Incidence and Risk Factors for Dementia in Type 2 Diabetes Mellitus: A Nationwide Population-Based Study in Korea

Comparative risk of dementia in diabetic stroke patients prescribed SGLT2 vs. DPP-4 inhibitors: A propensity-matched retrospective cohort study

OBJECTIVE

Diabetes is a significant risk factor for both stroke and dementia. This study aimed to compare the risk of incident dementia between sodium-glucose cotransporter 2 (SGLT2) inhibitors and dipeptidyl peptidase-4 (DPP-4) inhibitors in diabetic patients with a history of ischemic stroke.

MATERIALS

We conducted a propensity-matched retrospective cohort study using observational data from the TriNetX global federated health research network. Patients aged 18 years or older with type 2 diabetes (T2D) and a history of ischemic stroke, newly prescribed either an SGLT2 or DPP-4 inhibitor from July 1, 2013, to June 30, 2024, were included. Propensity score matching was employed to balance baseline characteristics between treatment groups. The primary outcome was incident dementia, with secondary outcomes including degenerative and vascular dementia.

RESULTS

After propensity score matching, each group consisted of 15901 patients. Over a mean follow-up of 2.52 years, SGLT2 inhibitor use was associated with lower risks of overall dementia (hazard ratio [HR] 0.66; 95% confidence interval [CI] 0.59-0.74), degenerative dementia (HR 0.68; 95% CI 0.60-0.76), and vascular dementia (HR 0.59, 95% CI 0.49-0.70) compared to DPP-4 inhibitor use. These findings remained consistent across various sensitivity and subgroup analyses.

CONCLUSIONS

In diabetic patients with a history of ischemic stroke, initiating SGLT2 inhibitors, compared to DPP-4 inhibitors, is associated with a lower risk of incident dementia. This association was observed for both degenerative and vascular dementias. These findings support the preferential use of SGLT2 inhibitors in this high-risk population, warranting further investigation through randomized clinical trials.

Poor glycemic status as a risk factor for dementia in type 2 diabetes population: Findings from the Taiwan's National Health Insurance Database

AIM

This study explored the association between poor glycemic status (PGS; hyperglycemia, hypoglycemia, or their combination [mixed]) and dementia risk in patients with type 2 diabetes (T2D).

METHODS

In this retrospective cohort study, we conducted a secondary analysis using data from Taiwan's National Health Insurance Database spanning the years 2000 to 2015. We employed propensity score matching (1:1) based on sex, age, index year, and inclusion date to select a comparison cohort, the Cox proportional-hazards regression analysis was performed to assess the effect of PGS on the risk of dementia. Kaplan-Meier survival analysis was performed to compare the cumulative incidence of dementia between patients with T2D and PGS and those without PGS.

RESULTS

Among 192,977 patients with T2D, 57,893 had PGS during the follow-up period. Of them, 4,342 patients (7.5 %) developed dementia. PGS status was positively associated with dementia risk (adjusted hazard ratio: 2.01; 95 % confidence interval [CI]: 1.58-2.68). The risks of dementia were 1.56 (95 % CI: 1.22-2.08) for hypoglycemia, 1.64 (95 % CI: 1.30-2.18) for hyperglycemia, and 3.10 (95 % CI: 2.48-4.12) for mixed PGS.

CONCLUSIONS

In patients with T2D, PGS is associated with an increased risk of dementia, particularly in those experiencing significant fluctuations in glycemic levels.

Exploring Care Challenges and Needs of People With Diabetes Comorbid Cognitive Impairment From the Triangular Perspectives

The study explored the challenges and needs in diabetes care for people with diabetes and comorbid cognitive impairment from the triangular perspectives of diabetes educators, patients, and family caregivers. The study employed a phenomenological research design with qualitative data collection, involving semi-structured interviews with 8 diabetes educators, 7 patients, and 6 caregivers. The data were gathered from a health education center in a hospital in Taiwan. Thematic analysis was utilized to analyze the qualitative data. Three categories with eight themes emerged. Challenges included "care challenges in compliance", "limited family involvement", and "caregiver distress". Needs were identified as "training for educators on cognitive impairments", "caregiver education", and "standard care procedures". Clinical realities showed "inconsistent awareness" and "lack of consensus on resource referrals among professionals". Diabetes care for people with cognitive impairment faces challenges including poor compliance and limited family cooperation, requiring better comorbidity training for educators and caregivers, and standardized care procedures for healthcare professionals. Findings can guide future training programs and serve as a resource for caregivers.

Risk of dementia in patients with age-related medical conditions: a retrospective cohort study

OBJECTIVE

This retrospective cohort study aimed to investigate the impact of age-related medical conditions on the incidence of dementia, considering factors such as hypertension, diabetes mellitus, cerebrovascular disease, cardiovascular disease, chronic kidney disease, osteoarthritis, osteoporosis, chronic obstructive pulmonary disease, and hearing difficulties.

METHODS

Data from 513 640 patients at Keimyung University Dongsan Hospital were analyzed using the Observational Medical Outcomes Partnership Common Data Model. Patients with and without age-related medical conditions were assigned to experimental and control groups, respectively, with propensity score matching. Cox proportional hazards models assessed the association between each condition and dementia incidence.

RESULTS

Hypertension, diabetes mellitus, cerebrovascular disease, cardiovascular disease, chronic kidney disease, osteoarthritis, osteoporosis, and hearing difficulties were associated with increased dementia risk. Chronic obstructive pulmonary disease showed no significant association with increased risk of dementia. Incidence rates ranged from 4.52 to 8.05 per 1000 person-years in the control group and 7.46 to 14.99 per 1000 person-years in the experimental group. Hazard ratios ranged from 1.38 to 2.36.

CONCLUSIONS

The study highlights the importance of managing age-related medical conditions to mitigate dementia risk. Understanding these risk factors can inform preventive strategies and improve cognitive health outcomes. Problems with deidentification data analysis and the need for further multicentred studies are among the limitations of this study.

Association of amyloid and cardiovascular risk with cognition: Findings from KBASE

BACKGROUND

Limited research has explored the effect of cardiovascular risk and amyloid interplay on cognitive decline in East Asians.

METHODS

Vascular burden was quantified using Framingham's General Cardiovascular Risk Score (FRS) in 526 Korean Brain Aging Study (KBASE) participants. Cognitive differences in groups stratified by FRS and amyloid positivity were assessed at baseline and longitudinally.

RESULTS

Baseline analyses revealed that amyloid-negative (Aβ-) cognitively normal (CN) individuals with high FRS had lower cognition compared to Aβ- CN individuals with low FRS (p < 0.0001). Longitudinally, amyloid pathology predominantly drove cognitive decline, while FRS alone had negligible effects on cognition in CN and mild cognitive impairment (MCI) groups.

CONCLUSION

Our findings indicate that managing vascular risk may be crucial in preserving cognition in Aβ- individuals early on and before the clinical manifestation of dementia. Within the CN and MCI groups, irrespective of FRS status, amyloid-positive individuals had worse cognitive performance than Aβ- individuals.

HIGHLIGHTS

Vascular risk significantly affects cognition in amyloid-negative older Koreans. Amyloid-negative CN older adults with high vascular risk had lower baseline cognition. Amyloid pathology drives cognitive decline in CN and MCI, regardless of vascular risk. The study underscores the impact of vascular health on the AD disease spectrum.

Microvascular disease and its association with dementia in patients with type 2 diabetes: A nationwide cohort study in Taiwan

AIM

To assess the likelihood of dementia in individuals with type 2 diabetes (T2D), distinguishing between those with and without microvascular diseases.

METHODS

Leveraging the National Health Insurance Research Database in Taiwan, we identified individuals newly diagnosed with T2D from 1 January 2009 through 31 December 2014. Multivariable Cox proportional hazard models were used to compare the risk of outcomes.

