Relationship between Insulin-Resistance Processing Speed and Specific Executive Function Profiles in Neurologically Intact Older Adults

NHANES 2011-2014 Reveals Decreased Cognitive Performance in U.S. Older Adults with Metabolic Syndrome Combinations

A relationship between metabolic syndrome and cognitive impairment has been evidenced across research; however, conflicting results have been observed. A cross-sectional study was conducted on 3179 adults older than 60 from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) to analyze the relationship between metabolic syndrome and cognitive impairment. In our results, we found that adults with abdominal obesity, high triglycerides, and low HDL cholesterol had 4.39 fewer points in the CERAD immediate recall test than adults without any metabolic syndrome factors [Beta = -4.39, SE = 1.32, 17.75 (1.36) vs. 22.14 (0.76)]. In addition, people with this metabolic syndrome combination exhibited 2.39 fewer points in the CERAD delayed recall test than those without metabolic syndrome criteria [Beta = -2.39, SE = 0.46, 4.32 (0.49) vs. 6.71 (0.30)]. It was also found that persons with high blood pressure, hyperglycemia, and low HDL-cholesterol levels reached 4.11 points less in the animal fluency test than people with no factors [Beta = -4.11, SE = 1.55, 12.67 (2.12) vs. 16.79 (1.35)]. These findings suggest that specific metabolic syndrome combinations are essential predictors of cognitive impairment. In this study, metabolic syndrome combinations that included obesity, fasting hyperglycemia, high triglycerides, and low HDL-cholesterol were among the most frequent criteria observed.

Endophenotypic correlates of cognitive function in reproductive-age individuals with polycystic ovary syndrome

Objective

To characterize cognitive performance in relation to hormonal and metabolic factors in women with polycystic ovary syndrome (PCOS).

Design

Cross-sectional study.

Setting

Tertiary university center.

Patients

A total of 48 individuals, aged 21-46 years, with PCOS according to the Rotterdam criteria.

Interventions

Complete history and physical examinations, endovaginal ultrasounds, dermatologic assessments, neuropsychological assessments, and metabolic and hormonal serum tests.

Main Outcome Measures

Sample-based z-scores on a comprehensive cognitive test battery.

Results

Subjects were defined as having an androgenic (n = 31) or a nonandrogenic (n = 17) PCOS phenotype. Compared with their nonandrogenized counterparts, subjects with hyperandrogenism demonstrated lower relative performance on the tests of executive function (β-coefficient for the executive function composite z-score, -0.44; 95% confidence interval, -0.79 to -0.09), despite similar performance on the tests of memory, verbal reasoning, and perceptual reasoning. These differences were independent of age, years of education, and obesity. In an exploratory analysis in which subjects were stratified by the presence of insulin resistance (IR), subjects with PCOS with both IR and hyperandrogenism showed the lowest performance on a composite score of executive function, followed by those with hyperandrogenism alone.

Conclusions

In this small study, subjects with hyperandrogenic PCOS demonstrated lower performance on the tests of executive function than subjects with nonandrogenic PCOS. Additional research is needed to confirm these findings in larger cohorts and investigate the role of modifiable factors, including IR, on cognitive outcomes.

Differences between young and older adults in unity and diversity of executive functions

Miyake and colleagues (2000) identified three independent but correlated components of executive function in young adults - set shifting, inhibition, and updating. The present study compared the factor structure in young adults to two groups of older adults (ages 60-73 and 74-98). A three-factor model of shifting, inhibition and updating was confirmed in young adults, but the factors were weakly or uncorrelated. In both older groups, a two-factor solution was indicated, updating/inhibition and shifting, which were moderately correlated in young-older adults, and strongly correlated in the old-older group. A nested factors model in the oldest group revealed a common factor, which loaded on all but one of the tests, and a shifting-specific factor. We concluded that in young adulthood, shifting, updating and inhibition may operate relatively independently. As people age and processing becomes less efficient, they may rely increasingly on general executive control processes, reallocating their limited resources to optimize performance.

A systematic review of existing peripheral biomarkers of cognitive aging: Is there enough evidence for biomarker proxies in behavioral modification interventions?: An initiative in association with the nutrition, exercise and lifestyle team of the Canadian Consortium on Neurodegeneration in Aging

Peripheral biomarkers have shown significant value in predicting brain health and may serve as a useful proxy measurement in the assessment of evidence-based lifestyle behavior modification programs, including physical activity and nutrition programs, that aim to maintain cognitive function in late life. The aim of this systematic review was to elucidate which peripheral biomarkers are robustly associated with cognitive function among relatively healthy non-demented older adults. Following the standards for systematic reviews (PICO, PRIMSA), and employing MEDLINE and Scopus search engines, 222 articles were included in the review. Based on the review of biomarker proxies of cognitive health, it is recommended that a comprehensive biomarker panel, or biomarker signature, be developed as a clinical end point for behavior modification trials aimed at enhancing cognitive function in late life. The biomarker signature should take a multisystemic approach, including lipid, immune/inflammatory, and metabolic biomarkers in the biological signature index of cognitive health.

Type 2 diabetes and later cognitive function in older American Indians: The Strong Heart Study

OBJECTIVES

Insulin resistance is a substantial health issue for American Indians, with type 2 diabetes overrepresented in this population as compared with non-Hispanic whites. Insulin resistance and its related conditions in turn increase risk for dementia and cognitive impairment. The aim of the current study was to determine whether type 2 diabetes and insulin resistance at midlife was associated with later-life cognitive testing in a large sample of older American Indians, aged 65 and older.

METHODS

American Indian participants who underwent both fasting blood draw as part of the Strong Heart Study and had subsequent cognitive testing as part of the later adjunct Cerebrovascular Disease and its Consequences in American Indians study were included (n = 790). Regression models examined type 2 diabetes and impaired fasting glucose and subsequent cognitive test performance as part of a longitudinal study design. The relationship between a continuous measure of insulin resistance and later cognitive test performance was assessed using generalized estimating equations.

