Retinopathy—and its accompanying microvascular changes—may be associated with faster rates of cognitive decline over 20 years, according to researchers who found that in individuals exhibiting such changes at the age of 60, cognitive and memory problems are more likely by the time they reach 80. They published their results in Neurology.
“Problems with the small blood vessels in the brain are likely as important a factor in cognitive decline as problems with larger arteries, but we don’t have the ability to take pictures of these small vessels with brain imaging,” said study author Jennifer A. Deal, PhD, assistant scientist, Johns Hopkins University, Baltimore, MD. “Because the blood vessels in the eye and the brain are so similar anatomically, we hypothesized that looking at the blood vessels in the eye would help us understand what was happening in the brain.”
Dr. Deal and colleagues, therefore, conducted this study in subjects from the Atherosclerosis Risk in Communities Study to assess whether retinal vascular signs are associated with greater cognitive decline over 2 decades. They enrolled 12,317 subjects 50 to 73 years old at baseline and created a composite cognitive score comprised of three neuropsychological tests taken at three different time points between 1990-1992 and 2011-2013.
Between 1993 and 1995, researchers measured retinal signs in these patients using fundus photography. Using linear mixed modelling, Dr. Deal and fellow researchers estimated differences in cognitive change by retinal signs status. They imputed cognitive scores in subjects with incomplete cognitive tests.
In all, 11,692 subjects had no signs of retinopathy, 365 had mild retinopathy, and 256 had moderate-to-severe retinopathy.
Upon multivariate-adjusted analyses, researchers found that the loss of vascular integrity, or retinopathy and all of its components, was associated with a greater 20-year decline in cognition. Differences in 20-year cognitive change for subjects with moderate-to-severe retinopathy were greater than those in subjects with no retinopathy (-0.53 standard deviation [SD]; 95% CI: -0.74 to -0.33). In subjects with moderate-to-severe retinopathy, this translates to a decline in average tests scores of 1.22 SD units over 20 years, compared with a decline of only 0.91 in those with healthy eyes. Neither diabetes nor race changed these estimated differences.
“To put this in perspective, a previous study using the same methods found that the effect of diabetes on cognitive decline was equal to 0.21 standard deviation units,” said Dr. Deal. “If our study results can be confirmed, differences in retinal integrity could provide reasonable estimates of how much small blood vessel damage in the brain is contributing to cognitive decline.”
One of the limitations of this study is that these researchers performed only monocular fundus photography in each patient.
In the future, concluded Dr. Deal and colleagues, sensitive measurements of the eye with technologies such as optical coherence tomography angiography, may be useful in finding signs of microvascular lesions that may be associated with cognitive decline in older adults.
The study was supported by the National Heart, Lung, and Blood Institute and the National Institutes of Health.