Effect of Continuous Glucose Monitoring on Glycemic Control in Patients With Type 2 Diabetes Treated With Basal Insulin: A Randomized Clinical Trial

Abstract

Importance: Continuous glucose monitoring (CGM) has been shown to be beneficial for adults with type 2 diabetes using intensive insulin therapy, but its use in type 2 diabetes treated with basal insulin without prandial insulin has not been well studied.

Objective: To determine the effectiveness of CGM in adults with type 2 diabetes treated with basal insulin without prandial insulin in primary care practices.

Design, setting, and participants: This randomized clinical trial was conducted at 15 centers in the US (enrollment from July 30, 2018, to October 30, 2019; follow-up completed July 7, 2020) and included adults with type 2 diabetes receiving their diabetes care from a primary care clinician and treated with 1 or 2 daily injections of long- or intermediate-acting basal insulin without prandial insulin, with or without noninsulin glucose-lowering medications.

Interventions: Random assignment 2:1 to CGM (n = 116) or traditional blood glucose meter (BGM) monitoring (n = 59).

Main outcomes and measures: The primary outcome was hemoglobin A1c (HbA1c) level at 8 months. Key secondary outcomes were CGM-measured time in target glucose range of 70 to 180 mg/dL, time with glucose level at greater than 250 mg/dL, and mean glucose level at 8 months.

Results: Among 175 randomized participants (mean [SD] age, 57 [9] years; 88 women [50%]; 92 racial/ethnic minority individuals [53%]; mean [SD] baseline HbA1c level, 9.1% [0.9%]), 165 (94%) completed the trial. Mean HbA1c level decreased from 9.1% at baseline to 8.0% at 8 months in the CGM group and from 9.0% to 8.4% in the BGM group (adjusted difference, -0.4% [95% CI, -0.8% to -0.1%]; P = .02). In the CGM group, compared with the BGM group, the mean percentage of CGM-measured time in the target glucose range of 70 to 180 mg/dL was 59% vs 43% (adjusted difference, 15% [95% CI, 8% to 23%]; P < .001), the mean percentage of time at greater than 250 mg/dL was 11% vs 27% (adjusted difference, -16% [95% CI, -21% to -11%]; P < .001), and the means of the mean glucose values were 179 mg/dL vs 206 mg/dL (adjusted difference, -26 mg/dL [95% CI, -41 to -12]; P < .001). Severe hypoglycemic events occurred in 1 participant (1%) in the CGM group and in 1 (2%) in the BGM group.

Conclusions and relevance: Among adults with poorly controlled type 2 diabetes treated with basal insulin without prandial insulin, continuous glucose monitoring, as compared with blood glucose meter monitoring, resulted in significantly lower HbA1c levels at 8 months.

Trial registration: ClinicalTrials.gov Identifier: NCT03566693.

