Glaucoma was the only condition in this study to be associated with cognitive decline. Photo: Michael Chaglasian, OD, and Sarah B. Klein, OD. Click image to enlarge.
Previous studies have shown a relationship between vision impairment (VI) and declining cognitive function in older adults, but few have examined the relationship between eye disease and cognitive functionality. Researchers recently examined the association between VI or eye disease and three-year changes in cognitive test scores to explore whether sex, education and hearing loss act as effect modifiers.
The investigation included 32,000 people between the ages of 45 and 85 who underwent five cognitive tests. VI was defined as binocular presenting visual acuity worse than 20/40.
VI, age-related macular degeneration (AMD) and cataract were not associated with changes on any of the five cognitive tests after adjusting for age, sex, ethnicity, education, income, smoking, diabetes, stroke, heart disease and province.
“VI was not associated with change in cognitive function, although in a sensitivity analysis, VI was associated with worse change scores on three of five cognitive tests when we adjusted for baseline cognitive function,” the authors explained in their study.
Glaucoma, on the other hand, was associated with a greater decline on the mental alternation test, which measures processing speed. This didn’t come as a surprise to the authors, as slower processing is thought to be a key component of cognitive aging.
“In support of our finding, small clinical studies have reported that glaucoma patients have structural brain abnormalities and altered anatomical and functional brain connectivity,” the authors explained. “It is possible that age-related conditions like glaucoma and cognitive decline share a common pathology.” For example, a previous study described how eye diseases like glaucoma share common characteristics with Alzheimer’s disease, such as neuroinflammation and oxidative stress.
The authors suggest further research, including comprehensive eye examination, is needed to confirm and explain this finding.
Grant A, Aubin MJ, Buhrmann R, et al. Visual impairment, eye disease, and 3-year cognitive decline: the Canadian longitudinal study on aging. Ophthalmic Epidemiology. September 5, 2021. [Epub ahead of print].