Longitudinal Associations Between Visual Impairment and Cognitive Functioning: The Salisbury Eye Evaluation Study

D. Diane Zheng, Bonnielin K. Swenor, Sharon L. Christ, Sheila K. West, Byron L. Lam, David J. Lee

Worsening vision and declining cognitive functioning are common conditions among elderly individuals. Understanding the association between them could be beneficial in mitigating age-related cognitive changes. To evaluate the longitudinal associations between visual impairment and cognitive function over time in a population-based study of older US adults. Prospective longitudinal population-based study of older adults in the greater Salisbury area in Maryland. Overall, 2520 community-residing adults aged 65 to 84 years were assessed at baseline between September 1993 and August 1995 (round 1) and 2 (round 2), 6 (round 3), and 8 (round 4) years later. Visual acuity (VA) was measured using Early Treatment Diabetic Retinopathy Study charts, and cognitive status was assessed using the Mini-Mental State Examination (MMSE). Of 2520 individuals, the mean (SD) age was 73.5 (5.1) years, 1458 (58%) were women, and 666 (26%) were black. There were 2240 (89%), 1504 (61%), and 1250 (50%) participants in the second, third, and fourth round of study, respectively, with more than half of the loss being due to death. Both VA and MMSE score worsened over time. The mean biannual decline of VA was 0.022 logMAR (approximately 1 line during 8 years; 95% CI, 0.018-0.026), and the mean biannual worsening of MMSE score was -0.59 (95% CI, -0.64 to -0.54; both P < .001). Worse baseline VA was associated with worse baseline MMSE score (r = -0.226; 95% CI, -0.291 to -0.16; P < .001). The rate of worsening VA was associated with the rate of declining MMSE score (r = -0.139; 95% CI, -0.261 to -0.017; P = .03). Cross-lagged models indicated VA in the previous round was associated with MMSE score in the subsequent round (β = -0.995, P < .001), and MMSE score in the previous round was associated with VA in the following round (β = -0.003, P < .001). However, the standardized effect size of VA on MMSE score (β = -0.074; SE, 0.015; P < .001) is larger relative to the reverse effect (β = -0.038; SE, 0.013; P < .001), demonstrating VA is likely the driving force in these dynamic associations. In a population-based sample of older US adults, visual impairment measured at distance is associated with declining cognitive function both cross-sectionally and longitudinally over time with worsening vision having a stronger association with declining cognition than the reverse. Worsening vision in older adults may be adversely associated with future cognitive functioning. Maintaining good vision may be an important interventional strategy for mitigating age-related cognitive declines.