Publications by authors named "Yong-S Shim"

Background And Purpose: To ensure data privacy, the development of defacing processes, which anonymize brain images by obscuring facial features, is crucial. However, the impact of these defacing methods on brain imaging analysis poses significant concern. This study aimed to evaluate the reliability of three different defacing methods in automated brain volumetry.

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Background And Purpose: Physical frailty is known to be closely associated with cognitive impairment and to be an early sign of Alzheimer's disease. We aimed to understand the characteristics of physical frailty and define factors associated with physical frailty in subjects with subjective cognitive decline (SCD) by analyzing amyloid data.

Methods: We prospectively enrolled subjects with SCD from a cohort study to identify predictors for the clinical progression to mild cognitive impairment or dementia from SCD (CoSCo).

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A quantitative analysis of brain volume can assist in the diagnosis of Alzheimer's disease (AD) which is ususally accompanied by brain atrophy. With an automated analysis program Quick Brain Volumetry (QBraVo) developed for volumetric measurements, we measured regional volumes and ratios to evaluate their performance in discriminating AD dementia (ADD) and mild cognitive impairment (MCI) patients from normal controls (NC). Validation of QBraVo was based on intra-rater and inter-rater reliability with a manual measurement.

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Background And Purpose: The rate of donepezil discontinuation and the underlying reasons for discontinuation in Asian patients with Alzheimer's disease (AD) are currently unknown. We aimed to determine the treatment discontinuation rates in AD patients who had newly been prescribed donepezil in routine clinical practice in Asia.

Methods: This 1-year observational study involved 38 institutions in seven Asian countries, and it evaluated 398 participants aged 50-90 years with a diagnosis of probable AD and on newly prescribed donepezil monotherapy.

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Background And Purpose: Reportedly 30-50% of patients being treated for chronic illnesses do not adhere to their medication regimen. We assessed the impact of a nurse-led education program for caregivers of Korean de novo Alzheimer's disease patients who had newly been prescribed donepezil.

Methods: This multicenter study analyzed 93 participants in a caregiver education group and 92 participants in a caregiver no-education group.

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Background: This study investigated the differences in caregiver activity, caregiver burden, and awareness of both caregivers and patients with Alzheimer's disease (AD) across different Asian locations.

Methods: This was a secondary analysis of a multi-national cohort study that aimed to assess caregiver activity and caregiver burden using the Caregiver Activity Scale (CAS) and Zarit Burden Interview (ZBI), respectively. Patients' awareness of their dementia diagnosis was assessed by asking the following yes/no question: "Do you have dementia?" Caregivers' awareness of the patient's dementia diagnosis was assessed by asking the following yes/no question: "Does your patient have dementia?"

Results: In total, 524 caregivers of patients with AD from China, Hong Kong, South Korea, the Philippines, Singapore, Thailand, and Taiwan participated.

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We investigated ambulatory blood pressure (BP) monitoring (ABPM) profiles and magnetic resonance imaging (MRI) findings of cerebral small-vessel disease (cSVD) in older adults with cognitive complaints who were grouped as follows: subjective cognitive decline, mild cognitive impairment, and dementia of Alzheimer's type. Group comparisons and correlation analyses among demographic characteristics, cognitive and MRI findings, and ABPM profiles were performed. Furthermore, multivariate logistic regression analyses for dependent variables of (1) dementia or not and (2) MRI criteria of subcortical vascular dementia (SVaD) or not were conducted with independent variables of dichotomized ABPM profiles.

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Objective: The electrocortical activities associated with the neuropsychiatric symptoms (NPSs) of Alzheimer's disease (AD) were investigated using frequency-domain electroencephalography (EEG) spectral source analysis, and the potential electrocortical indices identified.

Materials And Methods: Scalp EEG data were obtained from 51 patients with AD to investigate the presence of four NPS subdomains, hyperactivity, psychosis, affective symptoms, and apathy. EEG power spectra and the standardized low-resolution brain electromagnetic tomography (sLORETA)-localized EEG cortical sources were compared between the groups with and without the four NPS subdomains in eight frequency bands: 1-4, 4-8, 8-10, 10-12, 12-18, 18-20, 20-30, and 30-45 Hz.

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Background And Purpose: We investigated the prevalence of amyloid positivity and cerebral microbleeds (CMBs) in subjects with cognitive complaints with the aim of identifying differences in clinical parameters and cognitive function according to the pattern of coexistence.

Methods: We retrospectively enrolled 200 subjects with memory impairment and applied both standardized ¹⁸F-florbetaben PET and brain MRI, including susceptibility-weighted imaging. The amyloid burden was visually classified as positive or negative, and the number and location of CMBs were also analyzed visually.

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Background And Purpose: Cerebral small vessel disease (CSVD) is the most common cause of vascular dementia and a major contributor to mixed dementia. CSVD is characterized by progressive cerebral white matter changes (WMC) due to chronic low perfusion and loss of autoregulation. In addition to its antiplatelet effect, cilostazol exerts a vasodilating effect and improves endothelial function.

