Visual Impairment, Eye Disease, and 3-Year Cognitive Decline: The Canadian Longitudinal Study on Aging

Purpose To examine the longitudinal association between vision-related variables and the 3-year change in cognitive test scores in a community-dwelling sample of adults and to explore whether sex, education, or hearing loss act as effect modifiers. Methods Data came from two waves of a 3-year population-based prospective cohort study (Canadian Longitudinal Study on Aging), which consisted of 30,097 randomly selected people aged 45-85 years from 7 Canadian provinces. Visual impairment (VI) was defined as binocular presenting visual acuity worse than 20/40. Participants were asked if they had ever had a diagnosis of age-related macular degeneration (AMD), glaucoma, or cataract. Cognitive change over 3 years was examined by calculating the difference between baseline and follow-up scores for the Rey Auditory Verbal Learning Test (RAVLT) and the RAVLT delayed test (memory tests), the Controlled Oral Word Association Test (COWAT) and the Animal Naming Test (ANT) (verbal fluency tests), and the Mental Alternation Test (MAT) (processing speed test). Multiple linear regression was used. Results VI, AMD, and cataract were not associated with 3-year changes on any of the 5 cognitive tests after adjusting for age, sex, ethnicity, education, income, smoking, diabetes, stroke, heart disease, and province. A report of glaucoma was associated with greater declines in MAT scores (beta = -0.60, 95% CI -1.03, -0.18). No effect modification was detected. Conclusions Glaucoma was associated with worsening processing speed. Further research to confirm this finding and to understand the possible reason is necessary.