The fact that obesity increases the risk of cardiovascular disease and some cancers is well known. A new study suggests that memory loss—and Alzheimer’s disease—should also be a top concern.
Researchers discovered a strong association between insulin resistance and memory function decline, increasing the risk for Alzheimer’s disease. Insulin resistance is common in people who are obese, pre-diabetic, or have type 2 diabetes.
For the study, scientists examined brain scans in 150 late middle-aged adults, who were at risk for Alzheimer’s disease, but showed no sign of memory loss. The scans detected if people with higher levels of insulin resistance used less blood sugar in areas of the brain most susceptible to Alzheimer’s.
When that happens, the brain has less energy to relay information and function, says Auriel Willette, a research scientist in the food science and human nutrition department at Iowa State University.
Not enough fuel
“If you don’t have as much fuel, you’re not going to be as adept at remembering something or doing something,” he says. “This is important with Alzheimer’s disease, because over the course of the disease there is a progressive decrease in the amount of blood sugar used in certain brain regions. Those regions end up using less and less.
The work, published in JAMA Neurology, focuses on the medial temporal lobe, specifically the hippocampus—a critical region of the brain for learning new things and sending information to long-term memory. It is also one of the areas of the brain that first show massive atrophy or shrinkage due to Alzheimer’s disease.
This is the first study to look at insulin resistance in late middle-aged people (average age was 60), identify a pattern of decreased blood sugar use related to Alzheimer’s, and link that to memory decline, Willette says. Participants were recruited through the University of Wisconsin-Madison and Wisconsin Registry for Alzheimer’s Prevention study, an ongoing study that examines genetic, biological and lifestyle factors that contribute to dementia.
More immediate risk
The link between insulin resistance and Alzheimer’s disease is important for prevention, but the risk is much more immediate, Willette says. Problems regulating blood sugar may impact cognitive function at any age. Testing for insulin resistance in obese patients and taking corrective action, through improved nutrition and moderate exercise, is a crucial first step.
“We are terrible at adjusting our behavior based on what might happen in the future. That’s why people need to know that insulin resistance or related problems with metabolism can have an effect in the here and now on how they think, and it’s important to treat.
“For Alzheimer’s, it’s not just people with type 2 diabetes. Even people with mild or moderate insulin resistance who don’t have type 2 diabetes might have an increased risk for Alzheimer’s disease because they’re showing many of the same sorts of brain and memory relationships.”
Understanding the progression of cognitive decline will take additional research. Willette says following those who are at-risk through the different stages of dementia and Alzheimer’s will offer insight as to what happens as their cognitive function declines.
The Oral Component
Oral health and diabetes have long been bi-directionally linked, with each increasing risk for and severity of the other. Indeed, some of the first signs of insulin resistance and diabetes show up in the mouth.
Recent research on the subject found that periodontal disease and the pathogens that cause it is directly associated with increased insulin resistance and predictive of future Type 2 diabetes. Results from the first National Health and Nutrition Examination Survey and its epidemiologic follow-up study reports that “the presence of periodontal disease predicted a two-fold increase in incidence of Type 2 diabetes in a sample of 9,000 initially diabetes-free men and women.”
Research shows us that a healthy mouth reduces health complications from diabetes, improves blood sugar control, assists with lowering A1c levels, and reduces medical costs as much as 25% for patients with diabetes.
Similarly, research confirms that oral infection and inflammation are able to affect the progression of cognitive impairment and Alzheimer’s disease. There is a lot of research lately showing that Alzheimer’s disease is of an infectious origin caused by the transmission of oral pathogens to the brain—it is thought that these bacteria lay the groundwork for Alzheimer’s disease.
Based on what we know about the way periodontal disease, diabetes, and Alzheimer’s disease are all interconnected, it’s especially imperative to address the impact of oral inflammation on patients who are insulin resistant, diabetic, or at risk for cognitive decline and Alzheimer’s disease. Timely, advanced periodontal therapy will result in the lowering of key markers, reduced risk for both diabetes and Alzheimer’s disease, and lower healthcare costs and complications for all.