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Background And Purpose: Subjective cognitive decline (SCD) may be the first stage corresponding to subtle cognitive changes in patients with Alzheimer's disease (AD) spectrum disorders. We evaluated the differences in cortical thinning patterns among patients with SCD who progressed to mild cognitive impairment or dementia (pSCD), those who remained stable (sSCD), and healthy normal controls (NCs).

Methods: We retrospectively recruited SCD subjects (14 pSCD and 21 sSCD cases) and 29 NCs.

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Background: Neuropsychological tests (NPTs) are important tools for informing diagnoses of cognitive impairment (CI). However, interpreting NPTs requires specialists and is thus time-consuming. To streamline the application of NPTs in clinical settings, we developed and evaluated the accuracy of a machine learning algorithm using multi-center NPT data.

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Objective: The aims of this study were to investigate the effects of daily low-dose tadalafil on cognitive function and to examine whether there was a change in cerebral blood flow (CBF) in patients with erectile dysfunction (ED) and mild cognitive impairment.

Methods: Male patients aged 50 to 75 years with at least three months of ED (International Index of Erectile Function [IIEF]-5 score ≤ 21) and mild cognitive impairment (Montreal Cognitive Assessment [MoCA] score ≤ 22) were included in the study. The subjects were prescribed a low-dose PDE5 inhibitor (tadalafil 5 mg) to be taken once daily for eight weeks.

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In this study, we fabricate solution processable, flexible, and transparent hybrid electrodes. The hybrid electrodes are designed by depositing a tungsten trioxide (WO3) buffer layer on silver nanowires. The fabrication method is solution based, and the electrodes can be fabricated directly on a flexible substrate at low temperatures.

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Organic light-emitting diodes with a quasi-periodic nano-structure (QPS) were fabricated via a combination of laser interference lithography (LIL) and reactive ion etching (RIE). The LIL process was used to generate a periodic pattern, whereas the RIE process was used as a supplement to add randomness to the periodic pattern. The period of the fabricated periodic pattern was determined by finite difference time domain solutions.

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Organic light-emitting diodes (OLEDs) with an enhanced outcoupling efficiency and a suppressed efficiency roll-off were fabricated by inserting a nanosize pixel-defining layer (nPDL) that defines the OLED emission region as an array of nanoholes. The outcoupling efficiency of the nano-arrayed OLEDs was increased through the reduced surface plasmon polariton loss caused by the wavy diffraction grating at the metal-organic interface, and their efficiency roll-off was suppressed through the diffusive exciton outside the exciton-formation zone. As a result, the nano-arrayed OLEDs exhibited enhancements of 148.

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Background/objective: Vascular risk factors and neurovascular dysfunction may be closely related to cognitive impairment and dementia. In this study, we evaluated the association between hemodynamic markers and longitudinal cognitive changes in patients with mild cognitive impairment (MCI). Furthermore, we investigated whether hemodynamic markers could predict the risk of progression to Alzheimer's disease (AD) in patients with MCI.

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Fabrication of junction-free Ag fiber electrodes for flexible organic light-emitting diodes (OLEDs) is demonstrated. The junction-free Ag fiber electrodes are fabricated by electrospun polymer fibers used as an etch mask and wet etching of Ag thin film. This process facilitates surface roughness control, which is important in transparent electrodes based on metal wires to prevent electrical instability of the OLEDs.

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Background And Objective: Studies investigating the impact of white matter hyperintensities (WMHs) on the response of acetylcholinesterase inhibitors in patients with Alzheimer's disease (AD) have presented inconsistent results. We aimed to compare the effects of the rivastigmine patch between patients with AD with minimal WMHs and those with moderate WMHs.

Methods: Three hundred patients with mild to moderate AD were enrolled in this multicenter prospective open-label study and divided into two groups.

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Background: The mini-mental state examination (MMSE) was adapted by individual countries according to their languages and cultures, though it has not been systematically compared. The objective of this study was to compare the linguistic and cultural variations of the MMSE used in various Asian countries. With this, we can analyze the strengths and weaknesses of the MMSE and consider using a common version in future international clinical studies in Asia.

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Background: We investigated differences in the prevalence of anosognosia and neuropsychiatric symptoms (NPSs) characteristics according to disease severity in patients with early-onset Alzheimer disease (EOAD).

Methods: We recruited 616 patients with EOAD. We subdivided participants into 2 groups based on the presence or absence of anosognosia and then again by Clinical Dementia Rating (CDR) scale.

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Background: Subjective memory impairment (SMI) is common among older adults. Increasing evidence suggests that SMI is a risk factor for future cognitive decline, as well as for mild cognitive impairment and dementia. Medial temporal lobe structures, including the hippocampus and entorhinal cortex, are affected in the early stages of Alzheimer's disease.

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