Diabetes and Alzheimer's Disease
Alzheimer's is a type, and the most common form, of dementia that causes problems with memory, thinking and behavior. Alzheimer's is the sixth leading cause of death in the United States. Alzheimer's affects one in 10 Americans over 65 years of age and nearly 50 percent of those over 85 years old.
Although the two primary risk factors for Alzheimer’s is age and family history of the disease, there is new evidence that shows diabetes may also be a risk factor for developing Alzheimer’s. Recent studies have shown that people with type 1 and type 2 diabetes have a 30 to 65 percent higher risk of developing Alzheimer's disease compared to non-diabetics.
There is also growing evidence that Alzheimer's is primarily a metabolic disease and has led some researchers to propose reclassifying it as Type 3 diabetes.
A study conducted by University of Medicine and Dentistry of New Jersey (UMDNJ) and Northwestern University noted that characteristics of type 2 diabetes, including abnormal glucose levels, metabolic “dysregulation”, and insulin resistance or deficiency, are seen in the early stage of Alzheimer's disease without the presence of diabetes.
The numbers of people with Alzheimer’s and diabetes are expected to rise over the next several decades. These increases may be correlated with increasing obesity rates. The correlation is so disquieting that scientists are now investigating a causal relationship between all three epidemics, with disturbing results.
Type 2 diabetes has already been strongly linked with obesity and diet as well as with dementia and Alzheimer's. The link between Alzheimer's and obesity has been studied less, but a growing body of research is filling that gap. New studies have linked obesity to Alzheimer's. Fitness and healthy diets have also been linked to a decreased occurrence of dementia.
"It's really important for the [public's] health to understand that diabetes is a significant risk factor for all of these types of dementia," says Rachel Whitmer, epidemiologist for Kaiser Permanente Northern California, a nonprofit health-care organization.
A spokesperson for the Alzheimer's Society said “These results back up existing evidence that obesity in mid-life increases the risk of developing dementia, as well as adding to our understanding of the relationship between dementia and our metabolism.”
Now, new studies are suggesting that Alzheimer's may be caused directly by the brain's impaired response to insulin. Insulin has a well-defined role in the brain's chemistry including the regulation of the transmission of signals between neurons.
A study by CCNY-CUNY shows how there is a single gene that creates a relationship between the two diseases. The gene influences the insulin pathway and a tell-tale sign of diabetes is the disruption of that particular pathway.
“People with type 2 diabetes have an increased risk of dementia. The insulin pathways are involved in many metabolic processes, including helping to keep the nervous system healthy,” stated Professor Chris Li, a researcher at CCNY-CUNY.
Insulin resistance, which causes high blood sugar and in some cases leads to type 2 diabetes, may interfere with the body's ability to break down a protein (amyloid) that forms brain plaques that have been linked to Alzheimer's. High glucose levels also produce certain oxygen-containing molecules that can damage cells, in a process known as oxidative stress.
"Many studies have focused on altered insulin signaling in the brain as a possible mechanism for the association between Alzheimer's disease and diabetes but researchers paid much less attention to the direct effects of increased blood glucose levels on brain function and the pathogenesis of Alzheimer's," explains Joseph R. Burdo, Ph.D., assistant professor at Bridgewater State College.
Another link between diabetes and Alzheimer's has been identified: the role of insulin in the formation of memories. It appears that when amyloid beta configurations called oligomers, believed to cause memory loss in Alzheimer's disease, attach to neurons in the brain it contributes to insulin resistance in the brain. This then triggers a cycle in which diabetes causes oligomers to accumulate, which in turn makes neurons more insulin resistant.
A 2005 report found that levels of both insulin and insulin-like growth factors in the brains of Alzheimer's patients were lower than normal, with the lowest levels being found in the brain regions most devastated by the disease.
Because diabetes damages blood vessels, it has long been recognized as a risk factor for vascular dementia, a type of cognitive decline caused by damaged blood vessels in the brain. High blood sugar and high cholesterol levels also play a role in the hardening and narrowing of arteries in the brain. This condition, known as atherosclerosis, can bring about vascular dementia, which occurs when artery blockages or strokes kill brain tissue.
Diabetes may also increase the risk of developing mild cognitive impairment (MCI), a transition stage between the cognitive changes of normal aging and the more serious problems caused by Alzheimer's disease and other types of dementia.
Meanwhile, a report released last year found that an insulin spray (which proved an unpopular treatment for diabetes) helped improve memory skills in people with Alzheimer’s.
More About Alzheimer ’s disease
People with Alzheimer's live an average of eight years after their symptoms become noticeable to others, but they can live from four to 20 years, depending on age and other health conditions.
Alzheimer's disease accounts for 50 to 80 percent of dementia cases. Alzheimer's is a progressive disease, where symptoms gradually worsen over time. In its early stages, memory loss is mild, but with late-stage Alzheimer's, individuals lose the ability to communicate and respond to their environment.
