Background: Dementia is associated with individual vision impairment (VI) and hearing impairment (HI). However, little is known about their associations with motoric cognitive risk syndrome (MCR), a pre-dementia stage. We investigated the association of VI, HI, and dual sensory impairment (DSI) with MCR and to further evaluate causal relationships using Mendelian randomization (MR) approach.
Methods: First, an observational study was conducted in the China Health and Retirement Longitudinal Study (CHARLS). Evaluate the cross-sectional and longitudinal associations of VI, HI, and DSI with MCR using the logistic regression models and Cox proportional hazard models, respectively. Second, evaluate the causal association between VI and HI with MCR using MR analysis. The GWAS data was used for genetic instruments, including 88,250 of European ancestry (43,877 cases and 44,373 controls) and 504,307 with "white British" ancestry (100,234 cases and 404,073 controls), respectively; MCR information was obtained from the GWAS with 22,593 individuals. Inverse variance weighted was the primary method and sensitivity analysis was used to evaluate the robustness of MR methods.
Results: In the observational study, VI (HR: 1.767, 95%CI: 1.331-2.346; p < 0.001), HI (HR: 1.461, 95%CI: 1.196-1.783; p < 0.001), and DSI (HR: 1.507, 95%CI: 1.245-1.823; p < 0.001) were significantly associated with increased risk of MCR. For the MR, no causal relationship between VI (OR: 0.902, 95% CI: 0.593-1.372; p = 0.631) and HI (OR: 1.016, 95% CI: 0.989-1.043; p = 0.248) with MCR risk, which is consistent with the sensitivity analysis.
Conclusion: VI, HI, and DSI were significantly associated with MCR, but MR analysis failed to provide evidence of their causal relationship. Emphasized the importance of sensory impairment screening in identifying high-risk populations for dementia.
Keywords: dual sensory impairment; hearing impairment; motoric cognitive risk syndrome; older adults; vision impairment.
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