The clinical significance of subjective memory complaints in the diagnosis of mild cognitive impairment and dementia: a meta-analysis

Functional neural network analysis in frontotemporal dementia and Alzheimer's disease using EEG and graph theory

BACKGROUND

Although a large body of knowledge about both brain structure and function has been gathered over the last decades, we still have a poor understanding of their exact relationship. Graph theory provides a method to study the relation between network structure and function, and its application to neuroscientific data is an emerging research field. We investigated topological changes in large-scale functional brain networks in patients with Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) by means of graph theoretical analysis of resting-state EEG recordings. EEGs of 20 patients with mild to moderate AD, 15 FTLD patients, and 23 non-demented individuals were recorded in an eyes-closed resting-state. The synchronization likelihood (SL), a measure of functional connectivity, was calculated for each sensor pair in 0.5-4 Hz, 4-8 Hz, 8-10 Hz, 10-13 Hz, 13-30 Hz and 30-45 Hz frequency bands. The resulting connectivity matrices were converted to unweighted graphs, whose structure was characterized with several measures: mean clustering coefficient (local connectivity), characteristic path length (global connectivity) and degree correlation (network 'assortativity'). All results were normalized for network size and compared with random control networks.

RESULTS

In AD, the clustering coefficient decreased in the lower alpha and beta bands (p < 0.001), and the characteristic path length decreased in the lower alpha and gamma bands (p < 0.05) compared to controls. In FTLD no significant differences with controls were found in these measures. The degree correlation decreased in both alpha bands in AD compared to controls (p < 0.05), but increased in the FTLD lower alpha band compared with controls (p < 0.01).

CONCLUSION

With decreasing local and global connectivity parameters, the large-scale functional brain network organization in AD deviates from the optimal 'small-world' network structure towards a more 'random' type. This is associated with less efficient information exchange between brain areas, supporting the disconnection hypothesis of AD. Surprisingly, FTLD patients show changes in the opposite direction, towards a (perhaps excessively) more 'ordered' network structure, possibly reflecting a different underlying pathophysiological process.

Stability in the clinical characteristics of patients with memory complaints

The objectives of this study were to examine potential clinical and neuropsychological changes over time in non-demented patients with subjective memory complaints (<or=70 years) and to compare the patients with objective memory impairment (OMI) with those who suffer from subjective memory impairment (SMI). OMI and SMI patients did not differ regarding duration of memory problems, age or education. At baseline no differences were revealed between the OMI and SMI patients regarding self-reported cognitive deficits, self-reported worry about deficits, and symptoms of anxiety or depression. None of the patients had converted to dementia at follow-up. Eighty percent of the OMI patients and 61% of the SMI patients reported cognitive deficits to the same degree at follow-up as at baseline. Despite a significant reduction of depressive symptoms in the OMI patients, a considerable portion of both OMI and SMI patients scored above the cut off score on both anxiety and depression subscales at baseline as well as at follow-up. Our study reveals close points of similarity between patients with memory complaints, verified by test, and patients with memory complaints, not verified by test, as well as stability over time regarding important clinical aspects.

Self-reported symptoms of depression and memory dysfunction in survivors of ARDS

BACKGROUND

Survivors of ARDS have well documented physical limitations, but psychological effects are less clear. We determined the prevalence of self-reported depression and memory dysfunction in ARDS survivors.

METHODS

Six to 48 (median 22) months after ICU discharge, we administered instruments assessing depression symptoms (Beck Depression Inventory-II [BDI-II]) and memory dysfunction (Memory Assessment Clinics Self-Rating Scale [MAC-S]) to 82 ARDS patients who were enrolled in a prospective cohort study in four university-affiliated ICUs.

RESULTS

Sixty-one (74%), 64 (78%), and 61 (74%) patients fully completed the BDI-II, MAC-S (Ability subscale), and MAC-S (Frequency of Occurrence subscale) instruments. Responders (similar to nonresponders) were young (median 42 years, interquartile range [IQR] 35 to 56), with high admission illness severity and organ dysfunction. The median BDI-II score was 12 (IQR 5 to 25). Twenty-five (41%) patients reported moderate-severe depression symptoms and were less likely to return to work than those with minimal-mild symptoms (8/25 [32%] vs 25/36 [69%]; p = 0.005). Median MAC-S (Ability) and MAC-S (Frequency of Occurrence) scores were 76 (IQR 61 to 93) and 91 (IQR 77 to 102), respectively; 8%, 16%, and 20% scored > 2, > 1.5, and > 1 SD(s), respectively, below age-adjusted population norms for each subscale. BDI-II and MAC-S scores were negatively correlated (Spearman coefficient -0.58 and -0.50 for Ability and Frequency of Occurrence subscales, respectively; p < 0.0001). Univariable analyses showed no demographic or illness-severity predictors of BDI-II (including the Cognitive subscale) or MAC-S (both subscales); results were similar when restricted to patients whose primary language was English.

CONCLUSIONS

ARDS survivors report a high prevalence of depression symptoms and a lower prevalence of memory dysfunction 6 to 48 months after ICU discharge. Depression symptoms may hinder the return to work, or patients may report these symptoms because of inability to re-enter the workforce.

Study design and methods of the Ansan Geriatric Study (AGE study)

Background

The overall objective of the Ansan Geriatric Study (AGE study) was to describe the prevalence, incidence, and related risk factors for geriatric diseases in elderly Koreans.

Methods/Design

The AGE study was designed as a population-based prospective cohort study on health, aging, and common geriatric diseases of elderly Koreans aged 60 to 84 years. The inception cohort was recruited in May 2002. The first-wave and second-wave studies were performed using uniform and structured procedures. At the screening study, 2,767 participants were enrolled. Participants (1391 in the first wave study and 841 in the second wave study) were recruited and completed the evaluation. The prevalence of geriatric disease and related factors in elderly Koreans were estimated.

Discussion

Here, we report the design and sampling participants, measurement tools, and characteristics of the AGE study. This cohort study will allow a detailed study of the longitudinal comprehensive data on health information of elderly Koreans, thereby contributing to policy formulation and planning of health, welfare management, and other social services in Korea.

Clinical conditions and memory complaints in outpatient elderly

Memory complaints are common in elderly, and may be associated with many clinical problems.