Insulin resistance, caused in part by obesity and physical inactivity, is also linked to a more rapid decline in cognitive performance, researchers say.

Insulin resistance is a condition in which cells fail to respond normally to the hormone insulin. The resistance prevents muscle, fat, and liver cells from easily absorbing glucose. As a result, the body requires higher levels of insulin to usher glucose into its cells.

The study, appearing in the Journal of Alzheimer's Disease, showed that both diabetic and non-diabetic subjects with insulin resistance experienced accelerated cognitive decline in cognitive functions such as memory, executive function, visual spatial processing, and attention. "The findings may help to identify a group of individuals at increased risk of cognitive decline and dementia in older age," said David Tanne, Professor at Tel Aviv University in Israel. 

Without sufficient insulin, excess glucose builds up in the bloodstream, leading to prediabetes, diabetes, and other serious health disorders. However, "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," Tanne added.

For the study, the team followed a group of nearly 500 patients with existing cardiovascular disease for more than two decades and assessed their insulin resistance with the homeostasis model assessment (HOMA) -- calculated using fasting blood glucose and fasting insulin levels --, and cognitive functions.