RESULTS

Individuals with microvascular disease had a significantly higher risk of all-cause dementia (adjusted hazard ratio [95% confidence interval] 1.13 [1.09, 1.17]) compared with matched individuals without microvascular disease. In addition, individuals with diabetic kidney disease and diabetic neuropathy were associated with a significantly increased risk of Alzheimer's disease (1.16 [1.02, 1.32] and 1.14 [1.03, 1.27]), vascular dementia (1.21 [1.06, 1.38] and 1.14 [1.02, 1.28]) and other dementia (1.11 [1.04, 1.19] and 1.10 [1.04, 1.16]), respectively, compared with those without microvascular disease.

CONCLUSIONS

This nationwide cohort study showed that patients with T2D and microvascular disease, particularly diabetic kidney disease and diabetic neuropathy, were associated with a significantly higher risk of Alzheimer's disease, vascular dementia, other dementia and all-cause dementia than those without microvascular disease.

SGLT2 Inhibitor Use and Risk of Dementia and Parkinson Disease Among Patients With Type 2 Diabetes

BACKGROUND AND OBJECTIVES

Despite the mechanistic potential of sodium-glucose cotransporter 2 inhibitor (SGLT2i) to improve neurologic outcomes, the efficacy of SGLT2i in neurodegenerative disorders among patients with type 2 diabetes is not well established. This population-based cohort study aimed to investigate the association of SGLT2i use with risks of incident dementia and Parkinson disease (PD) in patients with type 2 diabetes.

METHODS

This was a retrospective examination of data from a cohort of 1,348,362 participants with type 2 diabetes (≥40 years), who started antidiabetic drugs from 2014 to 2019, evaluated using the Korean National Health Insurance Service Database. Propensity score matching (1:1; SGLT2i to other oral antidiabetic drugs [OADs]) produced a cohort of 358,862 participants. Primary outcomes were the individual incidence of Alzheimer disease (AD), vascular dementia (VaD), and PD. Secondary outcomes were all-cause dementia (AD, VaD, and other dementia) and a composite of all-cause dementia and PD. Cox proportional hazards models were used to investigate the association between SGLT2i use and the risks of dementia and PD.

RESULTS

From the 358,862 participants analyzed (mean [SD] age, 57.8 [9.6] years; 58.0% male), 6,837 incident dementia or PD events occurred. Regarding the individual endpoints, SGLT2i use was associated with reduced risks of AD (adjusted hazard ratio [aHR] 0.81, 95% CI 0.76-0.87), VaD (aHR 0.69, 95% CI 0.60-0.78), and PD (aHR 0.80, 95% CI 0.69-0.91) with a 6-month drug use lag period. In addition, use of SGLT2i was associated with a 21% lower risk of all-cause dementia (aHR 0.79, 95% CI 0.69-0.90) and a 22% lower risk of all-cause dementia and PD than use of other OADs (aHR 0.78, 95% CI 0.73-0.83). The association between the use of SGLT2i and the lowered risk of these neurodegenerative disorders was not affected by sex, Charlson Comorbidity Index, diabetic complications, comorbidities, and medications. Sensitivity analysis further adjusting for bioclinical variables from health screening tests, including blood pressure, glucose, lipid profiles, and kidney function, yielded generally consistent results.

DISCUSSION

In this nationwide population-based study, SGLT2i use significantly reduced the risks of neurodegenerative disorders in patients with type 2 diabetes independent of various factors including comorbidities and bioclinical parameters.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that SGLT2 antidiabetic drugs decrease the risk of dementia and PD in people with diabetes.

Machine Learning-Based Prediction of Neurodegenerative Disease in Patients With Type 2 Diabetes by Derivation and Validation in 2 Independent Korean Cohorts: Model Development and Validation Study

BACKGROUND

Several machine learning (ML) prediction models for neurodegenerative diseases (NDs) in type 2 diabetes mellitus (T2DM) have recently been developed. However, the predictive power of these models is limited by the lack of multiple risk factors.

OBJECTIVE

This study aimed to assess the validity and use of an ML model for predicting the 3-year incidence of ND in patients with T2DM.

METHODS

We used data from 2 independent cohorts-the discovery cohort (1 hospital; n=22,311) and the validation cohort (2 hospitals; n=2915)-to predict ND. The outcome of interest was the presence or absence of ND at 3 years. We selected different ML-based models with hyperparameter tuning in the discovery cohort and conducted an area under the receiver operating characteristic curve (AUROC) analysis in the validation cohort.

RESULTS

The study dataset included 22,311 (discovery) and 2915 (validation) patients with T2DM recruited between 2008 and 2022. ND was observed in 133 (0.6%) and 15 patients (0.5%) in the discovery and validation cohorts, respectively. The AdaBoost model had a mean AUROC of 0.82 (95% CI 0.79-0.85) in the discovery dataset. When this result was applied to the validation dataset, the AdaBoost model exhibited the best performance among the models, with an AUROC of 0.83 (accuracy of 78.6%, sensitivity of 78.6%, specificity of 78.6%, and balanced accuracy of 78.6%). The most influential factors in the AdaBoost model were age and cardiovascular disease.

CONCLUSIONS

This study shows the use and feasibility of ML for assessing the incidence of ND in patients with T2DM and suggests its potential for use in screening patients. Further international studies are required to validate these findings.

Type-2 Diabetes Alters Hippocampal Neural Oscillations and Disrupts Synchrony between the Hippocampus and Cortex

Type 2 diabetes mellitus (T2DM) increases the risk of neurological diseases, yet how brain oscillations change as age and T2DM interact is not well characterized. To delineate the age and diabetic effect on neurophysiology, we recorded local field potentials with multichannel electrodes spanning the somatosensory cortex and hippocampus (HPC) under urethane anesthesia in diabetic and normoglycemic control mice, at 200 and 400 days of age. We analyzed the signal power of brain oscillations, brain state, sharp wave associate ripples (SPW-Rs), and functional connectivity between the cortex and HPC. We found that while both age and T2DM were correlated with a breakdown in long-range functional connectivity and reduced neurogenesis in the dentate gyrus and subventricular zone, T2DM further slowed brain oscillations and reduced theta-gamma coupling. Age and T2DM also prolonged the duration of SPW-Rs and increased gamma power during SPW-R phase. Our results have identified potential electrophysiological substrates of hippocampal changes associated with T2DM and age. The perturbed brain oscillation features and diminished neurogenesis may underlie T2DM-accelerated cognitive impairment.

Risk factors for the neurodegenerative dementias in the Western Pacific region

The Western Pacific Region (WPR) is characterized by a group of socioeconomically, culturally, and geopolitically heterogenous countries and represents a microcosm of the global endemic of neurodegeneration. This review will chart the known risk factors for dementia across the WPR. We explore the intersection between the established risk factors for dementia including the biomedical and lifestyle (cardiovascular and metabolic disease, sleep, hearing loss, depression, alcohol, smoking, traumatic brain injury, genetics) and social determinants (social disadvantage, limited education, systemic racism) as well as incorporate neuroimaging data, where available, to predict disease progression in the WPR. In doing so, we highlight core risk factors for dementia in the WPR, as well as geographical epicentres at heightened risk for dementia, to orient future research towards addressing these disparities.

Sex Differences in the Trajectories of Cognitive Decline and Affected Cognitive Domains Among Older Adults With Controlled and Uncontrolled Glycemia

BACKGROUND

We aimed to analyze the trajectories of cognitive decline as a function of the presence of type 2 diabetes and glycemic control in analyzes stratified by sex in an 8-year follow-up period.

METHODS

A total of 1 752 men and 2 232 women aged ≥50 years who participated in the English Longitudinal Study of Ageing (ELSA), conducted from 2004 to 2012, were analyzed. The outcomes of interest were performance on the cognitive domains of memory, executive function, and temporal orientation as well as the global cognition score. Cognitive performance was standardized in z-scores in strata based on schooling and age. The participants were classified as without diabetes, with controlled glycemia, and with uncontrolled glycemia, according to medical diagnosis, glucose-lowering medications use and HbA1c levels. Generalized linear mixed models controlled by sociodemographic, behavioral, and health-related characteristics were used for the trajectory analyses.

