High Rise in Blood Sugar After Meals Increases Risk for Dementia


At age 45, you have a 20 percent chance of developing dementia as you age (Dementia, 2015;11(3):310-20). By age 85, more than 35 percent of North Americans have early or full-blown dementia (JAMA Neurol, 2022;79(12):1242-1249).

High blood sugar and high blood pressure are major risk factors for dementia. A study from Johns Hopkins showed that the younger a person develops diabetes or pre-diabetes, the more likely they are to become demented (Diabetologia, May 24, 2023). People who developed diabetes before age 60 were three times more likely to develop dementia than those who did not develop diabetes before age 60. Those who developed diabetes after age 70 were only 23 percent more likely to suffer from dementia, and those who developed diabetes in their 80s or 90s had no increased risk for developing dementia.

Pre-Diabetes Associated with Increased Risk for Dementia
Pre-diabetes can be diagnosed when a person with normal fasting blood sugar (below 100 mg/dL) has:
• blood sugar greater than 145 mg/dL one hour after eating a meal, and/or
• HbA1c between 5.7 and 6.4
(HbA1c is a blood test that measures sugar stuck on cells. Any high rise in blood sugar can cause sugar to stick to the outer membranes of all the cells in your body. Once stuck on a cell membrane, sugar cannot get off and it eventually destroys that cell. If it sticks to brain cells, it damages your brain. If it sticks to the inner linings of your arteries, it can cause plaques to form that eventually may break off to cause a heart attack.)

More clues that you may be pre-diabetic:
• you can pinch more than two inches of fat under the skin near your belly button
• you have a big belly
• you have small buttocks compared to your belly
• your triglycerides are greater than 150 mg/dL
• your HDL is less than 40 mg/dL

Links Between Dementia and Diabetes or Pre-Diabetes
Pre-diabetes and diabetes put a person at increased risk for loss of memory, decreased executive function, and loss of verbal fluency, processing speed, cognitive flexibility, and cognitive control (Lancet, 2012;379:2291-2299). Blood sugar control can help to preserve brain function (J Gerontology, A Biol Sci Med Sci, 2016;71(Suppl 1):S62-S71).

  • To prevent blood sugar from rising too high, your pancreas is supposed to release insulin, which lowers blood sugar by driving sugar from the bloodstream into the liver and muscles. However, if your liver is full of fat, it does not accept the sugar and blood sugar levels rise even higher. This is called insulin resistance. Skinny people can be diabetic just because their liver is full of fat (“fatty liver“). A simple sonogram of your liver can show if you have excess fat in your liver.
  • One study says “Elevated blood glucose levels can increase brain excitability and amyloid-beta release, offering a mechanistic link between type 2 diabetes and Alzheimer’s disease” (JCI Insight, 2023;8(10):e162454). Another recent study found that risk factors for developing diabetes are also major risk factors for dementia: decrease in muscle strength and size, and increase in fat in muscle, liver and underneath belly skin (J Am Geriatr Soc, June 7, 2023).
  • Lifestyle changes that help to improve brain function can be made at any age. Previously sedentary people who started exercising in their 70s and 80s, including those who had already experienced some cognitive decline, showed improvement in brain function after they started an exercise program (Journal of Alzheimer’s Disease Reports, May, 12, 2023;7(1): 399-413).

Anti-Inflammatory Diet to Help Prevent Dementia
Researchers have not proven that diet changes can help to prevent or treat dementia, but strong data associate a pro-inflammatory diet with increased risk for dementia (Neurology, Nov 10, 2021;10.1212). In this study, 1059 non-demented people, average age 73, were divided into three groups based on high, medium and low inflammatory diet scores. At the end of the three-year study period, 62 of the participants had become demented. Those with the worst inflammatory diet scores were 3.5 times more likely to become demented than those with the best scores. Each week for three years, the people with the best anti-inflammatory scores had eaten an average of 20 servings of fruit, 19 servings of vegetables, and 4 servings of beans or other legumes. Those with the worst scores had eaten only an average of 9 servings of fruit, 10 servings of vegetables and 2 servings of legumes.

My Recommendations
If you have any of the risk factors for diabetes, you are at increased risk for dementia and should immediately begin a program to lower the rise in blood sugar after you eat. There’s a lot that you can do to help protect yourself from dementia (BMJ Neurology, April 13, 2022;377:e068390). If you are pre-diabetic, you can reverse the progression toward diabetes by losing enough weight to get fat out of your liver, by whatever means works for you (I recommend intermittent fasting). All diabetics and pre-diabetics should:
• try to exercise for at least 30 minutes every day
• avoid smoke, and and avoid or severely restrict alcohol
• eat a healthful plant-based diet with plenty of vegetables, whole (un-ground) grains, beans, nuts and other seeds
• restrict or avoid meat from mammals, processed meats, sugar-added foods and fried foods
• limit other refined carbohydrates (found in foods made from flour and many processed foods)
• drink only water, coffee or tea with no added calories