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

The Effects of Type 2 Diabetes on Cognitive Performance: A Review of Reviews

BACKGROUND

Multiple systematic reviews have found that type 2 diabetes is associated with cognitive decrements. However, these reviews are heterogeneous in terms of methodology, quality and results, making it difficult for researchers and clinicians to build an informed overall picture. We therefore conducted a review of systematic reviews on the association between type 2 diabetes and cognitive decrements in relation to healthy controls.

METHODS

Following a pre-registered research protocol, we searched four major databases. Nine systematic reviews met our inclusion criteria: seven were meta-analyses and two were narrative syntheses. We assessed the risk of bias in each review and reported all effect sizes and confidence intervals obtained.

RESULTS

Type 2 diabetes was associated with cognitive decrements in all reviews, with small or negligible effect sizes obtained in the largest meta-analyses. The most studied cognitive domains were attention, executive functions, memory, processing speed and working memory. All reviews had methodological issues and were rated as having a high or an unclear risk of bias.

CONCLUSIONS

Type 2 diabetes appears to be associated with lower cognitive performance in several cognitive domains and in different age groups. However, high-quality meta-analyses on the subject are still needed. Future reviews must follow the PRISMA guidelines and take into account the risk of bias of the original studies through sensitivity analyses and the heterogeneity of the studies by conducting subgroup analyses for example according to age group and disease duration. The meta-analyses that aim to study the entire type 2 diabetes population without excluding severe comorbidities, should assess concept formation and reasoning, construction and motor performance, perception, and verbal functions and language skills in addition to the cognitive domains that have been most frequently analysed in the reviews conducted so far.

Effect of Combined Exercise Training on Physical and Cognitive Function in Women With Type 2 Diabetes

OBJECTIVES

One of the consequences of old age is cognitive and physical decline, which can cause a wide range of problems. These complications are more pronounced in those with type 2 diabetes (T2D). The aim of this pilot study was to investigate the effect of combined exercise training on blood biomarkers, physical fitness, and cognitive function in elderly women with T2D.

METHODS

Twenty-one elderly women with T2D were randomly allocated to training (n=12) and control (n=9) groups. The exercise training program was a combination of aerobic, resistance, and balance exercises performed 3 times per week over 12 weeks. In the same period, the control group received no training intervention. Blood markers, including brain-derived neurotrophic factor (BDNF), irisin, glycated hemoglobin (A1C), fasting blood sugar (FBS), cardiorespiratory fitness (CRF), lower and upper body strength, and cognitive function, were measured in all participants at baseline and after 12 weeks.

RESULTS

Serum BDNF levels were not significantly different between the exercise and control groups at 12 weeks (p>0.05). FBS and A1C levels in the exercise group decreased significantly compared with the control group (p<0.05). CRF, dynamic balance, and both upper and lower body strength in the exercise group improved significantly compared with the control group (p<0.05). Irisin levels decreased significantly in the control group, but levels did not change significantly in the exercise group. Greater improvements from exercise were observed on the Montreal Cognitive Assessment index compared with the control group (p=0.05), but no other group differences in cognitive function were noted.

CONCLUSIONS

Combined exercise improved some physical fitness and diabetes-related surrogate factors, as well as select cognitive functions, but had no significant effect on cognition-related biochemical factors (i.e. BDNF) in women with T2D.

Nonlinear Phase Synchronization Analysis of EEG Signals in Amnesic Mild Cognitive Impairment with Type 2 Diabetes Mellitus

Studying the nonlinear synchronization of electroencephalogram (EEG) in type 2 diabetic mellitus (T2DM) to find the EEG characteristics related to cognitive impairment is beneficial to the early prevention and diagnosis of mild cognitive impairment. Correlation between probabilities of recurrence (CPR) is a nonlinear phase synchronization method based on recurrence and recurrence probability, which had shown its superiority in detecting epilepsy. In this study, CPR method was used for the first time to analyze the synchronization of eye-closed resting EEG signals with T2DM. The 27 participants were divided into amnesic mild cognitive impairment (aMCI) group (17 case) and control group (10 cases with age and education matched). The CPR values in two groups were statistically analyzed by Mann-Whitney U test, and the correlation between EEG synchronization and cognitive function was studied by Spearman's correlation. The results showed that aMCI group had lower CPR values at each electrode pair than control group, and two groups had decreased CPR values with the increase of the spatial distance of the electrode pair in inter hemispheric. The CPR values were significantly different in frontal, parietal and temporal regions in intra hemispheric between two groups. The CPR values of C3-F7, F4-C4 and FP2-T6 were significantly positively correlated with the MOCA values. This study showed that the synchronization values of EEG signals obtained by the CPR method were significantly different between aMCI and control group, and they were the EEG characteristics associated with cognitive impairment in T2DM.

