Background: The influences of demographics, culture, language, and environmental changes on Mini-Mental State Examination (MMSE) scores are considerable.

Methods: Using a sample of 7452 healthy, community-dwelling elderly Koreans, aged 55 to 94 years, who participated in the four ongoing geriatric cohorts in Korea, we investigated demographic influences on MMSE scores and derived normative data for this population. Geropsychiatrists strictly excluded subjects with cognitive disorders according to the protocol of the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet (CERAD-K) Clinical Assessment Battery (CERAD-K-C).

Results: Education (standardized β = 0.463), age (standardized β = −0.303), and gender (standardized β = −0.057) had significant effects on MMSE scores (p < 0.001). The score of MMSE increase 0.379 point per 1-year education, decrease 0.188 per 1-year older, and decrease 0.491 in women compared to men. Education explained 30.4% of the scores’ total variance, which was much larger than the variances explained by age (8.4%) or gender (0.3%). Accordingly, we present normative data for the MMSE stratified by education (0, 1–3, 4–6, 7–9, 10–12, and ≥ 13 years), age (60–69, 70–79, and 80–89 years), and gender.

Conclusions: We provide contemporary education-, age-, and gender-stratified norms for the MMSE, derived from a large, community-dwelling elderly Korean population sample, which could be useful in evaluating individual MMSE scores.

Background: Several studies of patients with mild cognitive impairment (MCI) have revealed that this population, like people with dementia, have neuropsychiatric symptoms (NPS) as well as memory impairment. No study has reported on the natural history and course of NPS in MCI although this is important in terms of management. We aimed to determine the persistence of NPS over six months in participants with MCI.

Method: The Neuropsychiatric Inventory (NPI) was used to rate the severity of NPS in 241 consecutive referrals with MCI from a Korean clinic at baseline and in 220 patients at 6-month follow-up. We also collected information about the cognition and quality of life of patients and their caregivers.

Results: Ninety-seven (44.1%) MCI participants who completed the 6-month follow-up exhibited at least one NPS at baseline; 60 (27.3%) were clinically significant NPS. Seventy (72.1%) of those with any symptom had at least one persistent NPS at 6-month follow-up, and 44 (73.3%) of those with clinically significant symptoms had at least one significant and persistent NPS at 6-month follow-up. Those with persistent symptoms had more severe baseline symptoms. Both patients and caregivers had a poorer quality of life when the patient had at least one clinically significant symptom.

Conclusions: NPS were highly persistent overall in older people with MCI. Persistence was predicted by having more severe symptoms at baseline. Clinically significant levels of NPS were associated with decreased quality of life. We conclude that clinicians should be aware that NPS symptoms in MCI usually persist.

Background: Low education and illiteracy are associated with an increased risk of dementia. This study aimed to develop a neuropsychological test battery applicable to both illiterate and literate elderly and to assess its reliability and validity for a diagnosis of dementia.

Methods: We developed the Literacy Independent Cognitive Assessment (LICA), which consists of 13 subtests assessing memory, language, visuoconstruction, executive function, attention and calculation. We investigated its reliability and validity on 152 patients with dementia, 66 with mild cognitive impairment and 639 normal controls.

Results: The subtests were found to be applicable to most of the illiterate normal controls (97.3%) and were found to have high inter-rater reliabilities (r = 0.85–1.00, p < 0.001) and moderate to high test-retest reliabilities (r = 0.50–0.86, p < 0.001). The LICA performed well in discriminating participants across Clinical Dementia Rating stages and showed excellent internal consistency and good concurrent validity with the Korean Mini-mental State Examination in both literate and illiterate participants. The area under the curve of the receiver operating characteristic was 0.985 in each of the two literacy groups. Sensitivity and specificity of the LICA to make a diagnosis of dementia was 91.9% and 91.8% at the cutoff point of 186.0 in the literate subjects and 96.2% and 91.1% at the cutoff point of 154.5 in the illiterate subjects. The battery was factored into two separate factors consisting of verbal memory tests and tests for other cognitive domains.

Conclusion: The LICA is a valid and reliable instrument for a diagnosis of dementia in both illiterate and literate elderly.

The creep behaviors of 20 vol% SiCw/2124Al, extruded with different ratios, and SiCp/2124Al, reinforced with 10–30 vol% SiC particles, were investigated to clarify the effects of aspect ratio, alignment, and volume fraction of reinforcement on creep deformation. The effective stresses on the matrix of SiC/Al composites are calculated based on the generalized shear-lag model. The minimum creep rates of SiCw/2124Al extruded with different ratios and SiCp/2124Al reinforced with different volume fractions of SiC particles are found to be similar under a same effective stress on matrix, which is calculated by the generalized shear-lag model. The subgrain sizes in matrices of crept SiC/Al composites are dependent on the effective stress on matrix but not on the applied stress on the composite. It is suggested that the role of SiC reinforcements is to increase the creep resistance of SiC/Al composite by reducing the effective stress on matrix.

The load-transfer efficiency of reinforcement, in cylindrical forms in metal-matrix composite (MMC), was analyzed based on the shear-lag model. Both the geometric shape and alignment of reinforcement were considered. The stress transferred to a misaligned whisker was calculated from differential equations based on the force equilibrium in longitudinal and transverse directions. A new parameter, defined as effective aspect ratio, was used to indicate the load-transfer efficiency of misaligned reinforcement. The effective aspect ratio was formulated as a function of aspect ratio and misorientation angle of reinforcement in MMC. A probability density function of misorientation distribution was used to estimate the strengthening effect of all misaligned whiskers distributed in the matrix. Considering the contributions of both effective aspect ratio and misorientation distribution on load-transfer efficiency, a generalized shear-lag model was proposed to explain the mechanical anisotropy of discontinuous reinforced MMC.