During aging, loss of vision and cognition often coincide. In a new study, researchers, funded by the National Eye Institute (NEI) and the National Institute on Aging (NIA), have found that vision loss precedes loss of mental capacity. The findings, published in JAMA Ophthalmology, suggest that maintaining eye health could help protect cognition in older adults.

Researchers led by D. Diane Zheng, MS, and David J. Lee, PhD, from the University of Miami, in collaboration with Sheila West, PhD, and Bonnie Swenor, PhD, of Johns Hopkins University, analyzed visual acuity and cognitive function data collected between 1993 and 2003 by the Salisbury Eye Evaluation (SEE) study, which enrolled 2,520 older adults. By tracking changes in participants’ scores on visual acuity (VA) and a 30-point questionnaire called the Mini Mental-State Examination (MMSE) at several timepoints, the researchers studied how vision and cognition relate. The MMSE tests cognitive abilities, such as memory, orientation to time and space, attention span, language capacity, calculations, and the completion of other cognitive tasks.

While previous studies have suggested a relationship between MMSE and VA scores, Zheng and colleagues tested whether changes in VA scores and changes in MMSE scores were related over time. They found correlations not only between baseline VA and MMSE scores, but also between the rate of change in the scores, meaning that individuals with biggest loss in visual acuity were also likely to have the worst drop in cognitive ability.

The data were originally collected at multiple points in time—at enrollment, then at 2, 6, and 8 years later. Having multiple rounds of data allowed the researchers to use a cross-lagged statistical analysis model to examine how the different variables depended on each other over time. While this test doesn’t explicitly prove that one variable causes the other, it can provide strong evidence about how they relate.

Using this cross-lagged model, the researchers found that VA and cognitive function affect each other over time, and, most importantly, that vision has a stronger influence on cognition than the reverse. “To our knowledge, this is the first time this dependency has been shown,” said Zheng. She believes that this phenomenon may occur because older individuals who have significant vision loss may be less likely to engage in activities that keep their mind sharp.

A potential key next step will be using more specific cognition measures than the MMSE, Zheng said, and including seniors with a wide variety of cognitive abilities to see if the relationship between vision and cognition holds up. Nevertheless, she added, preserving vision may be key to helping older adults maintain their mental capacity.

“This study is remarkable in that it concludes that visual impairment may be associated with declining cognition in adult population. This work was carried out by one of our individual National Research Service Act F31-funded graduate students,” said Neeraj Agarwal, PhD, program director for translational research at NEI.

—Newswise