Association of cumulative average sensory impairments with cognitive function and depressive symptoms: Two prospective cohort studies

Background
Globally, over 2.2 billion people have a vision impairment and over 1.5 billion live with hearing impairment, which are significant public health concerns given the meaningful impacts on individual and society. We aimed to investigate whether long-term average visual, hearing, and dual sensory impairment was independently associated with cognitive impairment, incident dementia, and incident depressive symptoms.
Methods
We used data from the Health and Retirement Study (HRS) and the China Health and Retirement Longitudinal Study (CHARLS), two nationally representative and prospective cohorts of community middle aged and older adults. Average sensory impairment was calculated using the area under the curve divided by follow-up time from wave 3 (1996) to wave 15 (2020) in HRS and wave 1 (2011) to wave 4 (2018) in CHARLS. Cox regression models adjusted for multiple covariates were used to estimate adjusted hazard ratios (HRs) and 95 % confidence intervals (95 % CIs).
Results
For each one standard deviation (SD) increment in average visual impairment, the risk of developing cognitive impairment, incident dementia, and incident depressive symptoms increased by 12 %, 34 %, and 39 % in CHARLS and 11 %, 14 % and 10 % in HRS. Similar results were found for each SD increment in average hearing impairment and dual sensory impairment. Nonlinear dose-response relationships were identified between visual impairment and dementia, as well as dual sensory impairment and dementia in both cohorts.
Limitations
The diagnosis of cognitive impairment, dementia, and depression were based on subjective assessment.
Conclusion
Multi-level approaches aimed at improving access to sensory care are needed to improve middle-aged and older adults' visual and auditory functions.