Dual Sensory Impairment and Cognitive Impairment in the Korean Longitudinal Elderly Cohort

To investigate the effects of single sensory impairment (SSI; visual or auditory) or dual sensory impairment (DSI; visual and auditory) on dementia and longitudinal changes of neuropsychological test scores. In this nationwide, prospective, community-based elderly cohort study, Korean Longitudinal Study on Cognitive Aging and Dementia (KLOSCAD), 6,520 elderly individuals (58-101 year) representing the general population were included. We defined visual and auditory sensory impairment via self-report questionnaire: 932 had a normal sensory function, 2957 had a SSI, and 2631 had a DSI. Demographic and clinical variables including cognitive outcomes were evaluated every two years over six years. Through logistic regression, Cox regression, and linear mixed model analysis, the relationship between SSI or DSI and dementia prevalence, dementia incidence, and change in neuropsychological scores were evaluated. At baseline, DSI was significantly associated with increased dementia prevalence compared to normal sensory function (OR=2.17, 95% CI [1.17-4.02]), but SSI was not (OR=1.27, 95% CI [0.66-2.41]). During the 6-year follow-up, the incidence of dementia was significantly higher in the DSI group than in the normal sensory function (HR=1.9, 95% CI [1.04-3.46]), and neuropsychological scores significantly decreased (β=-0.87, 95% CI [-1.17--0.58]). Our results suggest that coexisting visual and hearing impairments facilitate dementia prevalence, dementia incidence, and cognitive decline, but visual or hearing impairment alone do not. Additionally, visual and hearing impairment may lead to dementia or cognitive decline independent of Alzheimer's pathology.