RESULTS

No differences in z-scores were found for global cognition or cognitive domains based on diabetes classification in men and women at baseline. More than 8 years of follow up, women with uncontrolled glycemia had a greater decline in z-scores for global cognition (-0.037 SD/year [95% CI: -0.073; -0.001]) and executive function (-0.049 SD/year [95% CI: -0.092; -0.007]) compared with those without diabetes. No significant difference in trajectories of global cognition or any cognitive domain was found in men as a function of diabetes classification.

CONCLUSIONS

Women with uncontrolled glycemia are at greater risk of a decline in global cognition and executive function than those without diabetes.

Hepatopancreatic metabolic disorders and their implications in the development of Alzheimer's disease and vascular dementia

Dementia has been faced with significant public health challenges and economic burdens that urges the need to develop safe and effective interventions. In recent years, an increasing number of studies have focused on the relationship between dementia and liver and pancreatic metabolic disorders that result in diseases such as diabetes, obesity, hypertension and dyslipidemia. Previous reports have shown that there is a plausible correlation between pathologies caused by hepatopancreatic dysfunctions and dementia. Glucose, insulin and IGF-1 metabolized in the liver and pancreas probably have an important influence on the pathophysiology of the most common dementias: Alzheimer's and vascular dementia. This current review highlights recent studies aimed at identifying convergent mechanisms, such as insulin resistance and other diseases, linked to altered hepatic and pancreatic metabolism, which are capable of causing brain changes that ultimately lead to dementia.

Unlocking the Protective Potential of Upper Respiratory Infection Treatment Histories against Alzheimer's Disease: A Korean Adult Population Study

With increasing interest in the inflammation-pathogen infection hypothesis and its potential links to Alzheimer's disease (AD) development, there is growing consideration of using upper respiratory infection (URI) treatments as interventions for AD. This nested case-control study explored the potential association between prior URI histories and AD development in a Korean adult population using the national health screening cohort data (2002-2019). The study included 26,920 AD patients and 107,680 matched control individuals, focusing on those seeking respiratory treatment. Logistic regression analyses assessed the impact of URI histories and treatment on AD risk while adjusting for covariates. Our results revealed that over a 1-year period, individuals with URI histories (≥1, ≥2, or ≥3 instances) exhibited decreasing probabilities of developing AD, with risk reductions of 19%, 15%, and 12%, respectively. Expanding our investigation to a 2-year period consistently showed a 17% reduction in AD risk. This effect remained robust across diverse demographic groups and after adjusting for covariates, encompassing comorbidities, hypertension, hyperlipidemia, blood glucose levels, and lifestyle factors. Subgroup analyses further substantiated this association. In conclusion, our findings cautiously suggest a potential protective role of prior URI treatment histories in mitigating the risk of AD development.

Sarcopenia and diabetes-induced dementia risk

This study aimed to investigate whether sarcopenia independently increases the risk of diabetes-induced dementia in elderly individuals diagnosed with type 2 diabetes mellitus. The study cohort consisted of a large sample of elderly individuals aged 60 years and above, who were diagnosed with type 2 diabetes mellitus between 2008 and 2018. To minimize potential bias and achieve covariate balance between the sarcopenia and non-sarcopenia groups, we employed propensity score matching. Various statistical analyses, including Cox regression models to assess dementia risk and associations, competing risk analysis to account for mortality and Poisson regression analysis for incidence rates, were used. Before propensity score matching, the study included 406 573 elderly type 2 diabetes mellitus patients, with 20 674 in the sarcopenia group. Following propensity score matching, the analysis included a total of 41 294 individuals, with 20 647 in the sarcopenia group and 20 647 in the non-sarcopenia group. Prior to propensity score matching, elderly type 2 diabetes mellitus patients with sarcopenia exhibited a significantly higher risk of dementia (adjusted hazard ratio: 1.12, 95% confidence interval: 1.07-1.17). After propensity score matching, the risk remained significant (adjusted hazard ratio: 1.14, 95% confidence interval: 1.07-1.21). Incidence rates of dementia were notably higher in the sarcopenia group both before and after propensity score matching, underscoring the importance of sarcopenia as an independent risk factor. Our study highlights sarcopenia as an independent risk factor for diabetes-induced dementia in elderly type 2 diabetes mellitus patients. Advanced age, female gender, lower income levels, rural residency, higher adapted diabetes complication severity index and Charlson Comorbidity Index scores and various comorbidities were associated with increased dementia risk. Notably, the use of statins was linked to a reduced risk of dementia. This research underscores the need to identify and address modifiable risk factors for dementia in elderly type 2 diabetes mellitus patients, offering valuable insights for targeted interventions and healthcare policies.

Risk of Neurodegenerative Diseases in Elderly Koreans with an Initial Diagnosis of Type 2 Diabetes: A Nationwide Retrospective Cohort Study

Type 2 diabetes (T2D) and neurodegenerative diseases (NDs) are common among elderly individuals. Growing evidence has indicated a strong link between T2D and NDs, such as Alzheimer's disease. However, previous studies have limitations in exploring the epidemiological relationship among these diseases as a group of NDs rather than as a specific type of ND. We aimed to investigate the risk of NDs in elderly Koreans who were first diagnosed with T2D and determine the association between T2D and NDs. We conducted a retrospective longitudinal cohort study of patients with who were initially diagnosed with T2D using the Korean National Health Information Database. The study participants were categorized into a T2D group (n = 155,459) and a control group (n = 155,459), aged 60-84 years, that were matched for age, sex, and comorbidities. We followed the participants for 10 years to investigate the incidence of NDs. The Cox proportional hazards regression model was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for NDs. The numbers of patients diagnosed with ND at the end of follow-up were as follows: 51,096/155,459 (32.9%) in the T2D group and 44,673/155,459 (28.7%) in the control group (χ2 = 622.53, p < 0.001). The incidences of NDs in the T2D and control groups were 44.68 (95% CI: 44.29, 45.07) and 36.89 (95% CI: 36.55, 37.24) cases per 1,000 person-years at risk, respectively. The overall incidence of NDs was higher in the T2D group than that in the control group (HR: 1.23, 95% CI: 1.22, 1.25, p < 0.001). This study revealed a higher incidence of NDs in elderly Koreans who were initially diagnosed with T2D. This suggests that T2D is a risk factor for NDs in elderly Koreans.

The Association Between Eye Disease and Incidence of Dementia: Systematic Review and Meta-Analysis

OBJECTIVES

To better demonstrate the relationship between common eye diseases and the risk of dementia, we conducted a systematic review and meta-analysis of cohort studies to investigate the relationship between common eye diseases and dementia.

DESIGN

Systematic review and meta-analysis.

SETTING AND PARTICIPANTS

Patients with common eye diseases.

METHODS

We conducted a systematic search of articles published up to August 25, 2022, of online databases including PubMed, EMBASE, and Web of Science. We included cohort studies that evaluated the association of glaucoma, age-related macular degeneration (AMD), diabetic retinopathy (DR), and cataracts with all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VaD). Relative risks (RRs) and 95% CIs were pooled using random effects model, and heterogeneity was assessed by the I2 statistic. Subgroup analysis and sensitivity analysis were also performed.

RESULTS

In total, 25 studies were included in the meta-analysis, with a total of 11,410,709 participants. Pooled estimates suggested an increased risk of all-cause dementia associated with AMD (RR, 1.29; 95% CI, 1.13-1.48), glaucoma (RR, 1.16; 95% CI, 1.03-1.32), DR (RR, 1.40; 95% CI, 1.21-1.63), and cataract (RR,1.23; 95% CI, 1.09-1.40); an increased risk of AD associated with AMD (RR, 1.27; 95% CI, 1.06-1.52), glaucoma (RR, 1.18; 95% CI, 1.02-1.38), DR (RR, 1.21; 95% CI, 1.04-1.41), and cataracts (RR,1.22; 95% CI, 1.07-1.38). No association was observed between incident VaD and any eye diseases. The results of subgroup analyses were consistent with those in meta-analysis of DR and risk of all-cause dementia. Meta-regressions suggested geographic regions as potential sources of heterogeneity for the association between AMD and all-cause dementia, AMD and AD, glaucoma and dementia, glaucoma, and AD, respectively.

