Type 1 diabetes

Glucose variability in drivers: could dashboard display enhance safety?

Drivers with insulin-treated diabetes might benefit from a CGM-based, in-vehicle display monitoring their blood glucose, Australian researchers say.

A Victorian study, set within a trial of hybrid closed loop, monitored sensor glucose in 18 adults with type 1 diabetes across 475 vehicle-logged driving trips.

The study, published in Diabetes Technology & Therapeutics, found most people (52.8%) drove within range and 45.9% above range. The median sensor glucose during the study was 181 mg/dL (10 mmol/L) although a number of trips involved glucose levels >270 and >300 mg/dL.

Importantly, none of the trips where the glucose started at >90 mg/dL (5 mmol/L) involved glucose dropping during the trip to <70 mg/dL (3.9 mmol/L)

However, in 38% of trips where the driver started with a glucose <90 mg/dL, their glucose dropped to <70 mg/dL.

“One driver (ID3) undertook six of these trips, half of which met the criteria for a level 2 hypoglycemia (<54 mg/dL),” the study said.

“Five drivers experienced a glucose drop of 36 mg/dL or larger after 20 min of driving, with a significant association between the maximum absolute glucose change and longer trip duration.”

“While this relationship is not surprising, it provides novel insight into the magnitude of glucose variation while driving. This point is fundamental to the argument that drivers with insulin-treated diabetes need access to real-time glucose data and alerts in a format that is suitable (i.e., easily comprehended and not distracting) while driving.”

“It is also important to consider that clinically significant glucose changes can occur well before the 1 to 4 h advised in current guidelines for when to stop driving and perform a glucose check.”

Don’t Drive Under Five

Lead author and psychologist Dr Steven Trawley told the limbic that it was the first objective evidence supporting the public awareness message of ‘Don’t Drive Under Five’.

He said the variation in glucose was not unexpected but the study provided an opportunity to put a timeline on it.

“In a relatively healthy and small group, and in the context of driving, this variation is occurring in an unmonitored fashion,” he said.

“It does highlight the importance of having auditory alarms on CGMs and why having access to CGM is a good thing for many people.”

However he said alarms on different CGMs were variable.

“It might have an alarm but it might not be immediately obvious what that alarm is for. It could be that they’re going low or it could be a calibration issue.”

Dr Trawley, from the Cairnmillar Institute and the Australian Centre for Behavioural Research in Diabetes,  Melbourne, said there was nothing on the market that allows someone to monitor their glucose whilst driving.

“There are some work-arounds, for example with some of the new devices you can have CGM information on your phone which you could have on a dashboard mount.”

He said the study highlights just how much variation can occur while driving – even after just 20 minutes – with clinically significant changes for a number of trips.

Diabetes Australia recommend drivers re-check their blood glucose level at least every two hours to make sure it stays above 5 mmol/L.

“The key message is it’s important to find ways in which people can monitor glucose whilst driving. We need to find better ways to inform drivers while they are behind the wheel.”

“Anecdotally, speaking to people, they tend to be cautious when driving and probably drive a little bit higher in terms of their glucose than they would normally, knowing there is no opportunity to check once they start the trip.”

He stressed that type 1 diabetes and using insulin was not necessarily a barrier to driving.

“For the most part, people‘s glucose was in a range that wouldn’t necessarily affect their driving. What makes driving challenging with people who use insulin for type 1 diabetes is it’s difficult if not impossible to monitor your blood glucose. The more people who can be informed about their glucose whilst driving, the better.”

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