Real-time vs flash monitoring for T1D

This study compared real-time continuous glucose monitoring (CGM) to flash CGM for patients with type 1 diabetes (T1D). It found that real-time CGM led to better glucose control and less hypoglycemia, both during daily activity and exercise.

Patients with T1D are unable to create the hormone insulin to regulate blood glucose levels. Instead, they use injections of synthetic insulin. Insulin directs cells in the body to take in glucose (sugar) from the blood. This controls the amount of glucose in the blood, which must stay in a narrow range to prevent negative effects. Glucose also provides cells with the energy they need. During exercise, cells require more glucose and become more sensitive to insulin. For 24 hours after exercise, patients with T1D are more likely to have hypoglycemia (dangerously low blood sugar).

Patients with T1D use monitors to track their blood glucose. The most effective type is CGM, which uses a patch attached to the body to continuously test blood glucose. There are two varieties of CGM. Real-time CGM continuously sends out glucose information to a receiver or smartphone, which can then audibly alert the user if their blood glucose is going out of range. Flash CGM requires the patient to scan the sensor with their smartphone to update the data. It is not clear whether one type of CGM leads to better glucose control.

This study included 60 patients with T1D who had not previously used CGM. Half of the patients were randomly assigned to real-time CGM, and the other half to flash CGM. Basic alarms were set for real-time CGM, while there were no alarms for flash CGM. Patients spent four days at a training program which included high amounts of exercise. They were then followed for four weeks during their typical routine at home.

Patients using real-time CGM had significantly less time with high blood sugar while at home (3.5% vs. 7.7%). They also had significantly less time with low blood sugar (5.3% vs. 7.3%).

While at the high-exercise training, the two groups had similarly low amounts of time with high blood sugar. However, patients using real-time CGM were significantly less likely to experience low blood sugar during the day (6.5% vs. 10.5%). For real-time CGM users, there was also a dramatically lower rate of overnight low blood sugar following an exercise day (7.7% vs. 20.1%).

This study found that real-time CGM led to better glucose control than flash CGM. In particular, there was a lower risk of hypoglycemia after exercise.

It is not clear whether blood glucose control changes as patients become more experienced in using their CGM.