Introduction
According to the Centers for Disease Control and Prevention (CDC), in the United States, about 38 million people have diabetes. Another 98 million have prediabetes. Diabetes rates in the United States has more than doubled in the past 20 years. Most people know about diabetes to some degree. But, how is diabetes impacting your brain health?
Most people don’t connect diabetes with the brain and brain health. In this blog post, I want you to discover the potential impact of diabetes on your brain health so you can take steps to do something about it, before it becomes more difficulty to reverse the changes. I will primarily be writing about type 2 diabetes, which accounts for about 90-95% of those with diabetes.
What Is Type 2 Diabetes and What Causes it?
Just briefly, let’s talk about what diabetes is and what causes it. Diabetes is a metabolic disorder resulting from the body’s inability to make enough, or properly use, insulin. Insulin is a hormone produced in the pancreas. In type 2 diabetes, the pancreas is not able to effectively use the insulin it produces, referred to as insulin resistance. Type 2 diabetes is generally preventable. It can usually be delayed or prevented entirely by eating a healthy diet, regular physical activity, and maintaining a normal body weight. You can find out more about diabetes and it causes at the National Institute of Health.
Health Problems Linked to Diabetes
Diabetes has been linked to a number of health and medical problems. Over time it can damage blood vessels in the kidneys, eyes, heart, and nerves. Poor blood flow as a result of diabetes can also start to affect the feet.
Diabetes can also negatively impact your brain health and cognitive skills. Additionally, being diagnosed with diabetes in midlife is a risk factor for later developing dementia, with a 50% increased risk. Vascular dementia is particularly more common in diabetics, though risk for developing Alzheimer’s disease is also greater. Aside from dementia, diabetes in midlife is associated with an approximately 20% greater cognitive decline over 20 years compared to those without diabetes,
How Brain Health is Affected
Different cognitive skills can be negatively affected by diabetes. One skill that can show decline is information processing speed, or the ability of the brain to think quickly. Executive functioning and new learning can also be diminished.
Executive functioning refers to the ability to shift back and forth and be mentally flexible in your thinking. One study followed thousands of people over a 10 year time span. It showed that those with higher H1c levels (a measure of worsening diabetes) has worse verbal memory and executive functioning.
Another study following a group of type 2 diabetics after four years found moderate decline in information processing speed, attention, and executive functioning. This was compared to a control group matched for age, sex, and estimated IQ.
Neuroimaging has demonstrated a link between impaired executive function with reduced gray matter density and reduced glucose metabolism. This was found in regions of the brain including the orbital and prefrontal cortex, temporal cortex and cerebellar area. A meta-analysis with over 26,000 participants (diabetics and nondiabetic controls) found that those with type 2 diabetes performed worse in areas of processing speed, memory, executive function, and motor skills.
Why Brain Health Problems in Diabetes?
There are a few ways that diabetes can lead to brain health problems. First, if your glucose levels are too high (hyperglycemia) or too low (hypoglycemia), this can put stress on the brain’s blood vessels. Damage to the brain can occur if you have frequent swings in highs and lows of glucose levels, or have long periods of hyperglycemia.
There is also some evidence to suggest there can be weaker connections between structures in the brain, resulting in slowed processing time. Additionally, there is suggestion that impaired insulin signaling and insulin receptor sensitivity that occurs in Alzheimer’s disease may be a linked to how type 2 diabetes may increase the risk for Alzheimer’s disease. These insulin receptors have shown to have a role in the memory region of the brain (hippocampus).
The impact of insulin on the mitochondria of cells has also been linked to cognition. Mitochondria are the energy producing powerhouse of the cell and important for healthy cellular function. Insulin helps with the regulation of mitochondria in the hippocampus, the important memory structure I talked about earlier.
Yet another mechanism of how diabetes can affect cognition is related to inflammation. In diabetes, there is an increase in the expression of pro-inflammatory cytokines in the brain, which leads to neuronal damage.
Neuroinflammation and oxidative stress are also linked to cognitive changes in diabetes. Diabetes can increased the generation of reactive oxygen species (ROS) in the brain. These ROS are generally thought of as neurotoxic molecules in the brain. However, they can take a positive role in brain plasticity when kept in check by various neuropathways and antioxidants. However, in diabetics there can be increased generation of ROS, which then activates other pathways that leads to increased brain inflammation and neurodegeneration.
Actionable Strategies to Reduce Cognitive Risk
- Maintain daily physical activity levels
- Try to get 20-30 minutes of aerobic exercise about 5 days/week. You can read more about the positive benefits of aerobic exercise on the brain here.
- Consider adding in resistance training to your activity. Maintaining and improving skeletal muscle is a great way to improve blood glucose regulation.
- Eat a health diet- Nutritional needs can be highly individual and you should consider speaking to your doctor or a specialist about your personal nutritional needs. With this information in mind, below are a few considerations.
- Consider the Mediterranean style dietary pattern or the MIND diet. You can read more on my post about the MIND diet here
- Abstain from, or limit, consumption of sugary drinks and ultra processed foods
- Keep up to date with your individual medical needs and conditions. Get regular medical check ups to help detect problems before they become more challenging to manage.
References
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- Biessels GJ, et al. Risk of dementia in diabetes mellitus: a systematic review. Lancet Neurology. 2006;5(1):64–74.
- Garcia-Casares N, et al. Cognitive dysfunctions in middle-aged type 2 diabetic patients and neuroimaging correlations: a cross-sectional study. Journal of Alzheimers Disease. 2014;42(4):1337–46.
- Gaspar JM, Baptista FI, Macedo MP, Ambrosio AF. Inside the diabetic brain: role of different players involved in cognitive decline. ACS Chemical Neuroscience. 2016;7(2):131–42.
- Heras-Sandoval D, Ferrera P, Arias C. Amyloid-beta protein modulates insulin signaling in presynaptic terminals. Neurochemical Research. 2012;37(9):1879–85.
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- Palta P, Schneider AL, Biessels GJ, Touradji P, Hill-Briggs F. Magnitude of cognitive dysfunction in adults with type 2 diabetes: a meta-analysis of six cognitive domains and the most frequently reported neuropsychological tests within domains. Journal of the International Neuropsychological Society. 2014;20(3):278–91.
- Rawlings AM, et al. Diabetes in midlife and cognitive change over 20 years: a cohort study. Annals of Internal Medicine. 2014;161(11):785–93
- Reijmer, Y.D. Disruption of the cerebral white matter network is related to slowing of information processing speed in patients with type 2 diabetes. Diabetes, 2013; 62, 2112-2115.
- Van den Berg E, et al. A 4 year follow-up study of cognitive functioning in patients with type 2 diabetes mellitus. Diabetologia. 2010;53(1):58–65.
- Zhao W, et al. Brain insulin receptors and spatial memory. Correlated changes in gene expression, tyrosine phosphorylation, and signaling molecules in the hippocampus of water maze trained rats. The Journal of Biological Chemistry. 1999;274(49):34893–902.
- Zheng, F, et al. HbA1c, diabetes and cognitive decline: The English Longitudinal Study of Ageing, Diabetologia, 2018; 61, 839-848.
