Closed-Loop Insulin Delivery Has Glycemic Benefits During Sleep at Cost of Sleep Quality

Compared with sensor-augmented pump therapy, closed-loop insulin delivery increased glucose time in range and reduced hypoglycemia episodes but detracted from sleep quality.

Compared with sensor-augmented pump therapy, first-generation closed-loop therapy has glycemic benefits during sleep for older adults with type 1 diabetes (T1D) but deteriorates some sleep quality measures, according to a study published in Diabetes Technology & Therapeutics.

First-generation closed-loop systems incorporate continuous glucose monitoring communicating with an insulin pump and glucose-responsive automated basal insulin dosing. The glycemic benefits of closed-loop therapy are greatest overnight when dietary intake and physical activity have less impact on insulin requirements.

While advances in diabetes technology have the potential to improve both glycemia and sleep quality, the technology may also reduce sleep quality due to system alarms, requirements for user intervention, and device-related physical discomfort.

The researchers conducted a randomized trial to report the glycemic impact of closed-loop therapy during objectively measured sleep. They compared glucose outcomes during sleep and sleep quality of closed-loop therapy with sensor-augmented pump therapy among older adults with T1D.

In the OldeR Adult Closed-Loop (ORACL) randomized, crossover trial of first-generation closed-loop therapy (MiniMed 670G), participants wore a noninvasive actigraphy and completed sleep diaries for 14-day periods. Participants were aged 60 years old or older with T1D for 10 years or more and using an insulin pump.

A total of 30 older adults participated with a mean age of 68 years and mean T1D duration of 38 years.

At baseline, 14 participants (47%) reported inadequate sleep quality. Another 3 participants reported using pharmacological therapy to aid sleep, and 3 were taking antidepressants that may affect sleep.

None reported taking stimulant medications.

During objectively measured sleep with closed-loop versus sensor-augmented pump therapy, glucose time-in-range 70-180 mg/dL (3.9–10.0 mmol/L) was greater (90.3% vs. 78.7%, respectively; difference, 8.2 percentage points; 95% CI, 1.5-13.0; P  =  .008).

Additionally, time in narrow glucose range 70–140 mg/dL (3.9–7.8 mmol/L) during sleep was greater with closed-loop therapy (difference, 12.8 percentage points; 95% CI, 6.0 to 19.5; P  < .001).

There were also fewer sensor hypoglycemia episodes (18 vs. 43, respectively; incident rate ratio, 0.40; 95% CI, 0.20-0.55; P = .007).

The favorable between-treatment effects of closed loop improving time-in-range were generally observed from the fourth hour of sleep onward. For both therapies, almost all time below range occurred within 5  hours after sleep onset. More time below range was seen with sensor-augmented therapy during this period.

Mean sleep efficiency was high overall, although lower with closed-loop than sensor-augmented pump therapy (82% vs. 85%, respectively; difference, −2.9 percentage points; 95% CI; −5.0 to −0.8; P = .009).

Sleep quality recorded in daily sleep diaries was worse with closed-loop therapy (P = .006). Pittsburgh Sleep Quality Index did not differ.

System alarms were experienced during most nights’ sleep with both treatments.

During monitored sleep with closed-loop therapy, there were 30% more system alarms (P < .001). However, low-glucose alarm rates were almost half with closed-loop therapy (incident rate ratio, 0.54; 95% CI, 0.39 to 0.75; P < .001).

“This benefit is clinically important as hypoglycemia-related situations generally require intervention for treatment and/or insulin pump adjustment before resuming sleep,” wrote the authors.

No episodes of severe hypoglycemia or other significant adverse outcomes during sleep occurred throughout the 8-month trial.

Overall, the findings suggest that first-generation closed-loop therapy has glycemic benefits during sleep for older adults, with deterioration in some sleep quality measures. The results build upon previous evidence that closed-loop therapy reduces hypoglycemia overnight. Simultaneously, they highlight the potential burden of closed-loop system use on sleep quality.

The authors suggest that, although sleep quality did not improve with first-generation closed-loop therapy, it is clinically reassuring that sleep quality did not markedly deteriorate. While total sleep time and sleep efficiency were marginally lower with closed loop, the participants met recommendations for minimum sleep duration per night.

The authors encourage prioritizing sleep quality during the advancement of closed-loop technology. “As closed-loop technologies improve in the future, with advanced glucose sensors and increasingly automated algorithms, less sleep disruption by system alarms is anticipated,” they wrote.

“Future developments in diabetes technology, including more automated closed-loop algorithms and enhanced glucose sensor technology, are likely to further improve glycemia during sleep and sleep quality in people with type 1 diabetes,” they concluded.


Chakrabarti A, Trawley S, Kubilay E, et al. Closed-loop insulin delivery effects on glycemia during sleep and sleep quality in older adults with type 1 diabetes: results from the ORACL trial. Published online July 4, 2022. Diabetes Technol Ther. doi:10.1089/dia.2022.0110