As people age, it’s normal to experience a decline in both vision and cognition. Research recently published in Ophthalmology suggests a possible relationship may exist between the two, with visual impairment increasing the risk of cognitive impairment.

The systematic review and meta-analysis examined the findings of 40 studies that included a total of 47,913,570 patients aged 40 or older.

The investigators found that adults with visual impairment were two times more likely to develop prevalent or incident cognitive impairment. Significant heterogeneity was partially explained by differences in age, sex and follow-up duration. The study also reported that adults with cognitive impairment may be more likely to have visual problems, with most papers (89%) reporting significantly positive associations.

The researchers noted the following to explain why visual impairment is linked with cognitive decline:

• A loss of visual sensory information may lead to cortical atrophy and subsequent neural reorganization, as evidenced by neuroimaging and pathology.
• Alternatively, degraded and impaired visual input may result in errors in perceptual processing, with consequent decline in higher-order cognitive performance.
• Visual impairment may lead to cognitive decline indirectly by limiting the interactive experience of individuals with the environment, resulting in social isolation and restricted participation in mentally stimulating activities.
• Many age-related eye diseases (AMD, glaucoma, diabetic retinopathy) associated with visual impairment have also been linked with cognitive issues and dementia.

The results indicate that vision screening and timely treatment in middle-aged patients may be appropriate risk-reduction approaches for cognitive impairment, the study authors concluded.