The prevalence of comorbid depression in patients with type 2 diabetes: an updated systematic review and meta-analysis on huge number of observational studies

AIMS

Depression is a common co-morbidity in patients with type 2 diabetes mellitus (T2DM). Untreated depression in these patients adversely affects self-care activities and other diabetes complications. The aim of this study is to estimate the prevalence of depression among patients with T2DM by conducting a meta-analysis of observational studies.

METHODS

MEDLINE, Web of Science, Science Direct, and Google Scholar databases were searched for all observational studies that assessed depression in T2DM. Relevant articles were searched using the combination of Medical Subject Heading (MeSH) terms of "depression", "depressive disorder", and "diabetes mellitus" published between January 2007 and July 2018. Random effects model was used to estimate the weighted prevalence rates and 95% CI using "metaprop program in STATA 11".

RESULTS

In total, the 248 included studies (with 273 reported prevalence) identified 83,020,812 participants; of them, 23,245,827 (28%; 95% CI 27, 29) suffered from different severity levels of depressive disorders. The prevalence of depression was separately reported in 137,372 males and 134,332 females. Of them, 31,396 males (23%, 95% CI: 20, 26) and 45,673 females (34%, 95% CI: 31, 38) were depressed. Compared with global estimate, depression prevalence was lower in Europe (24%) and Africa (27%), but higher in Australia (29%) and Asia (32%). The prevalence in America was equal to the estimated prevalence in the world (28%). Depression was more common in subjects younger than 65 compared with elderlies (31% vs. 21%).

CONCLUSION

Our findings demonstrated that almost one in four adults with T2DM experienced depression. Given the high prevalence of depressive disorders in diabetic patients, screening these patients for co-morbid depression and its relevant risk factors is highly recommended.

Diabetes, but Not Hypertension and Obesity, Is Associated with Postoperative Cognitive Dysfunction

BACKGROUND/AIMS

Older people undergoing surgery are at risk of developing postoperative cognitive dysfunction (POCD), but little is known of risk factors predisposing patients to POCD. Our objective was to estimate the risk of POCD associated with exposure to preoperative diabetes, hypertension, and obesity.

METHODS

Original data from 3 randomised controlled trials (OCTOPUS, DECS, SuDoCo) were obtained for secondary analysis on diabetes, hypertension, baseline blood pressure, obesity (BMI ≥30 kg/m2), and BMI as risk factors for POCD in multiple logistic regression models. Risk estimates were pooled across the 3 studies.

RESULTS

Analyses totalled 1,034 patients. POCD occurred in 5.2% of patients in DECS, in 9.4% in SuDoCo, and in 32.1% of patients in OCTOPUS. After adjustment for age, sex, surgery type, randomisation, obesity, and hypertension, diabetes was associated with a 1.84-fold increased risk of POCD (OR 1.84; 95% CI 1.14, 2.97; p = 0.01). Obesity, BMI, hypertension, and baseline blood pressure were each not associated with POCD in fully adjusted models (all p > 0.05).

CONCLUSION

Diabetes, but not obesity or hypertension, is associated with increased POCD risk. Consideration of diabetes status may be helpful for risk assessment of surgical patients.

Risk factors for cognitive impairment in older people with diabetes: a community-based study

AIM

The aim of this study was to investigate the risk factors for cognitive impairment in older people with diabetes.

METHODS

This cross-sectional study included 2626 community-dwelling participants with diabetes aged ⩾55 years, living in Beijing, China. The participants were screened for risk factors, including smoking, obesity, hypertension, stroke, coronary heart disease, dyslipidemia, depression, apolipoprotein E (APOE) genotype, and low physical activity. Cognitive function was assessed with the scholarship-adjusted Mini-Mental State Examination (MMSE): MMSE ⩽17 for iliterate participants; MMSE ⩽20 for primary school graduates (⩾6 years of education); and MMSE ⩽24 for junior school graduates or above (⩾9 years of education).

