Diabetes and life-long cognitive ability

Multimorbidity, lifestyle, and cognitive function: A cross-cultural study on the role of diabetes, cardiovascular disease, cancer, and chronic respiratory diseases

BACKGROUND

The effect of lifestyle factors on cognitive function related to four major noncommunicable diseases (NCDs) including diabetes, cardiovascular disease, cancer, and chronic respiratory diseases, and the relationship between these NCDs and cognitive function have not been fully studied. We aimed to investigate the longitudinal associations between these NCDs and cognitive function in middle-aged and older people, and the combined effects of lifestyle factors.

METHODS

By employing the data from three large-scale cohort studies from the U.S. Health and Retirement Study (2010-2019), English Longitudinal Study of Aging (2014-2019), and China Health and Retirement Longitudinal Study (2011-2019), this study carried out a multi-cohort analysis to 77, 210 participants. Fixed-effects regression models were used to examine associations between NCD status and cognitive function. Margin plots were used to illustrate the effect of lifestyle factors.

RESULTS

Our findings revealed the dose-dependent association between mounting these NCDs and declining cognitive performance, ranging from one NCD (β = -0.05, 95 % CI: -0.08 to -0.02) to four NCDs (β = -0.51, 95 % CI: -0.75 to -0.28). Decline in cognitive function associated with NCDs was exacerbated with physical inactivity, current smoking status, and an increase in unhealthy lifestyle behaviors.

LIMITATIONS

The observational study design precludes causal interrogation of lifestyles and four NCDs on cognitive function.

CONCLUSIONS

An increasing number of these NCDs were dose-dependently associated with the decline in cognitive function score. Unhealthy lifestyle factors expedite decline in cognitive function linked to these NCDs.

Metabolic syndrome and the risk of postoperative delirium and postoperative cognitive dysfunction: a multi-centre cohort study

BACKGROUND

Metabolic syndrome and its components are risk factors for cognitive impairment, but their contribution to perioperative neurocognitive disorders is unknown. We examined their associations with the risk of postoperative delirium (POD) and postoperative cognitive dysfunction (POCD) in older patients.

METHODS

In 765 male and female participants aged ≥65 years, we measured preoperative metabolic parameters and screened for POD for 7 days or until discharge. POCD was defined through comparison of cognitive change on six neuropsychological tests with non-surgical controls. Multiple logistic regression analyses examined the association of metabolic parameters with risk of POD and POCD with adjustment for age, sex, and surgery type.

RESULTS

A total of 149 patients (19.5% of 765) developed POD and 53 (10.1% of 520 attendees) had POCD at 3 months. Patients with metabolic syndrome were at 1.85-fold higher risk of POD (95% confidence interval [CI] 1.26-2.70). Each 1 mmol L^-1 higher high-density lipoprotein cholesterol (HDL-C) was associated with a 0.47-fold lower POD risk (95% CI 0.30-0.74). Each 1 kg m^-2 higher body mass index (BMI) was associated with a 1.09-fold higher POCD risk (95% CI 1.02- 1.16).

CONCLUSIONS

Older surgical patients with metabolic syndrome were at increased risk of POD. Only reduced HDL-C was significantly associated with POD. For POCD, a higher preoperative BMI was identified as a risk factor. These findings add to mounting evidence of a distinct epidemiology of POD and POCD. Screening programmes taking advantage of HDL-C and BMI measurements and of metabolic interventions in reducing perioperative neurocognitive disorders should be evaluated.

CLINICAL TRIAL REGISTRATION

NCT02265263.

Ecological Momentary Assessment of Cognition in Clinical and Community Samples: Reliability and Validity Study

BACKGROUND

The current methods of evaluating cognitive functioning typically rely on a single time point to assess and characterize an individual's performance. However, cognitive functioning fluctuates within individuals over time in relation to environmental, psychological, and physiological contexts. This limits the generalizability and diagnostic utility of single time point assessments, particularly among individuals who may exhibit large variations in cognition depending on physiological or psychological context (eg, those with type 1 diabetes [T1D], who may have fluctuating glucose concentrations throughout the day).

OBJECTIVE

We aimed to report the reliability and validity of cognitive ecological momentary assessment (EMA) as a method for understanding between-person differences and capturing within-person variation in cognition over time in a community sample and sample of adults with T1D.

METHODS

Cognitive performance was measured 3 times a day for 15 days in the sample of adults with T1D (n=198, recruited through endocrinology clinics) and for 10 days in the community sample (n=128, recruited from TestMyBrain, a web-based citizen science platform) using ultrabrief cognitive tests developed for cognitive EMA. Our cognitive EMA platform allowed for remote, automated assessment in participants' natural environments, enabling the measurement of within-person cognitive variation without the burden of repeated laboratory or clinic visits. This allowed us to evaluate reliability and validity in samples that differed in their expected degree of cognitive variability as well as the method of recruitment.

RESULTS

The results demonstrate excellent between-person reliability (ranging from 0.95 to 0.99) and construct validity of cognitive EMA in both the sample of adults with T1D and community sample. Within-person reliability in both samples (ranging from 0.20 to 0.80) was comparable with that observed in previous studies in healthy older adults. As expected, the full-length baseline and EMA versions of TestMyBrain tests correlated highly with one another and loaded together on the expected cognitive domains when using exploratory factor analysis. Interruptions had higher negative impacts on accuracy-based outcomes (β=-.34 to -.26; all P values <.001) than on reaction time-based outcomes (β=-.07 to -.02; P<.001 to P=.40).

