Cognitive Decline in People with Diabetes Associated with Reduced Brain Size

Old people with diabetes are more likely to have brain impairment due to shrinking brain size than due to cerebrovascular lesions, according to a new study.

In the U.S., the number of people being diagnosed with diabetes has tripled from 5.6 million in 1980 to 26.9 million in 2010. According to CDC, by 2050 1 in 3 US adults will have diabetes. The condition leads to many health problems including heart and blood vessel disease, damage to nerves, eyes and kidneys. Diabetes type-2 has even been linked to vascular dementia and Alzheimer's disease.  

Type-2 diabetes is the most common type of diabetes, accounting for 90 to 95 percent of the cases. In this type, the body responds poorly to the hormone insulin leading to a condition called insulin-resistance.

One theory that explains the link between diabetes and dementia is that the disease leads to heart problems, which then restrict the flow of blood to the brain. Another theory is that high level of insulin in the blood leads to inflammation that damages brain.

A new study by Chris Moran, from Monash University in Melbourne, Australia, and colleagues found that brain atrophy rather than cerebrovascular damage explains the association between diabetes and loss of brain function, Healthday reported.

The study was based on brain scans obtained from 350 participants with type 2 diabetes mellitus (T2DM)  and 363 participants without T2DM. Researchers looked at damage to the brain as well as the volume of gray matter, white matter, and the hippocampus.

Researchers also found that people with diabetes type-2 were also more likely to have poor memory, speed and planning ability. The study also controlled for other factors such as age, gender, education and heart problems that could alter the results, but they found that diabetes was independently associated with brain atrophy.

"Cortical atrophy in T2DM resembles patterns seen in preclinical Alzheimer's disease," the authors wrote, Healthday reported. "Neurodegeneration rather than cerebrovascular lesions may play a key role in T2DM-related cognitive impairment."

The study is published in the journal Diabetes Care.