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Abstract Background Cognitive impairment is a common health problem among older adults. Previous studies have proven the association between sleep quality and cognitive impairment, but the specific underlying mechanisms need to be further explored. This study aimed to examine the relationship between sleep quality and cognitive impairment and the mediating effect of frailty in this relationship among the rural older adults. Methods Data from a cross-sectional study conducted in rural areas of Shandong Province from September to December in 2023. A total of 695 rural older adults were included. The Pittsburgh Sleep Quality Index (PSQI) was used to measure sleep quality. Frailty was defined using the FRAIL scale. We assessed cognitive impairment using the Dementia Screening Interview (AD8). Logistic regression analyse was used to assess the relationship between sleep quality and cognitive impairment. And the Karlson-Holm-Breen (KHB) method was performed to test the mediating role of frailty in this relationship. Results After adjusting for all covariates, sleep quality was significantly associated with cognitive impairment (OR = 1.047, 95% CI: 1.005—1.090). Frailty mediated the relationship between sleep quality and cognitive impairment, with a mediation effect value of 0.010 (95% CI: 0.001—0.020), accounting for 17.86% of the total effect. Conclusions We found there was an association between sleep quality and cognitive impairment, and frailty mediated the above relationship. Comprehensive intervention measures should be taken to reduce the incidence of frailty in the older adults and to improve their sleep quality, thereby preventing and delaying the occurrence and development of cognitive impairment.

This study investigated the effects of laser energy density at different scanning speeds on the microstructure evolution, phase equilibrium, mechanical properties, and fracture modes of welds in dissimilar steel welded joints (Q345D and 20Mn2). The connection of dissimilar steel welded joints is achieved by using a laser synchronous powder feeding method. The microstructure and phase evolution of the joint were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical property testing was performed on the joint via a micro-Vickers hardness tester and an electronic testing machine, and the fracture surface morphology was observed via a scanning electron microscope. The results show that when the laser energy density is 1125 J/mm2, the fine cellular crystals, columnar crystals, and equiaxed crystal structures of the joint are more uniformly distributed. As the laser energy density increased, the transition of the Q345D side structure from cellular to columnar crystals and the transition of the 20Mn2 side structure from cellular to equiaxed crystals became more pronounced. Mechanical property testing revealed that an increase in the laser energy density can significantly improve the microhardness and tensile strength of a joint. However, a large amount of the Fe matrix from the 20Mn2 side permeates into the coating, making the mechanical properties of the dilution zone lower than those of the crystallization zone, and making it more prone to fracture on this side. The fracture analysis results show that the fracture mode has strong ductility, and the fracture mode is judged to be ductile fracture. [ABSTRACT FROM AUTHOR]