Impact of sensory impairments on dementia incidence and symptoms among Japanese older adults.

Abstract

Dementia and behavioural and psychological symptoms of dementia affect older adults' care-need levels. With aging comes an increase in the incidence of sensory impairments, which promotes the development of dementia. We investigated the association between sensory impairments - visual impairment (VI), hearing impairment (HI), and dual sensory impairment (DSI), the behavioural and psychological symptoms of dementia, and dementia incidence. This was a retrospective study that used Japanese long-term care insurance certification data from 2010 to 2017 of City A. The 2190 older adults who did not have dementia in 2010 were classified into four impairment categories: VI, HI, DSI, and no sensory impairment. The incidence of dementia was examined using Kaplan-Meier survival analysis and log-rank testing. Cox proportional hazards analysis was used to investigate the risk of developing dementia associated with sensory impairments, compared to the risk for no sensory impairment. Pearson's χ2 tests were used to compare the prevalence of behavioural and psychological symptoms of dementia among the four groups. HI and DSI were associated with a higher cumulative dementia incidence compared to no sensory impairment (log-rank χ2 = 10.42; P < 0.001, and log-rank χ2 = 39.92; P < 0.001, respectively), and DSI showed higher cumulative dementia incidence than HI (log-rank χ2 = 11.37; P = 0.001). Cox proportional hazards analysis showed that DSI is the greatest risk factor for developing dementia among sensory impairments (hazard ratio, 1.45; 95% CI, 1.22-1.71; P < 0.001). Older adults with VI had a significantly higher prevalence of day-night reversal than the other groups. Our results indicate that older adults with sensory impairments have a high incidence of dementia, with DSI presenting the greatest risk. Older adults with VI were found to be more likely to have day-night reversal symptoms when dementia occurs.