CONCLUSIONS

We demonstrated that ultrabrief mobile assessments are both reliable and valid across 2 very different clinic versus community samples, despite the conditions in which cognitive EMAs are administered, which are often associated with more noise and variability. The psychometric characteristics described here should be leveraged appropriately depending on the goals of the cognitive assessment (eg, diagnostic vs everyday functioning) and the population being studied.

Association of functional health literacy and cognitive ability with self-reported diabetes in the English Longitudinal Study of Ageing: a prospective cohort study

OBJECTIVES

We investigated whether functional health literacy and cognitive ability were associated with self-reported diabetes.

DESIGN

Prospective cohort study.

SETTING

Data were from waves 2 (2004-2005) to 7 (2014-2015) of the English Longitudinal Study of Ageing (ELSA), a cohort study designed to be representative of adults aged 50 years and older living in England.

PARTICIPANTS

8669 ELSA participants (mean age=66.7, SD=9.7) who completed a brief functional health literacy test assessing health-related reading comprehension, and 4 cognitive tests assessing declarative memory, processing speed and executive function at wave 2.

PRIMARY OUTCOME MEASURE

Self-reported doctor diagnosis of diabetes.

RESULTS

Logistic regression was used to examine cross-sectional (wave 2) associations of functional health literacy and cognitive ability with diabetes status. Adequate (compared with limited) functional health literacy (OR 0.71, 95% CI 0.61 to 0.84) and higher cognitive ability (OR per 1 SD=0.73, 95% CI 0.67 to 0.80) were associated with lower odds of self-reporting diabetes at wave 2. Cox regression was used to test the associations of functional health literacy and cognitive ability measured at wave 2 with self-reporting diabetes over a median of 9.5 years follow-up (n=6961). Adequate functional health literacy (HR 0.64; 95% CI 0.53 to 0.77) and higher cognitive ability (HR 0.77, 95% CI 0.69 to 0.85) at wave 2 were associated with lower risk of self-reporting diabetes during follow-up. When both functional health literacy and cognitive ability were added to the same model, these associations were slightly attenuated. Additionally adjusting for health behaviours and body mass index fully attenuated cross-sectional associations between functional health literacy and cognitive ability with diabetes status, and partly attenuated associations between functional health literacy and cognitive ability with self-reporting diabetes during follow-up.

CONCLUSIONS

Adequate functional health literacy and better cognitive ability were independently associated with lower likelihood of reporting diabetes.

Synergistic Associations of Depressive Symptoms and Executive Functions With Longitudinal Trajectories of Diabetes Biomarkers Among Urban-Dwelling Adults Without Diabetes

OBJECTIVE

Depressive symptoms and executive functions (EFs) have recently emerged as novel risk factors for type 2 diabetes, but it is unknown if these factors interact to influence diabetes pathophysiology across the life span. We examined the synergistic associations of depressive symptoms and EFs with longitudinal trajectories of diabetes diagnostic criteria among middle-aged and older adults without diabetes.

METHODS

Participants were 1257 African American and White, urban-dwelling adults from the Healthy Aging in Neighborhoods of Diversity across the Life Span study who were assessed up to three times over a 13-year period (2004-2017). At baseline, participants completed the Center for Epidemiological Studies-Depression scale and measures of EFs-Trail Making Test Part B, verbal fluency, and Digit Span Backward-for a composite EFs score, and provided blood samples at each follow-up for glycated hemoglobin and fasting serum glucose.

RESULTS

A total of 155 and 220 individuals developed diabetes or prediabetes at wave 3 and wave 4, respectively. Linear mixed-effects regression models adjusting for sociodemographic factors, diabetes risk factors, and antidepressant medications revealed significant three-way interactions of Center for Epidemiological Studies-Depression, EFs, and age on change in glycated hemoglobin (b = -0.0001, p = .005) and in fasting serum glucose (b = -0.0004, p < .001), such that among individuals with lower but not higher EFs, elevated depressive symptoms were associated with steeper age-related increases in diabetes biomarkers over time.

CONCLUSIONS

Depressive symptoms and lower EFs may interactively accelerate trajectories of key diagnostic criteria, thereby increasing the risk for earlier diabetes incidence. Identifying individuals in this high-risk group may be an important clinical priority for earlier intervention, which has the promise of preventing or delaying this debilitating disease.

Cataloging the potential SNPs (single nucleotide polymorphisms) associated with quantitative traits, viz. BMI (body mass index), IQ (intelligence quotient) and BP (blood pressure): an updated review

Background

Single nucleotide polymorphism (SNP) variants are abundant, persistent and widely distributed across the genome and are frequently linked to the development of genetic diseases. Identifying SNPs that underpin complex diseases can aid scientists in the discovery of disease-related genes by allowing for early detection, effective medication and eventually disease prevention.