CONCLUSIONS AND IMPLICATIONS

AMD, glaucoma, DR, and cataract may be associated with an increased risk of all-cause dementia and AD, but not VaD. However, the results should be interpreted cautiously because of the high heterogeneity and unstable findings in some subgroup analyses.

Akkermansia muciniphila in neuropsychiatric disorders: friend or foe?

An accumulating body of evidence suggests that the bacterium Akkermansia muciniphila exhibits positive systemic effects on host health, mainly by improving immunological and metabolic functions, and it is therefore regarded as a promising potential probiotic. Recent clinical and preclinical studies have shown that A. muciniphila plays a vital role in a variety of neuropsychiatric disorders by influencing the host brain through the microbiota-gut-brain axis (MGBA). Numerous studies observed that A. muciniphila and its metabolic substances can effectively improve the symptoms of neuropsychiatric disorders by restoring the gut microbiota, reestablishing the integrity of the gut mucosal barrier, regulating host immunity, and modulating gut and neuroinflammation. However, A. muciniphila was also reported to participate in the development of neuropsychiatric disorders by aggravating inflammation and influencing mucus production. Therefore, the exact mechanism of action of A. muciniphila remains much controversial. This review summarizes the proposed roles and mechanisms of A. muciniphila in various neurological and psychiatric disorders such as depression, anxiety, Parkinson's disease, Alzheimer's disease, multiple sclerosis, strokes, and autism spectrum disorders, and provides insights into the potential therapeutic application of A. muciniphila for the treatment of these conditions.

Amygdala activity and amygdala-hippocampus connectivity: Metabolic diseases, dementia, and neuropsychiatric issues

With rapid aging of the population worldwide, the number of people with dementia is dramatically increasing. Some studies have emphasized that metabolic syndrome, which includes obesity and diabetes, leads to increased risks of dementia and cognitive decline. Factors such as insulin resistance, hyperglycemia, high blood pressure, dyslipidemia, and central obesity in metabolic syndrome are associated with synaptic failure, neuroinflammation, and imbalanced neurotransmitter levels, leading to the progression of dementia. Due to the positive correlation between diabetes and dementia, some studies have called it "type 3 diabetes". Recently, the number of patients with cognitive decline due to metabolic imbalances has considerably increased. In addition, recent studies have reported that neuropsychiatric issues such as anxiety, depressive behavior, and impaired attention are common factors in patients with metabolic disease and those with dementia. In the central nervous system (CNS), the amygdala is a central region that regulates emotional memory, mood disorders, anxiety, attention, and cognitive function. The connectivity of the amygdala with other brain regions, such as the hippocampus, and the activity of the amygdala contribute to diverse neuropathological and neuropsychiatric issues. Thus, this review summarizes the significant consequences of the critical roles of amygdala connectivity in both metabolic syndromes and dementia. Further studies on amygdala function in metabolic imbalance-related dementia are needed to treat neuropsychiatric problems in patients with this type of dementia.

Association of triglyceride/high-density lipoprotein cholesterol ratio with severe complications of COVID-19

Background

The coronavirus disease 2019 (COVID-19) caused by the SARS-CoV-2 virus can lead to serious complications such as respiratory failure, requiring mechanical ventilation or ICU care, and can even result in death, especially in older patients with comorbidities. The ratio of triglyceride to high-density lipoprotein cholesterol (TG/HDL), a biomarker of atherosclerotic dyslipidemia and insulin resistance, is related to cardiovascular mortality and morbidity. We aimed to evaluate the link between serious complications of COVID-19 and TG/HDL in the general population.

Methods

We conducted a comprehensive analysis of 3,933 COVID-19 patients from a nationwide cohort in Korea spanning from January 1 to June 4, 2020. TG/HDL ratio was calculated from the national health screening examination data underwent before the COVID-19 infection. Serious complications of COVID-19 were defined as a composite of high-flow oxygen therapy, mechanical ventilation, admission to the intensive care unit (ICU), and mortality. We employed logistic regression analysis to investigate the relationship between the TG/HDL ratio and the likelihood of developing severe complications within 2 months of the diagnosis. To visualize this association, we used a smoothing spline plot based on the generalized additive regression model. Multivariate analysis was performed with adjustment for age, gender, body mass index, lifestyle measures, and comorbidities.

Results

Among the 3,933 COVID-19 patients, the proportion of serious complications was 7.53%. Regarding individual outcomes, the number of patients who received high-flow oxygen therapy, mechanical ventilation, ICU care, and died was 84 (2.14%), 122 (3.10%), 173 (4.40%), and 118 (3.00%), respectively. In the multivariable logistic regression, a positive association was found between TG/HDL ratio and serious complications of COVID-19 (adjusted OR, 1.09; 95% CI [1.03-1.15], p = 0.004).

Conclusion

Our study revealed a significant positive association between TG/HDL ratio and the risk of developing severe complications in COVID-19-infected patients. While this finding provides valuable insight into the potential prognostic role of TG/HDL ratio in COVID-19, further studies are needed to fully elucidate the underlying mechanisms behind this relationship.

Type-2 diabetes alters hippocampal neural oscillations and disrupts synchrony between hippocampus and cortex

Type 2 diabetes mellitus (T2DM) increases the risk of neurological diseases, yet how brain oscillations change as age and T2DM interact is not well characterized. To delineate the age and diabetic effect on neurophysiology, we recorded local field potentials with multichannel electrodes spanning the somatosensory cortex and hippocampus (HPC) under urethane anesthesia in diabetic and normoglycemic control mice, at 200 and 400 days of age. We analyzed the signal power of brain oscillations, brain state, sharp wave associate ripples (SPW-Rs), and functional connectivity between the cortex and HPC. We found that while both age and T2DM were correlated with a breakdown in long-range functional connectivity and reduced neurogenesis in the dentate gyrus and subventricular zone, T2DM further slowed brain oscillations and reduced theta-gamma coupling. Age and T2DM also prolonged the duration of SPW-Rs and increased gamma power during SPW-R phase. Our results have identified potential electrophysiological substrates of hippocampal changes associated with T2DM and age. The perturbed brain oscillation features and diminished neurogenesis may underlie T2DM-accelerated cognitive impairment.

The effects of long-term cumulative HbA1c exposure on the development and onset time of dementia in the patients with type 2 diabetes mellitus: hospital based retrospective study (2005-2021)

AIMS

We examine cumulative effect of long-term glycemic exposure in patients with type 2 diabetes mellitus (T2DM) on the development of dementia.

METHODS

The study involved 20,487 records of patients with T2DM identified in the electronic medical record at Severance Hospital, Korea. Cumulative HbA1c (AUC_HbA1c) and mean HbA1c over time (HbA1c_avg) as measures of long-term glycemic exposure were compared for the development of dementia and the time to dementia.

RESULTS

AUC_HbA1c and HbA1c_avg were significantly higher in patients who later developed dementia than in those who did not dementia (AUC_HbA1c: 56.2 ± 26.4 vs. 52.1 ± 26.1 %*Year; HbA1c_avg: 7.0 ± 1.0 vs. 7.3 ± 1.0 %). Odds ratio of dementia increased when HbA1c_avg was 7.2% (55 mmol/mol) or above, and when AUC_HbA1c was 42 %*Year (e.g., HbA1c 7.0% maintained for 6 years) or above. Among those who developed dementia, as HbA1c_avg increased, the time to dementia onset decreased (β = -380.6 days, 95% confidence interval [CI]: -416.2 to -345.0).

