The study focused on older adults, assessing participants with an average age of 66.
When blood flow is regulated normally, the brain can redistribute blood to areas that become more active during specific tasks.
"People with type 2 diabetes have impaired blood flow regulation," explains study author Dr. Vera Novak, from Harvard Medical School in Boston, MA. "Our results suggest that diabetes and high blood sugar impose a chronic negative effect on cognitive and decision-making skills."
Type 2 diabetes has previously been established as an independent risk for the development of both cognitive impairment and dementia. In their study, published in Neurology, the researchers wanted to investigate how inflammation, blood flow regulation in the brain and cognitive decline were related in people with the metabolic disorder.
The researchers examined a small cohort of 40 people - 19 with type 2 diabetes and 21 without diabetes. The average age of the participants was 66. The participants that had type 2 diabetes had all been treated for the disease for more than 5 years, receiving an average of 13 years of treatment.
For the study, the researchers conducted an array of tests on the participants. They assessed their cognitive and memory functions while also taking magnetic resonance imaging (MRI) scans and blood tests to measure brain volume, blood flow and inflammation. After 2 years, the researchers repeated the tests.
They found that the participants with type 2 diabetes experienced a reduction in their capacity to regulate the blood flow in their brains. These participants also performed worse in the cognitive and memory function tests.
Participants whose blood flow regulation was poorest at the start of the study experienced the greatest declines in their ability to perform basic routine tasks such as bathing and cooking, defined as decline in executive function.
Additionally, the researchers found that the participants who experienced the highest levels of inflammation also had the greatest decreases in blood flow regulation, regardless of whether their diabetes and blood pressure were well controlled or not.
Blood flow regulation monitoring could help predict cognitive changes
Over the 2 years of the study, there was a marked difference in the learning and memory skills of the participants with type 2 diabetes compared with those without the disease. Average test scores fell by 12%, from 46 to 41, among those with type 2 diabetes while the scores of those without diabetes remained steady at 55 points.
Among the participants with type 2 diabetes, the researchers found that blood flow regulation decreased by around 65% overall.
"Early detection and monitoring of blood flow regulation may be an important predictor of accelerated changes in cognitive and decision-making skills," Dr. Novak suggests.
Only conducting the tests on the participants twice, at the start of the study and 2 years later, means that the study does not reveal much about how cognitive and executive function in people with type 2 diabetes alters over time.
The authors partially acknowledge this limitation, stating another study involving a larger sample size and longer duration is required to shed further light on the time sequence of the relationship between blood flow regulation and the disease.
Other limitations of the study are that the researchers did not measure for other factors that could have contributed to cognitive impairment among the participants and that younger participants were not involved in the study.
Despite these, the authors believe that their research provides clinical evidence regarding the mechanisms of the long-term effects of type 2 diabetes on the brain, with implications for health care and future treatment for older people with the disease.