Developing Topics

Background: Recent studies have identified visual impairment as a potentially modifiable dementia risk factor. However, the underlying mechanism linking visual impairment and cognitive decline is still not fully understood. Additionally, there has been a dearth of research focusing on Latinos.

Method: Data were obtained from the Los Angeles Latino Eye Study (LALES), a population-based longitudinal study of Mexican Americans aged 40 and above. The study performed comprehensive eye examination. Self-reported vision-related functioning was assessed using the National Eye Institute Visual Function Questionnaire (NEI-VFQ-25). Vision data were collected from the baseline visit, while the cognition data were obtained from the 8-year follow up visit using the Cognitive Abilities Screening Instrument-Short (CASI-S) form. Multivariable linear regression models were used to assess the association with cognition. We explored the mediation effect of vision-related health domains, such as driving difficulty, dependency, social function, and mental health. All analyses were conducted in R program.

Result: A total of 3904 participants had valid vision and cognition data available for analyses. Visual acuity was not associated with CASI-S score (P = 0.27) after adjusting for age, education level, and sex. However, greater visual field loss at baseline had a dose-dependent association with lower CASI-S score (P trend<0.001). Compared with individuals without visual field loss (mean deviation of ≥-2 decibels [dB]), those with mild (-6 dB ≤ to ←2dB), moderate (-12dB ≤ to ←6dB), and severe (←12dB) loss demonstrated CASI-S scores 0.45, 0.87, and 1.85 lower, respectively (Ps<0.001). With regards to individual vision disorders, such as cataracts, age-related maculopathy, and diabetic retinopathy, no significant associations with CASI-S scores were observed after adjusting for visual field loss, except for open-angle glaucoma (β = -0.69, P = 0.022). Of the 10 vision-related functioning indicators tested, driving difficulty had the largest mediatory effect. Notably, vision-related driving difficulty was found to mediate 15.8% of the relationship between visual field loss and CASI-S score, and social functioning accounted for 5.4%.

Conclusion: In a cohort of community-dwelling older Latinos, we found that visual field loss is associated with cognitive impairment. Vision-related driving difficulty was identified as a more important mediator than social functioning, dependency, and mental health.