CONCLUSIONS

Our results indicate poorly controlled T2DM was associated with an increased risk of developing dementia, as measured by AUC_HbA1c and HbA1c_avg. Higher cumulative glycemic exposure may lead to developing dementia in a shorter time.

Association between cholesterol levels and dementia risk according to the presence of diabetes and statin use: a nationwide cohort study

We explored the association between cholesterol levels and dementia risk according to the presence of diabetes and statin use. In this population-based longitudinal cohort study, the Korean National Health Insurance Service datasets (2002-2017) were used. Among individuals aged ≥ 40 years who underwent health examinations in 2009 (N = 6,883,494), the hazard of dementia was evaluated according to cholesterol levels. During a median 8.33 years, 263,185 dementia cases were detected. In statin non-users with or without diabetes, the hazards of all-cause dementia were highest for those in the lowest quartile or quintile of low-density lipoprotein-cholesterol (LDL-C) level, showing an inverted J-shaped relationship. Among statin users with or without diabetes, an advance in LDL-C group was associated with an increase in hazards of all-cause dementia. In statin users with diabetes, even very low LDL-C level was not associated with an increased risk of all-cause dementia. Although there was a seemingly paradoxical association between low LDL-C level and dementia risk in statin non-users, the trend was not observed in statin users and is not likely to be clinically relevant. Rather, an advance in LDL-C levels was associated with an increase in the hazard of all-cause dementia in statin users, regardless of the presence of diabetes.

Dysfunctional Glucose Metabolism in Alzheimer’s Disease Onset and Potential Pharmacological Interventions

Alzheimer’s disease (AD) is the most common age-related dementia. The alteration in metabolic characteristics determines the prognosis. Patients at risk show reduced glucose uptake in the brain. Additionally, type 2 diabetes mellitus increases the risk of AD with increasing age. Therefore, changes in glucose uptake in the cerebral cortex may predict the histopathological diagnosis of AD. The shifts in glucose uptake and metabolism, insulin resistance, oxidative stress, and abnormal autophagy advance the pathogenesis of AD syndrome. Here, we summarize the role of altered glucose metabolism in type 2 diabetes for AD prognosis. Additionally, we discuss diagnosis and potential pharmacological interventions for glucose metabolism defects in AD to encourage the development of novel therapeutic methods.

Cardiometabolic measures and cognition in early menopause - Analysis of baseline data from a randomized controlled trial

OBJECTIVE

The relationships between cardiometabolic indices and cognition were examined in recently menopausal women.

METHODS

Cross-sectional analysis of baseline data from the KEEPS (Kronos Early Estrogen Prevention Study)-Cognitive ancillary study (n = 621). Cognitive performance was assessed by the Modified Mini Mental Status (3MS) score (primary outcome). Physical cardiometabolic indices included body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and blood pressure (BP). Biochemical cardiometabolic indices included serum levels of high sensitivity C-reactive protein (hs-CRP), total cholesterol (TC), low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), non-HDL (non-HDL-C), triglycerides (TG), fasting serum glucose (FSG), and insulin resistance (HOMA-IR). Socio-demographic variables included age, race/ethnicity, education, and lifestyle (physical activity, smoking). Central adiposity was defined as WC > 88 cm (>35 in) and WHR > 0.8. Separate stepwise multivariable analyses (GLM, ordinal logistic regression and logistic regression) assessed relationships between 3MS scores (as continuous, in tertiles and dichotomized at 90 respectively) with the measures of central adiposity (predictor variables); socio-demographic variables (age, time since menopause, race, educational status and lifestyle) and cardiometabolic variables (BP, lipids, FSG, HOMA-IR and hs-CRP) were examined as covariates. The final multivariable models included time since menopause, race, ethnicity, educational status, strenuous exercise, BMI ≥30 kg/m2, non-HDL-C and hs-CRP as covariates. Due to the high collinearity between the two indices of central adiposity, within each analytic strategy, separate models examined the respective associations of WC > 88 cm and WHR > 0.8 with 3MS score.

RESULTS

On adjusted analyses, indices of central adiposity were independent predictors of significantly lower 3MS scores (p < 0.05). Consistency in this relationship was observed across the three different multivariable regression analytic approaches (GLM, ordinal and logistic regression).

CONCLUSIONS

Among recently menopausal women, WC > 88 cm and WHR > 0.8 were associated with significantly lower cognitive function, as reflected by lower 3MS scores. The mechanisms that might explain the observed negative implications of central adiposity for cognitive function warrant further study.

Diabetic retinopathy and cognitive dysfunction: a systematic review and meta-analysis

BACKGROUND

This study aims to determine the relationship between diabetic retinopathy (DR) and cognitive dysfunction as well as explores the effects of DR on different cognitive domains.

METHODS

A systematic search of PubMed, Embase, Web of Science, Wanfang data, CBM, CNKI, and VIP databases from their inception to October 2021. The pooled odds ratio (ORs), hazard ratio (HRs), and 95% confidence interval (CIs) were calculated.

RESULTS

Twenty-two studies met the inclusion criteria and meta-analysis included 15 studies. The presence of DR reflects a higher risk of cognitive dysfunction (OR = 2.45; 95% CI: 1.76-3.41; HR = 1.34 95% CI: 1.10-1.62). Cohort study combined risk was 2.62 (95% CI: 1.93-3.56), in cross-sectional study was 2.07 (95% CI: 1.11-3.88). The pooled OR was 2.38 (95% CI: 1.83-3.10) and 3.11 (95% CI: 1.15-8.40) in Asia and Oceania. No such association was found in North America (OR = 2.22; 95% CI: 0.77-6.38). The pooled risk was 2.47 (95% CI: 1.76-3.48) in patients with T2DM, while did not identify an association between these two conditions in T1DM. The combined unadjusted and adjusted ORs were 2.72 (95% CI: 1.99-3.73) and 2.06 (95% CI: 1.49-2.85). DR severity and the risk of cognitive impairment showed a positive correlation and mainly impaired the speeds of psychomotor and information processing.

CONCLUSIONS

DR can help to identify people at high risk of cognitive dysfunction. Further studies are indispensable for exploring the relationship between DR and cognitive impairment in the patients for different age, gender and race, as well as to assess the risk of cognitive impairment in different populations.

Type 2 Diabetes Mellitus as a Risk Factor for Alzheimer’s Disease: Review and Meta-Analysis

Alzheimer’s disease is the most common type of dementia, reaching 60–80% of case totals, and is one of the major global causes of the elderly population’s decline in functionality concerning daily life activities. Epidemiological research has already indicated that, in addition to several others metabolic factors, diabetes mellitus type 2 is a risk factor of Alzheimer’s disease. Many molecular pathways have been described, and at the same time, there are clues that suggest the connection between type 2 diabetes mellitus and Alzheimer’s disease, through specific genes, autophagy, and even inflammatory pathways. A systematic review with meta-analysis was conducted, and its main goal was to reveal the multilevel connection between these diseases.

Hypothyroidism and Diabetes-Related Dementia: Focused on Neuronal Dysfunction, Insulin Resistance, and Dyslipidemia

The incidence of dementia is steadily increasing worldwide. The risk factors for dementia are diverse, and include genetic background, environmental factors, sex differences, and vascular abnormalities. Among the subtypes of dementia, diabetes-related dementia is emerging as a complex type of dementia related to metabolic imbalance, due to the increase in the number of patients with metabolic syndrome and dementia worldwide. Thyroid hormones are considered metabolic regulatory hormones and affect various diseases, such as liver failure, obesity, and dementia. Thyroid dysregulation affects various cellular mechanisms and is linked to multiple disease pathologies. In particular, hypothyroidism is considered a critical cause for various neurological problems-such as metabolic disease, depressive symptoms, and dementia-in the central nervous system. Recent studies have demonstrated the relationship between hypothyroidism and brain insulin resistance and dyslipidemia, leading to diabetes-related dementia. Therefore, we reviewed the relationship between hypothyroidism and diabetes-related dementia, with a focus on major features of diabetes-related dementia such as insulin resistance, neuronal dysfunction, and dyslipidemia.

