Closed loop helps impaired awareness, but does not close the gap

Design

single-centre observational before-and-after study with age- and sex-matched comparison group, 28-day CGM datasets

Population

68 adults with type 1 diabetes; 32 with impaired awareness of hypoglycaemia (Gold score 4 or above) and 32 matched with normal awareness; mean age 38.0 years, diabetes duration 21.0 years

Primary outcome

time below range and frequency and duration of sensor-detected hypoglycaemia at baseline and 12 months after starting hybrid closed loop

Effect

time below range 2.8% to 1.7% (P=0.024) and weekly episodes 5.4 to 4.0 (P=0.026); at 12 months still higher than normal-awareness controls, 1.7% vs 0.7% (P=0.007)

Impaired awareness of hypoglycaemia is the problem automated insulin delivery is most often hoped to solve. This single-centre study followed 68 people with type 1 diabetes for twelve months after starting the Omnipod 5 hybrid closed-loop system - 32 with impaired awareness (Gold score 4 or above) and 32 age- and sex-matched controls with normal awareness (Gold score 2 or below). Outcomes came from 28 days of continuous glucose monitoring at each timepoint.

At baseline the impaired-awareness group had more time below 3.9 mmol/L, more sensor-detected hypoglycaemia episodes, and longer episodes when they occurred (median 33.5 against 24.5 minutes, P=0.007). Starting the closed loop helped: time below range fell from 2.8% to 1.7% (P=0.024) and weekly episodes below 3.9 mmol/L from 5.4 to 4.0 (P=0.026). But at twelve months the gap persisted - time below range 1.7% against 0.7% (P=0.007) and episodes 4.0 against 2.0 (P=0.013) - while the difference in episode duration was no longer significant (29.8 against 28.0 minutes, P=0.084).

So the system does what it is meant to do and does not do what people hope it does. A patient with impaired awareness starting a closed loop will have less hypoglycaemia than before, and still roughly twice as much as a comparable patient with intact awareness. That is worth saying out loud at the point of starting, because the alternative is a patient who concludes at twelve months that the technology has failed. It is also an argument for keeping the other interventions - structured education, awareness restoration, targets set deliberately higher - rather than treating the pump as the whole plan.

• Set the expectation at initiation: less hypoglycaemia, not the same as someone with intact awareness.
• Keep structured education and awareness-restoration approaches running alongside the technology.
• Consider deliberately higher glucose targets in impaired awareness, at least initially.
• Use the Gold score at baseline and repeat it - awareness is a tracked outcome, not a fixed label.
• Note this is single-centre, before-and-after, in 68 people; the direction is more reliable than the exact numbers.

The statistics, in plain English

This is a before-and-after comparison within a single centre, not a randomised trial, so improvement over twelve months could partly reflect the extra attention that accompanies starting new technology. The matched comparison group is what makes the persistent gap interpretable: both groups were observed over the same period, so the residual difference at twelve months is not explained by secular change. The loss of significance in episode duration (P=0.084) should be read as the study running out of power rather than as evidence that duration equalised - 29.8 against 28.0 minutes is a small absolute difference measured in 64 people.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.