Type 1 diabetes

Hybrid closed loop insulin delivery system has potential to restore hypoglycaemia awareness


Short term use of a hybrid closed loop system might preferentially benefit people with type 1 diabetes who have impaired awareness of hypoglycaemia (IAH), Australian research suggests.

In a pilot study of 16 patients aged 12 – 55 years, participants crossed between eight weeks of standard insulin pump therapy (control period) and eight weeks using an HCL system (Medtronic 670GTM) (intervention period).

The West Australian study found there was no difference in the epinephrine, norepinephrine, cortisol and growth hormone response between the intervention and control periods.

However symptom responses including peak adrenergic and neuroglycopenic scores differed significantly after intervention and control periods.

Glycaemic outcomes were also different based on the type of therapy.

For example, people spent a smaller proportion of their time in hypoglycaemia – blood glucose <3.9 mmol/L (<1.7% v 5.2%) and <3.0 mmol/L (0.3% v 2.0%) – when using the hybrid closed loop system compared to when using standard therapy.

“Participants spent a median of 4 minutes per day < 3 mmol/L with HCL compared to a median of 29 minutes per day during the control period,” the study said.

Participants also had more time in the target range (71.1% v 57.5%) when using the hybrid closed loop system.

The study, whose senior co-authors included Professor Tim Jones and Professor Elizabeth Davis, said the findings were significant as other studies had shown that meticulous avoidance of hypoglycaemia can help restore awareness of hypoglycaemia.

However there were inconsistent findings from two hypoglycaemia awareness questionnaires – a lower [more aware] Gold score after the intervention compared to the control period but no difference observed when using the Clarke score.

“Diabetes treatment satisfaction (DTSQ) was comparable after control and intervention, p=0.783, however the perceived frequency of hypoglycaemia was significantly lower after intervention compared to control, p=0.004.”

The study authors said the short duration of the intervention may have been a limitation by not allowing sufficient time for an improved catecholamine response.

They also noted that the self-reported hypoglycaemia awareness should always be interpreted with caution.

“A reduction may be attributed to “technological awareness” and not true restoration of physiological awareness.”

They said the limitations, including a small sample size, reduce the generalisability of the results.

“A long-term study with a higher number of participants using a parallel study design will address this further and evaluate if the trends towards improvements in hypoglycaemia awareness shown in this pilot study persist and if longer use of a hybrid closed loop system results in improved counter-regulatory hormonal response,” they concluded.

Professor Jones, from the Perth Children’s Hospital and Telethon Kids Institute, told the limbic the newer, more user-friendly closed loop systems were on the way.

“It has been shown to improve diabetes control, and what we need to do now is to prove it improves the burden of treatment that people have with type 1 diabetes.”

“We saw a very large education in the exposure to hypoglycaemia …we just need to give that time for awareness to restore.”

He said the next study will involve intervention periods of 3-6 months.

“We think it will also be useful for young children, 2-7 year olds, to protect against hypoglycaemia at night which is often a big fear of parents.”

He said severe IAH was one of the main reasons for transplants in Australia.

“Some people have no quality of life – they can’t even go for a walk because of severe unawareness.”

The study was published in Diabetes Technology and Therapeutics.

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