Above-normal blood sugar linked to dementia

There are many reasons to keep your blood sugar under control: protecting your arteries and nerves are two of them. Here’s another biggie: preventing dementia, the loss of memory and thinking skills that afflicts millions of older Americans.

A study published today in the New England Journal of Medicine shows that even in people without diabetes, above normal blood sugar is associated with an increased risk of developing dementia. This finding goes beyond previously seen links between diabetes and dementia. “It establishes for the first time, convincingly, that there is a link between dementia and elevated blood sugars in the non-diabetic range,” says study author Dr. David Nathan, a Harvard Medical School professor and the director of the Diabetes Center and Clinical Research Center at Massachusetts General Hospital.

Dr. Nathan teamed up with researchers across the country to look at blood sugar levels in more than 2,000 older adults—the average age was 76—taking part in the Adult Changes in Thought study. The vast majority of the study participants did not have diabetes. What the researchers found is that any incremental increase in blood sugar was associated with an increased risk of dementia—the higher the blood sugar, the higher the risk.

Why? There are only theories. “The speculation is that elevated blood sugar levels are causing more vascular disease, but it may be other metabolic issues. For example, people with elevated blood sugar often have insulin resistance which may be the link that affects our brain cells,” says Dr. Nathan.

The study does not prove that high blood sugar causes dementia, only that there is an association between the two. For that reason, don’t start trying to lower your blood sugar simply to preserve your thinking skills, cautions Dr. Nathan. There’s no evidence that strategy will work, although he says it should be studied.

But it is worth keeping an eye on your blood sugar to try to avoid developing type 2 diabetes. This disease is at epidemic proportions. Almost 26 million Americans—one in 12—have diabetes. High blood sugar is hallmark of this disease. Normal blood sugar is under 100 milligrams per deciliter of blood mg/dL after an eight-hour fast. You have diabetes if your blood sugar is 126 mg/dL or higher after a fast. People with a blood sugar reading of above 100 but below 126 have what’s called prediabetes. Nearly 80 million Americans are in that camp.

Excess blood sugar is a problem because it can lead to a variety of health problems including heart, eye, kidney, and nerve disease.

Taming blood sugar

What if your blood sugar is above normal? There’s good news in that department: You can lower your blood sugar by exercising and, if needed, losing weight. Shifting to a healthier diet with more vegetables, fruits, and whole grains and cutting back on highly refined grains can also help.

Try to get 150 minutes per week of moderate intensity activity, such as brisk walking. If that’s daunting, know that even a little activity can make a big difference in lowering blood sugar levels. Short but frequent walking breaks—as brief as a minute and forty seconds every half hour—can lower blood sugar. So can taking a walk after a meal.

And it doesn’t always have to be official “exercise.” Try taking the stairs more often, parking farther away from the store, and getting up and moving if you’ve been sitting too long. “It’s common sense,” says Dr. Nathan. “The more active you are and the less sedentary, the more likely it is that your muscles can uptake glucose, and the insulin you make will be more effective.”

Also helpful is cutting back your intake of highly refined carbohydrates, especially foods with added sugars such as sucrose, high fructose corn syrup, and also molasses, cane sugar, corn sweetener, raw sugar, syrup, honey or fruit juice concentrates. The American Heart Association recommends no more than 100 calories from sugar or six teaspoons of sugar per day for women, and 150 calories or nine teaspoons of sugar per day for men. If you’re in the prediabetic or diabetic range, you’ll want to work with a dietitian to determine your exact needs.

Making these changes is an investment, to be sure. But the payoff—better physical and mental health—is definitely worth it.


  1. Elsamma Chacko, PhD, MD

    A diabetes patient and practicing physician, I might have stumbled upon a finding, which, if correct, has the potential for a solid impact on obesity, diabetes and many other chronic conditions including, now, dementia. None of my colleagues I have sounded out has found a hole in the reasoning presented below.

    I have been controlling my blood glucose using this new approach for year and a half now. Although elements of this method have been well documented over the last 3 decades, the key element seems to have eluded patients and doctors until now. All I did was to connect a few dots of physiological facts.

