia is becoming increasingly common in western societies and carries with it a substantial clinical, social and economic burden. It is now well established that type 2 diabetes is a risk factor for dementia and it is likely that this association has a multifactorial aetiology. There is a relative paucity of data on interventions to improve cognitive function in people with type 2 diabetes. Two small randomized controlled trials have suggested that better glycaemic control, over a relatively short time period, can improve or prevent decline in cognitive function. There is also increasing interest in the link between intracerebral insulin and cognitive impairment. Several studies have suggested that relative and/or absolute deficiency of insulin may occur in Alzheimer's dementia and, although one small randomized trial was essentially negative, randomized trials are currently underway to investigate the impact of thiazolidinediones on cognitive function in dementia. The hypothalamic-pituitary-adrenal axis is also activated in people with type 2 diabetes and there are data linking increased cortisol concentrations with cognitive impairment. Inhibition of the 11 beta-hydroxysteroid dehydrogenase type 1 enzyme, which generates cortisol from inactive cortisone in many tissues including the brain, is an attractive therapeutic target to enhance cognition. Large-scale epidemiological and intervention studies are now underway, which should enhance our understanding and management of cognitive impairment in type 2 diabetes.

The Edinburgh Type 2 Diabetes Study: study protocol

BACKGROUND

Risk factors underlying the development and progression of some of the less well-recognised complications of type 2 diabetes, including cognitive impairment and non-alcoholic fatty liver disease, are poorly understood. The Edinburgh Type 2 Diabetes Study was established in 2006 in order to investigate the role of potential risk factors in these complications, as well as to further investigate mechanisms underlying the development and progression of micro and macrovascular disease in type 2 diabetes.

METHODS AND DESIGN

The study is designed as a prospective cohort study. Participants recruited at baseline (2006-2007) constitute 1066 men and women aged 60 to 75 years with established type 2 diabetes, living in the Lothian region of central Scotland. Subjects underwent detailed cognitive and physical examination, the latter including measures of micro- and macro-vascular disease, glycaemic control, body fat composition and plasma inflammatory markers, cortisol, lipids and liver function tests. Participants were re-examined after one year with hepatic ultrasonography and additional measures of vascular disease. This paper reports the methods of recruitment to the study and examinations performed at baseline and one year. Follow-up cognitive, vascular and liver assessments are scheduled for 2010-2011 when subjects will have been in the study for 4 years.

DISCUSSION

This study will provide a wealth of epidemiological and biomarker data that should be invaluable in the identification of potentially modifiable, causal risk factors for diabetes-related cognitive impairment, liver dysfunction and vascular disease, which can be targeted for the development of preventive and therapeutic interventions.

Burden of Alzheimer's disease: population-based estimates and projections for New Zealand, 2006-2031

OBJECTIVE

To estimate the burden of Alzheimer's disease (AD, including 'mixed' dementia) in New Zealand in 2006, and project this burden out to 2031.

METHOD

An incidence to prevalence methodology was utilized, the foundation of which is a discrete time Markov model allowing for multiple stages of disease (early vs late). Population estimates and projections, and all-cause mortality rates, were obtained from Statistics New Zealand. In the absence of usable New Zealand data, data on disease incidence and progression were obtained from systematic reviews of the international (mainly European, Australian and North American) literature. Projection scenarios included a demographic scenario in which change resulted only from increases in population size and ageing; a prevention scenario in which incidence rates were reduced by 25% from 2011; a treatment scenario in which disease progression rates were likewise reduced by 25% from 2011; and a combined scenario capturing both interventions.

RESULTS

The model estimated that approximately 28000 people are currently living with AD (whether formally diagnosed or not), approximately 55% in the early and 45% in the late stage of the disease; approximately 6600 people newly develop AD each year; and approximately 2300 people die from (as opposed to with) this condition. The model projected that the prevalence of AD will increase approximately 2.5-fold (to approx. 70,000 people) by 2031, if demographic drivers are unopposed. Plausible improvements in prevention and treatment, however, acting together, could reduce this growth by up to 50%, so that the prevalence of AD only doubles.

CONCLUSION

Even this more optimistic projection has profound implications for the funding and provision of dementia care services, as well as for patients, their families, informal carers and the psychogeriatric workforce. New service configurations and models of care will be necessary. Access, quality and coordination standards for home care, day care, respite care, residential care and specialist services (including memory clinics) will need to respond accordingly.

Physical control and coordination in childhood and adult obesity: Longitudinal Birth Cohort Study

OBJECTIVE

To identify whether measures of childhood physical control and coordination as markers of neurological function are associated with obesity in adults.

DESIGN

Longitudinal birth cohort study.

SETTING

National child development study in Great Britain.

PARTICIPANTS

11,042 people born during one week in 1958.

MAIN OUTCOME MEASURE

Obesity at age 33 years defined as body mass index >or=30.

RESULTS

Among 7990 cohort members at age 7 years, teachers reported that poor hand control, poor coordination, and clumsiness "certainly applied" more often among those who would be obese adults, producing adjusted odds ratios of 1.57 (95% confidence interval 1.13 to 2.20; P=0.008) for poor hand control, 2.30 (1.52 to 3.46; P<0.001) for poor coordination, and 3.91 (2.61 to 5.87; P<0.001) for clumsiness. Among 6875 participants who had doctor administered assessments with continuous scores at age 11 years, poorer function was associated with later obesity, indicated by adjusted odds ratios (change in risk per unit increase in score) of 0.88 (0.81 to 0.96; P=0.003) for copying designs, 0.84 (0.78 to 0.91; P<0.001) for marking squares, and 1.14 (1.06 to 1.24; P<0.001) for picking up matches (a higher score indicates poor function in this test). Further adjustment for contemporaneous body mass index at age 7 or 11 years did not eliminate statistical significance for any of the associations.

CONCLUSION

Some aspects of poorer neurological function associated with adult obesity may have their origins in childhood.

The relationship between type 2 diabetes and dementia

INTRODUCTION

The prevalence of type 2 diabetes and dementia are set to rise inexorably over the next 30-40 years. There are now substantial data to suggest that type 2 diabetes is associated with an increased risk of dementia.

SOURCES OF DATA

This is a narrative review using data from individual studies and review articles known to the authors. A Medline search was also undertaken and reference lists were reviewed to identify additional relevant studies.

AREAS OF AGREEMENT

Type 2 diabetes is associated with an increased risk of both Alzheimer's and Vascular dementia, although the reality is that many affected individuals have mixed forms of dementia.

AREAS OF CONTROVERSY

The mechanisms underpinning this association remain to be clearly delineated. Type 2 diabetes is a complex disorder and so it is likely that multiple different, synergistic processes may interact to promote cognitive decrements.

GROWING POINTS

Recent data suggest that glucocorticoids excess and elevated inflammatory markers may also have a role in the aetiology of diabetes-related cognitive impairment.

AREAS TIMELY FOR DEVELOPING RESEARCH

Large-scale, prospective epidemiological studies are now required to accurately delineate the pathogenesis of cognitive impairment in people with type 2 diabetes. These are underway and randomized trials of diabetes-specific interventions are also starting to include cognitive function as an outcome measure.