Main body

Various SNP or polymorphism-based studies were used to categorize different SNPs potentially related to three quantitative traits: body mass index (BMI), intelligence quotient (IQ) and blood pressure, and then uncovered common SNPs for these three traits. We employed SNPedia, RefSNP Report, GWAS Catalog, Gene Cards (Data Bases), PubMed and Google Scholar search engines to find relevant material on SNPs associated with three quantitative traits. As a result, we detected three common SNPs for all three quantitative traits in global populations: SNP rs6265 of the BDNF gene on chromosome 11p14.1, SNP rs131070325 of the SL39A8 gene on chromosome 4p24 and SNP rs4680 of the COMT gene on chromosome 22q11.21.

Conclusion

In our review, we focused on the prevalent SNPs and gene expression activities that influence these three quantitative traits. These SNPs have been used to detect and map complex, common illnesses in communities for homogeneity testing and pharmacogenetic studies. High blood pressure, diabetes and heart disease, as well as BMI, schizophrenia and IQ, can all be predicted using common SNPs. Finally, the results of our work can be used to find common SNPs and genes that regulate these three quantitative features across the genome.

Adolescent cognitive function and incident early-onset type 2 diabetes

BACKGROUND

Cognitive function among apparently healthy adolescents has been associated with cardiovascular morbidity and mortality. We examined the relationship between global and subdomain cognitive scores in adolescence and early-onset type 2 diabetes (T2D) in men and women.

METHODS

A nationwide, population-based study of 971,677 Israeli born adolescents (56% men; mean age 17.4 years) who were medically examined and their cognitive performance was assessed before compulsory military service during 1992-2010. Data included global and subdomain cognitive Z-scores (problem-solving, verbal abstraction and categorization, verbal comprehension, and mathematical abilities). Data were linked to the Israeli National Diabetes Registry. The relations between global and subdomain scores and incident T2D was determined using Cox proportional hazard models and logistic regression models. Analyses were conducted separately for men and women.

FINDINGS

During 16,095,122 person-years, 3,570 individuals developed T2D. After adjustment, those in the low compared to the high quintile of global cognitive Z-score had the highest risk for T2D; HR 2.46, (95% CI 2.10-2.88) for men and 2.33 (95% CI 1.88-2.89) for women. A one-unit lower global cognitive Z-score was associated with 1.41 (95% CI 1.34-1.48) and 1.46 (95% CI 1.36-1.56) increased risks for men and women, respectively. The relationship was noted for the cognitive subdomains scores as well as for the global cognitive score, with no heterogeneity across cognitive subdomains.

INTERPRETATION

This large nationally representative cohort suggests relationship between global, as well as subdomain cognitive scores in late adolescence, and incident early onset T2D in both sexes, which was independent of socioeconomic status.

Construct validity, ecological validity and acceptance of self-administered online neuropsychological assessment in adults

Objective: The goal of this project was to explore the initial psychometric properties (construct and ecological validity) of self-administered online (SAO) neuropsychological assessment (using the www.testmybrain.org platform), compared to traditional testing, in a clinical sample, as well as to evaluate participant acceptance. SAO assessment has the potential to expand the reach of in-person neuropsychological assessment approaches.Method: Counterbalanced, within-subjects design comparing SAO performance to in-person performance in adults with diabetes with and without Chronic Kidney Disease (CKD). Forty-nine participants completed both assessment modalities (type 1 diabetes N = 14, type 2 diabetes N = 35; CKD N = 18).Results: Associations between SAO and analogous in-person tests were adequate to good (r = 0.49-0.66). Association strength between divergent cognitive tests did not differ between SAO versus in-person tests. SAO testing was more strongly associated with age than in-person testing (age R2=0.54 versus 0.23), while prediction of education, HbA1c, and estimated glomerular filtration rate (eGFR) did not differ significantly between test modalities (education R2=0.37 versus 0.30; HbA1c R2=0.20 versus 0.12; eGFR R2 = 0.41 versus 0.33). Associations with measures of everyday functioning were also similar (Functional Activities Questionnaire R2=0.08 versus 0.07; Neuro-QoL R2=0.14 versus 0.16; Diabetes Self-Management Questionnaire R2=0.19 versus 0.19).Conclusions: The selected SAO neuropsychological tests had acceptable construct validity (including divergent, convergent, and criterion-related validity), and similar ecological validity to that of traditional testing. These SAO assessments were acceptable to participants and appear appropriate for use in research applications, although further research is needed to better understand the strengths and weaknesses in other clinical populations.

Genetic Contributions to Health Literacy

Higher health literacy is associated with higher cognitive function and better health. Despite its wide use in medical research, no study has investigated the genetic contributions to health literacy. Using 5783 English Longitudinal Study of Ageing (ELSA) participants (mean age = 65.49, SD = 9.55) who had genotyping data and had completed a health literacy test at wave 2 (2004-2005), we carried out a genome-wide association study (GWAS) of health literacy. We estimated the proportion of variance in health literacy explained by all common single nucleotide polymorphisms (SNPs). Polygenic profile scores were calculated using summary statistics from GWAS of 21 cognitive and health measures. Logistic regression was used to test whether polygenic scores for cognitive and health-related traits were associated with having adequate, compared to limited, health literacy. No SNPs achieved genome-wide significance for association with health literacy. The proportion of variance in health literacy accounted for by common SNPs was 8.5% (SE = 7.2%). Greater odds of having adequate health literacy were associated with a 1 standard deviation higher polygenic score for general cognitive ability [OR = 1.34, 95% CI (1.26, 1.42)], verbal-numerical reasoning [OR = 1.30, 95% CI (1.23, 1.39)], and years of schooling [OR = 1.29, 95% CI (1.21, 1.36)]. Reduced odds of having adequate health literacy were associated with higher polygenic profiles for poorer self-rated health [OR = 0.92, 95% CI (0.87, 0.98)] and schizophrenia [OR = 0.91, 95% CI (0.85, 0.96)). The well-documented associations between health literacy, cognitive function and health may partly be due to shared genetic etiology. Larger studies are required to obtain accurate estimates of SNP-based heritability and to discover specific health literacy-associated genetic variants.

