Diabetics With Low Blood Sugar at Risk for Driving Accidents
Feb. 25, 2000 (Atlanta) -- Diabetics with even mildly low blood sugar --
hypoglycemia -- can find their driving performance seriously impaired, leading
to more missed stop signs, inappropriate braking, fast driving, and sudden-stop
crashes, according to a small study in Diabetes Care.
What's more, when drivers don't take immediate corrective action -- drinking
a soda or pulling off the road -- brain activity changes may prevent their ever
taking any corrective action, leading to a stuporous state that can
cause serious accidents, the study shows.
"There were individual differences, of course, but as a group [diabetic
patients in the study] drove worse when they were mildly hypoglycemic than when
[blood sugars were normal]. But the [impaired judgment it caused] was most
interesting and quite distressing," lead author Daniel J. Cox, PhD, of the
Behavioral Medicine Center at University of Virginia Health System in
Charlottesville, tells WebMD.
Chronic low blood sugar causes brain function and judgment to become
temporarily impaired. "We had patients telling us, 'I knew I was going
hypoglycemic, I knew I needed to treat myself. I had a sandwich right next to
me but I couldn't make myself take it, I couldn't make myself eat it,'" Cox
says. "That's why it's so critical to treat yourself right away. Don't wait
till you get to the office to treat yourself. Do it immediately."
Using a sophisticated driving simulator (developed with help from NASA
flight simulator engineers), Cox's team was able to document that driving
impairments occur at relatively mild degrees of hypoglycemia (blood glucose
levels in the 60s).
The study involved 37 adults with type 1 diabetes and an average age 35 --
all of whom had been taking insulin for at least two years. During the
30-minute driving test, each was given insulin intravenously to progressively
lower blood glucose levels.
During the first hour, each volunteer drove the simulator for 30 minutes
while blood sugar levels were normal; during the second 30-minute test, blood
sugar levels were decreased to hypoglycemic levels. Patients were unaware that
their blood glucose levels were being altered. Driving performance, brain
activity, and corrective behaviors were continually monitored -- every five
minutes -- as were blood glucose levels, perception of symptoms, and impaired
Every five minutes during the 30-minute tests, volunteers were asked to rate
their symptoms, their driving ability, and their need to treat themselves (a
soft drink was in the glove compartment). "They were continually being
reminded," says Cox. "They were instructed that any time they couldn't
drive, they should pull over and treat themselves. Yet only one-third of our
volunteers both recognized their driving impairments and took corrective
During hypoglycemia, there was more driving off the road, more speeding, and
brakes were used more often on the open road, says Cox. Fourteen volunteers
(38%) demonstrated extreme impairments in their driving while hypoglycemic. For
example, during the last 15 minutes of driving, volunteers failed to stop at
stop signs significantly more often and were involved in more crashes at sudden