Prevalence of the apolipoprotein E ε4 allele in amyloid ß positive subjects across the spectrum of Alzheimer's disease.

INTRODUCTION: Apolipoprotein E (APOE) ε4 is the major genetic risk factor for Alzheimer's disease (AD), but its prevalence is unclear because earlier studies did not require biomarker evidence of amyloid ß (Aß) pathology. METHODS: We included 3451 Aß+ subjects (853 AD-type dementia, 1810 mild cognitive impairment, and 788 cognitively normal). Generalized estimating equation models were used to assess APOE ε4 prevalence in relation to age, sex, education, and geographical location. RESULTS: The APOE ε4 prevalence was 66% in AD-type dementia, 64% in mild cognitive impairment, and 51% in cognitively normal, and it decreased with advancing age in Aß+ cognitively normal and Aß+ mild cognitive impairment (P < .05) but not in Aß+ AD dementia (P = .66). The prevalence was highest in Northern Europe but did not vary by sex or education. DISCUSSION: The APOE ε4 prevalence in AD was higher than that in previous studies, which did not require presence of Aß pathology. Furthermore, our results highlight disease heterogeneity related to age and geographical location.

[Wishes for the future of science: an analysis of dementia and ageing on The National Research Agenda (NWA)]. / De (gewenste) toekomst van de wetenschap in Nederland: een analyse van de Nationale Wetenschapsagenda met betrekking tot dementie en veroudering.

INTRODUCTION: The National Research Agenda (NWA) assembles topics on which scientist can focus in the coming years. A study carried out by de Radboudumc in Nijmegen examined how many questions are put to the NWA on dementia and ageing. What priority does society give to this research field and who ask questions about this? With the method of the NWA as reference frame a supplementary route on dementia/ageing was proposed. RESULTS: Of the 11.700 questions submitted to the NWA almost 2.5% is about dementia/ageing. Compared to other medical issues this is a relatively high percentage. This analysis provides 21 research questions which give a good idea of the questions that where asked about the themes of ageing and dementia. Half of the questions came from citizens, therefore we can speak of a socially supported agenda in this area. However, most of the valid questions came from professional organizations involved in dementia. CONCLUSION: In the Netherlands a relatively high priority is given by authors of questions for the NWA to research on dementia and ageing. Questions from professionals are complemented by citizens who ask other relevant questions that provide a new perspective and are an addition to the knowledge questions from scientists.

How does additional diagnostic testing influence the initial diagnosis in patients with cognitive complaints in a memory clinic setting?

BACKGROUND: patients suspected of dementia frequently undergo additional diagnostic testing (e.g. brain imaging or neuropsychological assessment) after standard clinical assessment at a memory clinic. This study investigates the use of additional testing in an academic outpatient memory clinic and how it influences the initial diagnosis. METHODS: the initial diagnosis after standard clinical assessment (history, laboratory tests, cognitive screening and physical and neurological examination) and the final diagnosis after additional testing of 752 memory clinic patients were collected. We specifically registered if, and what type of, additional testing was requested. RESULTS: additional testing was performed in 518 patients (69%), 67% of whom underwent magnetic resonance imaging, 45% had neuropsychological assessment, 14% had cerebrospinal fluid analysis and 49% had (combinations of) other tests. This led to a modification of the initial diagnosis in 17% of the patients. The frequency of change was highest in patients with an initial non-Alzheimer's disease (AD) dementia diagnosis (54%, compared with 11 and 14% in patients with AD and 'no dementia'; P < 0.01). Finally, after additional testing 44% was diagnosed with AD, 9% with non-AD dementia and 47% with 'no dementia'. CONCLUSION: additional testing should especially be considered in non-AD patients. In the large group of patients with an initial AD or 'no dementia' diagnosis, additional tests have little diagnostic impact and may perhaps be used with more restraint.

White Matter Hyperintensities Are No Major Confounder for Alzheimer's Disease Cerebrospinal Fluid Biomarkers.

