Continuous Glucose Monitoring Aids Some With Type 2 Diabetes

Miriam E Tucker

August 21, 2017

Continuous glucose monitoring (CGM) may benefit adults with type 2 diabetes who use multiple daily insulin injections, new research suggests.

The findings were published online August 21 in the Annals of Internal Medicine by Roy W Beck, MD, PhD, executive director of the Jaeb Center for Health Research, Tampa, Florida, and colleagues.

In the trial of 158 patients with type 2 diabetes using multiple daily insulin injections, improvements in HbA1c at 24 weeks were significantly better among the 79 randomized to use CGM than in a control group of the same number, which used only blood glucose meter testing.

While the benefit of CGM has been well-established in patients with type 1 diabetes, use in those with insulin-using type 2 patients has been less well-studied, even though far more insulin users have type 2 and their glycemic control remains suboptimal despite their insulin use, Dr Beck and colleagues note.

"This randomized trial demonstrates that CGM can be beneficial for adults with type 2 diabetes treated with basal–bolus insulin therapy….Because few insulin-treated patients with type 2 diabetes are currently prescribed CGM, the study results indicate an additional management method that may be beneficial for these patients," the authors write.

In an accompanying editorial, Vanessa Arguello, MD and Matthew Freeby, MD, of the David Geffen School of Medicine at the University of California, Los Angeles, called the study "well-executed" and said it showed that real-time CGM "improves diabetes control, albeit modestly, compared with [meter testing]."

However, Drs Arguello and Freeby also note several remaining caveats to widespread CGM use, including the need for education on its use and cost concerns. Insurance coverage for CGM in type 2 diabetes patients in the United States is currently limited, pending more cost/benefit data.

And, they add, the requirement for daily calibration using blood glucose meter readings and the invasive nature of the CGM devices may also limit wider acceptance.

"Clinicians should carefully select [real-time] CGM candidates who may achieve maximum clinical utility, such as those who have [type 1 diabetes], high risk for hypoglycemia, and high medical literacy; those who adhere to medical device instructions; and now patients with [type 2 diabetes] receiving multiple daily injections of insulin," the editorialists say.

Greater Drop in HbA1c, Longer Time in Target Range

Study eligibility criteria included age at least 25 years, type 2 diabetes treated with multiple daily injections for at least 1 year, and HbA1c 7.5% to 10.0%. The subjects had a mean age of 60 years and median diabetes duration of 17 years.

At 12 weeks, mean HbA1c levels had dropped from baseline 8.5% in both groups to 7.5% in the CGM group and 7.9% in the controls (= .005). From week 12 to week 24, HbA1c increased slightly, to 7.7% in the CGM group vs 8.0% in the controls (= .022 for adjusted difference in mean change from baseline to 24 weeks).

That difference of -0.3% in HbA1c reduction between the groups at 24 weeks "is a meaningful improvement on a patient level, particularly because it was achieved without a pharmacologic change," according to the authors.

None of the prespecified secondary outcomes, including proportion of patients with HbA1c < 7.0% or 7.5% or a relative reduction of at least 10%, reached statistical significance, although they favored the CGM group. HbA1c results also favored CGM in subgroup analyses based on educational level and diabetes numeracy.

Median time in the range of 3.89 to 9.99 mmol/L (70 to 180 mg/dL) increased more in the CGM group than in the control group (measured via blinded CGM 1 week each before the 12-week and 24-week visits), from 802 minutes per day at baseline to 882 minutes per day at 24 weeks in the CGM group and from 794 to 836 minutes per day in the control group.

Hypoglycemia rates were extremely low at baseline in both groups (median time below 3.89 mmol/L [70 mg/dL], 11 minutes/day in the CGM group and 12 minutes/day in the control group), so the ability to assess the impact of CGM on that parameter was limited. There were no episodes of severe hypoglycemia or diabetic ketoacidosis in either group.

The CGM group gained a mean of 1.3-kg body weight from baseline, while this figure dropped by 0.2 kg in the controls. The two groups didn't differ in any of five quality-of-life measures, but the CGM group had high satisfaction with use of CGM, as indicated by the mean score of 4.3 (from a range of 1 to 5) on the CGM Satisfaction Scale.

Drs Arguello and Freeby write: "With these data, we should seek to further understand patient populations that will benefit most from CGM intervention, such as those with the skills to address glucose variability.

"Future randomized-trial CGM studies must also assess whether this approach improves healthcare outcomes for [type 2 diabetes]; its financial effects on the healthcare system; and further generalizability in [type 2 diabetes] subgroups, such as those with higher risk for hypoglycemia," they conclude.

The study was funded by Dexcom. Dr. Beck reports grants from Dexcom during the conduct of the study and other support from Dexcom and Abbott Diabetes Care outside the submitted work. Disclosures for the coauthors are listed in the paper. The editorialists report no relevant financial relationships.

Ann Intern Med. Published online August 21, 2017. Abstract,  Editorial

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