Effect of age and glucoregulation on cognitive performance

Effects of prediabetes and type 2 diabetes on cognitive functions

INTRODUCTION

We aimed to investigate the effect of glycemic impairment in prediabetes on cognitive impairment and the impact of glycemic control on cognitive function in patients with diabetes.

MATERIALS AND METHODS

This age- and sex-matched case-control study included a total of 80 individuals: 20 patients with prediabetes, 20 patients with well-controlled type 2 diabetes mellitus (T2DM) (HbA1C < %7.5), 20 patients with poorly controlled T2DM (HbA1C >% 7.5), and 20 healthy controls.

RESULTS

The poorly controlled T2DM patients performed significantly worse than controls and patients with prediabetes in the verbal memory process test (p = 0.041). In Trail Making Test B, the well-controlled and poorly-controlled groups with diabetes performed significantly worse (p = 0.015) than patients with prediabetes and controls, and in the Wisconsin Card Sorting Test (WCST), all three patient groups performed significantly worse (p = 0.007) than controls.

CONCLUSION

T2DM causes early brain aging and declines cognitive functions since the prediabetic stage. Poor glycemic control in T2DM patients contributes to cognitive impairments, especially in learning.

Comparing the effects of dietary sugars on cognitive performance and reaction time: A randomized, placebo- controlled and double-blind experimental trial

The aim of the study was to compare the effects of acute intake dietary sugars on cognitive performance and reaction time. This study was, randomized, placebo-controlled, double-blind experimental design, conducted with 75 healthy adults. At the beginning of the study, the participants (36 male, 39 female; 21.6 ± 1.3 years of age; body mass index: 21.59 ± 1.94 kg/m²) were randomly divided into equal five groups (n:15) (glucose (10 g), fructose (10 g), sucrose (10 g), saccharin (0.24 g), placebo), and received dietary sugars dissolved in 200 mL of water. Cognitive performance was determined with Cancelation Test, and the Simple Response Time and Ruler Drop Tests were used in order to response and reaction time of participants, respectively. General score of cognitive performance (0.93 ± 0.1), reaction (295 ± 20 ms), and response (204 ms) were highest in glucose and lowest in placebo (0.63 ± 0.1; 368 ± 22 ms; 251 ms, respectively) (p < .001). Saccharin groups had a higher reaction (312 ± 22 ms) and response (216 ms) time score compared to consumed fructose (316 ± 39; 227 ms), sucrose (354 ± 26; 246 ms), and placebo (368 ± 22; 251 ms) groups, respectively (p < .001). These findings show that differences in the absorption pattern and sweetness levels of sugar types may have different effects on cognitive performance and reaction time.

Factors Associated With Mild Cognitive Impairment in Patients With Type 2 Diabetes: A Cohort Study

Background

Cognitive dysfunction is increasingly recognized as an important comorbidity of diabetes mellitus (DM).

Objective

The purpose of this study was to determine the prevalence and predictors of cognitive decline in individuals with type 2 diabetes mellitus (T2DM).

Methods

This cohort study included patients with type 2 diabetes mellitus aged between 40 and 75 years and with a duration of the evolution of diabetes that is greater than five years admitted in endocrinology consultation of the Sheikh Khalifa ibn Zaid Hospital in Casablanca, Morocco. For each patient, we collected clinical characteristics and biological assessments. All subjects provided screening test results as defined by the Mini-Mental State Examination (MMSE).

Results

We included a total of 100 patients with diabetes between May and September 2021. The median age of the patients was 65 years (interquartile range (IQR): 59-70 years), 65% were males, and the median duration of diabetes was 15 years (IQR: 9-20 years). The most common cardiovascular risk factors (CVRFs) were hypertension (72.7%) and dyslipidemia (53%). The most common complications of diabetes were peripheral neuropathy (50%), diabetic retinopathy (DR) (39%), peripheral artery disease (33%), and coronary artery disease (27%). Cognitive impairment was present in 47.5% of our patients. For the multivariate analysis, we found that the decrease in the MMSE score is associated with the increase in age (p-value = 0.004) and the occurrence of diabetic retinopathy (p-value < 0.001), dyslipidemia (p-value = 0.006), and elevated creatinine (p-value < 0.001).

