Patient Guide to Diabetic Neuropathy

Diabetic Neuropathy: Causes and Symptoms

The many factors that lead to diabetic nerve pain

Diabetic peripheral neuropathy—DPN for short—is diabetes-related damage to nerves that sit near the surface of your skin. DPN usually affects the feet and the hands but can also harm nerves in arms and legs.

Approximately 50 percent of people with type 2 diabetes and 20% of those with type 1 diabetes develop this kind of nerve damage.1  DPN can be extremely painful—or cause numbness so that you have little feeling, especially in your feet.

Diabetic neuropathy occurs in two different types of nerves close to the surface of your skin. DPN can affect small nerves that protect your body by sending signals about pain and temperature changes to your brain. This condition can also attack large nerves that detect touch, pressure and help you keep your balance.2 Symptoms are different for each type of neuropathy but most people with DPN have damage that occurs to both types of nerves.

This diabetes-related complication usually affects extremities—feet, hands, legs and arms—where nerve fibers are the longest and most numerous.2

Experts are still investigating exactly how diabetes harms and kills these nerve cells. “The causes remain unknown,”1 according to findings shared in a position paper issued by the American Diabetes Association (ADA).

One thing is certain: The conventional wisdom that—high blood sugar is the cause—of diabetic peripheral neuropathy is only part of the story. New research is revealing a much bigger cast of culprits. These other contributing factors may include high total cholesterol, high triglycerides (a specific type of blood fat), high blood pressure, obesity, and smoking,3 according to a widely-cited British research study that tracked 1,172 people with diabetes for seven years.

The major threats are:

  • Obesity and high triglyceride. Each of these factors doubled the risk of developing DPN in people with diabetes based on results of a University of Utah study of 218 people with type 2 diabetes.4
  • Smoking increased risk by as much as 42% says a Harvard Medical School review of 38 studies on tobacco use and diabetic peripheral neuropathy that included more than 5,000 people.5
  • High blood pressure increased risk from 11% to 65% based on data collected by tracking more than 37,000 people with type 2 diabetes for up to nine years;6 these findings are available in a report published in the journal Medicine.
  • In the same study,6 low levels of “good” HDL cholesterol and high levels of heart-threatening LDLs also boosted risk for diabetic peripheral neuropathy by up to 67%.

What’s behind the numbers? According to a review appearing in the Journal of Diabetes Research,7 metabolic changes associated with diabetes and related health problems may damage nerve cells by boosting levels of rogue oxygen molecules called free radicals that attack the DNA inside cells, by zapping antioxidant compounds that normally protect cells from free radicals and by increasing inflammation.  

In addition, nerve fibers are extra-vulnerable to damage because the tiny blood vessels they rely on for oxygen and nutrients may also be damaged by high blood sugar, high blood pressure and unhealthy levels of blood fats.

Problems begin surprisingly early. In a University of Toronto study of 467 people, ages 45 to 64, about half of those with prediabetes or newly diagnosed type 2 diabetes had early signs of peripheral neuropathy.8 (Researchers measured how well nerves in their feet detected pain and vibration and also asked about symptoms.)

Those with higher blood sugar levels were more likely to have nerve damage. In people with type 1 diabetes, whose high blood sugar problems are usually diagnosed very early, about 20% have peripheral neuropathy after 20 years.3 Your risk may also rise with age, but even children and young adults with type 1 and type 2 diabetes have signs of peripheral neuropathy.

However, the nerves get damaged, the end result is the same: they aren’t able to convey messages as well as they should to the brain, and they lose their ability to help you feel and move.

The good news? If you have type 1 diabetes, type 2 diabetes or prediabetes and do not yet have nerve damage, controlling blood sugar and taking other healthy steps can help prevent it from happening. For people with type 1 diabetes, tight glucose control can cut risk for DPN by 78%; for those with type 2, it may reduce risk 5-9%.9

Why the big difference in risk for neuropathy between those with type 1 and type 2 diabetes?

Experts believe  that because people with type 1 diabetes are diagnosed earlier in life and after only having the condition for a short time, there is a smaller period of time that they are exposed to high blood sugar levels, and therefore less time for sugar to damage nerves.3

Equally problematic, people who are diagnosed with type 2 diabetes often experience high blood sugar levels for years (yet, nerve damage often begins much earlier, even in the prediabetic stage), which can mean lots of nerve damage by the time diagnosis is made.8

There are other factors that you should be aware of, which are likely to contribute to an increased risk of developing peripheral nerve damage, and its progression, including:

  • Overweight and obesity
  • Cigarette smoking
  • High total blood cholesterol
  • High blood pressure
  • High triglycerides 

Right now, there is no way to cure nerve damage once it arises. Certainly, if you are already experiencing signs of nerve damage, making some lifestyle adjustments can slow the progression of any more damage to the nerves. 

You may need medication to effectively control the pain.11 In fact, the ADA position paper on nerve damage states that there’s “no compelling evidence” that blood sugar control and a healthy lifestyle can ease the pain.1,11,12 But many experts strongly advocate for keeping blood sugar under control for many reasons, and might just help reduce neuropathy in at least some people.

One reason for the focus on good blood sugar control is that people who experience hyperglycemia, or high sugar “spikes,” may notice increased nerve discomfort, for example. And there’s exciting early evidence that regular exercise may actually help nerves regenerate somewhat in people with type 2 diabetes who have peripheral neuropathy, based on a University of Utah study of 100 women and men in their 50s and 60s.13

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Diabetic Neuropathy: Your Diagnosis