Insulin resistance: Genetic associations with depression and cognition in population based cohorts

Insulin resistance, broadly defined as the reduced ability of insulin to exert its biological action, has been associated with depression and cognitive dysfunction in observational studies. However, it is unclear whether these associations are causal and whether they might be underpinned by other shared factors. To address this knowledge gap, we capitalized on the stability of genetic biomarkers through the lifetime, and on their unidirectional relationship with depression and cognition. Specifically, we determined the association between quantitative measures of cognitive function and depression and genetic instruments of insulin resistance traits in two large-scale population samples, the Generation Scotland: Scottish Family Health Study (GS: SFHS; N = 19,994) and in the UK Biobank (N = 331,374). In the GS:SFHS, the polygenic risk score (PRS) for fasting insulin was associated with verbal intelligence and depression while the PRS for the homeostasis model assessment of insulin resistance was associated with verbal intelligence. Despite this overlap in genetic architecture, Mendelian randomization analyses in the GS:SFHS and in the UK Biobank samples did not yield evidence for causal associations from insulin resistance traits to either depression or cognition. These findings may be due to weak genetic instruments, limited cognitive measures and insufficient power but they may also indicate the need to identify other biological mechanisms that may mediate the relationship from insulin resistance to depression and cognition.

Clinically significant cognitive impairment in older adults with type 1 diabetes

AIMS

Little is known about cognition in older adults with type 1 diabetes. The aim of this study was to identify correlates of clinically significant cognitive impairment.

METHODS

Neuropsychological, diabetes-related and glycemic (HbA1c, Continuous Glucose Monitoring; CGM) data were collected from 201 older adults (≥60 years) with longstanding type 1 diabetes.

RESULTS

Clinically significant cognitive impairment (≥2 cognitive tests ≥1.5 SD below normative data) occurred in 48% of the sample. After controlling for age, gender, education and diabetes duration, we found that hypoglycemia unawareness, recent severe hypoglycemic events, any microvascular complication, higher HbA1c and CGM average nocturnal glucose were all associated with increased odds of clinically significant cognitive impairment (ORs = 1.01-2.61), while CGM nocturnal % time below 60 mg/dL was associated with a decreased odds of cognitive impairment (OR = 0.94). Diabetes duration, diagnosis age, daytime CGM, and lifetime severe hypoglycemic events were not related to cognitive impairment status.

CONCLUSIONS

Clinically significant cognitive impairment was common in older adults with type 1 diabetes. Diabetes-related correlates of cognitive impairment were identified, including hypoglycemia unawareness, recent severe hypoglycemic events, and CGM variables. Longitudinal research is needed to determine if these variables predict cognitive decline and if their modification alters outcomes.

The chicken or the egg? Does glycaemic control predict cognitive function or the other way around?

The association between type 2 diabetes and cognitive dysfunction is well established. Prevention of the development of type 2 diabetes and its complications, as well as cognitive dysfunction and dementia, are leading goals in these fields. Deciphering the causality direction of the interplay between type 2 diabetes and cognitive dysfunction, and understanding the timeline of disease progression, are crucial for developing efficient prevention strategies. The prevailing perception is that type 2 diabetes leads to cognitive dysfunction and dementia. There is substantial evidence showing that accelerated cognitive decline in type 2 diabetes starts in midlife (mean age 40-60 years) and that it may even begin at the prediabetes stage. However, in this issue of Diabetologia, Altschul et al (doi: https://doi.org/10.1007/s00125-018-4645-8 ) show evidence for the reverse causality hypothesis, i.e. that lower cognitive function precedes poor glycaemic control. They found that cognitive function at early adolescence (age 11 years) predicts both HbA_1c levels and cognitive function at age 70 years. Moreover, they found that lower cognitive function at age 70 is associated with an increase in HbA_1c from age 70 to 79 years. Based on these findings, future studies should explore whether developing prevention strategies that target young adolescents with lower cognitive function will result in prevention of type 2 diabetes, breaking the vicious cycle of type 2 diabetes and cognitive dysfunction.

Cognitive function in early and later life is associated with blood glucose in older individuals: analysis of the Lothian Birth Cohort of 1936

AIMS/HYPOTHESIS

The aim of this study was to examine whether cognitive function in early and later life, and decline in cognitive function from age 70 to 79 years, are associated with high blood glucose, as measured by HbA1c, at baseline (age 70), and changes in blood glucose from age 70 to 79.

METHODS

Participants (n = 1091) in the Lothian Birth Cohort of 1936 were examined. Fourteen tests were used to assess cognitive functions, grouped into four domains: visuospatial ability, processing speed, memory and crystallised ability. Test results, and measurements of HbA1c and other health variables, were collected at each of four waves of assessment: at the mean age of 70, 73, 76 and 79 years. Data on cognitive function at age 11 was also available for this cohort. Latent growth curve modelling was performed and statistical controls for known risk factors were introduced.

