Insulin resistance, a condition in which cells fail to respond normally to the hormone insulin, is as harmful to cognitive health as it is to blood sugar, researchers from Tel Aviv University (TAU) reported in the Journal of Alzheimer’s Disease.
This new study found that both diabetic and non-diabetic people with insulin resistance experienced faster cognitive decline in executive function and memory compared to people without insulin resistance. Executive function refers to mental skills that help you complete tasks throughout the day such as managing time, paying attention, planning and organizing, switching focus, and remembering details.
Insulin resistance is common in people who are overweight or obese and who don’t get a lot of exercise. It stops muscle, fat, and liver cells from easily absorbing glucose.
This means the body needs higher levels of insulin to escort glucose into cells. The body can’t keep up with the required insulin levels and too much glucose builds up in the bloodstream. This leads to pre-diabetes, diabetes, and many other serious health concerns.
“These are exciting findings because they may help to identify a group of individuals at increased risk of cognitive decline and dementia in older age,” says study author professor David Tanne of TAU’s Sackler School of Medicine. “We know that insulin resistance can be prevented and treated by lifestyle changes and certain insulin-sensitizing drugs. Exercising, maintaining a balanced and healthy diet, and watching your weight will help you prevent insulin resistance and, as a result, protect your brain as you get older.”
The study included nearly 500 participants with existing cardiovascular disease. The researchers followed the subjects for more than 20 years. At the beginning of the study, the authors determined whether the patients had insulin resistance by using what’s known as the homeostasis model assessment (HOMA). The researchers also evaluated the subjects’ fasting blood glucose and fasting insulin levels. In addition, the research team investigated cognitive function by administering computerized tests that examined memory, executive function, visual spatial processing, and attention. After 15 years and again five years after that, the researchers repeated their evaluations of insulin resistance and cognitive function.
Study participants who were in the top quarter of the HOMA index—in other words, had the greatest insulin resistance—were more likely to have poor cognitive performance and faster cognitive decline compared to subjects in the remaining three-quarters of the HOMA index. The researchers adjusted for factors that might weaken the association, but the link between insulin resistance and poor cognitive function remained strong even after they did so.
“This study lends support for more research to test the cognitive benefits of interventions such as exercise, diet, and medications that improve insulin resistance in order to prevent dementia,” says Professor Tanne.
The research team is currently studying the vascular and non-vascular ways that insulin resistance may lead to cognitive dysfunction.
Source: Miri Lutski, Galit Weinstein, Uri Goldbourt, David Tanne. Insulin Resistance and Future Cognitive Performance and Cognitive Decline in Elderly Patients with Cardiovascular Disease. Journal of Alzheimer’s Disease, 2017; 1 DOI: 10.3233/JAD-161016