CGM metrics for adults with type 1 diabetes do not differ between daytime, overnight hours
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Glycemic control was similar during the day compared with overnight for adults with type 1 diabetes using continuous glucose monitoring, regardless of HbA1c, according to study data.
In an analysis of CGM data from adults with type 1 diabetes participating in two studies, no differences in mean glucose, time in range or time in hyperglycemia were observed between daytime and overnight hours across five subgroups divided by HbA1c.
“Traditionally, providers usually focus on fasting glucose by changing long-acting insulin dose or basal rate on insulin pump,” Viral Shah, MD, associate professor of medicine and pediatrics in the adult clinic of the Barbara Davis Center for Diabetes at the University of Colorado Anschutz Medical Campus, told Healio. “Reduction in fasting glucose has been shown to reduce HbA1c, especially when HbA1c is higher. However, this approach leads to excessive basal relative to short-acting insulin. Higher basal rates may cause hypoglycemia. Our study suggests that HbA1c reduction can be obtained equally either by optimizing daytime or nighttime glucose. Therefore, providers should focus not only on fasting glucose reduction, but also postprandial glucose reduction.”
Shah and colleagues analyzed CGM data collected in two studies conducted at the Barbara Davis Center for Diabetes. The first study included adults with type 1 diabetes for at least 2 years using a Dexcom G6 CGM for at least 6 months. The second study included adults with type 1 diabetes who used their CGM at least 70% of the time in the previous 14 days. Mean sensor glucose, time in range between 70 mg/dL and 180 mg/dL and time in hyperglycemia were calculated using the last 14 days of the CGM data. Time in tighter range between 70 mg/dL and 140 mg/dL was also calculated. Daytime glycemic control was determined with CGM data from 6 a.m. to 10:59 p.m., and nighttime data were collected from 11 p.m. to 5:59 a.m. HbA1c was measured in the clinic. Participants were stratified into five groups based on HbA1c: less than 7%, between 7% and 7.9%, between 8% and 8.9%, between 9% and 9.9%, and 10% or more. Daytime and nighttime CGM data were compared within all five groups.
The findings were published in Diabetes Technology & Therapeutics.
There were 407 adults included in the study (mean age, 39.1 years; 53% women; mean HbA1c 7.3%). Across the full cohort, mean glucose and time in hyperglycemia increased, and time in range decreased as HbA1c increased. A strong correlation was observed between HbA1c and mean glucose in daytime (r = 0.83) and nighttime (r = 0.73). Shah said this correlation reveals a possible utility for GLP-1 receptor agonists and SGLT2 inhibitors among people with type 1 diabetes
“Though GLP-1 receptor agonists and SGLT2 inhibitors are not approved for managing type 1 diabetes, they are being used off-label in certain patients for weight and or cardiorenal benefits,” Shah said. “These drugs mainly affect postprandial glucose levels. Based on the findings of our study, despite the minimal effect of these agents on fasting glucose, these agents should be able to reduce HbA1c in people with type 1 diabetes because they would lower mean glucose by reducing postprandial blood glucose levels.”
A strong negative correlation was observed between HbA1c and time in range during the daytime (r = –0.8) and nighttime (r = –0.67). When daytime CGM data were compared with nighttime, however, there were no differences observed in mean glucose, time in hyperglycemia, time in range or time in tighter range. Additionally, within the five HbA1c groups, no differences were found with any CGM metrics.
Shah noted most of the participants in the study were white adults and more research is needed to confirm the findings within Hispanic and Black adults.
For more information:
Viral Shah, MD, can be reached at viral.shah@cuanschutz.edu.
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