Bidirectional Association between Visual Impairment and Dementia Among Older Adults in the United States Over Time.

Purpose: Although visual impairment (VI) has been associated with worse cognitive performance among older adults, the temporal relationship between the 2 remains subject to debate. Our objective was to investigate the longitudinal impact of VI on cognitive function and vice versa.
Design: Retrospective, time-to-event study.
Participants: National Health and Aging Trends Study (NHATS) participants from 2011 to 2018 cycles.
Methods: A total of 10 676 participants aged 65 years and older were included. Cox proportional hazards regression models evaluated the impact of baseline VI on subsequent dementia and impact of baseline dementia on subsequent VI. Models were adjusted for potential confounding variables, including demographics, clinical comorbidities, and hearing and physical function limitations.
Main Outcome Measures: Hazard ratio (HR) for incident dementia among participants with baseline self-reported VI and HR for incident VI among participants with baseline dementia.
Results: Of the 10 676 participants included in the analysis, approximately 40% were aged 65-74 years, 40% were aged 75-84 years, and the remaining 20% were aged 85 years and older. The majority were female (59%), and 68% self-identified as non-Hispanic White. Among participants with normal cognitive status at baseline, subsequent dementia was observed in 1753 (16%), and among participants with normal self-reported vision at baseline, subsequent VI was reported in 2371 (22%). In adjusted regression models, participants with baseline VI had higher likelihood of developing dementia over subsequent follow-up (HR, 2.3; 95% confidence interval [CI], 2.0-2.6; P < 0.001). Likewise, participants with baseline dementia had a higher likelihood of developing self-reported VI over time (HR, 2.5; 95% CI, 2.2-2.8; P < 0.001).
Conclusions: Self-reported VI in the US Medicare population is associated with greater dementia likelihood over time, and dementia is similarly associated with greater VI likelihood over time. Associations are likely multifactorial and bidirectional and could be explained by intervening variables in the path from VI to dementia, or vice versa, or by common risk factors for pathological processes in both eyes and brain. These findings suggest the need for early identification of older adults with visual compromise and consideration of visual disability in the cognitively impaired.
(Published by Elsevier Inc.)