Associations between depression and cognition, mild cognitive impairment and dementia in persons with diabetes mellitus: A systematic review and meta-analysis

AIMS

This systematic review aimed to examine whether persons with diabetes and depression had poorer cognition and higher dementia risk than persons with diabetes only. Moreover, the impact of timing, frequency of depressive episodes throughout life, and antidepressant treatment were examined.

METHODS

PubMed, Embase and PsycINFO were searched to obtain observational studies between August 2015 and June 2021 that examined the association between depression and cognition, mild cognitive impairment or dementia in people with diabetes. Studies published before August 2015 were retrieved from a previous systematic review. Findings were pooled using meta-analyses.

RESULTS

10 out of 19 included articles were appropriate for the meta-analyses. Persons with diabetes and depression experienced greater declines in executive function (SMD = -0.39 (-0.69, -0.08)), language (SMD = -0.80 (-1.52, -0.09)), memory (SMD = -0.63 (-1.12, -0.14)) and overall cognition (SMD = -0.77 (-1.33, -0.20)), and greater dementia risk (HR = 1.82 (1.79, 1.85)) than persons with diabetes only. No significant differences were observed for complex attention. No studies examined the role of timing and frequency of depressive episodes and antidepressant treatment.

CONCLUSION

In persons with diabetes, depression is associated with worse cognition and higher dementia risk. The potential mitigating effect of antidepressant treatment remains unclear.

Diabetes Mellitus: A Path to Amnesia, Personality, and Behavior Change

Simple Summary

Diabetes Mellitus (DM) is a metabolic disorder resulting from a disturbance of insulin secretion, action, or both. Hyperglycemia and overproduction of superoxide induce the development and progression of chronic complications of DM. The impact of DM and its complication on the central nervous system (CNS) such as dementia and Alzheimer’s Disease (AD) still remain obscure. In dementia, there is a gradual decline in cognitive function. The incidence of dementia increases with age, and patient become socially, physically, and mentally more vulnerable and dependent. The symptoms often emerge decades after the onset of pathophysiology, thus impairing early therapeutic intervention. Most diabetic subjects who develop dementia are above the age of 65, but diabetes may also cause an increased risk of developing dementia before 65 years. Vascular dementia is the second most common form of dementia after AD. Type 2 DM (T2DM) increases the incidence of vascular dementia (since its covers the vascular system) and AD. The functional and structural integrity of the CNS is altered in T2DM due to increased synthesis of Aβ. Additionally, hyperphosphorylation of Tau protein also results from dysregulation of various signaling cascades in T2DM, thereby causing neuronal damage and AD. There is the prospect for development of a therapy that may help prevent or halt the progress of dementia resulting from T2DM.

Abstract

Type 2 diabetes mellitus is increasingly being associated with cognition dysfunction. Dementia, including vascular dementia and Alzheimer’s Disease, is being recognized as comorbidities of this metabolic disorder. The progressive hallmarks of this cognitive dysfunction include mild impairment of cognition and cognitive decline. Dementia and mild impairment of cognition appear primarily in older patients. Studies on risk factors, neuropathology, and brain imaging have provided important suggestions for mechanisms that lie behind the development of dementia. It is a significant challenge to understand the disease processes related to diabetes that affect the brain and lead to dementia development. The connection between diabetes mellitus and dysfunction of cognition has been observed in many human and animal studies that have noted that mechanisms related to diabetes mellitus are possibly responsible for aggravating cognitive dysfunction. This article attempts to narrate the possible association between Type 2 diabetes and dementia, reviewing studies that have noted this association in vascular dementia and Alzheimer’s Disease and helping to explain the potential mechanisms behind the disease process. A Google search for “Diabetes Mellitus and Dementia” was carried out. Search was also done for “Diabetes Mellitus”, “Vascular Dementia”, and “Alzheimer’s Disease”. The literature search was done using Google Scholar, Pubmed, Embase, ScienceDirect, and MEDLINE. Keeping in mind the increasing rate of Diabetes Mellitus, it is important to establish the Type 2 diabetes’ effect on the brain and diseases of neurodegeneration. This narrative review aims to build awareness regarding the different types of dementia and their relationship with diabetes.

Association between oral health and cardiovascular outcomes in patients with hypertension: a nationwide cohort study

OBJECTIVE

Studies on the association of oral hygiene indicators with cardiovascular disease in hypertensive patients have been lacking. Oral hygiene is directly or indirectly associated with systemic inflammation, one of the essential mechanisms of cardiovascular disease. Therefore, we hypothesized that oral hygiene would be related to the risk of cardiovascular diseases in hypertensive patients.

METHODS

We included 52 677 hypertensive participants who completed oral health checkups from the Korean National Health Insurance Service-National Health Screening Cohort between 2003 and 2004. We collected data on periodontitis diagnosis and treatment history, number of teeth loss, number of dental caries, and frequency of tooth brushing from medical records of health claims and oral health examination. The primary outcome was defined as composite outcomes of stroke and myocardial infarction. Follow-up was done until the date of primary outcome, or 31 December 2015.

RESULTS

During the 11.26 ± 2.39 years (mean ± standard deviation) of the study follow-up, 3292 participants developed primary outcomes [stroke (n = 2430), myocardial infarction (n = 862)]. In multivariable Cox regression analyses, participants with dental caries (≥ 5) were independently associated with occurrence of a primary outcome [adjusted hazard ratio: 1.37; 95% confidence interval (CI):1.10-1.72; P = 0.006]. Frequent tooth brushing (≥ 2 times/day) was significantly related to lower risk of primary outcomes (adjusted hazard ratio: 0.88; 95% CI: 0.81-0.96; P = 0.002).

CONCLUSION

Our study demonstrated that multiple dental caries were related to the risk of cardiovascular diseases in hypertensive patients. Better oral hygiene may attenuate the risk of cardiovascular events in hypertensive patients.

Association of periodontitis with microvascular complications of diabetes mellitus: A nationwide cohort study

BACKGROUND

Periodontitis is a common chronic inflammatory disease and one of oral complications in diabetes. Diabetes-related microvascular complications and periodontitis are also closely related to systemic inflammation. We hypothesized that periodontitis and oral hygiene markers might increase the risk of microvascular complications in diabetes mellitus.

METHODS

We enrolled 11,353 diabetes participants without prior microvascular complications who received complete oral health checkups in the National Health Insurance Service-National Health Screening Cohort in 2003-2004. The primary outcome was the first development of diabetes-related microvascular complications, including nephropathy, neuropathy, and retinopathy.

RESULTS

The age of all participants was 55.27 ± 9.46 years, and 7833 (68.99%) participants were male. Periodontitis was noted in 8.37%. During the 7.03 ± 4.30 year of the mean follow-up period, 7227 patients experienced diabetes-related microvascular complications (2645 with nephropathy, 2513 with neuropathy, 2069 with retinopathy). Multivariable Cox regression analyses revealed that periodontitis was an independent risk factor for diabetes-related microvascular complications (adjusted hazard ratio (HR):1.13; 95% confidence interval (CI):1.04-1.23; p = 0.004). In the secondary analysis for individual microvascular complications, periodontitis was an independent risk factor for retinopathy (adjusted HR: 1.21; 95% CI: 1.04-1.40; p = 0.013).

CONCLUSIONS

The presence of periodontitis was associated with an increased risk of microvascular complications in diabetes patients.

The identification of established modifiable mid-life risk factors for cardiovascular disease which contribute to cognitive decline: Korean Longitudinal Study of Aging (KLoSA)

INTRODUCTION

We explored how different chronic diseases, risk factors, and protective factors highly associated with cardiovascular diseases (CVD) are associated with dementia or Mild Cognitive Impairment (MCI) in Korean elders, with a focus on those that manifest in mid-life.

METHODS

A CVD-free cohort (n = 4289) from the Korean Longitudinal Study of Aging was selected to perform Cox mixed-effects proportional hazard regressions. Eighteen control variables with strong associations to CVD were chosen as explanatory variables, and Mini-Mental State Examination (MMSE) score cut-off for dementia and MCI were used as outcome variables.

