Diabetic Neuropathy Impairs Driving

Introduction

Diabetic neuropathy is a form of nerve damage that may occur if you have diabetes. High blood sugar (glucose) may damage nerve fibres throughout your body, but diabetic neuropathy commonly damages nerves in your legs and feet. (1)

Depending on the nerves affected, symptoms of diabetic neuropathy can range from numbness and pain in your extremities to problems with your blood vessels and heart, digestive system and urinary tract.

Symptoms may be mild for some people but for others, diabetic neuropathy may be disabling, painful or even fatal.

Diabetic neuropathy is a common serious complication of diabetes.

Yet you can often prevent diabetic neuropathy or slow its progress with tight blood sugar control and a healthy lifestyle.

Symptoms

There are 4 main types of diabetic neuropathy.

You can have just 1 type or symptoms of several types.

Most develop slowly, and you might not notice problems until considerable damage has occurred.

Signs and symptoms of diabetic neuropathy can vary depending on the type of neuropathy and which nerves are affected.

Peripheral Neuropathy

Peripheral neuropathy is the most common form of diabetic neuropathy.

Feet and legs are often initially affected, followed by hands and arms.

Signs and symptoms of peripheral neuropathy are frequently worse at night, and can include:

• A tingling or burning sensation
• Muscle weakness
• Loss of balance and coordination
• Sharp pains or cramps
• Increased sensitivity to touch — for some people, even the weight of a bed sheet can be very painful
• Numbness or reduced ability to feel pain or temperature changes
• Loss of reflexes, especially in the ankle
• Major foot problems, such as ulcers, infections, deformities, and bone and joint pain

Autonomic Neuropathy

Because the autonomic nervous system controls your heart, bladder, lungs, stomach, intestines, sex organs and eyes, diabetes may affect the nerves in any of these areas, possibly causing:

• Erectile dysfunction in men
• Bladder problems, including urinary tract infections or urinary retention or incontinence
• Constipation, uncontrolled diarrhoea or a combination of the two
• Slow stomach emptying (gastroparesis), leading to nausea, vomiting, bloating and loss of appetite
• Difficulty swallowing
• A lack of awareness that blood sugar levels are low ( hypoglycaemia unawareness)
• Vaginal dryness and other sexual difficulties in women
• Decreased or Increased sweating
• Inability of your body to adjust blood pressure and heart rate, leading to sharp drops in blood pressure after sitting or standing that may cause you to faint or feel lightheaded
• Problems regulating your body temperature
• Changes in the way your eyes adjust from light to dark
• Increased heart rate when you're at rest

Radiculoplexus neuropathy (diabetic amyotrophy)

Radiculoplexus neuropathy may affect nerves in the thighs, hips, buttocks or legs.

Also known as diabetic amyotrophic, femoral neuropathy or proximal neuropathy, this condition occurs more frequently in older adults or those with type 2 diabetes.

Symptoms usually occur on one side of the body, though in some cases they can spread to the other side.

Most people improve at least partially over time, though symptoms can worsen before they get better.

This condition is often marked by:

• Eventual weak and atrophied thigh muscles
• Difficulty rising from a sitting position
• Sudden, severe pain in your hip and thigh or buttock
• Abdominal swelling, if the abdomen is affected
• Weight loss

Mononeuropathy

Mononeuropathy encompasses damage to a specific nerve.

The nerve may be in the torso, face, or leg.

Mononeuropathy, is also known as focal neuropathy that can often come on suddenly.

 It's most frequent in older adults.

Although mononeuropathy may cause severe pain, it usually doesn't cause any long-term problems.

Symptoms usually diminish and disappear on their own over a few weeks or months. Signs and symptoms depend on which nerve is involved and can include:

• Paralysis on one side of your face (Bell's palsy)
• Pain in your shin or foot
• Pain in your chest or abdomen
• Pain in your lower back or pelvis
• Difficulty focussing your eyes, double vision or aching behind one eye
• Pain in the front of your thigh

Sometimes mononeuropathy may occur when a nerve is compressed.

Carpal tunnel syndrome is a common type of compression neuropathy in people with diabetes.

Signs and symptoms of carpal tunnel syndrome include:

• Numbness or tingling in your fingers or hand, especially in your thumb, index finger, middle finger and ring finger
• A sense of weakness in your hand and a tendency to drop things

Causes

Damage to nerves and blood vessels

Prolonged exposure to high blood sugar may damage delicate nerve fibres, causing diabetic neuropathy.

While the mechanism of diabetic neuropathy remains unknown a combination of factors likely plays a role, including the complex interaction between nerves and blood vessels.

High blood glucose interferes with the ability of the nerves to transmit signals.

It also weakens the walls of the small blood vessels (capillaries) that supply the nerves with oxygen and nutrients.

