Onset Of Cognitive Symptoms Research Articles

Patient Populations in Clinical Studies of Donepezil in Vascular Dementia

There are difficulties in accurately defining patients with vascular dementia (VaD) and, therefore, little is known about the characteristics of this population. To examine the population characteristics in patients with VaD enrolled in two randomized, double-blind, placebo-controlled, 24-week clinical trials of the efficacy and tolerability of the acetylcholinesterase inhibitor donepezil. Enrolled patients had probable or possible VaD, classified according to NINDS-AIREN criteria. Patients were excluded if they had a diagnosis of Alzheimer's disease or dementia caused by other conditions not associated with the cardiovascular system. A total of 1,219 patients, 73% with probable VaD and 27% with possible VaD, were enrolled. Patients had a mean Hachinski score of 9.7, with memory impairment the most prominent feature of their dementia. Sixty-eight percent of patients had a history of at least one stroke and 28% of patients had a history of transient ischemic attack before dementia. In the 99% of patients who had abnormal computer-assisted tomography or magnetic resonance imaging scans, cortical and subcortical infarcts were among the lesions observed, with significant white-matter lesions also present in some patients. Seventy-three percent of patients had experienced an abrupt onset of cognitive symptoms. Vascular risk factors were prominent and included hypertension (70%), smoking (62%), and hypercholesterolemia (39%). The patients enrolled in these trials had probable or possible VaD; these patients exhibited a history of cerebrovascular disease and a broad range of comorbid cardiovascular conditions. The large number of patients enrolled will permit a thorough examination of the efficacy and tolerability of donepezil in VaD.

Biological markers for therapeutic trials in Alzheimer’s disease: Proceedings of the biological markers working group; NIA initiative on neuroimaging in Alzheimer’s disease

Neuropathological hallmarks of Alzheimer's disease (AD) include pathogenic accumulation of amyloid-β (Aβ) peptides and age-dependent formation of amyloid plaques in the brain. AD-associated Aβ neuropathology begins decades before onset of cognitive symptoms and slowly progresses over the course of the disease. We previously reported discovery of Aβ deposition, β-amyloidopathy, and co-localizing supranuclear cataracts (SNC) in lenses from people with AD, but not other neurodegenerative disorders or normal aging. We confirmed AD-associated Aβ molecular pathology in the lens by immunohistopathology, amyloid histochemistry, immunoblot analysis, epitope mapping, immunogold electron microscopy, quantitative immunoassays, and tryptic digest mass spectrometry peptide sequencing. Ultrastructural analysis revealed that AD-associated Aβ deposits in AD lenses localize as electron-dense microaggregates in the cytoplasm of supranuclear (deep cortex) fiber cells. These Aβ microaggregates also contain αB-crystallin and scatter light, thus linking Aβ pathology and SNC phenotype expression in the lenses of people with AD. Subsequent research identified Aβ lens pathology as the molecular origin of the distinctive cataracts associated with Down syndrome (DS, trisomy 21), a chromosomal disorder invariantly associated with early-onset Aβ accumulation and Aβ amyloidopathy in the brain. Investigation of 1249 participants in the Framingham Eye Study found that AD-associated quantitative traits in brain and lens are co-heritable. Moreover, AD-associated lens traits preceded MRI brain traits and cognitive deficits by a decade or more and predicted future AD. A genome-wide association study of bivariate outcomes in the same subjects identified a new AD risk factor locus in the CTNND2 gene encoding δ-catenin, a protein that modulates Aβ production in brain and lens. Here we report identification of AD-related human Aβ (hAβ) lens pathology and age-dependent SNC phenotype expression in the Tg2576 transgenic mouse model of AD. Tg2576 mice express Swedish mutant human amyloid precursor protein (APP-Swe), accumulate hAβ peptides and amyloid pathology in the brain, and exhibit cognitive deficits that slowly progress with increasing age. We found that Tg2576 trangenic (Tg+) mice, but not non-transgenic (Tg–) control mice, also express human APP, accumulate hAβ peptides, and develop hAβ molecular and ultrastructural pathologies in the lens. Tg2576 Tg+ mice exhibit age-dependent Aβ supranuclear lens opacification that recapitulates lens pathology and SNC phenotype expression in human AD. In addition, we detected hAβ in conditioned medium from lens explant cultures prepared from Tg+ mice, but not Tg– control mice, a finding consistent with constitutive hAβ generation in the lens. In vitro studies showed that hAβ promoted mouse lens protein aggregation detected by quasi-elastic light scattering (QLS) spectroscopy. These results support mechanistic (genotype-phenotype) linkage between Aβ pathology and AD-related phenotypes in lens and brain. Collectively, our findings identify Aβ pathology as the shared molecular etiology of two age-dependent AD-related cataracts associated with two human diseases (AD, DS) and homologous murine cataracts in the Tg2576 transgenic mouse model of AD. These results represent the first evidence of AD-related Aβ pathology outside the brain and point to lens Aβ as an optically-accessible AD biomarker for early detection and longitudinal monitoring of this devastating neurodegenerative disease.

