Driving and Diabetes: An Increased Risk Of Motor Vehicle Accidents?

By Sheila Walker, RD, CDE, M.Ed posted in Healthy Living Professionals & Educators
Updated

Driving and Diabetes

driverWhen I began to think about this topic, I asked a friend at my gym what he thinks about driving and diabetes.  D is a fit 73 year old male who was diagnosed with type 1 diabetes 5 years ago.  He immediately replied with a serious look on his face that frequent monitoring is very important to his safety on the road.  He looks forward to his driving adventures in France every summer and understanding his blood sugar patterns throughout the day is just part of his new life with diabetes.

Are all of our clients this vigilant with respect to safe driving with diabetes?  The diabetes educator is in an ideal position to influence clients towards adopting certain behaviours which can help them stay safe on the road.

The purpose of this article is to discuss the concerns with respect to driving and diabetes, the CDA position paper and guidelines on driving and diabetes and strategies for the diabetes educator to start the dialogue with their patients.

Are clients with diabetes at an increased risk of motor vehicle accidents?

The short answer to this question is “Yes”.   Many studies support this finding.  A recent review of the literature (1) from 1965 to 2010 found that diabetes is associated with an increased risk of crashes and violations.  The authors feel that as the risk of diabetes continues to grow, these findings should serve as an impetus to develop new ways of improving driver safety in those with diabetes.  Of note is the fact that the authors state that the risk of crashes and violations may be underestimated as many studies did not control for mileage. The Canadian Diabetes Association warned that 1in 3 Canadians will be living with either diabetes or pre-diabetes by 2010.

The American Diabetes Association Position Paper on Diabetes and driving (2012)  states  that the risk of a motor vehicle accident is 12-19% higher for the person with diabetes than without (2).  An earlier study (3) in the USA reports that crash risk remains higher in persons with diabetes than those without diabetes throughout the age span.  Severe hypoglycemia was strongly correlated to crashes at all ages.

The concerns raised by diabetes include the following:

  1. Hypoglycemia
  2. Diabetes complications

1. Hypoglycemia – Hypoglycemia appears to be the major factor in raising the risk of motor vehicle accidents.  The goal in diabetes management has been the attainment of near normal blood sugars as safely as possible.  Of course this goal is individually determined with each patient according to many factors.   Studies have shown that complications of diabetes are directly related to blood glucose control.  The flip side of this of course is the increase in the risk of hypoglycemia and hypoglycemic unawareness.  In a Canadian study which looked at ministry records of crashes in patients with diabetes (4) three factors were associated with an increased risk.  These included a lower HbA1c (7.4 versus 7.9%), a history of severe hypoglycemia requiring outside assistance (a four- fold increase in risk) and a later age of diabetes diagnosis.

Another study (5) compared the decision to drive in patients with type 1 diabetes who had a normal awareness of hypoglycemia with Type 1 patients with an impaired awareness of hypoglycemia.  Hypoglycemic awareness was measured with epinephrine levels and a symptom score during hypoglycemia.  During this experiment the blood sugar was lowered with the use of a hyperinsulinemic clamp to 2.7mmol/L. The results demonstrated that with the use of a driving simulator, 42.9% of those with an impaired awareness of hypoglycemia would decide to drive with a low blood sugar.  Also worrying was the 25% of type 2 patients on oral agents with a normal awareness of hypoglycemia who would also decide to drive with a low blood sugar.

Further evidence about driving while hypoglycemic came from a study in 2009 (6).  Drivers (n = 452) with type 1 diabetes in 3 centers in the USA were interviewed about driving “mishaps” over a 12 month period.  Mishaps included collisions, citations, losing control, automatic driving, someone else taking over the wheel and moderate or severe hypoglycemia while driving.  Fifty-two percent of drivers reported at least 1 hypo-related driving mishap and 5% reported 6 or more.  Mishaps were related to mileage driven, history of severe hypoglycemia and use of insulin pump therapy.  Patients on pumps were 35% more likely to have a hypoglycemic driving mishap than those on insulin injections.

So why do some patients choose to drive despite a low blood sugar?  One study (7) has found in a simulated driving test that there is a subgroup of type 1 patients who are more vulnerable to hypoglycemia as they produce less epinephrine as their blood sugars drop.  They also experience more symptoms during euglycemia making it harder to detect hypoglycemia while driving.

2. Diabetes complications which may affect driving

  1. Eyes – This can include retinopathy and cataract formation which can cause loss of visual acuity , loss of  peripheral vision and poor dark adaptation.  It is noted that there can be tremendous variability in diabetic visual changes and each patient needs to be assessed individually. Also aging can cause reduced night vision and difficulty judging speed and distance (Ministry of Transportation).
  2. Neuropathy –  This may lead to loss of feeling in hands and/or feet which may affect one’s ability to drive safely.
  3. Obstructive sleep apnea may be as high as 23% in people with diabetes (International diabetes foundation).