Conclusion

It is necessary to consider the cognitive decline of patients with diabetes as one of the most important complications of this disease because of its impact on the evolution and compliance of these patients.

Diabetes and cognitive decline

Epidemiologic studies have documented an association between diabetes and increased risk of cognitive decline in the elderly. Based on animal model studies, several mechanisms have been proposed to explain such an association, including central insulin signaling, neurodegeneration, brain amyloidosis, and neuroinflammation. Nevertheless, the exact mechanisms in humans remain poorly defined. It is reasonable, however, that many pathways may be involved in these patients leading to cognitive impairment. A major aim of clinicians is identifying early onset of neurologic signs and symptoms in elderly diabetics to improve quality of life of those with cognitive impairment and reduce costs associated with long-term complications. Several biomarkers have been proposed to identify diabetics at higher risk of developing dementia and diagnose early stage dementia. Although biomarkers of brain amyloidosis, neurodegeneration and synaptic plasticity are commonly used to diagnose dementia, especially Alzheimer disease, their role in diabetes remains unclear. The aim of this review is to explore the molecular mechanisms linking diabetes with cognitive decline and present the most important findings on the clinical use of biomarkers for diagnosing and predicting early cognitive decline in diabetics.

Altered Functional Connectivity of Insular Subregions in Type 2 Diabetes Mellitus

Diabetes-related brain damage can lead to cognitive decline and increase the risk of depression, but the neuropathological mechanism of this phenomenon remains unclear. Different insular subregions have obvious functional heterogeneity, which is related to many aspects of type 2 diabetes mellitus (T2DM)-related brain damage. However, little is known about changes in functional connectivity (FC) in insular subregions in patients with T2DM. Therefore, we aimed to investigate FC between different insular subregions and clinical/cognitive variables in patients with T2DM. Fifty-seven patients with T2DM and 55 healthy controls (HCs) underwent a neuropsychological assessment and resting-state FC examination. We defined three insular subregions, including the bilateral dorsal anterior insula (dAI), bilateral ventral anterior insula (vAI), and bilateral posterior insula (PI). We examined differences in FC between insular subregions and the whole brain in patients with T2DM compared with HCs. A correlation analysis was performed to examine the relationship between FC and clinical/cognitive variables. Compared with HCs, patients with T2DM showed significantly decreased FC between the dAI and the right inferior frontal gyrus, right superior/middle temporal gyrus, right hippocampus, and right precentral gyrus. FC between the vAI and the right supramarginal gyrus, as well as the PI and the right precentral/postcentral gyrus, was reduced in the T2DM group compared with the control group. In the T2DM group, we showed a significant negative correlation between glycated hemoglobin concentration and FC in the dAI and right hippocampus (r = −0.428, P = 0.001) after Bonferroni correction. We conclude that different insular subregions present distinct FC patterns with functional regions and that abnormal FC in these insular subregions may affect cognitive, emotional, and sensorimotor functions in patients with T2DM.

Aging is not equal across memory systems

The present experiments compared the effects of aging on learning several hippocampus- and striatum-sensitive tasks in young (3-4 month) and old (24-28 month) male Fischer-344 rats. Across three sets of tasks, aging was accompanied not only by deficits on hippocampal tasks but also by maintained or even enhanced abilities on striatal tasks. On two novel object recognition tasks, rats showed impaired performance on a hippocampal object location task but enhanced performance on a striatal object replacement task. On a dual solution task, young rats predominately used hippocampal solutions and old rats used striatal solutions. In addition, on two maze tasks optimally solved using either hippocampus-sensitive place or striatum-sensitive response strategies, relative to young rats, old rats had impaired learning on the place version but equivalent learning on the response version. Because glucose treatments can reverse deficits in learning and memory across many tasks and contexts, levels of available glucose in the brain may have particular importance in cognitive aging observed across tasks and memory systems. During place learning, training-related rises in extracellular glucose levels were attenuated in the hippocampus of old rats compared to young rats. In contrast, glucose levels in the striatum increased comparably in young and old rats trained on either the place or response task. These extracellular brain glucose responses to training paralleled the impairment in hippocampus-sensitive learning and the sparing of striatum-sensitive learning seen as rats age, suggesting a link between age-related changes in learning and metabolic substrate availability in these brain regions.

