Older adults with type 1 diabetes should be safe getting getting behind the wheel, provided they use CGM and adhere to ‘above five to drive’, according to research presented at the 2023 Australasian Diabetes Congress.

The message builds on a large body of evidence supporting the guideline – at least for younger motorists – in the form of driving simulator studies that found drivers became impaired once blood glucose levels fell below 5 mmol/L.

Nevertheless, data in older patients has been lacking, meaning many are advised to stay off the road entirely due to concerns about elevated hypoglycaemia risk and related issues, said University of Melbourne endocrinology research fellow Dr Hye Jin Kwon.

Conducted during a two-week period prior to a separate clinical trial, her study included 23 active drivers aged 60 years and older, each at least 10 years post T1D diagnosis, using sensor-augmented pump therapy.

Data from in-vehicle loggers captured 618 trips in total, with pre-trip CGM showing glucose levels greater than 5 mmol/L in 93%.

Of those 577 trips in which drivers started within the guidelines, none resulted in a patient falling into CGM-detected hypoglycaemia while driving, defined as CGM <3.9 mmol/L.

This suggested the ‘above five to drive’ guideline was beneficial even in older patients with T1D, Dr Kwon told the conference.

By contrast, of the remaining 41 trips which were commenced with blood glucose ≤5 mmol/L, hypoglycaemia was detected in nine (22%) journeys.

Additionally, drivers’ blood glucose levels fell below 3 mmol/L in three of the trips, she noted.

On the other hand, the study identified issues with relying on CGM alerts to detect low blood glucose levels.

Overall, 43 trips (7%) included CGM ≤5 mmol/L while driving but 29 of these (67%) had no low-glucose-related alerts during the trip.

“And if we look at the pre-trip glucose levels, only three alerts were actually useful for the drivers,” she said.

“A driving-specific threshold for CGM alerts could improve the safety of glucose management during journeys,” Dr Kwon added.

Another issue was that most trips were relatively short in length, with a median duration of just 10 minutes, while study participants were all independent with experience of using technology and had good glycaemic control as a baseline.

“We will now need to prioritise the safety of T1D drivers by improving hypoglycaemic alerts during driving but also decreasing distractions from alarms,” she concluded.

“We also need to improve education and awareness among older drivers with diabetes.”