Sensory Impairment and Risk of Neurodegenerative Diseases: A Nationwide Cohort Study in Korea

Objectives.: Sensory impairments are common in older adults. However, their association with neurodegenerative diseases across multiple sensory domains remains unclear. This study aimed to investigate the associations between visual, hearing, and olfactory impairments and incident neurodegenerative diseases. Methods.: We analyzed data from the Korean National Health Insurance Service-Health Screening Cohort (2002-2015), excluding participants with pre-existing sensory impairment or neurodegenerative disease during a washout period (2002-2004). Sensory impairment was classified as visual, hearing, olfactory, or multisensory between 2005 and 2015. The outcomes were overall neurodegenerative diseases and their subtypes (Alzheimer's disease and related dementias, Parkinson's disease, and Huntington's and other neurodegenerative disorders). Kaplan-Meier curves and adjusted Cox models were used. Results.: Among the 410,749 participants, 389,659 were controls and 21,007 had sensory impairment (hearing, 16,651; olfactory, 642; visual, 3,426; multisensory, 288). The incidence differed by sensory status (log-rank p < 0.001) and was highest in multisensory impairment. Versus controls, multisensory impairment had the largest adjusted risk for overall neurodegenerative disease (Hazard ratio [HR] 5.23, 95% confidence interval [CI] 4.20-6.52) and across major disease subtypes (Alzheimer's disease, HR 4.43; Parkinson's disease, HR 5.07; and Huntington's and other neurodegenerative disorders, HR 9.90). In post hoc analyses using multisensory impairment as a reference, all single-sensory impairment groups showed significantly lower hazards. Conclusion.: : Sensory impairment across the visual, hearing, and olfactory domains was associated with an increased risk of neurodegenerative 73 diseases, showing a graded pattern with a greater sensory burden. The sensory status may serve as an accessible early risk marker for neurodegenerative diseases in older adults.