RESULTS

Higher age 11 cognitive function predicted lower HbA1c level at age 70 (p < 0.001). Higher cognitive function at age 70 was related to a comparatively smaller increase in HbA1c levels from age 70 to 79 (p < 0.001). HbA1c from age 70 to 79 did not have any consistent association with change in cognitive function from age 70 to 79. These associations survived adjustments for age, sex, education, APOE*ε4, smoking history, cardiovascular disease history, hypertension history, BMI and corrections for multiple testing.

CONCLUSIONS/INTERPRETATION

Our results show that, among older individuals, high blood glucose is consistently predicted by lower cognitive function. Clinical care that examines and tracks cognitive function, while also taking the positive effects of maintaining cognitive function and emulating healthy behaviours associated with higher cognitive function into account, may be one approach for protecting at-risk individuals from elevated blood glucose and subsequent type 2 diabetes mellitus.

Young adult cognitive ability and subsequent major depression in a cohort of 666,804 Danish men

BACKGROUND

Early life cognitive ability (CA) might influence the risk of developing major depression (MD). The aim was to investigate the association between young adult CA and subsequent MD in relation to different MD disease characteristics.

METHODS

Information on CA was assessed at conscription board examinations 1957-1984 (mean age 19 years) and information on MD was based on hospital diagnosis retrieved from Danish Patient registers 1969-2015. Associations between CA and MD were examined using Cox regression analyses.

RESULTS

A total of 666,804 men (born 1939-1959) were followed and 25,841 (3.9%) developed MD during a mean follow-up of 40.8 years. Lower CA was associated with an increased risk of incident MD. The association was stronger for early-onset (<60 years) (HR_{per1SDdecrease} = 1.23; 95%CI:1.21,1.24) compared to late-onset (≥60 years) MD (HR_{per1SDdecrease} = 1.14; 95%CI:1.11,1.16), but CA was not related to number of depressive episodes. The association was stronger for single depressive episodes (HR_{per1SDdecrease} = 1.21; 95%CI:1.19,1.23) compared to recurrent depression (HR_{per1SDdecrease} = 1.13; 95%CI:1.09,1.16), while the strength of the association did not differ according to MD disease severity (ICD10: mild, moderate, and severe depression).

LIMITATIONS

The study sample only included men and only MD cases diagnosed at hospital were included which limits the generalizability.

CONCLUSION

Low CA could be a risk factor for especially early onset MD in men, whereas the influence of CA on re-occurrence seems less strong. Lower pre-morbid CA increases the risk of MD and should therefore be part of the depression risk assessment in clinical practice.

Healthy cognitive ageing in the Lothian Birth Cohort studies: marginal gains not magic bullet

In the face of shifting demographics and an increase in human longevity, it is important to examine carefully what is known about cognitive ageing, and to identify and promote possibly malleable lifestyle and health-related factors that might mitigate age-associated cognitive decline. The Lothian Birth Cohorts of 1921 (LBC1921, n = 550) and 1936 (LBC1936, n = 1091) are longitudinal studies of cognitive and brain ageing based in Scotland. Childhood IQ data are available for these participants, who were recruited in later life and then followed up regularly. This overview summarises some of the main LBC findings to date, illustrating the possible genetic and environmental contributions to cognitive function (level and change) and brain imaging biomarkers in later life. Key associations include genetic variation, health and fitness, psychosocial and lifestyle factors, and aspects of the brain's structure. It addresses some key methodological issues such as confounding by early-life intelligence and social factors and emphasises areas requiring further investigation. Overall, the findings that have emerged from the LBC studies highlight that there are multiple correlates of cognitive ability level in later life, many of which have small effects, that there are as yet few reliable predictors of cognitive change, and that not all of the correlates have independent additive associations. The concept of marginal gains, whereby there might be a cumulative effect of small incremental improvements across a wide range of lifestyle and health-related factors, may offer a useful way to think about and promote a multivariate recipe for healthy cognitive and brain ageing.

Diabetes is associated with risk of postoperative cognitive dysfunction: A meta-analysis

BACKGROUND

Postoperative cognitive dysfunction (POCD) occurs frequently after surgery, particularly among older people. Diabetes, chronic hyperglycemia, and a history of hypoglycemia are related to cognitive impairment, but little is known about their roles in POCD. Here, we estimated their associations with risk of POCD on the basis of published epidemiological research.

METHODS

The PubMed and Cochrane databases were searched for longitudinal studies of adults undergoing surgery with reporting of associations of diabetes status, glycemic levels, and/or a history of hypoglycemia with risk of POCD as relative risks or odds ratios. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) and Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed.

RESULTS

The search identified 246 publications of which 14 met inclusion criteria, reporting on a total of 2642 patients (mean age 64 y). Follow-up periods spanned 1 day to 5 years. Overall, patients with diabetes had a 1.26-fold higher risk of POCD compared with diabetes-free patients (95% CI, 1.12-1.42). A single study assessed glycemic control in patients with diabetes and identified a higher hemoglobin A1c (HbA1c) level as associated with higher POCD risk (relative risk per percent higher HbA1c, 2.0; 95% CI, 1.4-2.6). We did not find studies on glycemic levels in the nondiabetic range or on hypoglycemia as potential predictors of POCD.

