Cognitive Test Battery of Cascade: Tasks and Data

Serum neurofilament light and tau as prognostic markers for all-cause mortality in the elderly general population-an analysis from the MEMO study

BACKGROUND

Neurofilament light chain (NfL) is a cytoskeletal protein component whose release into blood is indicative of neuronal damage. Tau is a microtubule-associated protein in neurons and strongly associated with overall brain degeneration. NfL and tau levels are associated with mortality in different neurological diseases, but studies in the general population are missing. We investigated whether NfL and tau serum levels could serve as prognostic markers for overall mortality in elderly individuals without pre-defined neurological conditions. Further, we investigated the cross-sectional associations between NfL, tau, neuropsychological functioning, and brain structures.

METHODS

In 1997, 385 inhabitants of Augsburg who were aged 65 years and older were included in the Memory and Morbidity in Augsburg Elderly (MEMO) study. They participated in a face-to-face medical interview including neuropsychological tests and magnetic resonance imaging (MRI) of the brain. NfL and tau were measured from non-fasting blood samples using highly sensitive single molecule array assays. To assess the prognostic accuracy of the biomarkers, concordance statistics based on the predicted 5-year survival probabilities were calculated for different Cox regression models. Associations between the biomarkers and the neuropsychological test scores or brain structures were investigated using linear or logistic regression.

RESULTS

NfL (HR 1.27, 95% CI [1.14-1.42]) and tau (1.20 [1.07-1.35]) serum levels were independently associated with all-cause mortality. NfL, but not tau, increased the prognostic accuracy when added to a model containing sociodemographic characteristics (concordance statistic 0.684 [0.612-0.755] vs. 0.663 [0.593-0.733]), but not when added to a model containing sociodemographic characteristics and brain atrophy or neuropsychological test scores. NfL serum levels were cross-sectionally associated with neuropsychological test scores and brain structures.

CONCLUSIONS

The association between NfL serum levels and brain atrophy and neuropsychological performance in individuals without overt neurological disease is similar to that seen in patients with neurodegenerative diseases. These findings support the concept of a continuum of physiological aging and incipient, subclinical pathology, and manifest disease. NfL, but not tau, serum levels might serve as a prognostic marker for all-cause mortality if no other clinical information is available.

Genetics of structural connectivity and information processing in the brain

Understanding the genetic factors underlying brain structural connectivity is a major challenge in imaging genetics. Here, we present results from genome-wide association studies (GWASs) of whole-brain white matter (WM) fractional anisotropy (FA), an index of microstructural coherence measured using diffusion tensor imaging. Data from independent GWASs of 355 Swedish and 250 Norwegian healthy adults were integrated by meta-analysis to enhance power. Complementary GWASs on behavioral data reflecting processing speed, which is related to microstructural properties of WM pathways, were performed and integrated with WM FA results via multimodal analysis to identify shared genetic associations. One locus on chromosome 17 (rs145994492) showed genome-wide significant association with WM FA (meta P value = 1.87 × 10^-08). Suggestive associations (Meta P value <1 × 10^-06) were observed for 12 loci, including one containing ZFPM2 (lowest meta P value = 7.44 × 10^-08). This locus was also implicated in multimodal analysis of WM FA and processing speed (lowest Fisher P value = 8.56 × 10^-07). ZFPM2 is relevant in specification of corticothalamic neurons during brain development. Analysis of SNPs associated with processing speed revealed association with a locus that included SSPO (lowest meta P value = 4.37 × 10^-08), which has been linked to commissural axon growth. An intergenic SNP (rs183854424) 14 kb downstream of CSMD1, which is implicated in schizophrenia, showed suggestive evidence of association in the WM FA meta-analysis (meta P value = 1.43 × 10^-07) and the multimodal analysis (Fisher P value = 1 × 10^-07). These findings provide novel data on the genetics of WM pathways and processing speed, and highlight a role of ZFPM2 and CSMD1 in information processing in the brain.

Brain-derived neurotrophic factor (BDNF) gene: a gender-specific role in cognitive function during normal cognitive aging of the MEMO-Study?