Current Alzheimer's treatments cannot stop Alzheimer's from progressing, though they can temporarily slow the worsening of dementia symptoms. The earlier you recognize the symptoms of Alzheimer’s and begin treatment the quicker you can delay the symptoms of the disease.
Signs of Alzheimer’s Disease
• Memory Loss – people forget things all the time but if someone you know seems to be more forgetful, or if they forget what has just happened or repeat conversations it may be a cause for concern.
• Agitation and Mood Swings – the individual may move around and pace, get upset in certain places, or become fixated on specific details. Agitation and mood swings are usually the result of fear, confusion, fatigue, and feeling overwhelmed from trying to make sense of the world that now seems unfamiliar.
• Impaired Judgment – someone with Alzheimer’s will begin to make decisions that seem silly, irresponsible, or even inappropriate and are a departure from past behavior.
• Problems paying bills or handling finances - AD sufferers have problems with abstract thinking as the disease progresses, which make dealing with numbers and money particularly troublesome.
• Difficulty with familiar tasks - A person with dementia often takes longer to complete, or have trouble finishing, common tasks they have done hundreds of times before.
• Trouble Planning or Problem Solving - they may struggle to develop and follow a plan, like creating and using a grocery list, following a recipe, or tackling new problems.
• Misplacing things – if you are routinely discovering “missing” items in strange spots such as the car keys in the freezer, is a strong indicator that the individual may be suffering from dementia.
• Confusion with time or place - Disorientation to time and place, such as forgetting where they live, getting easily lost, and losing track of dates, seasons, and the passage of time is a common experience for individuals with AD.
• Difficulty communicating - As Alzheimer’s progresses, a person’s language and communication skills diminish. Vocabulary can be especially troublesome. A person may struggle to find the right word; call things by the wrong names (e.g., a car a TV); substitute unusual or incorrect words for familiar words and names; invent new words; or use familiar words over and over again. They may stop in the middle of a conversation and not know how to continue.
• Wandering - Unfortunately, about 60% of people with dementia have a tendency to walk off, wander aimlessly, and become lost, often repeatedly.
• Repetitive Speech or Actions - The frequent repetition of words, statements, questions, or activities is a hallmark of dementia and AD.
• Seemingly purposeless activity - routinely engaging in pointless activity, like opening and closing a drawer, packing and unpacking, pacing, or repeating demands or questions, may be a sign of dementia.
• Withdrawl - People with Alzheimer’s may give up hobbies, social activities, or sports they previously loved, because they forget how to perform their favorite pastimes.
• Don’t recognize family and friends - Recognition of others may come and go for a while. The individual is more likely to forget what they just learned or whom they just met, then friends, and family. Though in late stages they may not remember even a spouse of 50 years or more.
• Difficulty dressing, wearing the same clothes for days at a time or disregard for hygiene.
• Forgetting to eat meals
• Delusions and paranoia
• Clingy or childlike behavior
Reducing your risk of Alzheimer’s
As with all complications of diabetes, working with your health care team to manage your diabetes effectively is your best strategy to avoid complications, including those that may affect your brain.
Researchers at Columbia University found that keeping blood sugar levels in check can lessen or possibly stave off even normal age-related cognitive decline in those that have diabetes and those who do not.
"Having high glucose is a stressor to the nervous system and to the blood vessels," says David Geldmacher, M.D., a professor of neurology at the University of Alabama at Birmingham. "The emerging information on Alzheimer's disease and glucose shows us that we do need to remain vigilant on blood sugar levels as we get older."
Steps you can take to prevent or manage diabetes include:
• Follow your health care team's recommendations about the best plan for monitoring your blood glucose, cholesterol level and blood pressure.
• Eat healthy foods, including fruits and vegetables, lean meats, whole grains, and low-fat milk and cheese. [link to my plate]
• Exercise at least 30 minutes most days of the week.
• If your doctor prescribes medication, take it on schedule.
Although much more research needs to be conducted to clarify the relationship between diabetes and Alzheimer's, it seems clear based on current science that preventing or controlling diabetes could be very good for your brain.
Bitel CL et al. Amyloid-B and tau pathology of Alzheimer's disease induced by diabetes in an animal model. Journal of Alzheimer's Disease 2012 / UMDNJ
Steen E, Terry BM, Rivera EJ, Cannon JL, Neely TR, Tavares R, Xu XJ, Wands JR, & de la Monte SM. (2005) Impaired insulin and insulin-like growth factor expression and signaling mechanisms in Alzheimer's disease--is this type 3 diabetes
?. Journal of Alzheimer's disease : JAD, 7(1), 63-80.
Diabetes Link To Alzheimer's Disease Explained, ScienceDaily (May 2, 2008)