RESULTS

Controlling for demographic and clinical factors, verbal fluency and processing speed/working memory were significantly negatively associated with having type 2 diabetes and with insulin resistance, but not with impaired fasting glucose.

CONCLUSION

In this sample of American Indians, type 2 diabetes at midlife was associated with subsequent lower performance on measures of executive function. These results may have important implications for future implementation of diagnostic and intervention services in this population.

The unity and diversity of executive functions: A systematic review and re-analysis of latent variable studies

Confirmatory factor analysis (CFA) has been frequently applied to executive function measurement since first used to identify a three-factor model of inhibition, updating, and shifting; however, subsequent CFAs have supported inconsistent models across the life span, ranging from unidimensional to nested-factor models (i.e., bifactor without inhibition). This systematic review summarized CFAs on performance-based tests of executive functions and reanalyzed summary data to identify best-fitting models. Eligible CFAs involved 46 samples (N = 9,756). The most frequently accepted models varied by age (i.e., preschool = one/two-factor; school-age = three-factor; adolescent/adult = three/nested-factor; older adult = two/three-factor), and most often included updating/working memory, inhibition, and shifting factors. A bootstrap reanalysis simulated 5,000 samples from 21 correlation matrices (11 child/adolescent; 10 adult) from studies including the three most common factors, fitting seven competing models. Model results were summarized as the mean percent accepted (i.e., average rate at which models converged and met fit thresholds: CFI ≥ .90/RMSEA ≤ .08) and mean percent selected (i.e., average rate at which a model showed superior fit to other models: ΔCFI ≥ .005/.010/ΔRMSEA ≤ -.010/-.015). No model consistently converged and met fit criteria in all samples. Among adult samples, the nested-factor was accepted (41-42%) and selected (8-30%) most often. Among child/adolescent samples, the unidimensional model was accepted (32-36%) and selected (21-53%) most often, with some support for two-factor models without a differentiated shifting factor. Results show some evidence for greater unidimensionality of executive function among child/adolescent samples and both unity and diversity among adult samples. However, low rates of model acceptance/selection suggest possible bias toward the publication of well-fitting but potentially nonreplicable models with underpowered samples. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Triglycerides are negatively correlated with cognitive function in nondemented aging adults

OBJECTIVE

Vascular risk factors like hyperlipidemia may adversely affect brain function. We hypothesized that increased serum triglycerides are associated with decreased executive function and memory in nondemented elderly subjects. We also researched possible vascular mediators and white matter microstructure as assessed with diffusion tensor imaging (DTI).

DESIGN/METHOD

Participants were 251 nondemented elderly adults (54% male) with a mean age of 78 (SD = 6.4; range: 62-94) years and a mean education of 15.6 (SD = 2.9; range: 8-23) years. Fasting blood samples were used to detect serum triglyceride and low-density lipoprotein (LDL) levels along with ApoE4 status. DTI was used to determine whole brain fractional anisotropy (FA). Composite executive and memory scores were derived from item response theory. Clinical Dementia Rating (CDR) scores provided informant-based measures of daily functioning.

RESULTS

Triglyceride levels were inversely correlated with executive function, but there was no relationship with memory. Controlling for age, gender, and education did not affect this correlation. This relationship persisted after controlling for vascular risk factors like LDL, total cholesterol, CDR and ApoE4 status. Lastly, adding whole-brain FA to the model did not affect the correlation between triglycerides and executive function.

CONCLUSION

Triglyceride levels are inversely correlated with executive function in nondemented elderly adults after controlling for age, education, gender, total cholesterol, LDL, ApoE4 status, CDR, and white-matter microstructure. The fact that the effect of triglycerides on cognition was not clearly mediated by vascular risks or cerebrovascular injury raises questions about widely held assumptions of how triglycerides might impact cognition function. (PsycINFO Database Record

Youthful Processing Speed in Older Adults: Genetic, Biological, and Behavioral Predictors of Cognitive Processing Speed Trajectories in Aging

Objective: To examine the impact of genetic, inflammatory, cardiovascular, lifestyle, and neuroanatomical factors on cognitive processing speed (CPS) change over time in functionally intact older adults.

Methods: This observational study conducted over two time points, included 120 community dwelling cognitively normal older adults between the ages of 60 and 80 from the University of California San Francisco Memory and Aging Center. Participants were followed with composite measures of CPS, calculated based on norms for 20–30 year-olds. Variables of interest were AD risk genes (APOE, CR1), markers of inflammation (interleukin 6) and cardiovascular health (BMI, LDL, HDL, mean arterial pressure, fasting insulin), self-reported physical activity, and corpus callosum (CC) volumes. The sample was divided into three groups: 17 “resilient-agers” with fast and stable processing speed; 56 “average-agers” with average and stable processing speed; and 47 “sub-agers” with average baseline speed who were slower at follow-up.

Results: Resilient-agers had larger baseline CC volumes than sub-agers (p < 0.05). Resilient-agers displayed lower levels of interleukin-6 (IL-6) and insulin (ps < 0.05) than sub-agers, and reported more physical activity than both average- and sub-agers (ps < 0.01). In a multinomial logistic regression, physical activity and IL-6 predicted average- and sub-ager groups. Resilient-agers displayed a higher frequency of APOE e4 and CR1 AA/AG alleles.

Conclusion: Robust and stable CPS is associated with larger baseline CC volumes, lower levels of inflammation and insulin, and greater self-reported physical activity. These findings highlight the relevance of neuroanatomical, biological, and lifestyle factors in the identification and prediction of heterogeneous cognitive aging change over time.