RESULTS

The prevalence of cognitive impairment in older people with diabetes was 9.90%. Multiple logistic regression analysis demonstrated that stroke [odds ratio (OR) = 1.71, 95% confidence interval (CI) = 1.20-2.43], less than 0.5 h exercise per day (OR = 1.89, 95% CI = 1.37-2.61), and depression (OR = 1.64, 95% CI = 1.06-2.54), but not smoking, obesity, hypertension, dyslipidemia, and coronary heart disease, were independent risks for cognitive impairment in older people with diabetes. In addition, being married (OR = 0.66, 95% CI = 0.47-0.93) and urban living (OR = 0.33, 95% CI = 0.22-0.48) could decrease the risk of cognitive impairment.

CONCLUSIONS

Stroke, depression, and less than 0.5 h exercise per day were independent risks for cognitive impairment in older people with diabetes, whereas being married and urban living were protective.

Different risk factors for cognitive impairment among community-dwelling elderly, with impaired fasting glucose or diabetes

AIM

The aim of this study was to investigate whether elderly people with impaired fasting glucose (IFG) or diabetes mellitus (DM) share the common risk factors for cognitive impairment as compared to normal blood glucose population.

METHODS

This cross-sectional study assessed 10,039 community-dwelling participants aged ≥ 55 years in Beijing, China. According to the glycemic status, subjects were classified into three groups: normal fasting plasma glucose (NG, n=6399), impaired fasting glucose (IFG, n=873) and DM (n=2626). The Mini-Mental State Examination (MMSE) was applied to evaluate the cognitive function status of the study population. Potential demographic, clinical, and genetic risk factors for cognitive impairment were collected and compared across the three groups. Multivariate logistic regression model was performed to explore the risk factors associated with cognitive impairment.

RESULTS

Education-modified MMSE scores in the participants with NG, IFG, and DM were 26.91±3.94, 26.67±4.00, and 26.58±4.11, respectively (P=0.0008). In the age- and sex-adjusted comparisons, the MMSE scores in subjects with DM and IFG were significantly lower than that in subjects with normal glucose (P=0.01 and P=0.02, respectively). The logistic regression analysis showed that risk factors only in the NG population were older age, female, apoEε4 carrier, normal or lower uric acid (UA) levels. Hypertension was an independent risk factor only in IFG group, and the history of stroke and depression were the risk factors associated with cognitive impairment only in the DM group.

CONCLUSION

Subjects with DM or IFG had a lower performance on the MMSE test compared with subjects who had normal blood glucose. The elderly with diabetes and IFG have some different risk factors for cognitive impairment as compared to those with normal blood glucose.

Type 2 diabetes, depressive symptoms and trajectories of cognitive decline in a national sample of community-dwellers: A prospective cohort study

We examined the individual and synergistic effects of type 2 diabetes and elevated depressive symptoms on memory and executive function trajectories over 10 and eight years of follow-up, respectively. Our sample comprised 10,524 community-dwellers aged ≥50 years in 2002–03 from the English Longitudinal Study of Ageing. With respect to memory (word recall), participants with either diabetes or elevated depressive symptoms recalled significantly fewer words compared with those free of these conditions (reference category), but more words compared with those with both conditions. There was a significant acceleration in the rate of memory decline in participants aged 50–64 years with both conditions (-0.27, 95% CI, -0.45 to -0.08, per study wave), which was not observed in those with either condition or aged ≥65 years. With respect to executive function (animal naming), participants aged ≥65 years with diabetes or those with elevated depressive symptoms named significantly fewer animals compared with the reference category, while those with both conditions named fewer animals compared with any other category. The rate of executive function decline was significantly greater in participants with both conditions (-0.54, 95% CI, -0.99 to -0.10; and –0.71, 95% CI, -1.16 to -0.27, per study wave, for those aged 50–64 and ≥65 years, respectively), but not in participants with either condition. Diabetes and elevated depressive symptoms are inversely associated with memory and executive function, but, individually, do not accelerate cognitive decline. The co-occurrence of diabetes and elevated depressive symptoms significantly accelerates cognitive decline over time, especially among those aged 50–64 years.

