Age-Related Eye Disease and Cognitive Function: The Search for Mediators

Abstract

Age-related eye disease may be associated with cognitive decline, but the scientific literature has not been consistent. Furthermore, no studies have been able to explain the relationship. Our objective was to assess whether older adults with age-related macular degeneration (AMD) or glaucoma performed worse on 6 cognitive tests compared with older adults with normal vision and, if so, to understand why. Cross-sectional analysis of hospital-based study (Maisonneuve-Rosemont Hospital Ophthalmology Clinics, Montréal, Canada). Three hundred thirty-six adults 65 years of age or older with either AMD, glaucoma, or normal vision. Cognition was measured with 6 cognitive tests administered orally. Activity levels were measured using the Victoria Longitudinal Study Activity Lifestyle Questionnaire. Visual acuity and visual field were measured. Multiple linear regression was used. Mediation was assessed using structural equation modeling. Results of the verbal fluency test (animal and letter versions), the digit span test (forward and backward versions), and the logical memory test (immediate and delayed recall). People with glaucoma showed lower scores on 3 cognitive tests than the group with normal vision: the digit span forward and backward tests (β= -0.8 [95% confidence interval (CI), -1.5 to -0.2] and β= -0.7 [95% CI, -1.3 to -0.1], respectively) and the logical memory test with immediate recall (β= -1.3 [95% CI, -2.4 to -0.2]). Activity levels statistically significantly mediated the relationship between glaucoma and the digit span forward test (P= 0.043; percentage of the total effect mediated, 17%). People with glaucoma showed lower scores on cognitive tests that may depend on verbal working memory and encoding. If confirmed in longitudinal studies, interventions should be developed that are appropriate for a visually impaired population to slow this cognitive decline.