Potential overestimation of cognitive impairment because of hearing loss: impact of test modalities on cognitive test scores.

OBJECTIVE: Hearing impairment in older adults may affect cognitive function and increase the risk of dementia. Most cognitive tests are delivered auditorily, and individuals with hearing loss may fail to hear verbal instructions. Greater listening difficulty and fatigue in acoustic conditions may impact test performance. This study aimed to examine the effect of decreased audibility on cognitive screening test performance in older adults. METHOD: Older adults (n = 63) with different levels of hearing loss completed a standard auditory Mini-Mental State Examination test and a written version of the test. RESULTS: Individuals with moderate to moderately severe hearing loss (41-70 dB) performed significantly better on the written (24.34 ± 4.90) than on the standard test (22.55 ± 6.25), whereas scores were not impacted for mild hearing loss (less than 40 dB). CONCLUSION: Hearing evaluations should be included in cognitive assessment, and test performance should be carefully interpreted in individuals with hearing loss to avoid overestimating cognitive decline.

Cultivation characteristics of immobilized Aspergillus oryzae for kojic acid production.

Aspergillus oryzae in situ grown from spores entrapped in calcium alginate gel beads was used for the production of kojic acid. The immobilized cells in flask cultures produced kojic acid in a linear proportion while maintaining the stable metabolic activity for a prolonged production period. Kojic acid was accumulated up to a high concentration of 83 g/L, at which the kojic acid began to crystallize, and, thus, the culture had to be replaced with fresh media for the next batch culture. The overall productivities of two consecutive cultivations were higher than that of free mycelial fermentation. However, the production rate of kojic acid by the immobilized cells was suddenly decreased with the appearance of central cavernae inside the immobilized gel beads after 12 days of the third batch cultivation.

Controlled mycelial growth for kojic acid production using Ca-alginate-immobilized fungal cells.

Conidia of Aspergillus oryzae were immobilized in Ca-alginate beads and then incubated in a nutrient medium to yield an immobilized biocatalyst producing kojic acid. The immobilized cell cultures produced kojic acid linearly during cultivation. Regardless of the size of the immobilized particles, there existed an optimal nitrogen concentration for the maximum production rate of kojic acid, at which smaller bead sizes resulted in a higher production rate. When the growth of mycelia were confined within the bead surface and segregated from each other by gel material, they produced kojic acid with maximal catalytic activity and exhibited the highest conversion yield of glucose. The extent of mycelial segregation was especially higher in cultures of smaller bead particles, and the depth of mycelial growth was 150 to 250 microns from the gel bead surface in all cultures of different nitrogen concentrations and bead sizes. Therefore, for the maximum expression of catalytic activities of immobilized mycelial cultures, it was found very critical to optimally control the mycelial distribution in gel beads by the culture conditions affecting mycelial growth.