Objectives-Operational definitions of cognitive impairment have varied widely in diagnosing mild cognitive impairment (MCI). Identifying clinical subtypes of MCI has further challenged diagnostic approaches, since varying the components of the objective cognitive assessment can significantly impact diagnosis. Therefore, we investigated the applicability of diagnostic criteria for clinical subtypes of MCI in a naturalistic research sample of community elders and quantified the variability in diagnostic outcomes that results from modifying the neuropsychological definition of objective cognitive impairment. Design-Cross-sectional and longitudinal studySetting-San Diego, CA, Veterans Administration Hospital Participants-90 nondemented, neurologically normal, community-dwelling older adults were initially assessed and 73 were seen for follow-up approximately 17 months later.Measurements-Participants were classified via consensus diagnosis as either normally aging or having MCI via each of five diagnostic strategies, which varied the cutoff for objective impairment as well as the number of neuropsychological tests considered in the diagnostic process.Results-A range of differences in the percentages identified as MCI versus cognitively normal were demonstrated, depending on the classification criteria employed. A substantial minority of individuals demonstrated diagnostic instability over time as well as across diagnostic approaches. The single domain non-amnestic subtype diagnosis was particularly unstable (e.g., prone to reclassification as normal at follow up).Conclusion-Our findings provide empirical support for a neuropsychologically derived operational definition of clinical subtypes of MCI and point to the importance of using comprehensive neuropsychological assessments. Diagnoses, particularly involving non-amnestic MCI, were variable over time. The applicability and utility of this particular MCI subtype warrants further investigation.

Article abstract-Objective: To update the 1994 practice parameter for the diagnosis of dementia in the elderly. Background: The AAN previously published a practice parameter on dementia in 1994. New research and clinical developments warrant an update of some aspects of diagnosis. Methods: Studies published in English from 1985 through 1999 were identified that addressed four questions: 1) Are the current criteria for the diagnosis of dementia reliable? 2) Are the current diagnostic criteria able to establish a diagnosis for the prevalent dementias in the elderly? 3) Do laboratory tests improve the accuracy of the clinical diagnosis of dementing illness? 4) What comorbidities should be evaluated in elderly patients undergoing an initial assessment for dementia? Recommendations: Based on evidence in the literature, the following recommendations are made.

Deterioration in Alzheimer disease appears to be driven by neuritic plaques and neurofibrillary tangles at different stages of the disease. The significant increase in neuritic plaques, but not neurofibrillary tangles, in patients with even mild Alzheimer disease at death compared with normal control subjects suggests that only neuritic plaques are associated with the earliest symptoms of Alzheimer disease.

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OBJECTIVE: To examine whether treatment of obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) in patients with Alzheimer's disease (AD) would result in improved cognitive function. DESIGN: Randomized double-blind placebo-controlled trial. Participants were randomized to either therapeutic CPAP for six weeks or placebo CPAP for three weeks followed by therapeutic CPAP for three weeks. SETTING: General clinical research center PARTICIPANTS: 52 men and women with mild-moderate AD and OSA INTERVENTION: Continuous positive airway pressure MEASUREMENTS: A complete neuropsychological test battery was administered before treatment, at three and at six-weeks. RESULTS: A comparison of subjects randomized to 3 weeks of therapeutic versus placebo CPAP suggested no significant improvements in cognition. A comparison of pre- versus post-treatment neuropsychological test scores after 3 weeks of therapeutic CPAP in both groups showed a significant improvement in cognition. The study was underpowered to make definitive statements about improvements within specific cognitive constructs. However, exploratory post-hoc examination of change scores for individual tests suggested improvements in episodic verbal learning and memory and some aspects of executive functioning such as cognitive flexibility, and mental processing speed. CONCLUSIONS: OSA may aggravate cognitive dysfunction in dementia and thus may be a reversible cause of cognitive loss in AD patients. OSA treatment seems to improve some of the cognitive functioning. Clinicians who care for AD patients should consider implementing CPAP treatment when OSA is present.

The degree of concomitant AD tangle pathology has an important influence on the clinical characteristics and, therefore, the clinical diagnostic accuracy of DLB.

Weight loss precedes mild to moderate dementia; early weight loss is, therefore, unlikely to be a consequence of AD patients being unable or unwilling to eat.

Marked losses in midfrontal ChAT activity occur in diseases with LB, independent of coexistent AD changes. A greater midfrontal, as opposed to hippocampal, cholinergic deficit may differentiate LBV from AD. The lack of a relationship between epsilon4 allele dosage and midfrontal ChAT activity suggests that other factors may play a role in its decline in LBV.