Case reports of three adults with type 1 diabetes describe how hybrid closed-loop technology that gives insulin doses informed by an integrated insulin pump algorithm enabled them to run marathons in Tokyo, Santiago, and Paris.
The technology allowed the adults with type 1 diabetes to better manage their blood sugars enabling them to lead more active lives. The AID system contains an advanced hybrid closed loop algorithm that automates the delivery of both basal and correction bolus insulin every five minutes based on sensor glucose values.
“It is great to see advances in diabetes technology come to fruition and deliver such improvements to people’s lives,” said lead author Dr. Maria Onetto from Pontificia Universidad Católica Chile, Santiago, Chile.
“This technology is game changing, allowing more people with diabetes to have safer, healthier, more active lives.”
In type 1 diabetes, a person’s blood glucose level becomes too high (hyperglycaemia) because there is no, production of insulin by the pancreas. Blood glucose levels can only be regulated by giving insulin to prevent hyperglycaemia.
If the condition is not well controlled, people are at increased risk of long-term complications of hyperglycaemia, including microvascular damage such as eye, kidney or nerve damage, heart disease or stroke.
“Despite better systems for monitoring blood sugars and delivering insulin, maintaining glucose levels in target range during aerobic training and athletic competition is especially difficult,” explained Onetto.
“The use of automated insulin delivery technology is increasing, but exercise continues to be a challenge for individuals with type 1 diabetes, who can still struggle to reach the recommended blood sugar targets.”
Although there are some published recommendations of how to adjust insulin delivery and carbohydrate intake for exercise, there are few reports of real-world examples of people with type 1 diabetes using automated insulin delivery systems during intensive exercise or competition.
The technology known as Advance-Hybrid Closed-Loop consists of an algorithm on an insulin pump which communicates with the traditional continuous glucose monitoring.
The patient delivers boluses for meals and snacks by entering the total grams of carbohydrates they are consuming. The algorithm targets a glucose level chosen by the user, which can be adjusted to be 100, 110 or 120 mg/dL. The patient can also set a temporary sensor glucose target (Temp Target) of 150 mg/dL for situations where hypoglycaemia risk may be increased, such as during exercise. When the Temp Target is on, auto-bolus corrections are disabled.
To assess blood sugar control during the marathons, the researchers measured: time in range (TIR) that shows the percentage of time a person spends within a target glucose range (3.9 to 10 mmol/litre); time below range (TBR; below 70 mg/dL or 3.9 mmol/litre) target to less than 4 per cent of the time; and time above range (TAR) when blood glucose levels exceed 180 mg/dL.
Case studies
50-year-old man with T1D for 22 years ran Tokyo marathon in around 3.5 hours
The first report details a 50-year-old man who had been living with T1D for 22 years before he ran the Tokyo Marathon in March 2023 in 3 hours and 34 minutes.
Thirty days before the race his time in the target glucose range (TIR 70-180 mg/dL ) was 89 per cent, time above range (TAR>180 mg/dL) was 9 per cent, time below range (TBR<70 mg/dL) was 1 per cent, and HbA1c (average blood sugar over the last 8 to 12 weeks) was 6.9 per cent.
In order to prevent hypoglycaemia, on the morning of the marathon he reduced his breakfast insulin dose by 25 per cent and the insulin dose applied to the pre-race snack was also reduced by 50 per cent to better manage blood sugar levels.
He consumed glucose gels, the primary source of carbohydrates during the race, at a rate of 0.39 g/kg/hour, with 102g consumed overall.
During the race, the man maintained excellent glycaemic control, spending 96 per cent of the marathon within the correct glucose range, just 4% below range, and no time above the target range. He achieved an average blood glucose of 107mg/dl—well below the mean glucose of less than 154 mg/dl recommended in adults (see table in abstract).
40-year-old man with T1D for 4 years ran Santiago marathon in under five hours
The second report is of a 40-year-old man who had been living with T1D for the past four years. He took part in the Santiago (Chile) marathon in May 2023, completing the race in four hours and 56 minutes.
Before the marathon (30 days), his time in the target glucose range was 76 per cent, time above range was 9 per cent, time below range was 3 per cent, and HbA1c was 6.7 per cent.
The day of the race, he did not lower his breakfast insulin dose, but he reduced the insulin dose applied to the pre-race snack by 100 per cent. During the marathon, the man consumed glucose gels at a rate of 0.42 g/kg/hour, with 120g consumed in total.
The man spent 100 per cent of the marathon within the correct glucose range with an average blood glucose of 110mg/dl, underscoring the capability of the glucose monitoring system to respond in real time (see table in abstract).
34-year-old woman with T1D for 27 years ran Paris marathon in under four hours
The third report describes a 34-year-old woman who had been living with T1D for 27 years before she completed the Paris Marathon in April 2023 in three hours and 56 minutes.
Thirty days before the marathon, her time in the target glucose range was 83 per cent, time above range was 15 per cent, time below range was 1 per cent, and her HbA1c was 6.6 per cent.
On the morning of the marathon, she did not lower her breakfast insulin dose, but she reduced the insulin dose applied to her pre-race snack by 83 per cent.
During the marathon, she consumed glucose gels at a rate of 0.5 g/kg/hour, with 115g consumed in total. She spent the whole marathon well above the target glucose range, with an average blood glucose of 271mg/dl—well above the mean glucose of less than 154 mg/dl recommended in adults.
As Dr Onetto explained: “It is likely that the woman remained hyperglycaemic throughout the race for a number of reasons. She may have eaten too many carbs before the race without insulin, but she also didn’t deactivate the temporary sensor glucose target (temp target) because she hadn’t realised that disconnecting it would re-enable the auto-correction boluses.
“We hope these case studies provide insights for healthcare professionals who assist athletes with type 1 diabetes using automated insulin delivery systems during intense physical activities.
“Underscoring the importance of specialised education, planning, and personalised approaches, this research emphasises the substantial opportunities that automated insulin delivery technology offers to individuals with type 1 diabetes, enabling them to lead active lives.”
