A trial, using CGM sensors, has shown how exercise can increase the risk of night time hypoglycemia in children with type 1 diabetes.
The study included data from 59 children with type 1 diabetes aged between two and 17 years old. 29 of the children were male and 22 were female. The participants had
HbA1c levels of the participants varied between 49 and 81 mmol/mol (6.6 to 9.6%). 36 of the children were on multiple injection therapy and a further 15 were using insulin pumps.
The children wore CGM sensors for six consecutive days. This provided the researchers with 306 nights of CGM sensor usage. The CGM sensors worn took readings without displaying the results until after the trial period was complete.
The children wore an accelerometer to measure their level of physical activity through the day. Nocturnal hypoglycemia was defined as a glucose level of below 3.7 mmol/l.
Nocturnal hypoglycemia occurred during 97 of the 306 nights (32.7% of nights). The duration of hypoglycemia ranged from 10 minutes to over 11 hours.

36% of the episodes lasted under one hour
34% lasted between one and three hours
24% lasted between three to six hours
6% lasted more than six hours

There were 128 episodes of hypoglycemia in total and only eight of these were noticed by the children.
Effects of exercise and bedtime glucose levels
The results showed that an hour of moderate to vigorous physical activity increased the risk of nocturnal hypoglycemia occurring by 58% and an hour of vigorous physical activity increased the risk by 82%.
The other key factor linked with a significant increase in night time hypos was bedtime glucose level. Going to sleep with a glucose level below 6 mmol/l was linked with 2.5 times the risk of night time hypoglycemia occurring.
The researchers note, in the study, that: “Our data reveal that in children with diabetes, nocturnal hypoglycemia is very frequent, mostly asymptomatic, and often prolonged for hours. Two strong risk factors, low bedtime glucose and daytime physical activity, could be identified.”
Adding that: “Children with diabetes should be encouraged to participate in sports, but they must be trained how to prevent hypoglycemia. As bedtime glucose [below] 6 mmol/l more than doubles the risk of nocturnal hypoglycemia, it should be mandatory to instruct patients to increase carbohydrate intake, adapt insulin dosage, and retest blood glucose during the night, especially after exercise.”
The study was conducted by researchers from Basel and Zurich, in Switzerland, and was published in the July issue of the Diabetes Care journal.

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