by Jessica Pyhtila, PharmD, BCPS, BCGP
Diabetic neuropathy – often called diabetic nerve pain – is the most common complication of diabetes. Nearly half of people with diabetes will eventually develop the condition, and up to 15% of people already have some amount of diabetic nerve pain by the time they get a diabetes diagnosis. Diabetic neuropathy can be painful, leading to a negative impact on your quality of life. Although the condition is often part of the natural progression of diabetes, by learning about it, you can identify and treat it early to prevent complications.
Even though the condition is common in diabetes, certain risk factors can increase your chances of developing diabetic neuropathy. These include:
-How long you have had diabetes: The longer you have had diabetes, the more time there is for nerve damage to develop. Age is also linked to this risk factor, with older people – who may have had diabetes longer – being more at risk for diabetic neuropathy than younger people.
-A1c control: The higher and less-controlled your A1c is, the more likely you are to develop diabetic neuropathy. However, what may seem like a simple cause-and-effect relationship is more complicated and depends on the type of diabetes you have. For example, well-controlled blood sugar can stop diabetic neuropathy in Type 1 diabetes, but has less of an impact on Type 2 diabetes. Further, having poorly controlled blood sugar is a risk factor for having painful neuropathy if you do go on to develop the condition.
-Metabolic factors: The presence of insulin resistance, high blood pressure, obesity, and poorly controlled cholesterol levels are linked to a higher risk of diabetic neuropathy. Further, obesity is a risk factor for painful neuropathy.
-Lifestyle factors: If you smoke or drink alcohol, you have more of a chance of developing diabetic neuropathy.
Many different types of diabetic neuropathy exist, with each impacting different parts of the body. In addition, although you can feel some types of neuropathy on your skin, other forms of neuropathy occur inside your body. These kinds of internal diabetic neuropathy – often termed autonomic neuropathies – can impair the function of your heart, gastrointestinal tract, urinary tract and even your sexual function. Scientists believe that each type of neuropathy may have its own specific chemical causes and nerve damage and are still investigating causes for many subtypes of the disease.
The most common type of diabetic neuropathy is DSPN, or distal symmetric polyneuropathy, impacting around 75% of people with a diagnosis of diabetic neuropathy. This type of diabetic neuropathy is what comes to mind when many people think of the condition. DSPN tends to first impact the longest nerves in the body – the ones that run down the arms and legs – so that the hands and feet are most likely to have symptoms. For this reason, being tall is a special risk factor for DSPN. As the name implies, DSPN tends to impact both sides of the body symmetrically, so that if the condition impacts one of your feet, it is likely to also impact the other. Symptoms of DSPN may be unnoticeable before they start to worsen. Sometimes, you might not even know that you are starting to experience DSPN until your doctor finds the condition during a diabetic foot exam. DSPN typically starts at the toes and then spreads back through the foot and leg. By the time symptoms reach the knees, they often also start to appear in the fingers of both hands. Symptoms of DSPN include:
Sometimes, DSPN symptoms may be different depending if you are moving or at rest. For example, symptoms of pain that people describe as burning, stabbing or freezing pain are often more common while you are resting than while you are moving. This is one reason that diabetic nerve pain is linked to insomnia: it is hard to fall asleep when you are in pain. It is important to note that not everyone with DSPN will experience pain: in fact, pain only occurs in 30% to 50% of people with DSPN.
The factors that lead to DSPN are complex. Scientists have learned that sensory neurons, the nerve cells that detect sensations on the skin, are the nerves that are first damaged by DSPN. It, therefore, makes sense that symptoms like numbness, burning and tingling occur when these sensory nerves are damaged. Scientists think this damage occurs due to several different causes:
-High blood sugar and high cholesterol: Cells called Schwann cells work with sensory nerves, helping the nerves transmit signals back and forth to the brain and spinal cord. Schwann cells need sugar and cholesterol to function. However, if there is too much sugar or cholesterol in your bloodstream, their chemical system can get overloaded, harming both the Schwann cell and the sensory nerve. In some cases, toxic products called acylcarnitines are formed by the cells when they get overloaded, also damaging both the Schwann cell and the sensory nerve. In other cases, unstable molecules called reactive oxygen species are formed, harming nerve cells and causing inflammation.
-Impaired blood flow to nerves: Just like other cells in your body, nerves require blood flow to properly function. Scientists have found abnormalities in the small blood vessels that bring oxygen and nutrients to nerves and suspect that this impaired blood flow may damage the nerves.
-Problems with insulin: Insulin is important for the health of nerve cells. In people with Type 1 diabetes, a condition in which a person cannot produce insulin on their own, taking insulin and keeping blood sugar at goal can prevent diabetic nerve pain. Unfortunately, the situation is more complex in Type 2 diabetes. People with Type 2 diabetes not only have problems making enough insulin, but their bodies have a hard time using the insulin they do make. This phenomenon, also known as insulin resistance, is likely a major reason that people with Type 2 diabetes commonly suffer diabetic nerve pain even if their blood sugar is well-controlled.
Your doctor will likely keep a close eye on your foot health in order to catch DSPN early. Besides asking about any symptoms of diabetic nerve pain, your doctor will likely have you take off your socks and shoes to do a foot exam. This normally includes an annual monofilament test to detect any areas of numbness on your feet and can help determine if you are at risk for diabetic nerve pain complications like ulcers or amputation. If you have symptoms of DSPN, your doctor can help you choose medication treatments to manage them.
You also play a key role in helping to keep your feet healthy and minimizing complications from DSPN. Things you can do at home include:
-Performing a daily foot exam: Checking for cuts or injuries you may not be able to feel due to DSPN will keep your feet healthy.
-Wash your feet in warm water daily and dry between your toes: Keeping your feet clean and dry will help to prevent foot infections you may not be able to feel.
-Never walk barefoot: Because the bottoms of your feet cannot feel the floor well when you have DSPN, wearing well-fitting shoes will protect your feet.
-Trim your toenails straight across or have a podiatrist do it for you: Trimming your toes straight across will minimize your risk of giving yourself an injury you may not otherwise notice.
Diabetic neuropathy can be a challenging condition. But being aware of DSPN is the first step in successfully managing the condition. With your doctor’s help, you can minimize your risk factors and prevent complications that can arise.
1. Pop-Busui, Rodica; Boulton, Andrew J.M.; Feldman, Eva L; et al. “Diabetic Neuropathy: A Position Statement by the American Diabetes Association.” January 2017. [Online]. Available: https://care.diabetesjournals.org/content/diacare/40/1/136.full.pdf
2. Feldman, Eva L; Callaghan, Brian C; Pop-Busui, Rodica; et al. “Diabetic Neuropathy.” June 13, 2019. [Online]. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7096070/
3. Centers for Disease Control and Prevention. “Diabetes and Your Feet.” December 4, 2019. [Online]. Available: https://www.cdc.gov/diabetes/library/features/healthy-feet.html