Poor glucose regulation is associated with declines in well-being among older men, but not women

Glucose regulation is a key aspect of healthy aging and has been linked to brain functioning and cognition. Here we examined the role of glucose regulation for within-person longitudinal trajectories of well-being. We applied growth models to data from the Berlin Aging Study II (N = 955), using insulin resistance as an index of glucoregulatory capacity. We found that poor glucose regulation (higher insulin resistance) was consistently associated with lower levels of well-being among older men but not women. Our study provides novel evidence for the relevance of glucose regulation for well-being among older men. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Glucose regulation and face recognition deficits in older adults: the role of attention

The present study investigated the perceptual, attentional, and memory processes underlying face recognition deficits observed in older adults with impaired glucoregulation. Participants were categorized as good glucoregulators or poor glucoregulators on the basis of an oral glucose tolerance test. Using event-related potential (ERP) methodology, 23 participants (62-88 years) performed a 2-stimulus oddball task. Participants were asked to rate and memorize 10 "target" faces, which were then presented amongst 120 unfamiliar foils. Behavioral results indicated that good glucoregulators were significantly more accurate at recognizing target faces. ERP markers of early visual perception (P1 and N170 components) and memory formation (P3 component) were unaffected by glucoregulatory efficiency. The P2 component, an index of attentional processing, was larger and delayed in the poor glucoregulators. To the best of our knowledge, this study is the first to suggest that face recognition deficits in poor glucoregulators may be due to impairments in attentional processing.

Effect of resistance training with elements of stretching on body composition and quality of life in postmenopausal women

INTRODUCTION

Physical activity in elderly persons contributes to prevention and treatment of chronic disease and, through its influence on the musculoskeletal system, increases physical capability and improves mental function.

AIM OF THE STUDY

Aim of the study was to assess the effect of resistance training with elements of stretching on body composition and quality of life in women of postmenopausal age.

MATERIAL AND METHODS

Thirty-eight postmenopausal women aged 62.5 ±5.8 years were randomly divided into two groups. One group participated in an 8-week training program (60 minutes, twice weekly; 4 MET [metabolic equivalent] 2 hours/week). The second group performed no training. A comparison was made of body composition and quality of life (SF-36 Health Survey) prior to and after 8 weeks of training.

RESULTS

In the training group, after 8 weeks there was a significant reduction in body fat (in%; p = 0.028), and an increase in fat-free mass (in%; p = 0.025) and total body water (in%; p = 0.021), which indicates increased muscle mass. Furthermore, there were statistically significant differences in the assessment of quality of life in physical (role-physical [RP], bodily pain [BP], general health [GH] scales; p < 0.005) and mental health (vitality [VT] scale; p = 0.05). In the non-exercising group no changes were observed in features examined in the initial and final test.

CONCLUSIONS

Resistance training with elements of stretching in postmenopausal women improved body composition to achieve a reduction in risk factors associated with excess fatty tissue and muscle mass deficiency. It raises the quality of life in terms of both physical and mental function.

Effects of glucose load on cognitive functions in elderly people

Glucose is the main fuel for the brain, and manipulation of the glucose supply may consequently affect brain function. The present review was conducted to provide an overview of studies that investigated the acute effects of glucose load on memory and other cognitive functions in elderly people. The effects of sucrose on cognition and suggested mechanisms were also explored. A total of twenty studies met the inclusion criteria. In the majority of studies, episodic memory was investigated and a beneficial role for glucose in that specific cognitive domain was suggested. Other cognitive domains, i.e., working memory, semantic memory, visual memory, information-processing speed, attention, executive function, and visual/spatial function, have been studied less frequently and evidence for a beneficial effect of glucose was equivocal. Mechanisms are suggested to be mainly related to the human body's need for glucose as a metabolic substrate for physiological mechanisms in both central and peripheral processes.

