Several concepts, which in the aggregate get might be used to account for "resilience" against age- and disease-related changes, have been the subject of much research. These include brain reserve, cognitive reserve, and brain maintenance. However, different investigators have use these terms in different ways, and there has never been an attempt to arrive at consensus on the definition of these concepts. Furthermore, there has been confusion regarding the measurement of these constructs and the appropriate ways to apply them to research. Therefore the reserve, resilience, and protective factors professional interest area, established under the auspices of the Alzheimer's Association, established a whitepaper workgroup to develop consensus definitions for cognitive reserve, brain reserve, and brain maintenance. The workgroup also evaluated measures that have been used to implement these concepts in research settings and developed guidelines for research that explores or utilizes these concepts. The workgroup hopes that this whitepaper will form a reference point for researchers in this area and facilitate research by supplying a common language.
Background
The promise of Alzheimer’s disease (AD) biomarkers has led to their incorporation in new diagnostic criteria and in therapeutic trials; however, significant barriers exist to widespread use. Chief among these is the lack of internationally accepted standards for quantitative metrics. Hippocampal volumetry is the most widely studied quantitative magnetic resonance imaging (MRI) measure in AD and thus represents the most rational target for an initial effort at standardization.
Methods and Results
The authors of this position paper propose a path toward this goal. The steps include: 1) Establish and empower an oversight board to manage and assess the effort, 2) Adopt the standardized definition of anatomic hippocampal boundaries on MRI arising from the EADC-ADNI hippocampal harmonization effort as a Reference Standard, 3) Establish a scientifically appropriate, publicly available Reference Standard Dataset based on manual delineation of the hippocampus in an appropriate sample of subjects (ADNI), and 4) Define minimum technical and prognostic performance metrics for validation of new measurement techniques using the Reference Standard Dataset as a benchmark.
Conclusions
Although manual delineation of the hippocampus is the best available reference standard, practical application of hippocampal volumetry will require automated methods. Our intent is to establish a mechanism for credentialing automated software applications to achieve internationally recognized accuracy and prognostic performance standards that lead to the systematic evaluation and then widespread acceptance and use of hippocampal volumetry. The standardization and assay validation process outlined for hippocampal volumetry is envisioned as a template that could be applied to other imaging biomarkers.
Affective symptoms are of prognostic utility, but interventions to prevent dementia syndromes are limited. Trials need to assess interventions targeting known dementia pathology, toward novel pathology, as well as using psychiatric medications. Research focusing explicitly on later life onset symptomatology will improve our understanding of the neurobiology of NPS and neurodegeneration, enrich the study sample, and inform observational and clinical trial design for prevention and treatment strategies.
Venlafaxine, a serotonin and norepinephrine reuptake inhibitor (SNRI), produces significantly higher remission rates in depressed patients than do the selective serotonin reuptake inhibitors (SSRIs). In this analysis of pooled data, we explored the relationship between differences in treatment efficacy, early improvement of symptoms, and severity of baseline anxiety in depressed patients treated with either venlafaxine or fluoxetine. A pooled analysis was performed on data from 1,454 outpatients with major depression from five double-blind, randomized studies comparing the 6-week efficacy of venlafaxine (542 patients) with fluoxetine (555 patients). The Hamilton rating scale for depression (HAM-D) total and item scores were analyzed at different treatment times up to 6 weeks. Venlafaxine and fluoxetine both produced statistically significant higher response and remission rates compared with placebo starting from week 2 for response and weeks 3 to 4 for remission. Venlafaxine was statistically significantly superior to fluoxetine from week 3 until week 6 in respect of response rate, and from week 2 until week 6 for remission rate. After 1 week of treatment, greater improvement in individual symptoms was observed in the depressed mood, suicide, and psychic anxiety items of the HAM-D scale for both venlafaxine- and fluoxetine-treated patients compared with placebo. Improvement in psychic anxiety was statistically significantly greater with venlafaxine than with fluoxetine. The presence of baseline psychic anxiety correlated significantly to treatment outcome when analyzing the remission rates. In depressed patients with moderate anxiety (HAM-D psychic anxiety score < or = 2), venlafaxine statistically significantly increased remission rates compared with placebo from week 4 until week 6, while a significant effect of fluoxetine on remission rates was observed starting at week 6. Remission rates in the severely anxious depressed patients (score > 2) were statistically significantly higher with venlafaxine than placebo starting from week 3 until the end of the study period, but no difference could be observed between fluoxetine and placebo. Baseline severity of psychic anxiety had a significant impact on remission rates after treatment of patients diagnosed with depression. Venlafaxine's superior remission rates in the more severely anxious patients and its ability to improve psychic anxiety as early as week 1 compared with fluoxetine suggest that venlafaxine's early efficacy on anxiety symptoms may be the basis for its superior efficacy in depression.
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