Prevalence of neuropsychiatric symptoms in dementia and mild cognitive impairment: results from the cardiovascular health study.

Mild cognitive impairment (MCI) may be a precursor to dementia, at least in some cases. Dementia and MCI are associated with neuropsychiatric symptoms in clinical samples. Only 2 population-based studies exist of the prevalence of these symptoms in dementia, and none exist for MCI. To estimate the prevalence of neuropsychiatric symptoms in dementia and MCI in a population-based study. Cross-sectional study derived from the Cardiovascular Health Study, a longitudinal cohort study. A total of 3608 participants were cognitively evaluated using data collected longitudinally over 10 years and additional data collected in 1999-2000 in 4 US counties. Dementia and MCI were classified using clinical criteria and adjudicated by committee review by expert neurologists and psychiatrists. A total of 824 individuals completed the Neuropsychiatric Inventory (NPI); 362 were classified as having dementia, 320 as having MCI; and 142 did not meet criteria for MCI or dementia. Prevalence of neuropsychiatric symptoms, based on ratings on the NPI in the previous month and from the onset of cognitive symptoms. Of the 682 individuals with dementia or MCI, 43% of MCI participants (n = 138) exhibited neuropsychiatric symptoms in the previous month (29% rated as clinically significant) with depression (20%), apathy (15%), and irritability (15%) being most common. Among the dementia participants, 75% (n = 270) had exhibited a neuropsychiatric symptom in the past month (62% were clinically significant); 55% (n = 199) reported 2 or more and 44% (n = 159) 3 or more disturbances in the past month. In participants with dementia, the most frequent disturbances were apathy (36%), depression (32%), and agitation/aggression (30%). Eighty percent of dementia participants (n = 233) and 50% of MCI participants (n = 139) exhibited at least 1 NPI symptom from the onset of cognitive symptoms. There were no differences in prevalence of neuropsychiatric symptoms between participants with Alzheimer-type dementia and those with other dementias, with the exception of aberrant motor behavior, which was more frequent in Alzheimer-type dementia (5.4% vs 1%; P =.02). Neuropsychiatric symptoms occur in the majority of persons with dementia over the course of the disease. These are the first population-based estimates for neuropsychiatric symptoms in MCI, indicating a high prevalence associated with this condition as well. These symptoms have serious adverse consequences and should be inquired about and treated as necessary. Study of neuropsychiatric symptoms in the context of dementia may improve our understanding of brain-behavior relationships.

Abnormalities of neural circuitry in Alzheimer's disease: hippocampus and cortical cholinergic innervation.

