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Do we use the right timeframe to capture nocturnal hypoglycaemia?

07th May 2024

New research suggests that hypoglycaemia during sleep may have been underestimated by up to 30% in previous studies. The results were obtained by using continuous glucose monitoring (CGM) in addition to customary sleep trackers and a smartphone app for patient reporting. But how do these findings relate to the lived experience of people with diabetes?

In their novel approach, Gilberte Martine-Edith and co-workers used a widely available sleep-tracking device in a study of 575 participants with type 1 or insulin-treated type 2 diabetes. Sleep times were analysed along with two other factors: blood glucose levels measured by continuous glucose monitoring (CGM) and details of hypoglycaemic episodes as reported by the participants using a smartphone app. Both sensor-detected and self-reported hypoglycaemic episodes were compared with nocturnal hypoglycaemia between 00:00 and 06:00.

The study found that the commonly used clock-based approach underestimated hypoglycaemia during sleep by 25–30%. “In fact, we showed that most hypoglycaemic episodes did not fall within the 00:00-to-06:00 window,” says first-author Gilberte Martine-Edith, a postdoctoral researcher at King’s College London. As a result, the study suggests that future hypoglycaemia research should consider using sleep trackers to adequately address the issue of hypoglycaemia during sleep. However, Martine-Edith emphasises that in addition to CGM, participant-reported episodes should also be taken into account.

Fig. 1: Distribution of bedtimes and waking up times in type 1 diabetic patients in the HYPO-METRICS study. The red-shaded area indicates the time reference period used to calculate clock-based nocturnal hypoglycaemia rates. Modified after Martine-Edith G et al, Diabetes Technol Ther 2024 Apr 17.

Balancing sensor readings and patient experience
The study data was collected as part of the Hypo-METRICS study, a 10-week long assessment across nine UK and EU sites. “Results from the Hypo-METRICS study have so far highlighted that many episodes of sensor-detected biochemical hypoglycaemia are asymptomatic. Also, many episodes that patients identify and treat as hypoglycaemia are not associated with low sensor glucose levels,” says Martine-Edith. In the context of hypoglycaemia during sleep, quality of life can be reduced when participants are awakened by hypoglycaemic episodes, for example by symptoms such as sweating, tremors and palpitations, or alarms from the CGM. “This is associated with a negative impact on quality of life and daily functioning, and can affect mood, productivity and fear of hypoglycaemia,” Martine-Edith adds.

Towards improved diabetes research
Sleep management in diabetes needs to balance glycaemic control with the psychological burden on patients. “Fear of hypoglycaemia can lead to people running their blood glucose levels higher than target levels, putting them at increased risk of diabetes-related complications,” explains Martine-Edith, highlighting the daily challenges faced by those living with diabetes. According to the diabetes researcher, new technologies such as automated insulin delivery (AID) promise to reduce the incidence of nocturnal hypoglycaemia as well as mitigate its effects when it does occur. However, the basis of such efforts is an accurate assessment of the time periods of high risk for hypoglycaemia during sleep. “The assessment of nocturnal hypoglycaemia is an important part of clinical care and often a key differentiator between therapies in clinical research, and it is important that it is done accurately,” Martine-Edith points out the significance of the results for clinical research and care. The study results suggest that current research underestimates the impact of hypoglycaemia during sleep. In addition, differences between sensor-detected hypoglycaemia and the patient experience of hypoglycaemia should be considered: “While biochemical hypoglycaemia can be associated with harmful effects on the heart and brain, symptomatic episodes have negative impacts on quality of life,” says Martine-Edith. Therefore, the recommendation for future clinical trials is to measure both sensor-detected and patient-reported events in combination with wearable sleep-tracking devices  

Key Points:
  • Nocturnal hypoglycaemia is associated with serious health risks and can negatively affect quality of life and productivity.
  • Recent evidence suggests that the traditional clock-based method, which defines nocturnal hypoglycaemia as occurring between 00:00 and 06:00, may underestimate rates of hypoglycaemia during sleep by up to 30%.
  • First-author Gilberte Martine-Edith suggests that both sensor-detected and patient-reported events should be used in combination with wearable sleep-tracking devices to report episodes of hypoglycaemia during sleep in clinical trials.

Author: Hanna Gabriel, BA MSc. Any opinions expressed in this article are the responsibility of EASD e-Learning.

To read this paper visit: Martine-Edith G, Divilly P, Zaremba N, Søholm U, Broadley M, Baumann PM, Mahmoudi Z, Gomes M, Ali N, Abbink EJ, de Galan B, Brøsen J, Pedersen-Bjergaard U, Vaag AA, McCrimmon R, Renard E, Heller S, Evans M, Cigler M, Mader JK, Speight J, Pouwer F, Amiel S, Choudhary P. A Comparison of the Rates of Clock-Based Nocturnal Hypoglycemia and Hypoglycemia While Asleep Among People Living with Diabetes: Findings from the Hypo-METRICS Study. Diabetes Technol Ther 2024 Apr 17. Online ahead of print.