    It turns out that the best time for elective physical activity is the interval between the 30th minute post-meal and the 90th minute post-meal following a typical meal, give or take. [I like to call this period of opportunity the “exercise window”]. In 4 months, my weight came down by 14%, A1C decreased by 17% and HDL shot up by 41%. Also, I was able to drop 2 medications and to reduce the dosage of a third. Many of my friends and colleagues also have had similar results. Here is the physiology:

    1.  Glucose, the product of the digestion of food in the stomach, begins to reach the blood stream 15 – 20 minutes after the first bite into a typical meal.  Thirty minutes after the first bite, the process is in full swing.  

If glucose is available in the blood stream when physical activity is required of the human body, it will readily utilize the blood glucose to fuel the activity.

Every glucose molecule utilized in this manner is one less available to contribute toward the glucose peak. The smaller the glucose peak the closer it is to the healthy response.

Patients who exercise during periods other than the exercise window not only miss the chance to blunt the post-meal glucose peak but may end up contending with another peak generated by liver glucose (which is controlled by stress hormones.)

    (I look forward to your views on this.)

  2. Hello, I log on to your blogs like every week. Your humoristic style is awesome, keep doing what you’re doing!

  3. boxing exercises

    My Father have this problems, thanks for the information.

  4. fire door regulations

    Blood sugar elevated is a no good sign at all.

  5. Katherine Elswick

    I find it interesting because my father who recently died, at 91, was very cogent until the last year, and pretty cogent until the last 3-6 months. He kept having teeth pulled, harder to eat, and very little taste remained and he was losing weight. He could taste strong SWEET, and so liked chocolate, ice cream, desserts and soda. He hadn’t been this kind of an eater his whole life, but it was almost all that tasted good at the end. We gave him what he wanted for quality of life issues as well as just trying to get some calories into him. Interesting if elevated BS was the result and contributed to his mental changes. May not have done it differently….don’t feel guilty, but good to know we can work at keeping ourselves nourihed as we age in other ways.

  6. suhuhasan

    Alzheimer’s disease is a rare disease there is no cure ..

  7. Jan G

    It is important to note that the study cited was limited to older adults (average age 76 yrs) and cannot be generalized to younger people. Despite this limitation there is other science suggesting some mechanism between glucose, insulin, inflammation have an impact on increasing risk for developing dementia in younger aged people with and without diabetes.

  8. It’s a great founding and worth to be watched out, especially for the older people. It’s no surprise that dementia may occurs to the older ones, but how about to us, the averages people? who knows? So, It’s wise to take this with full attention in order to not regret it in the future… 🙂

  9. Ian

    I also have a similar problem to this. Thanks so much for the article, it’s very informative and useful.

  10. Frances

    Here is the link between high blood sugars & dementia.

  11. Grant Paris

    Second last paragraph is the important one, but should go further though. I follow the paleo lifestyle and all grains, wheats, are just as bad as they turn into refined sugars, but also have other effects on our whole digestive tract amongst other things.

    It all comes down to inflammation, reduce inflammation and reduce disease.

  12. Gundi Kevin

    thanks to this team[Harvard] i have always found answers to my worries and how to go about some health issues, i now have hope of living longer almost twice than life expectancy of my country Kenya[49 yrs]. Thanks once more

  13. Ron Lott

    My brothers& sisters eat to much sugar, me too. 15 yrs ago I went to a church seminar , was converted with 76 0ther people. They stared a small church, kept us all together. The pastor’s wife started a health program, I was between 220 lbs & 230 lbs, with in 6 month I sit on 170 lbs to 175lbs.15 yrs later I have not been sick, take no pills, vaccinations, eat grains, nuts, fruit & veggies. Now the members of my family, My Dad die 42 ( heart ) oldest sister 49 (Heart + cancer), baby sister 72 very bad heart)+ Diabetes, she suffered before she died, Middle sister 73, many heart operations .My little Bro. Many heart operation 70yrs old ,at one time he was 364 lbs ,still over 300 lbs. The problem was too much sugar, too much meat, cheese, candy’s, cakes. Thank you for those videos ,I will use them on my family & pray that My sister & Bro. will listen ,I only have two family members left. USA & Canada eat too much sugar. God Bless U. All for the work U. Done getting the message out . Ron Lott

  14. Life Uninterrupted

    To remain healthy and free from any type of medical health problem it is very important to maintain and control our sugar level by adopting proper daily food diet and some precautions.

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