RESULTS

The statistically significant (P < 0.05) adverse factors that contribute in developing dementia were age (aHR 1.07, 1.05-1.09), Centre for Epidemiological Studies Depression Scale (CESD-10) (aHR 1.17, 1.12-1.23), diagnosis with cerebrovascular disease (aHR 3.73, 1.81-7.66), living with diabetes (aHR 2.30, 1.22-4.35), and living with high blood pressure (HBP) (aHR 2.05, 1.09-3.87). In contrast, the statistically significant protective factors against developing dementia were current alcohol consumption (aHR 0.67, 0.46-0.99), higher educational attainment (aHR 0.36, 0.26-0.56), and regular exercise (aHR 0.37, 0.26-0.51). The factors with a statistically significant adverse association with progression to MCI were age (aHR 1.02, 1.01-1.03) and CESD-10 (aHR 1.17, 1.14-1.19). In contrast, the statistically significant protective factors against developing MCI were BMI (aHR 0.96, 0.94-0.98), higher educational attainment (aHR 0.33, 0.26-0.43), and regular exercise (aHR 0.83, 0.74-0.92).

CONCLUSION

In lieu of the protective factor of MCI and dementia, implementing regular exercise routine well before mid-life and cognitive decline is significant, with adjustments made for those suffering from health conditions, so they can continue exercising despite their morbidity. Further attention in diabetes care and management is needed for patients who already show decline in cognitive ability as it is likely that their MCI impacts their ability to manage their existing chronic conditions, which may adversely affect their cognitive ability furthermore.

The risk of Alzheimer's disease according to dynamic changes in metabolic health and obesity: a nationwide population-based cohort study

We evaluated the association of metabolic health and obesity phenotypes with the risk of Alzheimer's disease (AD). This study enrolled 136,847 elderly participants aged 60 or above from the Korean National Health Insurance System. At baseline examinations in 2009 and 2010, subjects were categorized into four groups: the metabolically healthy non-obese (MHNO), metabolically healthy obese (MHO), metabolically unhealthy non-obese (MUNO), and metabolically unhealthy obese (MUO) groups. Based on the phenotypic transition after 2 years, the subjects were further categorized into 16 subgroups. They were followed from 2009 to 2015 to monitor for AD development. The MHO phenotype protected subjects from AD, relative to the MHNO phenotype (HR, 0.73; 95% CI, 0.65-0.81). Among subjects initially classified as MHO, 41.8% remained MHO, with a significantly lower risk of AD compared with the stable MHNO group (HR, 0.62; 95% CI, 0.50-0.77). Among MUO subjects at baseline, those who changed phenotype to MUNO were at higher risk of AD (HR, 1.47; 95% CI, 1.28-1.70), and the transition to the MHO phenotype protected subjects from AD (HR, 0.62; 95% CI, 0.50-0.78). The MHO phenotype conferred a decreased risk of AD. Maintenance or recovery of metabolic health might mitigate AD risk among obese individuals.

Improving Cognition with Nutraceuticals Targeting TGF-β1 Signaling

Rescue of cognitive function represents an unmet need in the treatment of neurodegenerative disorders such as Alzheimer's disease (AD). Nutraceuticals deliver a concentrated form of a presumed bioactive(s) agent(s) that can improve cognitive function alone or in combination with current approved drugs for the treatment of cognitive disorders. Nutraceuticals include different natural compounds such as flavonoids and their subclasses (flavan-3-ols, catechins, anthocyanins, and flavonols), omega-3, and carnosine that can improve synaptic plasticity and rescue cognitive deficits through multiple molecular mechanisms. A deficit of transforming growth factor-β1 (TGF-β1) pathway is an early event in the pathophysiology of cognitive impairment in different neuropsychiatric disorders, from depression to AD. In the present review, we provide evidence that different nutraceuticals, such as Hypericum perforatum (hypericin and hyperforin), flavonoids such as hesperidin, omega-3, and carnosine, can target TGF-β1 signaling and increase TGF-β1 production in the central nervous system as well as cognitive function. The bioavailability of these nutraceuticals, in particular carnosine, can be significantly improved with novel formulations (nanoparticulate systems, nanoliposomes) that increase the efficacy and stability of this peptide. Overall, these studies suggest that the synergism between nutraceuticals targeting the TGF-β1 pathway and current approved drugs might represent a novel pharmacological approach for reverting cognitive deficits in AD patients.

Association Between Diabetic Retinopathy and Cognitive Impairment: A Systematic Review and Meta-Analysis

Diabetic retinopathy (DR) is one of the most common microvascular complications associated with diabetes mellitus. However, its correlation with another diabetes-related disorder, cognitive impairment, has not been well studied. This systematic review and meta-analysis aimed to explore the association between DR and cognitive impairment. MEDLINE (PubMed), the Cochrane Library, and EMBASE databases were searched for observational studies that reported an association between DR and cognitive impairment. Data from selected studies were extracted, and a meta-analysis was conducted using fixed-effects modeling. Fifteen observational studies were included in the systematic review, and 10 studies were included in the meta-analysis. The odds ratio of the association between DR and cognitive impairment was 2.24 (95% confidence interval [CI], 1.89-2.66; I ² = 0.8%). The hazard ratio of the association between DR and cognitive impairment was significant in four studies, ranging from 1.09-1.32. Minimal or mild DR was not significantly associated with cognitive impairment (odds ratio [OR], 2.04; 95% CI, 0.87-4.77). However, the association between proliferative DR and cognitive impairment (OR, 3.57; 95% CI, 1.79-7.12; I ² = 16.6%) was not stronger than the association between moderate or worse DR and cognitive impairment (OR, 4.26; 95% CI, 2.01-9.07; I ² = 0.0%). DR is associated with cognitive impairment, and screening for DR will be helpful for the early identification of individuals with cognitive impairment. Further studies are needed to confirm the association between proliferative DR and cognitive impairment.

Examining the effects of multiple chronic conditions on cognitive decline and potential moderators among older Koreans: Findings from the Korean Longitudinal Study of Ageing 2006-2016

BACKGROUND

More than half of older Koreans have two or more chronic conditions, known as multiple chronic conditions (MCC). Successful self-management (e.g., diet control, exercise, taking medications) is critical to prevent worsening of condition or acquisition of additional chronic conditions. This study investigated the effects of MCC on cognitive decline and risk factors in each chronic condition group over a 10-year period.

METHODS

Six waves (2006-2016) of the Korean Longitudinal Study of Ageing were used, featuring 2,198 older adults who were cognitively healthy at baseline. MCC were categorized into three groups: no chronic condition (n=831), one chronic condition (n=813), and two or more chronic conditions (n=554). Linear mixed-effects model analyses were conducted using SAS 9.4.

RESULTS

Individuals with MCC showed greater cognitive decline than those with no or one chronic condition. Different factors were associated with cognition in each group. Among those with no chronic condition, age, income, education, and functional limitation were associated with cognitive decline. Among those with one chronic condition, age, marital status, working status, self-rated health, and arthritis were associated with cognitive decline. Among those with two or more chronic conditions, age, income, marital status, and living arrangement were associated with cognitive decline. Listed factors have p-values less than .05.

CONCLUSIONS

Findings indicate MCC is significantly related with cognitive decline. Risk factors for cognitive decline differed across three chronic condition groups. Self-management programs that target each group can be a promising strategy to mitigate cognitive decline among older Koreans.

Cardiovascular risks of periodontitis and oral hygiene indicators in patients with diabetes mellitus

AIM

Periodontitis is a common chronic inflammatory disease prevalent in diabetes. The aim of this study was to evaluate periodontitis and poor oral hygiene as independent risk factors for either cerebral or myocardial infarction in the diabetes population.