CONCLUSION

Patients with diabetes appear to have a higher risk of POCD compared with diabetes-free persons. Among patients with diabetes, POCD risk may further increase with poorer glycemic control as indexed by higher HbA1c. The roles of HbA1c levels among nondiabetic persons in POCD risk warrant further research.

Risk factors for dementia in the ninth decade of life and beyond: a study of the Lothian birth cohort 1921

BACKGROUND

With increasing numbers of people surviving beyond eighty years, this section of the population demands attention to reduce the impact of dementia. In order to develop effective preventative strategies, it is essential to understand age-specific risk factor profiles for dementia: do risk factors for dementia in those in their sixties and seventies persist into oldest age? The aims of this study were to determine incident dementia and to investigate the risk profile for dementia from age 79 to 95 years in a well-characterised cohort.

METHODS

Participants underwent intelligence testing at age 11 and were followed-up from at 79 years of age. Variables included: age, sex, age 11 IQ, APOE ɛ4, education, diabetes, hypertension, statin use, physical activity at leisure and in occupation, symptoms of depression, height, number of teeth, body mass index, blood pressure, cholesterol and HbA1c. Dementia cases were ascertained from death certificates, electronic patient records and clinical reviews. Logistic regression analysis determined the degree of risk for dementia associated with each variable. Analyses were completed both with and without the physical activity variables due to the significant number of missing data for these variables.

RESULTS

Of the eligible cohort, n = 410 participants remained dementia-free and n = 110 had developed probable dementia. When logistic regression analyses contained all variables, complete data was available for n = 234 (n = 48 with dementia). Results demonstrated that positive APOE ɛ4 carrier status (OR: 2.15, 95% CI: 1.04, 4.42) and greater lifetime physical activity (OR: 1.14, 95% CI: 1.02, 1.28) increased the risk for dementia. A reduction in risk for dementia was seen for hypertension (OR: 0.47, 95% CI: 0.23, 0.98). When physical activity variables were excluded, the number with complete data increased to n = 377 (n = 80 with dementia). APOE ɛ4 remained significant (OR: 2.37; 95% CI: 1.37, 4.07), as did hypertension (OR: 0.55; 95% CI: 0.32, 0.93).

CONCLUSIONS

Dementia incidence was consistent with expected rates. The risk profile for dementia in this cohort of participants aged 79-95 confirmed previous findings that risk factors differ for those over 79 years. Further evidence is recommended in order that the risk profile for this age group can be accurately determined.

Cognitive ability and physical health: a Mendelian randomization study

Causes of the association between cognitive ability and health remain unknown, but may reflect a shared genetic aetiology. This study examines the causal genetic associations between cognitive ability and physical health. We carried out two-sample Mendelian randomization analyses using the inverse-variance weighted method to test for causality between later life cognitive ability, educational attainment (as a proxy for cognitive ability in youth), BMI, height, systolic blood pressure, coronary artery disease, and type 2 diabetes using data from six independent GWAS consortia and the UK Biobank sample (N = 112 151). BMI, systolic blood pressure, coronary artery disease and type 2 diabetes showed negative associations with cognitive ability; height was positively associated with cognitive ability. The analyses provided no evidence for casual associations from health to cognitive ability. In the other direction, higher educational attainment predicted lower BMI, systolic blood pressure, coronary artery disease, type 2 diabetes, and taller stature. The analyses indicated no causal association from educational attainment to physical health. The lack of evidence for causal associations between cognitive ability, educational attainment, and physical health could be explained by weak instrumental variables, poorly measured outcomes, or the small number of disease cases.

COGNITOMICS: a new approach for the evaluation of the relationship between diseases and cognition to be designed based on normal behavioral tendencies in real life, a conceptual framework

The relationship between medical diseases and cognition has been a point of interest in the last decades. In recent years studies in this field have developed significantly applying various tools such as cognitive tests using psychometric assessments and brain imaging techniques. The main focus of cognitive function in this studies is the process through which this cognition is obtained. It seems a novel methodology is needed while assessing the impact of diseases such as diabetes on cognition based on heavenly religious teachings in which cognition is believed to be the main source of human bliss and not just some measurable quantitative components.

Spies C, Pischon T. Cognitive Reserve and the Risk of Postoperative Cognitive Dysfunction

BACKGROUND

Post-operative cognitive dysfunction (POCD) occurs in 10 to 54% of older patients during the first few weeks after surgery, but little is known about risk factors predisposing to POCD.

METHODS

Systematic literature review and meta-analysis of cognitive reserve indicators and POCD risk.

RESULTS

Fifteen studies on 5104 patients were included. Follow-up periods spanned 1 day to 6 months. Educational level was the most commonly assessed cognitive reserve indicator, and a longer time spent in education was associated with a reduced risk of POCD (relative risk [RR] per year increment 0.90; 95% confidence interval: [0.87; 0.94]), i.e. each year increase in education was associated with a 10% reduced risk. Similar findings were made for some analyses on education as a categorical predictor (high school versus further/higher education, RR 1.71, [1.30; 2.25]; lower than high school versus further/higher education, RR 1.69, [1.17; 2.44]) though risk was equivalent for patients with high school education and those with lower than high school education (RR 1.02; [0.78; 1.32]).