Association between Depressive Symptoms and Cognitive Function in Persons with Diabetes Mellitus: A Systematic Review

Depression and diabetes are independent risk factors for one another, and both are associated with increased risk of cognitive decline. Diabetes patients with lower cognitive function are more likely to suffer poorer health outcomes. However, the role of depression in cognitive decline among people with diabetes is not well understood. This systematic review assessed whether adults with comorbid diabetes and depression or depressive symptoms exhibit greater cognitive decline relative to individuals with diabetes alone. Searches were run in CINAHL, the Cochrane Central Register of Controlled Trials, EMBASE, PsycINFO, and PubMed (MEDLINE) with no time or language restrictions. Studies were eligible for inclusion if they were of any quantitative study design, included participants aged 18 years or older with diabetes mellitus of which some must have presented with current depression, and measured cognition as an outcome. The Cochrane Collaboration’s Risk Of Bias In Non-randomized Studies–of Interventions tool was used for quality assessment of each study and its collected outcome. Fifteen articles were included in the final analysis. The high degree of heterogeneity in exposures, outcomes, and participant characteristics precluded a meta-analysis of any of the studies, and the risk of bias observed in these studies limits the strength of the evidence. Nonetheless, this review found the presence of comorbid depression was associated with poorer cognitive outcomes than for persons with diabetes alone. While large-scale preventive efforts must address epidemic levels of diabetes and its comorbidities, on the patient level healthcare professionals must be cognizant of the added difficulties that depression poses to patients and the extra support required to management diabetes in these cases. This systematic review is registered with the University of York Centre for Reviews and Dissemination under registration number 2015:CRD42015025122.

Cognitive impairment and dependence of patients with diabetes older than 65 years old in an urban area (DERIVA study)

BACKGROUND

We analyzed the associations between diabetes and cognitive impairment (CI) and dependence in a population of patients 65 years or older.

METHODS

Cross-sectional study. We randomly selected 311 participants over the age of 65 living in an urban area of Spain. The mean age of the cohort was 75.89 ± 7.12 years, and 69 of the individuals (22.2%) had diabetes. Two questionnaires were used to assess cognitive performance (MMSE and Seven Minute Screen Test), and two assessments were used to evaluate patient dependence (Barthel Index and Lawton-Brody Index). Clinical information and sociodemographic data were also gathered.

RESULTS

Nearly one quarter of patients with diabetes (21.7%) lived alone. Diabetic patients were more sedentary (p = .033) than non-diabetic patients. Roughly one sixth (15.3%) of the diabetics and 10.1% of the non-diabetics were depressed (p = .332). CI was present in 26.1% of the diabetics and 14.5% of non-diabetics (p = .029). Diabetic patients had a MMSE score that was significantly worse than non-diabetics (24.88 ± 4.74 vs 26.05 ± 4.03; p <.05), but no differences were found in the Seven Minute Screen Test. Logistic regressions revealed that the presence of diabetes was independently associated with CI (adjusted for age, gender, years of education, sedentary lifestyle, body mass index, diastolic blood pressure, cholesterol, and depression (OR = 2.940, p = .013). Patients with diabetes showed greater dependence, as measured by the Barthel Index (p = .03) and Lawton-Brody Index (p <.01). Nevertheless, when dependence (dependence or not dependence for each questionnaire) used as a dependent variable in the logistic regression analyses, no significant association with diabetes was found, after adjusting for confounding variables.

CONCLUSIONS

Diabetic patients over the age of 65 are more likely to present CI but not dependence. These findings support the need to include both a functional and cognitive assessment as necessary components in a standard evaluation in both clinical guides and randomized trials of therapeutic interventions in patients with diabetes.

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.

Cortical source multivariate EEG synchronization analysis on amnestic mild cognitive impairment in type 2 diabetes

Is synchronization altered in amnestic mild cognitive impairment (aMCI) and normal cognitive functions subjects in type 2 diabetes mellitus (T2DM)? Resting eye-closed EEG data were recorded in 8 aMCI subjects and 11 age-matched controls in T2DM. Three multivariate synchronization algorithms (S-estimator (S), synchronization index (SI), and global synchronization index (GSI)) were used to measure the synchronization in five ROIs of sLORETA sources for seven bands. Results showed that aMCI group had lower synchronization values than control groups in parietal delta and beta2 bands, temporal delta and beta2 bands, and occipital theta and beta2 bands significantly. Temporal (r = 0.629; P = 0.004) and occipital (r = 0.648; P = 0.003) theta S values were significantly positive correlated with Boston Name Testing. In sum, each of methods reflected that the cortical source synchronization was significantly different between aMCI and control group, and these difference correlated with cognitive functions.

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.