Associations between Markers of Glucose and Insulin Function and Cognitive Function in Healthy African American Elders

BACKGROUND

Glucose and insulin are important moderators of cognitive function. African Americans have poorer glycemic control across the glycemic spectrum and are at increased risk for type 2 diabetes and poor cognitive health. It is unclear which glucoregulatory markers predict cognitive function in this at-risk population. The purpose of this study was to examine the association between cognitive function and common markers of glucoregulation in non-diabetic African Americans elders.

METHODS

Thirty-four, community-dwelling African Americans, aged 50-75 years completed cognitive testing and blood collection as part of a health screening assessment. Cognitive outcomes were composite scores derived from neuropsychological tests of executive function and verbal memory. Linear regression was used to examine relationships between cognitive composite scores and fasting blood levels of glucose, insulin, and hemoglobin A1C, with adjustments for age, education, body mass index, and antihypertensive medication use.

RESULTS

Fasting plasma glucose was negatively associated with executive function (β=-0.41, p=0.03). There was a trend of an association between fasting plasma glucose and verbal memory (β=-0.34, p=0.06). Fasting insulin and hemoglobin A1c were not associated with cognitive function.

CONCLUSION

High non-diabetic fasting glucose levels were associated with poorer executive function and verbal memory. These results provide preliminary support for proactive glucose control in older African Americans even before glycemic criteria for type 2 diabetes are met. Our findings suggests that high-normal FPG levels may represent an early red-flag to signify increased risk of cognitive impairment or decline.

Improved working memory performance following administration of a single dose of American ginseng (Panax quinquefolius L.) to healthy middle-age adults

OBJECTIVE

A ginsenoside-rich extract of American ginseng (Panax quinquefolius L.), Cereboost(TM), was previously shown to improve working memory and mood in healthy young individuals. The present study represented a partial replication investigating whether these effects extended to healthy middle-aged individuals.

METHODS

Fifty-two healthy volunteers (40-60 years old, mean age 51.63) received 200 mg of P. quinquefolius or a matching placebo according to a double-blind, placebo-controlled, balanced, crossover design. The Cognitive Drug Research battery and the Computerised Mental Performance Assessment System were used to evaluate cognitive performance at baseline then 1, 3 and 6 h following treatment. Blood glucose and mood were co-monitored.

RESULTS

Compared with placebo, P. quinquefolius improved cognitive performance on 'Working Memory' factor at 3 h. Similar effects were observed in one of the two tasks making up this factor, spatial working memory. There were no significant effects on mood or blood glucose levels.

CONCLUSIONS

These data confirm that P. quinquefolius can acutely benefit working memory and extend the age range of this effect to middle-aged individuals. These changes are unlikely to be underpinned by modulation of blood glucose in this population.

Fasting glucose and glucose tolerance as potential predictors of neurocognitive function among nondiabetic older adults

INTRODUCTION

Significant evidence has demonstrated that Type 2 diabetes mellitus and related precursors are associated with diminished neurocognitive function and risk of dementia among older adults. However, very little research has examined relations of glucose regulation to neurocognitive function among older adults free of these conditions. The primary aim of this investigation was to examine associations among fasting glucose, glucose tolerance, and neurocognitive function among nondiabetic older adults. The secondary aim was to examine age, gender, and education as potential effect modifiers.

METHOD

The study employed a cross-sectional, correlational study design. Participants were 172 older adults with a mean age of 64.43 years (SD = 13.09). The sample was 58% male and 87% White. Participants completed an oral glucose tolerance test as part of a larger study. Trained psychometricians administered neuropsychological tests that assessed performance in the domains of response inhibition, nonverbal memory, verbal memory, attention and working memory, visuoconstructional abilities, visuospatial abilities, psychomotor speed and executive function, and motor speed and manual dexterity. Linear multiple regressions were run to test study aims.

RESULTS

No significant main effects of fasting glucose and 2-hour glucose emerged for performance on any neurocognitive test; however, significant interactions were present. Higher fasting glucose was associated with poorer short-term verbal memory performance among men, but unexpectedly better response inhibition and long-term verbal memory performance for participants over age 70. Higher 2-hour glucose values were associated with reduced divided attention performance among participants with less than a high school education.

CONCLUSIONS

Mixed findings suggest that glucose levels may be both beneficial and deleterious to neurocognition among nondiabetic older adults. Additional studies with healthy older adults are needed to confirm this unexpected pattern of associations; however, findings have implications for the importance of maintaining healthy glucose levels in older adulthood.