CONCLUSION

Patients with a relatively higher level of education are at reduced risk of POCD. Risk stratification of surgical patients according to educational level may prove useful.

Lower verbal intelligence is associated with diabetic complications and slower walking speed in people with Type 2 diabetes: the Maastricht Study

AIMS

To determine the association of verbal intelligence, a core constituent of health literacy, with diabetic complications and walking speed in people with Type 2 diabetes.

METHODS

This study was performed in 228 people with Type 2 diabetes participating in the Maastricht Study, a population-based cohort study. We examined the cross-sectional associations of score on the vocabulary test of the Groningen Intelligence Test with: 1) determinants of diabetic complications (HbA_1c , blood pressure and lipid level); 2) diabetic complications: chronic kidney disease, neuropathic pain, self-reported history of cardiovascular disease and carotid intima-media thickness; and 3) walking speed. Analyses were performed using linear regression and adjusted in separate models for potential confounders and mediators. Significant age- and sex-adjusted associations were additionally adjusted for educational level in a separate model.

RESULTS

After full adjustment, lower verbal intelligence was associated with the presence of neuropathic pain [odds ratio (OR) 1.18, 95% CI 1.02;1.36], cardiovascular disease (OR 1.14, 95% CI 1.01;1.30), and slower walking speed (regression coefficient -0.011 m/s, 95% CI -0.021; -0.002 m/s). These associations were largely explained by education. Verbal intelligence was not associated with blood pressure, glycaemic control, lipid control, chronic kidney disease or carotid intima-media thickness.

CONCLUSIONS

Lower verbal intelligence was associated with the presence of some diabetic complications and with a slower walking speed, a measure of physical functioning. Educational level largely explained these associations. This implies that clinicians should be aware of the educational level of people with diabetes and should provide information at a level of complexity tailored to the patient.

Cognition in Adults and Older Adults With Type 1 Diabetes: Chicken or Egg?

IN BRIEF Cognitive impairment and cognitive decline are common in adults with type 1 diabetes. Although several diabetes-related variables have been associated with cognitive functioning in both cross-sectional and longitudinal studies, inconsistencies remain. This is particularly true in older adults. Cognitive impairment appears to be both a consequence of and a risk factor for poor diabetes self-management and associated glycemic outcomes. Interventions such as cognitive compensatory strategies, assistive technology, and simplified treatment regimens may limit the impact of cognitive impairment on self-management in adults and older adults with type 1 diabetes.

Assessing the genetic overlap between BMI and cognitive function

Obesity and low cognitive function are associated with multiple adverse health outcomes across the life course. They have a small phenotypic correlation (r=-0.11; high body mass index (BMI)-low cognitive function), but whether they have a shared genetic aetiology is unknown. We investigated the phenotypic and genetic correlations between the traits using data from 6815 unrelated, genotyped members of Generation Scotland, an ethnically homogeneous cohort from five sites across Scotland. Genetic correlations were estimated using the following: same-sample bivariate genome-wide complex trait analysis (GCTA)-GREML; independent samples bivariate GCTA-GREML using Generation Scotland for cognitive data and four other samples (n=20 806) for BMI; and bivariate LDSC analysis using the largest genome-wide association study (GWAS) summary data on cognitive function (n=48 462) and BMI (n=339 224) to date. The GWAS summary data were also used to create polygenic scores for the two traits, with within- and cross-trait prediction taking place in the independent Generation Scotland cohort. A large genetic correlation of -0.51 (s.e. 0.15) was observed using the same-sample GCTA-GREML approach compared with -0.10 (s.e. 0.08) from the independent-samples GCTA-GREML approach and -0.22 (s.e. 0.03) from the bivariate LDSC analysis. A genetic profile score using cognition-specific genetic variants accounts for 0.08% (P=0.020) of the variance in BMI and a genetic profile score using BMI-specific variants accounts for 0.42% (P=1.9 × 10(-7)) of the variance in cognitive function. Seven common genetic variants are significantly associated with both traits at P<5 × 10(-5), which is significantly more than expected by chance (P=0.007). All these results suggest there are shared genetic contributions to BMI and cognitive function.

Obesity and post-operative cognitive dysfunction: a systematic review and meta-analysis

BACKGROUND

Post-operative cognitive dysfunction, a condition distinct from post-operative delirium (POD), occurs frequently after surgery, and is related to dementia and premature death. Obesity increases the risk of late-life cognitive impairment, but little is known about its role in post-operative cognitive dysfunction. We conducted a systematic review and meta-analysis of studies on the association between obesity and risk of post-operative cognitive dysfunction.

METHODS

PubMed and the Cochrane Library were systematically searched. Studies were included if they had prospective designs, reported on human adults undergoing surgery, if cognitive function was measured pre- and post-surgery, if obesity, body mass index (BMI) and/or body weight were ascertained, and if associations with post-operative cognitive dysfunction were reported as relative risks or odds ratios. Underweight, weight loss, and post-operative delirium were not considered.

