Continuous glucose monitoring (CGM) may improve awareness and reduce the risk for severe hypoglycemia in patients with longstanding type 1 diabetes.
The findings were published online November 28 in the Journal of Clinical Endocrinology & Metabolism, by Michael R Rickels, MD, of the University of Pennsylvania, Philadelphia, and colleagues.
The study included 11 patients with type 1 diabetes of at least 10 years’ duration who had experienced either severe hypoglycemia or frequent episodes of moderate hypoglycemia despite efforts at intensive glycemic control.
Use of CGM (seven Dexcom, four Medtronic) for up to 18 months improved awareness of hypoglycemia and reduced the number of problematic episodes but did not completely restore the necessary endogenous glucose production for preventing or correcting low blood glucose.
“Significant residual defects in glucose counterregulation remain and will require alternative approaches to achieve more complete recovery of defense mechanisms against the development of low blood glucose,” Dr Rickels and colleagues write.
Once established, hypoglycemia unawareness in type 1 diabetes is associated with a 20-fold greater risk for severe hypoglycemia, which contributes to disease-related morbidity and mortality, the authors point out.
Asked to comment, Dr Mark L Evans, of the University of Cambridge, United Kingdom, told Medscape Medical News, “The clinical importance of this study is that it suggests that CGM may help reduce the burden of hypoglycemia.”
However, he added, “it is important to acknowledge that CGM was applied here in conjunction with an intense package of clinical support, so it is difficult to know how much of the benefit was attributable to CGM per se and how much to the extra contact.”
Dr Evans was a coinvestigator for the Hypo COMPASS trial, which showed improvement in hypoglycemic awareness with a focused training program.
“The good news is that, similar to previous studies like [Hypo COMPASS], there was a significant reduction in severe hypoglycemia episodes and an increase in self-reported awareness of low blood glucose. The perhaps-disappointing finding was that the underpinning physiological defenses against hypoglycemia measured experimentally here remained largely impaired.”
The implication, Dr Evans said, is that “CGM systems might not be helpful as a ‘short-term fix,’ being used temporarily to reset the body’s defenses and to reverse problematic hypoglycemia. Rather, the benefits would be realized only while still using CGM.”
Benefits Seen While Wearing the Devices
The 11 patients had a type 1 diabetes duration of 31 years and experienced severe and/or frequent hypoglycemia, often with extreme glycemic lability. Once equipped with and trained in use of the CGM, they had monthly visits until month 6 and then every 3 months until month 18. They also received frequent phone calls from the study team for the first month, but less so thereafter.
Endogenous glucose counterregulation was assessed with paired hyperinsulinemic stepped-hypoglycemic and euglycemic clamp testing before CGM initiation and at 6 and 18 months after.
A group of 13 controls without diabetes matched for sex, race, age, and body mass index (BMI) were also studied for comparison.
Over the 18 months, there were no changes in insulin-delivery method (pump or multiple daily injections), dose requirements, sensor mean glucose, or HbA1c. And, there were no differences in time spent in hyper- or hypoglycemia, including overnight.
However, there was a trend toward reduced glucose variability as assessed by the CGM (P = .07), a significant reduction in severe hypoglycemia events (P < .01), and significant improvement in both hypoglycemia awareness as assessed by the Clarke score (P < .01) and severity via the HYPO score (P < .001). There was also a trend for a reduction in glycemic lability assessed by finger-stick glucose measurements (P = .1).
In response to insulin-induced hypoglycemia during the clamp test, there were no differences from baseline to 6 or 18 months in glucagon or epinephrine levels, with both remaining significantly lower for the type 1 diabetes patients compared with the controls at all time points (P < .01 for glucagon, P < .001 for epinephrine).
Endogenous glucose production didn’t change from baseline to 6 months but had improved by 18 months in the type 1 diabetes patients (P < .05 compared with baseline), while still remaining lower than in controls (P ≤ .01).
Dr Evans told Medscape Medical News: “One major hope is that linking CGM systems to insulin delivery with ‘closed-loop’ insulin-delivery systems will bring greater benefits than CGM alone.…We all look forward to seeing how this area progresses.”
The authors report no relevant financial relationships. Dr Evans has sat on advisory boards for and received travel support from Medtronic.
J Clin Endocrinol Metab. Published online November 28, 2017. Abstract
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