BACKGROUND: The cerebrospinal fluid (CSF) biomarkers amyloid-ß 1-42 (Aß42), total and phosphorylated tau (t-tau, p-tau) are increasingly used to assist in the clinical diagnosis of Alzheimer's disease (AD). However, CSF biomarker levels can be affected by confounding factors. OBJECTIVE: To investigate the association of white matter hyperintensities (WMHs) present in the brain with AD CSF biomarker levels. METHODS: We included CSF biomarker and magnetic resonance imaging (MRI) data of 172 subjects (52 controls, 72 mild cognitive impairment (MCI), and 48 AD patients) from 9 European Memory Clinics. A computer aided detection system for standardized automated segmentation of WMHs was used on MRI scans to determine WMH volumes. Association of WMH volume with AD CSF biomarkers was determined using linear regression analysis. RESULTS: A small, negative association of CSF Aß42, but not p-tau and t-tau, levels with WMH volume was observed in the AD (r2 = 0.084, p = 0.046), but not the MCI and control groups, which was slightly increased when including the distance of WMHs to the ventricles in the analysis (r2 = 0.105, p = 0.025). Three global patterns of WMH distribution, either with 1) a low, 2) a peak close to the ventricles, or 3) a high, broadly-distributed WMH volume could be observed in brains of subjects in each diagnostic group. CONCLUSION: Despite an association of WMH volume with CSF Aß42 levels in AD patients, the occurrence of WMHs is not accompanied by excess release of cellular proteins in the CSF, suggesting that WMHs are no major confounder for AD CSF biomarker assessment.

Autobiographical memory retrieval in patients with Alzheimer's disease.

With aging, the content of self-reported autobiographical memories shifts from episodic to semantic. Onset of Alzheimer's disease enhances this pattern, but the neural underpinnings of this change in Autobiographical Memory (AM), in particular the role of hippocampal degradation, are unknown. We employed fMRI contrasting autobiographical and semantic retrieval, in 22 healthy elderly and 21 Alzheimer's patients. The shift towards semantic characteristics in AM retrieval was indeed enhanced in patients. Both groups activated brain regions commonly involved in AM retrieval, including occipital association areas, medial temporal lobes, lateral temporal and midline prefrontal areas. When compared to controls, Alzheimer's patients showed enhanced activity in the left inferior frontal gyrus (LIFG), ventromedial prefrontal cortex (vmPFC), right precuneus and left lingual gyrus. Activation of LIFG and vmPFC was significantly negatively correlated with hippocampal volume in patients only. Thus, we speculate that the linking function of the degraded hippocampus is taken over by the vmPFC; a shift recently observed during normal consolidation. This potentially compensatory process may support early Alzheimer's detection or prognosis.

Altered brain high-energy phosphate metabolism in mild Alzheimer's disease: A 3-dimensional 31P MR spectroscopic imaging study.

In Alzheimer's disease (AD), defects in essential metabolic processes for energy supply and phospholipid membrane function have been implicated in the pathological process. However, post-mortem investigations are generally limited to late stage disease and prone to tissue decay artifacts. In vivo assessments of high energy phosphates, tissue pH and phospholipid metabolites are possible by phosphorus MR spectroscopy (31P-MRS), but so far only small studies, mostly focusing on single brain regions, have been performed. Therefore, we assessed phospholipid and energy metabolism in multiple brain regions of 31 early stage AD patients and 31 age- and gender-matched controls using 31P-MRS imaging. An increase of phosphocreatine (PCr) was found in AD patients compared with controls in the retrosplenial cortex, and both hippocampi, but not in the anterior cingulate cortex. While PCr/inorganic phosphate and pH were also increased in AD, no changes were found for phospholipid metabolites. This study showed that PCr levels are specifically increased in regions that show early degeneration in AD. Together with an increased pH, this indicates an altered energy metabolism in mild AD.

Quantitative Genetics Validates Previous Genetic Variants and Identifies Novel Genetic Players Influencing Alzheimer's Disease Cerebrospinal Fluid Biomarkers.

Cerebrospinal fluid (CSF) biomarkers have been extensively investigated in the Alzheimer's disease (AD) field, and are now being applied in clinical practice. CSF amyloid-beta (Aß1-42), total tau (t-tau), and phosphorylated tau (p-tau) reflect disease pathology, and may be used as quantitative traits for genetic analyses, fostering the identification of new genetic factors and the proposal of novel biological pathways of the disease. In patients, the concentration of CSF Aß1-42 is decreased due to the accumulation of Aß1-42 in amyloid plaques in the brain, while t-tau and p-tau levels are increased, indicating the extent of neuronal damage. To better understand the biological mechanisms underlying the regulation of AD biomarkers, and its relation to AD, we examined the association between 36 selected single nucleotide polymorphisms (SNPs) and AD biomarkers Aß1-42, t-tau, and p-tau in CSF in a cohort of 672 samples (571 AD patients and 101 controls) collected within 10 European consortium centers.Our results highlighted five genes, APOE, LOC100129500, PVRL2, SNAR-I, and TOMM40, previously described as main players in the regulation of CSF biomarkers levels, further reinforcing a role for these in AD pathogenesis. Three new AD susceptibility loci, INPP5D, CD2AP, and CASS4, showed specific association with CSF tau biomarkers. The identification of genes that specifically influence tau biomarkers point out to mechanisms, independent of amyloid processing, but in turn related to tau biology that may open new venues to be explored for AD treatment.