Other Factors

Other factors that may contribute to diabetic neuropathy include:

• Inflammation in the nerves 
• Genetic factors 
• Smoking and alcohol abuse
• Inflammation in the nerves.

Risk Factors

Anyone who has diabetes can develop neuropathy, but these factors make you more susceptible to nerve damage:

• Poor blood sugar control. This is the most significant risk factor for every complication of diabetes, including nerve damage.

Keeping blood glucose consistently within your target range is the best way to protect the health of your nerves and blood vessels.

• Length of time you have diabetes. Your risk of diabetic neuropathy increases the longer you have diabetes, especially if your blood glucose isn't well-controlled.
• Kidney disease. Diabetes may cause damage to the kidneys, which may increase toxins in the blood and contribute to nerve damage.
• Being overweight. Having a body mass index greater than 24 can increase your risk of developing diabetic neuropathy.
• Smoking. Smoking narrows and hardens arteries and reduces blood flow to your legs and feet.

This makes it more difficult for wounds to heal and damages the integrity of the peripheral nerves.

Complications

Diabetic neuropathy may cause a number of serious complications, including:

• Loss of a limb
• Charcot joint. 
• Urinary tract infections and urinary incontinence. 
• Hypoglycaemia unawareness. Usually, when blood glucose falls too low — below 70 milligrams per decilitre (mg/dL), or 3.9 millimoles per liter (mmol/L) — you develop symptoms such as shakiness, sweating and a fast heartbeat. Autonomic neuropathy may interfere with your ability to notice these symptoms.
• Low blood pressure. This may cause a rapid drop in pressure when you stand after sitting (orthostatic hypotension), which can lead to dizziness and fainting.
• Digestive problems
• Sexual dysfunction. 
• Increased or decreased sweating. 

Prevention

You can help prevent or delay diabetic neuropathy and its complications by maintaining blood glucose consistently well-controlled, taking good care of your feet and following a healthy lifestyle.

Blood sugar control

Keeping your blood glucose consistently within your target range is the best way to help prevent neuropathy and other complications of diabetes.

Consistency is important because changes in blood glucose sugar levels may accelerate nerve damage.

The American Diabetes Association encourages people with diabetes to have a blood test known as A1C test at least twice a year to find out your average blood sugar level for the past two to three months.

Foot Care

Foot problems, including sores that don't heal, ulcers and even amputation, are a common complication of diabetic neuropathy.

To protect the health of your feet:

• Check your feet every day 
• Keep your feet clean and dry 
• Trim your toenails carefully.
• Wear clean, dry socks
• Wear cushioned shoes that fit well 

If problems occur, discuss these with your physician who can help treat them to prevent more-serious conditions.

Diagnosis and Treatment

These are thoroughly outlined by the Mayo Clinic (2)

Diabetic Driving Studies: Brake Response Time in Diabetic Drivers With Lower Extremity Neuropathy

AJ Meyr and KE Spiess studied the brake response time in diabetic drivers with lower extremity neuropathy. (3)

The objective of their case-control investigation was to evaluate the mean brake response time in diabetic drivers with lower extremity neuropathy compared to a control group and a brake response safety threshold.

Driving performances of participants were examined with a computerized driving simulator with specific measurement of the mean brake response time and frequency of abnormally delayed brake responses.

They studied a control group of 25 active drivers with neither diabetes nor lower extremity neuropathy and an experimental group of 25 active drivers with type 2 diabetes and lower extremity neuropathy.

The experimental group demonstrated a 37.89% slower mean brake response time (0.757 ± 0.180 versus 0.549 ± 0.076 second; p < .001), with abnormally delayed responses occurring at a greater frequency (57.5% versus 3.5%; p < .001).

Independent of a comparative statistical analysis, the detected mean brake response time in the experimental group was slower than the reported safety brake response threshold of 0.70 second.

Their results provide original data with respect to abnormally delayed brake responses in diabetic patients with lower extremity neuropathy and may raise the potential for impaired driving function in this population.

Diabetic Driving Studies. A Comparison of Brake Response Time Between Drivers With Diabetes With and Without Lower Extremity Sensorimotor Neuropathy

The objective of the second study by KE Spiess and fellow investigators was to examine a case-control study to compare the mean brake response time between 2 groups of drivers with diabetes that were with or without lower extremity sensorimotor neuropathy. (4)

Braking performances of the subjects were evaluated using a computerized driving simulator with specific measurement of the mean brake response time and the frequency of the abnormally delayed brake responses.

These researchers compared a control group of 25 active drivers with type 2 diabetes without lower extremity neuropathy and an experimental group of 25 active drivers with type 2 diabetes and lower extremity neuropathy from an urban U.S. podiatric medical clinic.