METHODS

This retrospective cohort study included 17,009 patients with diabetes who had participated in a nationwide health-screening programme, including oral health examination, during 2002-2003 in South Korea. Presence of periodontitis, tooth loss and carious teeth were assessed by professional dentists, and the number of tooth brushings per day was evaluated through self-reported questionnaires. The primary study outcome was the development of cerebral or myocardial infarction, based on International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) codes, up to 31 December 2015.

RESULTS

The study enrolled 17,009 patients with diabetes. Over the mean 11.64 years of follow-up, 1341 patients presented with either cerebral or myocardial infarction. On multivariable Cox proportional hazards regression analysis, presence of periodontitis was an independent risk factor for either cerebral or myocardial infarction [adjusted hazard ratio (HR): 1.17, 95% confidence interval (CI): 1.02-1.34; P = 0.030]. An increased number of carious teeth (≥5) was also associated with risk of cerebral or myocardial infarction (adjusted HR: 1.67, 95% CI: 1.20-2.32; P = 0.002), whereas frequent tooth brushing (≥2 times/day) was negatively associated with risk of cerebral or myocardial infarction (adjusted HR: 0.79, 95% CI: 0.70-0.90; P < 0.001) compared with tooth brushing ≤1 time/day.

CONCLUSION

Early identification and intervention of periodontal disease may be effective in reducing cardiovascular complications in the diabetes population, and improved oral hygiene would probably be associated with lower cardiovascular risk in diabetes.

Cumulative Exposure to Metabolic Syndrome Components and the Risk of Dementia: A Nationwide Population-Based Study

BACKGROUND

Metabolic disturbances are modifiable risk factors for dementia. Because the status of metabolic syndrome (MetS) and its components changes over time, we aimed to investigate the association of the cumulative exposure to MetS and its components with the risk of dementia.

METHODS

Adults (n=1,492,776; ≥45-years-old) who received health examinations for 4 consecutive years were identified from a nationwide population-based cohort in Korea. Two exposure-weighted scores were calculated: cumulative number of MetS diagnoses (MetS exposure score, range of 0 to 4) and the composite of its five components (MetS component exposure score, range of 0 to 20). Hazard ratio (HR) and 95% confidence interval (CI) values for dementia were analyzed using the multivariable Cox proportional-hazards model.

RESULTS

Overall, 47.1% of subjects were diagnosed with MetS at least once, and 11.5% had persistent MetS. During the mean 5.2 years of follow-up, there were 7,341 cases (0.5%) of incident dementia. There was a stepwise increase in the risk of all-cause dementia, Alzheimer's disease, and vascular dementia with increasing MetS exposure score and MetS component exposure score (each P for trend <0.0001). The HR of all-cause dementia was 2.62 (95% CI, 1.87 to 3.68) in subjects with a MetS component exposure score of 20 compared with those with a score of 0. People fulfilling only one MetS component out of 20 already had an approximately 40% increased risk of all-cause dementia and Alzheimer's disease.

CONCLUSION

More cumulative exposure to metabolic disturbances was associated with a higher risk of dementia. Of note, even minimal exposure to MetS components had a significant effect on the risk of dementia.

The insulin resistance by triglyceride glucose index and risk for dementia: population-based study

Background

Insulin resistance is suggested to have negative effects on cognition; however, results from large population studies are lacking. In this study, the potential relationships between the triglyceride glucose (TyG) index, a simple surrogate marker of insulin resistance, and dementia were evaluated using a large-scale population dataset.

Methods

This was a retrospective, observational, cohort study using data from the National Health Information Database from 2009 to 2015 and included 5,586,048 participants 40 years age or older. The TyG index was used as a measure of insulin resistance, and participants were divided into quartiles based on TyG index. The incidence of dementia was assessed using hazard ratios (HRs) estimated with Cox proportional hazard modeling.

Results

During a median follow-up of 7.21 years, dementia was diagnosed in 142,714 (2.55%) participants. Alzheimer’s disease (AD) and vascular dementia (VD) were diagnosed in 74.3% and 12.5% of the participants. Multivariate-adjusted HRs for patients in the TyG index 4th quartile were higher for dementia (HRs = 1.14; 95% confidence interval [CI] 1.12–1.16), AD (HRs = 1.12; 95% CI 1.09–1.14), and VD (HRs = 1.18; 95% CI 1.12–1.23) compared with the 1st quartile of TyG index; however, this had a small effect size (Cohen’s d = 0.10, 0.08, and 0.13, respectively). These effects were independent of age, sex, smoking status, physical activity, body mass index, systolic blood pressure, and total cholesterol.

Conclusion

In this large population study, TyG index was associated with an increased risk of dementia, including AD and VD, that was independent of traditional cardiovascular risk factors, although the effect size of the TyG index was small.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-020-00758-4.

Association between cytomegalovirus end-organ diseases and moderate-to-severe dementia: a population-based cohort study

BACKGROUND

The association between cytomegalovirus (CMV) and dementia remains controversial. Previous studies have suggested that CMV serostatus, as assessed by serum immunoglobulin G, plays a role in neurodegeneration with cognitive impairment. We aimed to evaluate the association between CMV tissue-invasive end-organ diseases and moderate-to-severe dementia.

METHODS

The ICD 10th revision codes from the National Health Insurance Database covering the entire population of the Republic of Korea were used to classify patients into exposed (n = 687, age ≥ 40 years, with CMV disease) and unexposed (n = 3435, without CMV disease) groups, matched by age and sex at a 1:5 ratio of exposed: unexposed. All non-HIV-1-infected subjects selected during 2010-2014 with a washout period of the previous 4 years were followed up until December 2016 to identify newly diagnosed cases of moderate-to-severe dementia.

RESULTS

Multivariate regression model (M3) adjusted for age, sex, low income, body mass index, transplantation status, malignant neoplasms, end-stage renal disease on dialysis, type 2 diabetes mellitus, hypertension, and dyslipidaemia showed a significantly higher incidence of dementia (odds ratio: 1.9; 95% confidence interval: 1.2-2.8) in the exposed group than that in the unexposed group. The risk of vascular dementia (2.9, 1.1-7.5) was higher than that of Alzheimer's disease (1.6, 1.0-2.6) in the exposed group in M3. In M3, patients aged 40-59 years with CMV diseases had a significantly higher risk of all kinds of dementia than those aged 60-79 and ≥ 80 years (11.7, 2.5-49.4 vs. 1.8, 1.1-3.2 vs. 1.3, 0.5-2.8; P = 0.025).

CONCLUSIONS

CMV diseases may be associated with the risk of moderate-to-severe dementia.

The Interplay between Diabetes and Alzheimer's Disease-In the Hunt for Biomarkers

The brain is an organ in which energy metabolism occurs most intensively and glucose is an essential and dominant energy substrate. There have been many studies in recent years suggesting a close relationship between type 2 diabetes mellitus (T2DM) and Alzheimer’s disease (AD) as they have many pathophysiological features in common. The condition of hyperglycemia exposes brain cells to the detrimental effects of glucose, increasing protein glycation and is the cause of different non-psychiatric complications. Numerous observational studies show that not only hyperglycemia but also blood glucose levels near lower fasting limits (72 to 99 mg/dL) increase the incidence of AD, regardless of whether T2DM will develop in the future. As the comorbidity of these diseases and earlier development of AD in T2DM sufferers exist, new AD biomarkers are being sought for etiopathogenetic changes associated with early neurodegenerative processes as a result of carbohydrate disorders. The S100B protein seem to be interesting in this respect as it may be a potential candidate, especially important in early diagnostics of these diseases, given that it plays a role in both carbohydrate metabolism disorders and neurodegenerative processes. It is therefore necessary to clarify the relationship between the concentration of the S100B protein and glucose and insulin levels. This paper draws attention to a valuable research objective that may in the future contribute to a better diagnosis of early neurodegenerative changes, in particular in subjects with T2DM and may be a good basis for planning experiments related to this issue as well as a more detailed explanation of the relationship between the neuropathological disturbances and changes of glucose and insulin concentrations in the brain.