The medical food Souvenaid affects brain phospholipid metabolism in mild Alzheimer's disease: results from a randomized controlled trial.

BACKGROUND: Synaptic dysfunction contributes to cognitive impairment in Alzheimer's disease and may be countered by increased intake of nutrients that target brain phospholipid metabolism. In this study, we explored whether the medical food Souvenaid affects brain phospholipid metabolism in patients with Alzheimer's disease. METHODS: Thirty-four drug-naive patients with mild Alzheimer's disease (Mini Mental State Examination score ≥20) were enrolled in this exploratory, double-blind, randomized controlled study. Before and after 4-week intervention with Souvenaid or an isocaloric control product, phosphorus and proton magnetic resonance spectroscopy (MRS) was performed to assess surrogate measures of phospholipid synthesis and breakdown (phosphomonoesters [PME] and phosphodiesters [PDEs]), neural integrity (N-acetyl aspartate), gliosis (myo-inositol), and choline metabolism (choline-containing compounds [tCho]). The main outcome parameters were PME and PDE signal intensities and the PME/PDE ratio. RESULTS: MRS data from 33 patients (60-86 years old; 42% males; Souvenaid arm n = 16; control arm n = 17) were analyzed. PME/PDE and tCho were higher after 4 weeks of Souvenaid compared with control (PME/PDE least squares [LS] mean difference [95% CI] 0.18 [0.06-0.30], p = 0.005; tCho LS mean difference [95% CI] 0.01 [0.00-0.02], p = 0.019). No significant differences were observed in the other MRS outcome parameters. CONCLUSIONS: MRS reveals that Souvenaid affects brain phospholipid metabolism in mild Alzheimer's disease, in line with findings in preclinical studies. TRIAL REGISTRATION: Netherlands Trial Register, NTR3346 . Registered on 13 March 2012.

Improved Cerebrospinal Fluid-Based Discrimination between Alzheimer's Disease Patients and Controls after Correction for Ventricular Volumes.

Cerebrospinal fluid (CSF) biomarkers may support the diagnosis of Alzheimer's disease (AD). We studied if the diagnostic power of AD CSF biomarker concentrations, i.e., Aß42, total tau (t-tau), and phosphorylated tau (p-tau), is affected by differences in lateral ventricular volume (VV), using CSF biomarker data and magnetic resonance imaging (MRI) scans of 730 subjects, from 13 European Memory Clinics. We developed a Matlab-algorithm for standardized automated segmentation analysis of T1 weighted MRI scans in SPM8 for determining VV, and computed its ratio with total intracranial volume (TIV) as proxy for total CSF volume. The diagnostic power of CSF biomarkers (and their combination), either corrected for VV/TIV ratio or not, was determined by ROC analysis. CSF Aß42 levels inversely correlated to VV/TIV in the whole study population (Aß42: r = -0.28; p < 0.0001). For CSF t-tau and p-tau, this association only reached statistical significance in the combined MCI and AD group (t-tau: r = -0.15; p-tau: r = -0.13; both p < 0.01). Correction for differences in VV/TIV improved the differentiation of AD versus controls based on CSF Aß42 alone (AUC: 0.75 versus 0.81) or in combination with t-tau (AUC: 0.81 versus 0.91). In conclusion, differences in VV may be an important confounder in interpreting CSF Aß42 levels.

European multicentre double-blind placebo-controlled trial of Nilvadipine in mild-to-moderate Alzheimer's disease-the substudy protocols: NILVAD frailty; NILVAD blood and genetic biomarkers; NILVAD cerebrospinal fluid biomarkers; NILVAD cerebral blood flow.

