According to health and disease experts, Type 2 diabetes is rapidly becoming a global epidemic, with the number of diagnosed cases tripling over the last 40 years. An estimated one out of three Americans will develop Type 2 diabetes in their lifetime, with another 54 million currently term pre-diabetic, or on their way to diagnosis without significant lifestyle intervention. These are staggering numbers – but what do they have to do with dementia? According to a growing amount of research, quite a lot.
First, doctors have known for years that Type 2 diabetics are predisposed to cognitive impairment, for a number of reasons. Their bodies produce little or no insulin, which is critical to healthy brain function: insulin not only helps maintain a healthy blood supply to the brain, but it also helps neurons break down glucose to achieve peak performance. Because diabetics have deteriorating circulatory function, they develop damaged blood vessels and impaired blood flow to the brain, weakening brain function even further. For these reasons, Type 2 diabetes has been termed a risk factor in vascular dementia, the second most common type of dementia, and one we explored in a recent blog post.
But one study in particular has caught the world’s attention as providing perhaps the most compelling evidence of a link between Type 2 diabetes and Alzheimer’s, the most common form of dementia. In 2011, Japanese scientists decided to look into a long-term study of heart disease and stroke that had been running since 1961. In 1988, more than 1000 subjects in that study had agreed to take a glucose tolerance test to see how effectively they were able to process sugar. Researchers followed them for the next 15 years, during which time 232 developed dementia.
The researchers discovered that, of those 232 people, those with Type 2 diabetes were 74% more likely to develop dementia over the span of the study. Alzheimer’s was by far the most common form diagnosed, with the diabetics in the study proving to be more than twice as likely to develop the disease than their glucose-tolerant counterparts.
There have also been recent findings indicating that people with Type 2 diabetes are more likely to develop the brain tangles commonly seen in those diagnosed with Alzheimer’s. Scientists are still terming this a correlation rather than a direct cause, pending further research into the role of other factors like obesity and aging.
Want more information? The Alzheimer’s Organization has put together a helpful pamphlet that goes into greater detail on both diseases, as well as offering tips for helping to prevent the development of Type 2 diabetes.