Severe pathology in Alzheimer's disease (AD) results in marked disruption of cortical circuitry. Formation of neurofibrillary tangles, neuronal loss, decrease in dendritic extent, and synaptic depletion combine to halt communication among various cortical areas, resulting in anatomic isolation and fragmentation of many cortical zones. The clinical manifestation of this disruption is severe and debilitating cognitive dysfunction, often accompanied by psychiatric and behavioral disturbances and a diminished ability to perform activities of daily living. However, different cortical circuits are not equally vulnerable to AD pathology. In particular, two cortical systems that appear to be involved in the neural processing of memory are selectively vulnerable to degeneration in AD. One consists of connections between the hippocampus and its neighboring cortical structures within the temporal lobe. The second is the cortical cholinergic system that originates in neurons within the basal forebrain and innervates the entire cortical mantle. The circuitry in these systems shows early and severe degenerative changes in the course of AD. The selective vulnerability of these circuits is the probable reason for the early and marked loss of memory observed in these patients. This review presents current knowledge of the general pattern of cortical circuitry, followed by a summary of abnormalities of this circuitry in AD. The cortical circuits that exhibit selective pathology in AD are described in greater detail. Therapeutic implications of the abnormal circuitry in AD are also discussed. For therapies to be effective, early diagnosis of AD is necessary. Future efforts at AD therapy must be combined with an equally intense effort to develop tools capable of early diagnosis of AD, preferably at a preclinical stage before the onset of cognitive symptoms.

Phosphate/calcium alterations in the first stages of Alzheimer's disease: Implications for etiology and pathogenesis

The present study tested aspects of a novel etiological/pathogenetic hypothesis of Alzheimer's disease (AD), which proposes that alterations in endocrine regulation of peripheral calcium/phosphate ( Ca PO 4 ) homeostasis (e.g., by glucocorticoids, vitamin D, etc.) induce and/or reflect altered calcium homeostasis and neurotoxicity in brain neurons. Two key predictions of this hypothesis were tested, namely that: (1) alterations in serum Ca and/or PO 4 regulation should be present before or near the onset of AD and (2) these alterations should be found consistently in subjects with unconfounded AD. Previous studies have sought evidence of changes in Ca regulation primarily late in the disease, and usually in severely demented, thin and immobile inpatients in whom Ca PO 4 measures are likely to be confounded. In the present study, only mobile, relatively healthy, adequately nourished outpatients with probable AD were selected. In comparison to age-matched controls or demented subjects with even mild indications of vascular contributions, the AD subjects were characterized by lower serum PO 4 and, to a lesser degree, lower serum Ca as well as a higher chloride PO 4 ratio. On serum chemistry tests from the first stages of AD (within 1 or 3 years after the onset of cognitive symptoms), these changes in serum PO 4 Ca were as pronounced as they were later in the disease. Moderately low values of either PO 4, Ca, or both (below −1.0 S.D. from the control group mean) identified 74% of all AD subjects and 100% of early onset AD subjects, in comparison to only 46% of mixed/vascular dementia subjects and 31% of normal age-matched controls. Thus, the results were consistent with the predictions and may have significant etiological/pathogenetic implications. If larger tests confirm these frequencies, serum Ca PO 4 indices may also prove useful in differential diagnosis.

Diagnosis of Multi-Infarct Dementia

Multi-infarct dementia (MID) is commonly considered a dementia syndrome evolving in connection with multiple ischemic brain lesions, without other changes known to cause dementia. The ischemic brain lesions result from various vascular mechanisms, and different brain mechanisms are involved in the genesis of MID. Typical features for MID are abrupt onset of cognitive symptoms, stepwise deterioration of mental functioning, and focal neurologic symptoms or signs, but in 20% of cases the onset is insidious and the course is even. The main steps in diagnosis of MID include diagnosis of dementia, diagnosis of specific causes of dementia and secondary factors potentially aggravating cognitive decline, and demonstration of ischemic brain changes assumed to be responsible for the evolution of dementia. Methods used for clinical diagnosis of MID include clinical history and examination, brain imaging, ischemic scores, neurophysiologic investigations, and a variety of laboratory investigations designed to detect concomitant illness. According to strict clinical criteria for MID, the accuracy of the antemortem diagnosis as verified postmortem in one series was approximately 90%.