INTRODUCTION: In conjunction with the NILVAD trial, a European Multicentre Double-Blind Placebo Controlled trial of Nilvadipine in Mild-to-Moderate Alzheimer's disease (AD), there are four NILVAD substudies in which eligible NILVAD patients are also invited to participate. The main NILVAD protocol was previously published in BMJ Open (2014). The objectives of the NILVAD substudies are to determine whether frailty, cerebrospinal fluid (CSF), blood biomarker profile and Apolipoprotein E (APOE) status predict response to Nilvadipine, and to investigate the effect of Nilvadipine on cerebral blood flow and blood biomarkers. METHODS AND ANALYSIS: All participants who fulfil criteria for the main NILVAD study are eligible for participation in the NILVAD substudies. Participation is subject to informed consent and whether the substudy is available at a particular NILVAD study site. Each substudy entails extra measurements during the course of the main NILVAD study. For example, in the blood and genetic biomarkers substudy, extra blood (30 mL) will be collected at week 0, week 13, week 52 and week 78, while in the cerebral blood flow substudy, participants will receive an MRI and transcranial Doppler measurements at week 0, week 26 and week 78. In the CSF substudy, 10 mL CSF is collected at week 0 and week 78. ETHICS AND DISSEMINATION: All NILVAD substudies and all subsequent amendments have received ethical approval within each participating country, according to national regulations. Each participant provides written consent to participate. All participants remain anonymised throughout and the results of each substudy will be published in an international peer reviewed journal. TRIAL REGISTRATION NUMBER: EUDRACT 2012-002764-27; Pre-results.

Cognitive functioning, wellbeing and brain correlates in HIV-1 infected patients on long-term combination antiretroviral therapy.

OBJECTIVE: The objective of the current study is to integrate results from extensive neuropsychological assessment, subjective wellbeing reports and structural neuroimaging findings in successfully treated HIV-infected patients in comparison with a HIV-negative control group. DESIGN: A cross-sectional study. METHODS: Neuropsychological functioning and self-reported wellbeing were assessed in a group of 102 virologically suppressed HIV-infected patients on combination antiretroviral therapy (cART) and 56 controls. Both groups underwent magnetic resonance (MR) examinations and grey matter, white matter and subcortical volumes were determined. Brain parenchymal fraction (BPF) was calculated as an estimated measure of global brain atrophy. RESULTS: HIV-infected patients showed worse information processing speed (P = 0.01) and motor function (P = 0.03) than controls. Also, higher levels of anxiety and depressive symptoms, somatic and cognitive complaints, sleep problems and health distress were found, as well as lower levels of general health perceptions, social functioning and energy (P < 0.05). No differences in wellbeing reports were found between patients on regimens containing either efavirenz or nevirapine and patients on cART without these drugs (P > 0.05). Patients had a smaller BPF (P = 0.04) and thalamus (P = 0.05) than controls. A lower BPF was related to worse motor function and information processing speed in the patients. A smaller thalamus volume was related to lower motor function in the patient group and lower speed of information processing in the controls. CONCLUSION: No profound deficits were found in the current study. The present results demonstrate that HIV has a minor impact on brain, cognition and wellbeing among HIV-infected patients who are otherwise healthy and maintained on a good control of cART.

Effects of Souvenaid on plasma micronutrient levels and fatty acid profiles in mild and mild-to-moderate Alzheimer's disease.

INTRODUCTION: Circulating levels of uridine, selenium, vitamins B12, E and C, folate, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) have been shown to be lower in patients with Alzheimer's disease (AD) than in healthy individuals. These low levels may affect disease pathways involved in synapse formation and neural functioning. Here, we investigated whether, and to what extent, circulating levels of micronutrients and fatty acids can be affected by oral supplementation with Souvenaid (containing a specific nutrient combination), using data derived from three randomized clinical trials (RCT) and an open-label extension (OLE) study with follow-up data from 12 to 48 weeks. METHODS: Subjects with mild (RCT1, RCT2) or mild-to-moderate AD (RCT3) received active or control product once daily for 12-24 weeks or active product during the 24-week OLE following RCT2 (n = 212-527). Measurements included plasma levels of B vitamins, choline, vitamin E, selenium, uridine and homocysteine and proportions of DHA, EPA and total n-3 long-chain polyunsaturated fatty acids in plasma and erythrocytes. Between-group comparisons were made using t tests or non-parametric alternatives. RESULTS: We found that 12-24-week active product intake increased plasma and/or erythrocyte micronutrients: uridine; choline; selenium; folate; vitamins B6, B12 and E; and fatty acid levels of DHA and EPA (all p < 0.001). In the OLE study, similar levels were reached in former control product/initial active product users, whereas 24-week continued active product intake showed no suggestion of a further increase in nutrient levels. CONCLUSIONS: These data show that circulating levels of nutrients known to be decreased in the AD population can be increased in patients with mild and mild-tomoderate AD by 24-48-week oral supplementation with Souvenaid. In addition, to our knowledge, this is the first report of the effects of sustained dietary intake of uridine monophosphate on plasma uridine levels in humans. Uptake of nutrients is observed within 6 weeks, and a plateau phase is reached for most nutrients during prolonged intake, thus increasing the availability of precursors and cofactors in the circulation that may be used for the formation and function of neuronal membranes and synapses in the brain.