The experimental group demonstrated an 11.49% slower mean brake response time (0.757 ± 0.180 versus 0.679 ± 0.120 second; p < .001), with abnormally delayed reactions occurring at a greater frequency (57.5% versus 35.0%; p < .001).

Independent of a comparative statistical analysis, diabetic drivers with neuropathy exhibited a mean brake response time slower than a suggested safety threshold of 0.70 second, and diabetic drivers without neuropathy demonstrated a mean brake response time faster than this threshold.

Their results provide evidence that the specific onset of lower extremity sensorimotor neuropathy associated with diabetes appears to impart a negative effect on automobile brake responses.

A Comparison of Mean Brake Response Time Between Neuropathic Diabetic Drivers With and Without Foot Pathology

Sansosti and colleagues examined a case-controlled study to compare the mean brake response time between neuropathic diabetic drivers with and without specific diabetic foot pathology. (5)

Braking performances of subjects were examined using a computerized driving simulator with specific measurement of the mean examined brake response time and the frequency of abnormally delayed brake responses.

These authors analysed a control group of 20 active drivers with type 2 diabetes, lower extremity neuropathy, and no history of diabetic foot pathology and an experimental group of 20 active drivers with type 2 diabetes, lower extremity neuropathy, and a history of diabetic foot pathology (ulceration, amputation, and/or Charcot neuroarthropathy) from an urban U.S. podiatric medical clinic.

 Neuropathic diabetic drivers without a history of specific foot pathology demonstrated an 11.11% slower mean brake response time (0.790 ± 0.223 versus 0.711 ± 0.135 second; p < .001), with abnormally delayed reactions occurring at a similar frequency (58.13% versus 48.13%; p = .0927).

Both groups demonstrated a mean brake response time slower than a suggested threshold of 0.70 second.

Findings of the present investigation provide evidence that diabetic patients across a spectrum of lower extremity sensorimotor neuropathy and foot pathology showed abnormal vehicle brake responses and might be at risk of impaired driving function.

Conclusion

All diabetic patients should be counselled to be extra vigilant when driving a motor vehicle, especially those with neuropathy.

This should be particular reinforced for those diabetic patients who are over 60 years of age who have further impairment of reaction times due to aging (6)

Furthermore wherever possible, all drugs prescribed for diabetic patients for any co-existing medical condition should be non-sedating or minimally sedating to avoid further exacerbating their risks of being involved in motor vehicle accidents.

This applies in particular to subpopulations of Bipolar Disorder patients who are considered at high risk for Diabetes Mellitus where the incidence of diabetes may be 3 times greater than the general population (7).

References

1)    Diabetic Neuropathy. Symptoms and Causes. https://www.mayoclinic.org/diseases-conditions/diabetic-neuropathy/diagnosis-treatment/drc-20371587 . ?. 1998 -2017 Mayo Foundation for Medical Education and Research (MFMER .All Rights reserved.

2)   Diabetic Neuropathy. Diagnosis and Treatment. https://www.mayoclinic.org/diseases-conditions/diabetic-neuropathy/diagnosis-treatment/drc-20371587 ?. 1998 -2017 Mayo Foundation for Medical Education and Research (MFMER .All Rights reserved.

3)   Meyr AJ, Spiess KE. Diabetic Driving Studies-Part 1: Brake Response Time in Diabetic Drivers With Lower Extremity Neuropathy. J Foot Ankle Surg. 2017 May - Jun; 56(3):568-572. doi: 10.1053/j.jfas.2017.01.042.

4)   Spiess KE, Sansosti LE, Meyr AJ. Diabetic Driving Studies-Part 2: A Comparison of Brake Response Time Between Drivers With Diabetes With and Without Lower Extremity Sensorimotor Neuropathy. J Foot Ankle Surg. 2017 May - Jun; 56(3):573-576. doi: 10.1053/j.jfas.2017.01.043.

5)   Sansosti LE, Spiess KE, Meyr AJ. Part 3: A Comparison of Mean Brake Response Time Between Neuropathic Diabetic Drivers With and Without Foot Pathology. J Foot Ankle Surg. 2017 May - Jun; 56(3):577-580. doi: 10.1053/j.jfas.2017.01.044.

6)   Doroudgar S, Chuang HM, Perry PJ, Thomas K, Bohnert K, Canedo J. Driving Performance Comparing Older versus Younger Drivers. Traffic Inj Prev. 2016 Jun 21:0. [Epub ahead of print] 

7)   Roger S. Mcintyre,Jakub Z. Konarski,Virginia L. Misener &Sidney H. Kennedy. Bipolar Disorder and Diabetes Mellitus: Epidemiology, Etiology, and Treatment Implications. Annals of Clinical Psychiatry. Volume 17, 2005. Issue 2.p83-93.