Alzheimer’s disease, which affects 5 million Americans, offers a powerful lesson on the limits of Western medicine. New technologies are allowing researchers to screen for genetic mutations, monitor real-time brain activity, and develop drugs from both biological and chemical materials. Yet the causes of Alzheimer’s disease remain a mystery, and drugs that seemed promising in early development have so far failed to slow the ravaging effects of the disease in real patients.
An emerging angle of research, highlighted in an annual summary of progress against the disease put out by the National Institutes of Health, shifts the focus away from amyloid beta and tau proteins in the brain and toward a better understood pair of biological actors: glucose and insulin. If the research ultimately proves that their interaction plays a role in causing Alzheimer’s disease, it would give doctors a clue about how to treat it.
The research began with the observation that diabetics have a greater risk of dementia than the general population.
And a University of Washington study published last year in the New England Journal of Medicine found that in diabetics and non-diabetics alike, higher average blood sugar levels were linked to an increased risk of Alzheimer’s, which is the most common type of dementia.
Those risky higher glucose levels are caused by a combination of poor diet, insufficient exercise, and an individual's metabolism. The findings line up with existing research that says exercise reduces the risk of dementia.
“In terms of data on what works with dementia prevention, we have a lot more data about calories out than we do calories in. There are many studies that suggest that exercise is good for cognitive function; there are very few studies based on caloric reduction. This seems to be further evidence consistent with the idea that moving your body more is a good idea,” lead researcher Dr. Paul Crane told Healthline.
Could Lower Blood Sugar Help Prevent Alzheimer's?
The hypothesis that high glucose levels might drive Alzheimer’s disease looks particularly promising in light of a growing understanding that patients start to amass the disease’s hallmark amyloid beta deposits in the brain years before they show symptoms of memory loss.
Insulin, which regulates glucose in the body, also plays a part in regulating amyloid beta.
“We believe insulin resistance starts in midlife, and this is a period in which many people begin to experience obesity and body weight gain and other metabolic changes,” Suzanne Craft, a co-author of the study now at Wake Forest University, explained in an HBO video on Alzheimer’s disease. “Simultaneously we believe beta amyloid is increasing, in large part because of these changes in insulin resistance and insulin, and as a result, we see symptoms begin to occur, problems with memory, which worsen over time until a person might be well on their way to developing Alzheimer’s disease.”
Lower blood sugar over the long term could slow amyloid beta deposits and reduce an individuals’ risk of dementia. Craft has shown that patients who eat a diet lower in saturated fats and simple carbohydrates can reduce the amount of amyloid beta in their spinal fluid in just four weeks.
Insulin Inhaler a Promising Treatment
Craft has investigated, in a series of studies, giving patients insulin in a nasal inhaler that sends the hormone directly to the brain. The brain has a number of insulin receptors, including in areas that play an important role in memory. The method doesn’t rely on patients to follow medical advice to eat well and exercise, since many patients resist efforts to change their lifestyle habits.
Amazingly, with just a few weeks or months of the inhaler therapy, patients in the studies have shown cognitive improvement. In various trials of the method, Craft has worked with diabetics and non-diabetics, patients with mild cognitive impairment and those with full-blown dementia.
“One of the most exciting things about our work, I think, is the prospect that it offers for preventing or delaying dementia,” Craft said. “Estimates are that if you delay the onset just five years, you’ll reduce half of all the cases.”