Latent profile analysis of cognitive function and depressive symptoms in Chinese elderly: results from the China Health and Retirement Longitudinal Study.

BACKGROUND: Geriatric cognitive impairment often occurs in conjunction with depressive symptoms. This study focuses on categorising the Chinese elderly with such co-occurring symptoms into homogeneous groups using latent profile analysis (LPA), a person-centred statistical approach. METHODS: Information on cognitive function and depressive states of the elderly was extracted from the China Health and Retirement Longitudinal Study. The underlying characteristics were identified by LPA, and based on those findings, differences in demographic characteristics of different subgroups were explored by chi-squared test and analysis of variance. RESULTS: A total of 6710 Chinese elderly who met the inclusion criteria were selected from the dataset. Four subgroups were identified among this sample by LPA, based on cognitive function associated with depressive symptoms, and named in this study as follows: mild cognitive impairment (n = 3747, 55.84%), moderate cognitive impairment (n = 1306, 19.46%), mild cognitive impairment combined with depressive symptoms (n = 1114, 16.6%), and moderate cognitive impairment combined with depression (n = 543, 8.09%). Age, gender, marital status, and educational level were all significantly different across subgroups (P < 0.001); religious belief and pension mode, however, were not (P > 0.05). CONCLUSIONS: In the present study, four subgroups of cognitive function combined with depressive symptoms were found in Chinese elderly individuals, and differences in demographic factors were noted between the subgroups. In clinical practise, these findings could help clinical workers identify patients accurately and consider the demographic features of each subgroup when designing medical treatment, care, and rehabilitation programmes for those with cognitive impairment and concomitant depressive symptoms.

New Zr-25Ti-xMo alloys for dental implant application: Properties characterization and surface analysis.

A series of Zr-25Ti-xMo (x = 0, 2.5, 5, 7.5, 10 and 12.5 wt %) as-cast alloys were designed to advance a new-brand Zr-based alloy with low Young's elastic, moderate compression strength, superior corrosion resistance and good wear behavior for the application of dental implant materials. In the present study, the microstructures of the alloys were evaluated by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The microhardness and uniaxial compression measurement were performed to evaluate the mechanical properties of the alloys. The electrochemical behaviors of the alloys was investigated in artificial saliva solution. The friction and wear performances of the Zr-25Ti-xMo alloys were examined by pin-on-disk under the load of 15 N. The results shows that the crystalline structure transforms from hexagonal close-pack (α phase, x = 0 wt %) to body-centered cubic structure (ß phase, 5 ≤ x ≤ 12.5 wt %) through a α + ß dual-phase region (x = 2.5 wt %). They exhibits excellent mechanical properties with low elastic modulus (from 17.7 to 24.4 GPa) and moderate compression strength (from 1154.4 to 1310.8 MPa). The Zr-25Ti-xMo alloys possess good corrosion resistance due to the formation of a protective passive film consisting mainly of ZrO2, TiO2 and minor MoO3. Especially, the polarization curves demonstrates that the Zr-25Ti-7.5Mo alloy has a wider passive region than the other five alloys and it possesses the lower corrosion current density and corrosion rate. Furthermore, this alloy exhibits good abrasion resistance with the lowest coefficients of friction and volume wear loss. Thus, the Zr-25Ti-7.5Mo alloy has a combination of excellent mechanical properties such as low elastic modulus, moderate yield strength and the compression strength, good electrochemical stability and well wear resistance, it is considered a promising candidate for orthopedic materials as dental implant.