Wider Use of CGM May Benefit People With Type 2 Diabetes

Miriam E. Tucker

June 02, 2021

Continuous glucose monitoring (CGM) can benefit a much broader group of patients with type 2 diabetes than those for whom it is currently recommended, and who have access to it, new research suggests.

The data come from two studies, both published online June 2 in JAMA.

One study, a randomized clinical trial, showed that CGM use resulted in significantly improved A1c at 8 months among adults with type 2 diabetes taking long-acting insulin alone without premeal insulin. The study will also be presented during the virtual 14th International Conference on Advanced Technologies & Treatments for Diabetes.

Currently, CGM use in type 2 diabetes is only strongly recommended for those taking both long-acting basal insulin and short-acting pre-meal bolus insulin.

"Until now we were unsure of the benefit [of CGM] for people with type 2 diabetes who were on less complicated background insulin regimens," said the study's lead author, Thomas Martens, MD, of the International Diabetes Center, Minneapolis, Minnesota, in a press release.

These data expand "the number of people who could benefit from these devices, and points to a possible future in which CGMs are common in primary care clinics across the US."

The other data come from a retrospective cohort study in a large California healthcare delivery system of insulin-treated patients with type 1 or type 2 diabetes selected by their primary care physicians for real-time CGM. Those with type 2 diabetes experienced a greater reduction in A1c than those with type 1 diabetes who initiated CGM.

Implications for Primary Care and Insurance Coverage  

The findings from both studies have important clinical and healthcare policy implications, Monica E. Peek, MD, and Celeste C. Thomas, MD, both of the University of Chicago, Illinois, write in an accompanying editorial.

First, they note that the randomized trial was conducted among people who don't typically have access to CGM. They were largely non-White, of lower educational attainment, and without private health insurance.

Moreover, that study was conducted in primary care settings in collaboration with study endocrinologists, a model the editorialists say could be implemented in primary care, particularly with telehealth.

Peek and Thomas also say the finding of a significant A1c reduction in patients on less intensive insulin regimens suggests the need for revision of the often-burdensome Medicare requirements that patients use multiple daily injections and conduct at least four fingerstick glucose measurements a day to qualify for reimbursement for CGM.   

"Important policy changes in Medicare eligibility to CGM for type 2 diabetes and institutional changes that promote its use in primary care will go a long way to improving diabetes control and reducing complications, particularly among the populations most in need. The time has come to broaden access to CGM for patients with type 2 diabetes," they write.

CGM Benefits Even Those With T2D Taking Basal Insulin Alone

In the randomized trial by Martens and coauthors, 176 patients with type 2 diabetes were recruited from primary care practices. All were on basal insulin but not pre-meal insulin, taking either one or two injections a day of long- or intermediate-acting insulin, with or without other glucose-lowering medications. They were randomized 2:1 to CGM (Dexcom G6, n = 116) or fingerstick blood glucose monitoring (n = 59).

At 8 months, mean A1c improved from 9.1% to 8.0% in the CGM group and from 9.0% to 8.4% in the control group, a significant adjusted difference of −0.4% (P = .02).

"This effect size may have been greater if the control group had received usual care rather than instructions on how to self-titrate insulin based on blood glucose monitoring data," Peek and Thomas write.

Time in range (time spent with blood glucose levels between 70-180 mg/dL) was 3.6 hours/day longer with CGM compared with fingerstick monitoring (59% vs 43%; P < .001). Mean length of time spent with glucose levels above 250 mg/dL was significantly lower with CGM (P < .001).

Mean overall glucose levels were 179 mg/dL with CGM versus 206 mg/dL among controls (P < .001). 

"Just because people are using background insulin doesn't mean they have control of their diabetes," said Martens.

"This is the first randomized controlled study to clearly show that CGM can be a key tool in allowing people with type 2 diabetes using background insulin to understand and effectively respond to their changing glucose levels." 

CGM Benefits Selected Insulin-Treated Patients With Type 2 Diabetes

In the second study, Andrew J. Karter, PhD, of Kaiser Permanente Northern California, Oakland, and colleagues, retrospectively analyzed data from 5673 patients with type 1 diabetes and 36,080 with type 2 diabetes who were taking insulin, mostly basal-bolus regimens. They compared the 3806 patients who started using CGM during 2014-2018 with 37,947 who did not initiate CGM. 

Over the 4 years, mean A1c levels dropped from 8.17% to 7.76% among CGM initiators and from 8.28% to 8.19% among noninitiators, a –0.40% difference in A1c reduction between groups (P < .001). The A1c reduction was greater among those with type 2 diabetes than type 1 diabetes (–0.56 vs –0.34 percentage points; P = .03).  

"The improvement in blood sugar control was comparable to what a patient might experience after starting a new diabetes medication," said Karter in a press release from Kaiser Permanente.

Rates of emergency department visits or hospitalizations for hypoglycemia dropped from 5.1% to 3.0% among CGM initiators, while increasing from 1.9% to 2.3% among noninitiators (P = .001 after adjustments). The difference in hypoglycemia reduction didn't differ between the two diabetes types.

"Selective prescribing of CGMs may partially explain the benefits we saw in these patients with type 2 diabetes," added Karter. "Doctors appeared to have preferentially prescribed monitors to patients with a history of hypoglycemia or at high risk of hypoglycemia."

There was no effect of CGM on emergency department visits or hospitalizations for hyperglycemia or any nondiabetes reason overall or by diabetes type.

Peek and Thomas write of both studies: "The glycemic benefits may be primarily due to patient factors, such as insulin adherence and lifestyle modifications, and provide a powerful narrative that CGM may be a useful technology that helps control diabetes among multiple patient groups."

Both studies were funded by Dexcom. Martens' employer has reported receiving funds on his behalf for research and speaking support from Dexcom, Abbott Diabetes Care, Medtronic, Insulet, and Novo Nordisk; funding for speaking support from Medscape, American Diabetes Association, American Medical Group Association, and American College of Physicians; funding for publication support from American College of Physicians and Eli Lilly; and consulting support from Bigfoot Biomedical outside the submitted work. Martens' employer has a pending patent for Ambulatory Glucose Profile. Karter has reported receiving grants from Dexcom, the National Institute of Diabetes and Digestive and Kidney Diseases, the National Institute on Aging, the National Library of Medicine, and the Patient-Centered Outcomes Research Institute.

JAMA. Published online June 2, 2021. Study 1, Study 2, Editorial

Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape, with other work appearing in The Washington Post, NPR's Shots blog, and Diabetes Forecast magazine. She is on Twitter: @MiriamETucker.

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