Ties Between Alzheimer’s Disease & Diabetes
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There are over 34 million people in the United States living with diabetes, and over 6 million with Alzheimer’s disease. As both these conditions increase in prevalence, it’s important to understand the ways in which they may be connected.
According to the Alzheimer’s Association, around 54 million adults in the United States have prediabetes, or blood sugar levels that are higher than average. Many of these adults will develop Type 2 diabetes within a decade.
Type 2 diabetes, which accounts for 90 – 95% of diabetes cases, usually develops over time, and often begins with insulin resistance. When a person’s blood sugar increases, the pancreas receives a signal to release insulin. Insulin is a hormone that helps blood sugar (also known as glucose) enter cells in the muscles, liver, and fat, providing energy for the body.
In diabetes, these cells cannot use insulin effectively. To compensate, the body requires increasingly large amounts of insulin to allow glucose into cells. Eventually, the pancreas is unable to meet demands and produce enough insulin, and glucose lingers in the bloodstream.
Over time, this excess glucose can damage various parts of the body, including the kidneys, eyes, and nerves.
The Impact of Diabetes on The Brain
High blood sugar can gradually damage the blood vessels in the brain. If the brain does not receive enough blood, brain cells can die, impacting a person’s memory and thinking.
Diabetes also increases a person’s risk for stroke and heart disease, which can both heighten Alzheimer’s risk.
Elevated blood sugar may also cause inflammation in the brain, harming brain cells, and possibly contributing to Alzheimer’s disease.
In a Harvard University study of over 10,000 adults in the UK, researchers examined the association between dementia onset and the age at which participants developed diabetes. Participants were monitored from 1985 until 2019. The researchers found that a person’s risk for developing dementia increased the younger they developed diabetes.
A Closer Connection
A key player in diabetes, insulin may also play a role in the formation of sticky plaques of beta-amyloid protein in the brain. Amyloid is an established hallmark of Alzheimer’s disease. Similarly, processes in diabetes may contribute to toxic clumping of tau protein in the brain, another key marker of Alzheimer’s disease.
Other research suggests that certain genetic factors and diabetes may work together to increase Alzheimer’s risk.
Some researchers are even testing the controversial hypothesis that Alzheimer’s is an additional type of diabetes — “type 3 diabetes” — but there is not clear-cut evidence to support this.
The relationship between Alzheimer’s disease and diabetes is complex, but research into this topic is continually evolving.