Cognitive aging processes are underpinned by multiple processes including genetic factors. The brain-derived neurotrophic factor (BDNF) has been suggested to be involved in age-related cognitive decline in otherwise healthy individuals. The gender-specific role of the BDNF gene in cognitive aging remains unclear. The identification of genetic biomarkers might be a useful approach to identify individuals at risk of cognitive decline during healthy aging processes. The aim of this study was to investigate the associations between three single-nucleotide polymorphisms (SNPs) in the BDNF gene and domains of cognitive functioning in normal cognitive aging. The sample, comprising 369 participants (M = 72.7 years, SD = 4.45 years), completed an extensive neuropsychological test battery measuring memory, motor function, and perceptual speed. The relationships between the SNPs rs6265, rs7103411, and rs7124442 and cognitive domains were examined. While significant main effects of BDNF SNPs on cognitive function were found for the association between rs7103411 and memory performance, gender-specific analyses revealed for females significant main effects of rs7103411 for memory and of rs6265 for perceptual speed independent of the APOE*E4 status and education. The finding for the association between rs6265 and perceptual speed in females remained significant after Bonferroni correction for multiple comparisons. None of the analyses showed significant results for males. This study is the first to implicate that the SNPs rs6265 and rs7103411 affect cognitive function in the elderly in a gender-specific way.

Population-based distribution and psychometric properties of a short cognitive performance measure in the population-based Heinz Nixdorf Recall Study

BACKGROUND

Providing a valid and sensitive measure of different domains of cognitive performance in epidemiologic studies of early old-age populations presents a methodological challenge, given the broad range of variability in cognitive functioning in this age group.

OBJECTIVES

(1) To provide data on the distribution of cognitive performance scores in a representative sample of an early old-age population, and (2) to assess psychometric properties of a short cognitive performance measure developed within the framework of a cohort study.

DESIGN

Population-based cohort study.

SETTING AND PARTICIPANTS

As part of the second examination of the Heinz Nixdorf Recall Study, 4,145 participants aged 50-80 years underwent a short cognitive performance assessment composed of 5 subtests with a mean duration of 7.31 min. Additionally, a subsample of 656 participants had a detailed neuropsychological and neurological examination.

METHODS

Age- and education-specific cognitive performance scores in the total sample were calculated. Based on data from the subsample, concurrent validity was examined by comparing findings with a clinically validated neuropsychological assessment.

RESULTS

In the total sample, younger and more highly educated participants had higher scores of cognitive performance. In the subsample, a good accuracy [area under the curve (AUC) = 0.81 (0.74-0.87)] of the short cognitive performance assessment compared with results from a clinically established Alzheimer disease assessment scale and diagnosis of mild cognitive impairment [AUC = 0.82 (0.78-0.82)] was observed.

CONCLUSION

This brief, cognitive performance measure, documenting good psychometric properties, can be useful in future epidemiological investigations exploring different domains and overall cognitive functioning in early old-age populations.

Single and combined effects of cerebral white matter lesions and lacunar infarctions on cognitive function in an elderly population

BACKGROUND

This study is to investigate the association between single and combined vascular brain changes (white matter lesions [WMLs], lacunar infarctions) and the cognitive domains of memory, processing speed, and motor function in the elderly adults.

METHODS

In a sample of 268 participants aged 65-83 years of the MEMO (Memory and Morbidity in Augsburg Elderly) population-based study in Augsburg, Germany, cerebral magnetic resonance imaging (MRI) was performed and a detailed neuropsychological test battery applied. Analysis of covariance determined the effects of vascular brain changes on domains of cognitive functioning.

RESULTS

Strong associations of large WMLs and of MRI-defined lacunar infarction with three different domains of cognitive function even after adjustment for age, gender, and education were found. The combined occurrence of both lesions affected about one in 10 participants and was associated with a strong decrease in cognitive function in all domains. The difference between the groups with only one lesion type (either large WMLs or MRI-defined infarction) and participants affected by both was significant in the domains of processing speed and memory, even after adjustment for important confounders such as age, gender, education, and comorbidities. The effects of both lesion types on cognitive function were not more than additive.

CONCLUSIONS

Our study shows that both large WMLs and MRI-defined lacunar infarction contribute to impairments in different cognitive domains. The results suggest that their combined occurrence is associated with stronger reductions in cognitive function than each of the two brain lesion types alone.

Association between IL-8 cytokine and cognitive performance in an elderly general population—The MEMO-Study

OBJECTIVES

To investigate the associations between circulating cytokines and specific neuropsychological domains of cognitive functioning (memory, processing speed and motor function) and general cognitive function (MMSE) in healthy elderly individuals.

METHODS

In a cross-sectional study of 369 community dwelling elderly subjects, we examined the relationship between serum IL-1beta, sIL-4R, IL-6, IL-8, IL-10, IL-12 and TNF-alpha concentrations and cognitive performance using an extensive standardized and validated cognitive test battery assessing memory, word fluency, perceptual/cognitive speed, attention and executive functioning, and motor speed.

RESULTS

Multivariate analysis adjusted for various confounders and Bonferroni correction for multiple comparisons demonstrated that increased serum concentrations of IL-8 were associated with poor performance in the memory and speed domains and in motor function. No significant associations were found between the remaining cytokines and domains of cognitive functioning. Global cognitive functioning, as measured with MMSE, was not associated with any cytokine.