Glucose but not insulin or insulin resistance is associated with memory performance in middle-aged non-diabetic women: a cross sectional study

BACKGROUND

Elevated concentrations of plasma glucose appear to play a role in memory impairment, and it has been suggested that insulin might also have a negative effect on cognitive function. Our aim was to study whether glucose, insulin or insulin resistance are associated with episodic or semantic memory in a non-diabetic and non-demented population.

METHODS

We linked and matched two population-based data sets identifying 291 participants (127 men and 164 women, mean age of 50.7 ± 8.0 years). Episodic and semantic memory functions were tested, and fasting plasma insulin, fasting plasma glucose, and 2-hour glucose were analysed along with other potential influencing factors on memory function. Since men and women display different results on memory functions they were analysed separately. Insulin resistance was calculated using the HOMA-IR method.

RESULTS

A higher fasting plasma glucose concentration was associated with lower episodic memory in women (r = -0.08, 95% CI -0.14; -0.01), but not in men. Plasma insulin levels and insulin resistance were not associated with episodic or semantic memory in women or in men after adjustments for age, fasting glucose, 2-hour glucose, BMI, education, smoking, cardiovascular disease, hypertension, cholesterol, and physical activity.

CONCLUSIONS

This indicates that fasting glucose but not insulin, might have impact on episodic memory in middle-aged women.

A systematic review of type 2 diabetes mellitus and hypertension in imaging studies of cognitive aging: time to establish new norms

The rising prevalence of type 2 diabetes (T2DM) and hypertension in older adults, and the deleterious effect of these conditions on cerebrovascular and brain health, is creating a growing discrepancy between the "typical" cognitive aging trajectory and a "healthy" cognitive aging trajectory. These changing health demographics make T2DM and hypertension important topics of study in their own right, and warrant attention from the perspective of cognitive aging neuroimaging research. Specifically, interpretation of individual or group differences in blood oxygenation level dependent magnetic resonance imaging (BOLD MRI) or positron emission tomography (PET H2O(15)) signals as reflective of differences in neural activation underlying a cognitive operation of interest requires assumptions of intact vascular health amongst the study participants. Without adequate screening, inclusion of individuals with T2DM or hypertension in "healthy" samples may introduce unwanted variability and bias to brain and/or cognitive measures, and increase potential for error. We conducted a systematic review of the cognitive aging neuroimaging literature to document the extent to which researchers account for these conditions. Of the 232 studies selected for review, few explicitly excluded individuals with T2DM (9%) or hypertension (13%). A large portion had exclusion criteria that made it difficult to determine whether T2DM or hypertension were excluded (44 and 37%), and many did not mention any selection criteria related to T2DM or hypertension (34 and 22%). Of all the surveyed studies, only 29% acknowledged or addressed the potential influence of intersubject vascular variability on the measured BOLD or PET signals. To reinforce the notion that individuals with T2DM and hypertension should not be overlooked as a potential source of bias, we also provide an overview of metabolic and vascular changes associated with T2DM and hypertension, as they relate to cerebrovascular and brain health.

Neurocognitive changes and their neural correlates in patients with type 2 diabetes mellitus

As the prevalence and life expectancy of type 2 diabetes mellitus (T2DM) continue to increase, the importance of effective detection and intervention for the complications of T2DM, especially neurocognitive complications including cognitive dysfunction and dementia, is receiving greater attention. T2DM is thought to influence cognitive function through an as yet unclear mechanism that involves multiple factors such as hyperglycemia, hypoglycemia, and vascular disease. Recent developments in neuroimaging methods have led to the identification of potential neural correlates of T2DM-related neurocognitive changes, which extend from structural to functional and metabolite alterations in the brain. The evidence indicates various changes in the T2DM brain, including global and regional atrophy, white matter hyperintensity, altered functional connectivity, and changes in neurometabolite levels. Continued neuroimaging research is expected to further elucidate the underpinnings of cognitive decline in T2DM and allow better diagnosis and treatment of the condition.