Spatial working memory in aging and mild cognitive impairment: effects of task load and contextual cueing.

Mild Cognitive Impairment (MCI) is characterized by episodic memory deficits, while aspects of working memory may also be implicated, but studies into this latter domain are scarce and results are inconclusive. Using a computerized search paradigm, this study compares 25 young adults, 25 typically aging older adults and 15 amnestic MCI patients as to their working-memory capacities for object-location information and potential differential effects of memory load and additional context cues. An age-related deficit in visuospatial working-memory maintenance was found that became more pronounced with increasing task demands. The MCI group additionally showed reduced maintenance of bound information, i.e., object-location associations, again especially at elevated memory load. No effects of contextual cueing were found. The current findings indicate that working memory should be considered when screening patients for suspected MCI and monitoring its progression.

Age-effects on associative object-location memory.

Aging is accompanied by an impairment of associative memory. The medial temporal lobe and fronto-striatal network, both involved in associative memory, are known to decline functionally and structurally with age, leading to the so-called associative binding deficit and the resource deficit. Because the MTL and fronto-striatal network interact, they might also be able to support each other. We therefore employed an episodic memory task probing memory for sequences of object-location associations, where the demand on self-initiated processing was manipulated during encoding: either all the objects were visible simultaneously (rich environmental support) or every object became visible transiently (poor environmental support). Following the concept of resource deficit, we hypothesised that the elderly probably have difficulty using their declarative memory system when demands on self-initiated processing are high (poor environmental support). Our behavioural study showed that only the young use the rich environmental support in a systematic way, by placing the objects next to each other. With the task adapted for fMRI, we found that elderly showed stronger activity than young subjects during retrieval of environmentally richly encoded information in the basal ganglia, thalamus, left middle temporal/fusiform gyrus and right medial temporal lobe (MTL). These results indicate that rich environmental support leads to recruitment of the declarative memory system in addition to the fronto-striatal network in elderly, while the young use more posterior brain regions likely related to imagery. We propose that elderly try to solve the task by additional recruitment of stimulus-response associations, which might partly compensate their limited attentional resources.

Age differences in neural correlates of route encoding and route recognition.

Spatial memory deficits are core features of aging-related changes in cognitive abilities. The neural correlates of these deficits are largely unknown. In the present study, we investigated the neural underpinnings of age-related differences in spatial memory by functional MRI using a navigational memory task with route encoding and route recognition conditions. We investigated 20 healthy young (18-29 years old) and 20 healthy old adults (53-78 years old) in a random effects analysis. Old subjects showed slightly poorer performance than young subjects. Compared to the control condition, route encoding and route recognition showed activation of the dorsal and ventral visual processing streams and the frontal eye fields in both groups of subjects. Compared to old adults, young subjects showed during route encoding stronger activations in the dorsal and the ventral visual processing stream (supramarginal gyrus and posterior fusiform/parahippocampal areas). In addition, young subjects showed weaker anterior parahippocampal activity during route recognition compared to the old group. In contrast, old compared to young subjects showed less suppressed activity in the left perisylvian region and the anterior cingulate cortex during route encoding. Our findings suggest that age-related navigational memory deficits might be caused by less effective route encoding based on reduced posterior fusiform/parahippocampal and parietal functionality combined with diminished inhibition of perisylvian and anterior cingulate cortices correlated with less effective suppression of task-irrelevant information. In contrast, age differences in neural correlates of route recognition seem to be rather subtle. Old subjects might show a diminished familiarity signal during route recognition in the anterior parahippocampal region.