CONCLUSIONS

This study suggests an association between circulating IL-8 concentrations and cognitive dysfunction in the elderly. An interaction between this cytokine and glial cells may help explain the pathophysiological mechanisms leading to cognitive impairment in our study group.

Association between genetic variants of IL-1beta, IL-6 and TNF-alpha cytokines and cognitive performance in the elderly general population of the MEMO-study

This study is to investigate the associations between specific polymorphisms in three cytokine genes and domains of cognitive functioning in a population based study in the elderly. In a cross-sectional study of 369 community dwelling elderly subjects we examined the relationships between the polymorphisms IL-1beta-1418C-->T, IL-6-572G-->C and TNF-alpha-308G-->A and the cognitive function domains memory, processing speed and motor function using an extensive neuropsychological test battery. Linear regression models were used in the analysis and results adjusted for multiple comparisons. A significant association between the IL-1beta-1418C-->T polymorphism and memory performance was found with carriers of the T allele (dominant model) having worse memory performance than those with the C allele. In addition, a significant association between the TNF-alpha-308G-->A polymorphism and processing speed was observed, indicating better performance for heterozygous or homozygous carriers of the A allele. These results remained significant after adjustment for known confounders of cognitive function and additional Bonferroni correction for multiple comparisons. Our study provides first results on detrimental effects of the IL-1beta-1418C-->T polymorphism on memory performance and neuroprotective effects of the TNF-alpha-308G-->A polymorphism on processing speed in elderly individuals. Further research is needed to prospectively examine changes in cognitive performance in relation to cytokine genotypes.

The relationship between psychological dimensions of depressive symptoms and cognitive functioning in the elderly - the MEMO-Study

Aim of this study was to examine the association of symptom dimensions of depressive symptoms and cognitive functioning in the elderly. In a population-based study with 365 participants 65-83 years of age, dimensions of depressive symptoms were assessed with the four subscales of the CES-D-score and standardized cognitive tests assessing attention, memory, cognitive speed, and motor speed were performed. Compared to men, women scored significantly higher on the subscales for depressed affect and somatic complaints. Older participants had a significantly higher score for interpersonal difficulties. Participants with lower education had higher scores on all four psychological dimensions of depressive symptoms than those with high education (only significant for depressive affect). Individuals scoring high on CES-D subscales for depressive affect and somatic complaints had statistically significant (after Bonferroni adjustment) lower scores in attention and motor function in multivariate analyses. No significant associations between the symptom dimensions of positive affect and interpersonal difficulties with any of the cognitive tests were found in univariate and multivariate analyses (after Bonferroni adjustment). Our findings suggest specific patterns in the relationships between symptom dimensions of depressive symptoms and cognitive dysfunction in the general elderly population. This novel approach might be useful in addressing the heterogeneity of cognitive impairment in depression and in predicting cognitive outcome in depression.

Cerebral changes on MRI and cognitive function: the CASCADE study

The aging, non-demented brain undergoes several physiological changes, some of which may affect cognitive function. The goal of the present study was to examine the associations between subcortical and periventricular white matter hyperintensities (WMHs), cortical and subcortical atrophy, and cognitive function (episodic memory, word fluency, attention, and perceptual, cognitive, and motor speed). This was done within a European collaborative study, Cardiovascular Determinants of Dementia (CASCADE), in which magnetic resonance imaging (MRI) was performed on community-dwelling individuals. The study includes 1254 persons from eight European study centers, ranging between 64 and 76 years of age (M 69.4+/-3.3; 55% men). When demographics (age, education, and sex), study center, and concurrent brain changes had been adjusted for, periventricular WMHS predicted lower performance in word fluency and the Stroop test (time), and subcortical atrophy predicted lower performance in motor speed and the Stroop test (errors). The findings are consistent with findings from lesion and functional neuroimaging studies.

Memory Processes, Aging, Cognitive Decline, and Neurodegenerative Diseases

This paper presents four domains of markers that have been found to predict later cognitive impairment and neurodegenerative disease. These four domains are (1) data patterns of memory performance, (2) cardiovascular factors, (3) genetic markers, and (4) brain activity. The critical features of each domain are illustrated with data from the longitudinal Betula Study on memory, aging, and health ( Nilsson et al., 1997 ; Nilsson et al., 2004 ). Up to now, early signs regarding these domains have been examined one by one and it has been found that they are associated with later cognitive impairment and neurodegenerative disease. However, it was also found that each marker accounts for only a very small part of the total variance, implying that single markers should not be used as predictors for cognitive decline or neurodegenerative disease. It is discussed whether modeling and simulations should be used as tools to combine markers at different levels to increase the amount of explained variance.