Eye study examines cognitive aging in people with diabetes

Little is known about how the brain ages — why some people lose their memory, decision-making abilities and attention spans years before their peers.

As the nation's elderly population grows, scientists are looking for clues in an unexpected place: the eye.

Tiny blood vessels at the back of the eye, closely linked with vessels in the brain, could help detect the arrival of cognitive impairment, said Dr. Caterina Rosano, an epidemiologist at the University of Pittsburgh's Graduate School of Public Health who studies cognitive aging.

By detecting the changes earlier, photos of the vessels could help improve treatment, she said.

“The key here is early detection, detecting changes in the brain that would be completely invisible, even to the best neurologists and the best psychologists,” she said.

With funding from the National Institutes of Health, Rosano is studying the eyes of a group of people with Type 1 diabetes, one of several chronic conditions that research shows may accelerate cognitive aging. If the method works for diabetics, it might work for the general population, she said.

Rosano thinks that poor blood flow to the brain, resulting from deterioration of the vessels, contributes to the brain's accelerated aging. Without blood, brain cells die, leading to impairment, she said.

Because diabetics lack the ability to regulate blood sugar, their bodies sometimes are flooded with the sticky substance. Their blood vessels become inelastic, losing the ability to smoothly accommodate the flow of blood. Blood pressure increases, hardening and scarring the vessels. In high-speed X-ray photos, the vessels appear “wormlike” or “tortured,” she said.

Rosano is comparing the vessel deterioration shown in the photos to the results of tests that measure mental abilities such as memory, information-processing speed and decision-making. She is looking at 30 years' worth of eye photos, MRIs and other information from 209 people who are part of the ongoing Pittsburgh Epidemiology of Diabetes Complications study. She plans to finish the study by the end of the year.

When judging brain health, neuropsychologists rely on tests that are imprecise and expensive, such as MRIs, said Luke Stoeckel, a National Institute of Diabetes & Digestive & Kidney Diseases project officer for Rosano's grant.

As a result, doctors often don't detect patients' cognitive impairment until it is fairly advanced, when treatment is less effective, Stoeckel said.

“Usually if you're detecting problems (in a doctor's office), they're already having more serious problems in their life,” he said.

Research among Type 2 diabetics supports that theory, Stoeckel said, but some researchers have suggested there could be other mechanisms at work in the aging of the brain.

“Unfortunately, a lot of the cognitive tests we've been rolling out to date may not have been sensitive enough to know if diabetes is impacting exactly the same areas of the brain as aging, or are there subtle differences,” he said.

If Rosano's photos work as planned, they could potentially be used in large clinical trials to test treatments that might slow brain aging, he said.

“Potentially these retinal markers could be cheap, kind of very accessible tools that physicians could roll out in most primary care clinics where most patients with diabetes are seen,” he said.

At this time, the best treatments to slow cognitive aging are similar to some of the treatments for the heart: a healthy diet, enough sleep and exercise, said Dr. Zoe Arvanitakis, medical director of the Rush Memory Clinic at Rush University Medical Center in Chicago.

Using the brain for things like crossword puzzles, reading and socializing appear to help, Arvanitakis said.

Increased blood pressure control shows promise in slowing the progression of cognitive aging, Rosano said.

Unlike diseases such as Alzheimer's, regular cognitive aging does not seem to kill neurons, the brain's cellular control centers, according to a 2015 Institute of Medicine report on cognitive aging. Aging is instead associated with changes in the circuitry connecting the neurons. That difference makes researchers, including Rosano, optimistic about slowing cognitive impairment when the first signs appear.

“If the person has cognitive problems, everything changes,” Rosano said. “(The patient) can do cognitive therapy in addition to taking close care of blood pressure, the usual stuff. If you know you have cognitive problems in your 50s, you can start planning things very differently.”

Wes Venteicher is a Tribune-Review staff writer. Reach him at 412-380-5676 or wventeicher@tribweb.com.