If you have diabetes, you likely know it can raise your chances of kidney and heart problems. But you may not know that diabetes can also affect your brain. "Even people who study diabetes may not always consider the impact of insulin in the brain," says Rita Kalyani, MD, assistant professor of medicine at Johns Hopkins University in Baltimore.
High blood sugar levels may be linked with worse memory in people with and without diabetes. High blood sugar may damage brain cells or disturb the transfer of information between cells. It may also damage small and large vessels to the brain, slowing the flow of blood and nutrients to the brain. Both could cause problems with memory.
Diabetes and insulin may be linked to serious conditions such as Alzheimer's and Parkinson's diseases. "I don't think we have the data yet, but it's possible that conditions like Alzheimer's disease are related to insulin problems," says C. Ronald Kahn, MD, professor of medicine at Harvard Medical School.
The idea of such a link concerns him. "Type 2 diabetes is already an epidemic and more and more people are developing it an earlier age," he says. "We just don't know what effect it will have on their brains."
So what can you do to stay healthy with diabetes? Here's what you need to know.
The Diabetes-Alzheimer's Link
Research suggests that people with diabetes may be more likely to have Alzheimer's disease. Experts don't know yet how diabetes and Alzheimer's may be linked, but very high insulin levels, also called insulin resistance, seem to play a part.
"In people with diabetes, the brain doesn't seem to become insulin resistant in the same way that other organs in the body do," Kahn says. "But there do seem to be changes in insulin signaling in the brain." If you have Alzheimer's disease, a protein called beta-amyloid builds up, forming plaques on your brain. lf you’re insulin resistant, it may be harder for your body to break down these plaques.
Diabetes and the Brain: Many Unknowns
Because of the seeming link between diabetes and Alzheimer's disease, some researchers argue that diabetes may not just raise a person's chance of having Alzheimer's disease. They say Alzheimer's disease is itself a form of diabetes that mostly affects the brain. Some have gone so far as to give Alzheimer's disease a new name: type 3 diabetes. But many diabetes experts do not agree.
"I think it's a real stretch to call Alzheimer's disease type 3 diabetes," says Janet B. McGill, MD, an endocrinologist and professor of medicine at the Washington University School of Medicine in St. Louis. "We just don't have the evidence."
Kalyani agrees. "We need more research," she says.
Kalyani notes that it's hard to tease out the effects of diabetes from those of conditions linked to diabetes. "High blood pressure and obesity often go along with diabetes," she says. "It's possible that they could play a role in the increased risk of Alzheimer's disease."