How Diabetes Effects the Nervous System

Diabetes is one of the most prevalent chronic medical conditions in today’s times. There is no doubt that fluctuating levels of blood glucose has a vast impact on the body. However, diabetes causes symptoms far more serious than excessive thirst, dry skin, and frequent infections. Continue reading to learn how diabetes effects the nervous system.

What is Diabetes?

The pancreas is a digestive organ that relies on insulin to digest food. The body’s primary energy source, carbohydrates, are broken down into glucose. In healthy individuals without diabetes, the pancreas releases insulin as glucose enters the bloodstream. Insulin allows the glucose to enter the body’s cells for use. Any additional glucose is stored in the liver as glycogen. The liver gradually releases glycogen into the bloodstream to maintain blood sugar levels between meals.

Diabetes, however, is a chronic metabolic condition occurring when the pancreas cannot produce insulin or when the body cannot utilize insulin appropriately. This leads to increased blood glucose levels that cause organ and tissue damage over time.

There are three main types of diabetes:

1. Type 1 Diabetes—Common in children and young adults, the immune system attacks the insulin producing beta cells of the pancreas. The pancreas produces little to no insulin and type 1 diabetics must rely on insulin injections to stabilize blood sugar levels.
2. Type 2 Diabetes—The pancreas produces insulin, but the body is unable to utilize it effectively. 90 percent of diabetes cases are type 2. It is associated with poor dietary and lifestyle choices.
3. Gestational Diabetes—During pregnancy, blood sugar levels rise. Prolonged hyperglycemia impacts both the mother and baby. The mother is prone to becoming a type 2 diabetic after giving birth.   

Symptoms of Diabetes

Having excessive glucose in the blood leads to symptoms in nearly every bodily system. The severity of symptoms depends on how elevated the blood sugar level is and the amount of time it remains high.

• Blurry Vision
• Excessive Thirst
• Frequent Urination
• Nausea
• Weightloss or Gain
• Numbness and Tingling
• Leg Pain
• Dry, Itchy Skin
• Hunger
• Poor Wound Healing
• Increased Infections
• Fatigue

Eventually, diabetes increases one’s risk for complications such as heart disease, a stroke, hearing loss, and kidney damage. This excludes the symptoms caused directly from damage to the nervous system that will be discussed below.

What Blood Sugar Fluctuations Do to the Brain

Diabetes can cause two distinct blood sugar conditions:

• Hyperglycemia—High blood sugar from excess glucose in the blood. Ideally, blood sugar should be 140 mg/dL or less two hours after consuming a meal.
• Hypoglycemia—Low blood sugar from too little glucose in the blood. In diabetes, hypoglycemia is often provoked as a side effect of blood sugar lowering medications. Any blood sugar reading below 60 mg/dL is considered hypoglycemia.

In all forms of diabetes, one is susceptible to high and low blood sugars. Like the rest of the body, the brain relies on glucose to function. When glucose processing is impaired, the blood sugar levels remain too high or too low for long periods. This has negative repercussions on the brain and nervous system.

Diabetes and Neurodegeneration

Diabetes is connected to neurodegeneration, which explains alterations in brain structure. Studies found that type 2 diabetics have significantly less brain volume. Their cerebrospinal fluid volume is increased—a typical finding in the presence of brain atrophy. The area of brain loss includes white matter. The white matter in the brain is a integral component of cognition because it is home to nerve fibers that send signals to other parts of the body. In some instances, high blood glucose induces oxidative stress on the nervous system that impairs the blood brain barrier. If the blood brain barrier is effected, widespread inflammation takes over causing cell death, and as a result, low brain volume.

Cognitive Dysfunction and Diabetes

As the white matter in the brain is reduced, diabetics have lower performances on cognition tests for attention, processing speed, and overall executive function (Moheet et al., 2015). Again, other studies reflect a drastic decline in the cognitive domains of memory, attention and psychomotor speed after 4 years if poor glycemic control.

Additionally, when blood sugar levels are low, cognitive symptoms like confusion, anxiety, and reduced mental clarity arise as the brain does not have sufficient fuel to function. This is the body’s warning sign to correct hypoglycemia without triggering hyperglycemia.

Diabetic Neuropathy

Along with the brain and spinal cord, nerves comprise the nervous system. There are multiple types of nerves in the body and each nerve performs a different function. While some nerves control significant bodily processes such as heart rate and blood pressure, others are responsible for muscle movements.

According to the American Diabetes Association, approximately 50 percent of people with diabetes develop some form of neuropathy. Prolonged high blood glucose levels damage nerves over time. Ensuring blood sugar levels are between normal parameters delays nerve damage.

Peripheral Neuropathy

The most common type of neuropathy is peripheral neuropathy. Diabetic peripheral neuropathy is neuropathy induced from chronically high blood sugar levels and primarily effects the hands and feet. The classic tingling, “pins and needles” sensation is indicative of peripheral neuropathy. Burning, stabbing, or shooting pains often occur with increased sensitivity. It is not unusual for those with diabetic peripheral neuropathy to experience numbness, weakness, or feelings of hot or cold. Symptoms are worse at night, and lead to poor sleep quality. A medical professional can discern whether there is peripheral neuropathy through a nerve conduction test that measures the function of the nerves.