Diabetes management and hyperglycemia in safety sensitive jobs

The chronic and acute effects of hyperglycemia affecting cognition and work are as important as those of hypoglycemia. Its impact, considering that majority of diabetic patients fail to reach therapeutic targets, would be potentially significant. Self monitoring of blood glucose, recognition of body cues and management interventions should be geared not only towards avoidance of disabling hypoglycemia, but also towards unwanted hyperglycemia. Over the long term, chronic hyperglycemia is a risk for cognitive decline. Acute episodes of hyperglycemia, above 15 mmol/L have also been shown to affect cognitive motor tasks. Maintaining blood sugar to avoid hyperglycemia in diabetic workers will help promote safety at work.

Carbohydrates for improving the cognitive performance of independent-living older adults with normal cognition or mild cognitive impairment

BACKGROUND

Mild cognitive impairment (MCI) is an intermediate state between normal cognition and dementia in which daily function is largely intact. This condition may present an opportunity for research into the prevention of dementia. Carbohydrate is an essential and easily accessible macronutrient which influences cognitive performance. A better understanding of carbohydrate-driven cognitive changes in normal cognition and mild cognitive impairment may suggest ways to prevent or reduce cognitive decline.

OBJECTIVES

To assess the effectiveness of carbohydrates in improving cognitive function in older adults.

SEARCH STRATEGY

We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group Specialized Register on 22 June 2010 using the terms: carbohydrates OR carbohydrate OR monosaccharides OR disaccharides OR oligosaccharides OR polysaccharides OR CARBS. ALOIS contains records from all major healthcare databases (The Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL, LILACS) as well as from many trial databases and grey literature sources.

SELECTION CRITERIA

All randomised controlled trials (RCT) that have examined the efficacy of any form of carbohydrates in normal cognition and MCI.

DATA COLLECTION AND ANALYSIS

One review author selected and retrieved relevant articles for further assessment. The remaining authors independently assessed whether any of the retrieved trials should be included. Disagreements were resolved by discussion. 

MAIN RESULTS

There is no suitable RCT of any form of carbohydrates involving independent-living older adults with normal cognition or mild cognitive impairment.

AUTHORS' CONCLUSIONS

There are no suitable RCTs on which to base any recommendations about the use of any form of carbohydrate for enhancing cognitive performance in older adults with normal cognition or mild cognitive impairment. More studies of many different carbohydrates are needed to tease out complex nutritional issues and further evaluate memory improvement.

Aerobic exercise improves cognition for older adults with glucose intolerance, a risk factor for Alzheimer's disease

Impaired glucose regulation is a defining characteristic of type 2 diabetes mellitus (T2DM) pathology and has been linked to increased risk of cognitive impairment and dementia. Although the benefits of aerobic exercise for physical health are well-documented, exercise effects on cognition have not been examined for older adults with poor glucose regulation associated with prediabetes and early T2DM. Using a randomized controlled design, twenty-eight adults (57-83 y old) meeting 2-h tolerance test criteria for glucose intolerance completed 6 months of aerobic exercise or stretching, which served as the control. The primary cognitive outcomes included measures of executive function (Trails B, Task Switching, Stroop, Self-ordered Pointing Test, and Verbal Fluency). Other outcomes included memory performance (Story Recall, List Learning), measures of cardiorespiratory fitness obtained via maximal-graded exercise treadmill test, glucose disposal during hyperinsulinemic-euglycemic clamp, body fat, and fasting plasma levels of insulin, cortisol, brain-derived neurotrophic factor, insulin-like growth factor-1, amyloid-β (Aβ40 and Aβ42). Six months of aerobic exercise improved executive function (MANCOVA, p=0.04), cardiorespiratory fitness (MANOVA, p=0.03), and insulin sensitivity (p=0.05). Across all subjects, 6-month changes in cardiorespiratory fitness and insulin sensitivity were positively correlated (p=0.01). For Aβ42, plasma levels tended to decrease for the aerobic group relative to controls (p=0.07). The results of our study using rigorous controlled methodology suggest a cognition-enhancing effect of aerobic exercise for older glucose intolerant adults. Although replication in a larger sample is needed, our findings potentially have important therapeutic implications for a growing number of adults at increased risk of cognitive decline.