Combining information of autonomic modulation and CGM measurements enables prediction and improves detection of spontaneous hypoglycemic events

Abstract

We have previously tested, in a laboratory setting, a novel algorithm that enables prediction of hypoglycemia. The algorithm integrates information of autonomic modulation, based on heart rate variability (HRV), and data based on a continuous glucose monitoring (CGM) device. Now, we investigate whether the algorithm is suitable for prediction of hypoglycemia and for improvement of hypoglycemic detection during normal daily activities. Twenty-one adults (13 men) with T1D prone to hypoglycemia were recruited and monitored with CGM and a Holter device while they performed normal daily activities. We used our developed algorithm (a pattern classification method) to predict spontaneous hypoglycemia based on CGM and HRV. We compared 3 different models; (i) a model containing raw data from the CGM device; (ii) a CGM* model containing data derived from the CGM device signal; and (iii) a CGM+HRV model-combining model (ii) with HRV data. A total of 12 hypoglycemic events (glucose levels < 3.9 mmol/L, 70 mg/dL) and 237 euglycemic measurements were included. For a 20-minute prediction, model (i) resulted in a ROC AUC of 0.69. If a high sensitivity of 100% was chosen, the corresponding specificity was 69%. (ii) The CGM* model yielded a ROC AUC of 0.92 with a corresponding sensitivity of 100% and specificity of 71%. (iii) The CGM+HRV model yielded a ROC AUC of 0.96 with a corresponding sensitivity of 100% and specificity of 91%. Data shows that adding information of autonomic modulation to CGM measurements enables prediction and improves the detection of hypoglycemia.

Keywords: continuous glucose monitoring; diabetes; heart rate variability; hypoglycemia; prediction.

Figure 1.

The line represents an individual patient CGM profile and the circles the corresponding single measurement of glucose (SMG), such as blood plasma glucose or self-monitoring of blood glucose levels from midnight Friday (F 00) to midnight Monday (M 00).

Figure 2.

An illustration of the window used for prediction of a single measurement of glucose (SMG) outcome. In this example, CGM and HRV data 10 minutes prior to the SMG reading are used for prediction.

Figure 3.

The left side (A) shows the performance (ROC, AUC, and specificity) of models ii and iii as a function of prediction time, such that a prediction of 30 minutes will give a 30-minute forecast. The right side (B) shows the ROC for the 3 models with a 20-minute prediction (i, ii, iii).