Autonomic Neuropathy

Autonomic neuropathy is a less common, but severe complication of uncontrolled diabetes. Autonomic neuropathy includes damage to the nerves that control the autonomic nervous system, which is the branch of the nervous system that regulates all bodily functions that are meant to occur “automatically.” For example, digestion, heart rate and blood pressure, bladder, and temperature are all autonomic processes. The symptoms of autonomic neuropathy are: dizziness, fainting from low blood pressure, exercise intolerance, difficulty urinating, nausea, vomiting, constipation, difficulty swallowing due to poor digestion, and delayed pupil reaction resulting in blurry vision.

Proximal Neuropathy

Diabetes can also damage the nerves of the lumbosacral plexus such as the leg, hip, or buttocks. When the nerves either of those location are compromised, patients develop muscle wasting. The secondary condition is called amyotrophy because myo means muscle and proximal neuropathy causes pain and weakness in the muscles on one side of the body. The pain is distinct, shooting down the leg from the lower back. In addition to elevated blood glucose levels, proximal neuropathy can result from high triglycerides too. It is the second most common type of neuropathy diagnosed in diabetics.

Focal Neuropathy

Also termed mononeuropathy, focal neuropathy is caused by damage to a single nerve. The symptoms depend on the specific nerve that is damaged. However, it can cause pain, loss of movement, or numbness. Focal neuropathy begins suddenly. The nerves in the head are more prone to damage than other areas of the body. Vision loss is a primary complaint.

Diabetic Neuropathy Testing

Identifying whether symptoms are related to diabetic neuropathy is easily accomplished by a medical professional. First, the doctor may do nerve conduction tests on the muscles, arms, and legs. Autonomic testing for autonomic neuropathy measures processes such as sweating, blood pressure regulation. Sensory testing measures how the nerves respond to varying degrees of temperature, as well as vibration. A filament test also measures sensitivity as microfiber brushes the skin.

Diabetes and Mental Health

Coping with a chronic condition is difficult. Those with diabetes are at an increased risk for depression, anxiety, and eating disorders. Up to 50 percent of patients experience diabetes distress, which is a mental disorder that includes characteristics of stress, anxiety, and depression surrounding aspects of living with diabetes. The fear of managing blood sugar levels provokes great fear. For example, one may worry about prolonged high blood sugars or developing complications.

Diabetes and Dementia

Dementia is a broad term defining a group of disorders that interfere with cognitive thinking processes. The brain based skills that allow us to carry out simple, daily tasks and interactions are effected by dementia. Unfortunately, type 2 diabetics are 50 percent more likely to develop dementia (Moheet et al., 2015).

Diabetes is a risk factor for dementia because it destroys the blood vessels in the brain. As blood vessels are compromised, brain cells die off. Forms of dementia common in diabetics include:

• Alzheimer’s Disease—A loss of cognitive (thinking) abilities because of brain cell degeneration.
• Vascular Dementia—Problems with basic thought processes (i.e., memory, attention, reasoning, planning) from a lack of blood flow to the brain. Frequently, vascular dementia is caused by a stroke.

Older patients with diabetes are at an even greater risk of dementia. Studies show that the cognitive abilities of type 2 diabetics decreases twice as rapidly as non-diabetics over a 5 year period (Tilvis et al., 2004). Associated with the risk of dementia, those with diabetes experience mild cognitive impairment sooner. Mild cognitive impairment is the stage between cognitive decline normal with aging and full dementia. Some experts claim mild cognitive impairment eventually progresses to dementia.

Diabetic Ketoacidosis: Cerebral Edema

Ketoacidosis happens when the body fails to produce sufficient amounts of insulin and begins to breakdown fat as an energy source. The blood becomes overly acidic during this process, as the body releases ketones. Diabetic ketoacidosis is a medical emergency from unmanaged diabetes.

A major complication of ketoacidosis is cerebral edema. Correcting blood sugar levels too quickly causes swelling of the brain. Younger children suffering from ketoacidosis are more likely to develop cerebral edema. Beginning signs of cerebral edema are mild changes in mental status such as confusion or irritability. The condition progresses into severe headaches, vomiting, seizures, low heart rate, high blood pressure, and increased intracranial pressure.

Treating the Neuro Symptoms of Diabetes

The primary treatment for the neurological symptoms of diabetes is managing the disease before nervous system symptoms begin. Aside from keeping blood glucose levels within range, there are a few treatment options when the neurological symptoms of diabetes hits.

• Injections—Injections into the nerves decreases inflammation caused by neuropathy.
• Pain Management—Anti-inflammatory medications such as ibuprofen reduce some of the swelling and inflammation.
• Anti-Depressants—Anti-depressant medications belonging to the class of Selective serotonin repuptake inhibitors (SSRIs) target depression and anxiety.

References

Moheet, A., Mangia, S., & Seaquist, E. R. (2015). Impact of diabetes on cognitive function and brain structure. Annals of the New York Academy of Sciences, 1353, 60–71. https://doi.org/10.1111/nyas.12807

Tilvis, R.S., Kahonen-Vare, M.H., Jolkkonen, J., Valvanne, J., Pitkala, K.H., & Strandberg, T.E. (2004). Predictors of cognitive decline and mortality of aged people over a 10-year period. J Gerontol A Biol Sci Med Sci 2004;59:268–274

Cheyanne Perry

Cheyanne is currently studying psychology at North Greenville University. As an avid patient advocate living with Ehlers Danlos Syndrome, she is interested in the biological processes that connect physical illness and mental health. In her spare time, she enjoys immersing herself in a good book, creating for her Etsy shop, or writing for her own blog.