CDA position on diabetes and driving (CDA website)

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The CDA Advocacy position (2011) states that “people with diabetes have the right to be assessed for a license to drive a motor vehicle on an individual basis in accordance with CDA guidelines for private and commercial driving”.

The CDA believes that a person with diabetes should not have difficulty obtaining and maintaining a license if:

  • You properly manage your diabetes
  • You are able to recognize and treat the early signs of hypoglycemia  and
  • You do not have complications that may interfere with your ability to drive

You do have to report diabetes to the Motor Vehicle licensing authority. Your physician is required to report anyone he or she considers unfit to drive.  This may include:

  • a newly diagnosed client, recently started on insulin
  • someone who does not recognize the early symptoms of hypoglycemia
  • someone who has just experienced a severe hypoglycemic reaction
  • someone who is not managing their diabetes responsibly

The Motor Vehicle licensing authority has the power to suspend your license.

The Medical Review section reviews each case to see whether a license will be reinstated.  The Medical review section will request a report from a diabetes specialist as well as records of self-monitoring blood glucose readings for a specific period of time.

Guidelines are also available for a commercial license on their website.

Patient education

The diabetes educator can help patients to stay safe on the road.   The ADA Diabetes and Driving Guidelines (2) suggest developing a short questionnaire which asks about driving mishaps while low and recent history of severe hypoglycemia.

The key factor appears to be identifying those patients who suffer from severe hypoglycemia.  It seems that 80% of episodes of severe hypoglycemia affect about 20% of people with type 1 diabetes.

Suggestions for this group can include:

  1. Testing before driving
  2. Encouraging a higher blood sugar before driving .  This may vary depending on the length of the trip and whether the blood sugar is rising or falling
  3. If a low occurs while driving, safely cease driving, eat fast acting carbohydrate (this is not fruit)
  4. Do not resume driving for at least 45-60 minutes
  5. Blood glucose awareness training (BGAT) may improve one’s ability to estimate blood sugar and four studies have demonstrated that it reduces the occurrence of collisions (ADA position paper on driving, 2012) (2).  This program can be delivered over the internet (diabetesdriving.com)

Summary

It is hard to know whether a patient is safe to drive or not (4).   D, my friend at the gym, has a routine that keeps him safe when he is on the road.  He prefers not to drive until 2 hours after his meals as he says  that only then do his blood sugars not change much.  He keeps a good supply of food available in the car for emergencies.  He also monitors every 2 hours.  He also keeps detailed logs of his driving adventures which help him to make good decisions regarding his diabetes.

Making patients aware of the high risk of driving with diabetes can help start the dialogue about this important part of life.

References

  1. Kagan A, Hashemi G, Korner-Bitensky N. Diabetes and Fitness to Drive:A Systematic Review of the Evidence with a
    Focus on Older Drivers. Canadian Journal of Diabetes. 2010;34:233-242.
  2. American Diabetes Association . Diabetes and driving. Diabetes Care.2012;35 supplement 1.
  3.  Songer TJ, Dorsey RR. High risk characteristics for motor vehicle crashes in persons with diabetes by age. Annu Proc Assoc Adv Automot Med 2006;50:335-351.
  4. Redelmeier DA, Kenshole AB, Ray JG. PLOS Medicine . Motor Vehicle Crashes in Diabetic Patients with Tight Glycemic Control: A Population-based Case Control Analysis. 2009;12:e1000192
  5. Stork AD, Van Haeften TW, Veneman TF. The Decision not to drive during hypoglycemia in patients with type 1 and type 2 diabetes according to hypoglycemia awareness. Diabetes Care. 2007;30:2822-2826.
  6. Cox  DJ, Ford D, Gonder-Frederick L, Clarke W, Mazze R, Weinger K, Ritterband L.  Driving Mishaps Among Individuals with Type 1 Diabetes.  Diabetes Care.2009;32: 2177-2180.
  7. Cox DJ, Kovatchev BP, Anderson SM, Clarke WL, Gonder-Frederick LA. Type 1 Diabetic Drivers with and without a History of Recurrent Hypoglycemia-Related Driving Mishaps. Diabetes Care. 2010; 33:2430-2435.
About the Author

Sheila Walker RD, CDE, M.Ed is a dietitian at Sunnybrook Health Sciences Centre in Toronto and counsels clients with Type 2 diabetes and those at risk of diabetes. She has also had type 1 diabetes for 41 years and is a strong believer in the benefits of a high fibre diet.

  • gerald doherty

    living alone, loss off my driver’s license would make life not worth living