RESULTS

Inclusion criteria were met by six articles. Samples totaled 1432 older patients (mean age ≥62 years) who were followed up for 24 h to 12 months after surgery. Analysis of studies with obesity defined as a categorical measure found a non-significantly higher risk of post-operative cognitive dysfunction among persons with BMI > 30 kg/m(2) versus ≤30 kg/m(2) (relative risk 1.27; 95% confidence interval 0.95, 1.70; p = 0.10). No such associations were found for studies that analysed BMI or body weight continuously as predictors of post-operative cognitive dysfunction (relative risk 0.98 per kg/m(2) ; 95% confidence interval 0.93, 1.03, p = 0.45; relative risk 0.99 per kg; 95% confidence interval 0.89, 1.09; p = 0.83, respectively).

CONCLUSIONS

Few studies have addressed the topic, and the results of these studies provide only limited support for an increased risk of post-operative cognitive dysfunction in patients who are obese. Further large-scale, prospective investigations are necessary for clarification. Copyright © 2016 John Wiley & Sons, Ltd.

Towards More Rigorous Personality Trait–Outcome Research

Much of personality research attempts to identify causal links between personality traits and various types of outcomes. I argue that causal interpretations require traits to be seen as existentially and holistically real and the associations to be independent of specific ways of operationalizing the traits. Among other things, this means that, to the extents that causality is to be ascribed to such holistic traits, items and facets of those traits should be similarly associated with specific outcomes, except for variability in the degrees to which they reflect the traits (i.e. factor loadings). I argue that, before drawing causal inferences about personality trait–outcome associations, the presence of this condition should be routinely tested by, for example, systematically comparing the outcome associations of individual items or facets, or sampling different indicators for measuring the same purported traits. Existing evidence suggests that observed associations between personality traits and outcomes at least sometimes depend on which particular items or facets have been included in trait operationalizations, calling trait–level causal interpretations into question. However, this has rarely been considered in the literature. I argue that when outcome associations are specific to facets, they should not be generalized to traits. Furthermore, when the associations are specific to particular items, they should not even be generalized to facets. Copyright © 2016 European Association of Personality Psychology

Markers of Psychological Differences and Social and Health Inequalities: Possible Genetic and Phenotypic Overlaps

Associations between markers of ostensible psychological characteristics and social and health inequalities are pervasive but difficult to explain. In some cases, there may be causal influence flowing from social and health inequalities to psychological differences, whereas sometimes it may be the other way around. Here, we focus on the possibility that some markers that we often consider as indexing different domains of individual differences may in fact reflect at least partially overlapping genetic and/or phenotypic bases. For example, individual differences in cognitive abilities and educational attainment appear to reflect largely overlapping genetic influences, whereas cognitive abilities and health literacy may be almost identical phenomena at the phenotypic, never mind genetic, level. We make the case for employing molecular genetic data and quantitative genetic techniques to better understand the associations of psychological individual differences with social and health inequalities. We illustrate these arguments by using published findings from the Lothian Birth Cohort and the Generation Scotland studies. We also present novel findings pertaining to longitudinal stability and change in older age personality traits and some correlates of the change, molecular genetic data-based heritability estimates of Neuroticism and Extraversion, and the genetic correlations of these personality traits with markers of social and health inequalities.

The impact of diabetes on cognitive decline: potential vascular, metabolic, and psychosocial risk factors

Older people with type 2 diabetes are at increased risk of developing cognitive impairment, for which several potential risk factors have been proposed. The present article reviews evidence in people with type 2 diabetes for associations of cognitive impairment with a range of vascular, metabolic, and psychosocial risk factors, many of which have a higher prevalence in people with type 2 diabetes than in non-diabetic adults of a similar age. Definitive research studies in this field are few in number. The risk factors may be involved in causal pathways or may act as useful markers of cerebrovascular damage (or both), and for which relatively consistent evidence is available, include poor glycemic control, hypoglycemia, microvascular disease, inflammation, and depression. For macrovascular disease, the strength of the association with cognitive impairment appears to depend on which vascular system has been examined. A role for pre-morbid ability in young adulthood as influencing the risk of both diabetes and cognitive impairment has also been suggested. The importance of considering inter-relationships between risk factors when investigating their potential contribution to cognitive impairment in future investigations is discussed.

Aerobic physical exercise improved the cognitive function of elderly males but did not modify their blood homocysteine levels

Background

Physical exercise influences homocysteine (Hcy) concentrations, cognitive function and the metabolic profile. The purpose of this study was to investigate the influence of regular physical exercise on Hcy levels, the metabolic profile and cognitive function in healthy elderly males before and after an endurance exercise program.

Methods

Forty-five healthy and sedentary volunteers were randomized into 2 groups: (1) a control group asked not to change their normal everyday activities and not to start any regular physical exercise program and (2) an experimental group trained at a heart rate intensity corresponding to ventilatory threshold 1 (VT-1) for 60 min/day 3 times weekly on alternate days for 6 months using a cycle ergometer. All volunteers underwent cognitive evaluations, blood sample analyses and ergospirometric assessments.

Results

A significant improvement in cognitive function was observed in the experimental group compared with the control group (p < 0.05). No significant changes in Hcy levels were observed in the experimental group (p > 0.05), but there was a significant increase in peak oxygen consumption and workload at VT-1 as well as a significant improvement in cholesterol, triglycerides, HDL, glucose, alkaline phosphatase, urea, T₃, T₄ and prostate-specific antigen compared with the control group (p < 0.05).

Conclusion

The data suggest that a physical exercise program does not reduce Hcy levels in healthy elderly males, although it improves the cardiovascular and metabolic profile as well as cognitive function.