Conflict of interest statement

Conflict of Interest Disclosures: All authors received grant funding from Dexcom to their institution for the conduct of the submitted study. Dr Martens’ employer, International Diabetes Center, participated in this study as a study site and was reimbursed for that participation by grant funding (Dexcom sponsor) during the conduct of the study. Additionally, Dr Martens’ employer has received 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. Dr Martens’ employer has a pending patent for Ambulatory Glucose Profile (issued to the International Diabetes Center). Dr Beck reported his institution receiving grant funding and study supplies from Tandem Diabetes Care and Beta Bionics; study supplies from Medtronic, Ascencia, and Roche; consulting fees and study supplies from Eli Lilly and Novo Nordisk; and consulting fees from Insulet, Bigfoot Biomedical, vTv Therapeutics, and Diasome. Ms Ruedy reported receiving grants to her institution from Tandem Diabetes Care and Beta Bionics and study supplies from Novo Nordisk and Eli Lilly outside the submitted work. Dr Calhoun reported being a former employee of Dexcom Inc and his current employer receiving consulting payments on his behalf from vTv Therapeutics, Beta Bionics, and Diasome. Dr Peters reported serving on advisory boards for Abbott Diabetes Care, Eli Lilly, Medscape, Novo Nordisk, and Zealand; receiving nonfinancial study supplies from Abbott Diabetes Care; and owning stock options for Omada Health and Teladoc. Dr Pop-Busui reported receiving personal fees from Averitas, Nevro, Novo Nordisk, Boehringer Ingelheim, and Bayer and grants from AstraZeneca outside the submitted work. Dr Philis-Tsimikas reported that her employer has received funds on her behalf for research support, education support, consulting, or serving on the scientific advisory boards for Abbott Diabetes Care, Johnson & Johnson, Eli Lilly, Medscape, Medtronic, Novo Nordisk, Roche, Sanofi, and UnitedHealthCare. Dr Bao reported receiving research funding, paid to her institution, from Novo Nordisk, Mylan, AstraZeneca, and Bristol Myers Squibb. Dr Umpierrez reported research funding paid to his institution from Novo Nordisk and AstraZeneca. Dr Davis reported grants paid to her institution from Insulet and the National Institutes of Health outside the submitted work. Ms Kruger reported receiving consulting and research funds from Abbott Diabetes, consulting and speaking fees from Eli Lilly, consulting fees from Sanofi Aventis, speaker fees from Xeris Pharmaceuticals, and speaking, consulting, and research funding from Novo Nordisk. Dr Bhargava reported receiving grants from Jaeb Center for Health Research during the conduct of the study and research grant–related funding from Abbott Diabetes, AbbVie, Amgen, AstraZeneca, Bayer, Boehringer Ingelheim Pharmaceuticals, Boston Therapeutics, Bristol Myers Squibb, Covance, Eli Lilly, Eversense, Gan & Lee Pharmaceuticals, Insulet, Janssen, Kowa Pharmaceuticals, Madrigal Pharmaceuticals, Medtronic, Merck, Mylan, Novo Nordisk, Poxel, Rhythm Pharmaceuticals, Quintiles, Sanofi Aventis, Senseonics, Teijin America Inc, Theracos Sub LLC, Tolerion, United Biosource Corp, and Viking and personal fees from AstraZeneca, Eli Lilly & Company, and Sanofi Aventis outside the submitted work. Dr Young reported grants to her institution from Eli Lily, vTv Therapeutics, Novo Nordisk, Boehringer Ingelheim Pharmaceuticals Inc, Sanofi, Tolerion, and Bayer outside the submitted work. Dr McGill reported her institution received grants from the National Institutes of Health and Beta Bionics and that she received advisory board fees from Bayer, Eli Lilly, Metavant, and Salix; personal fees from Aegerion, Bayer, Boehringer Ingelheim, Dexcom, Eli Lilly, Janssen, MannKind, Metavant, Novo Nordisk, and Valeritas; consultancy fees from Boehringer Ingelheim; and grants, paid to her employer, from Medtronic and Novo Nordisk. Dr Aleppo reported grants paid to her institution from AstraZeneca, Eli Lilly, Insulet, and Novo Nordisk and personal fees from Insulet outside the submitted work. Dr Nguyen reported receiving clinical trial fees from Las Vegas Endocrinology and that his employer has received funds on his behalf for research support, consulting, or serving on the scientific advisory boards for AstraZeneca, Sanofi Aventis, Novo Nordisk, Eli Lilly, Boehringer Ingelheim, and MannKind. Dr Biggs reported receiving research grant–related funding from Novo Nordisk, Mylan, Gan & Lee Pharmaceuticals, Roche Diabetes Care, and Dexcom outside the submitted work. Dr Polonsky reported receiving grants from Dexcom, Abbott Diabetes Care, Sanofi Aventis, Eli Lilly, Novo Nordisk, Boehringer Ingelheim, ProventionBio, Insulet, Adocia, and Intuity outside the submitted work. Dr Buse reported that his employer has received funds on his behalf for consulting and travel from Adocia, AstraZeneca, Dance Biopharm, Dexcom, Eli Lilly, Fractyl, GI Dynamics, Intarcia Therapeutics, Lexicon, MannKind, Metavention, NovaTarg, Novo Nordisk, Orexigen, PhaseBio, Sanofi Aventis, Senseonics, vTv Therapeutics, and Zafgen and research grants and travel support from AstraZeneca, Eli Lilly, Intarcia Therapeutics, Johnson & Johnson, Lexicon, Medtronic, NovaTarg, Novo Nordisk, Sanofi Aventis, Theracos, Tolerion, and vTv Therapeutics. Dr Price reported being an employee of Dexcom and holding stock in the company. Dr Bergenstal reported that his employer has received funds on his behalf for research support, consulting, or serving on the scientific advisory boards for Abbott Diabetes Care, Ascenia, Bigfoot Biomedical, Dexcom, Hygieia, Johnson & Johnson, Eli Lilly, Medscape, Medtronic, Novo Nordisk, Onduo, Roche, Sanofi Aventis, and UnitedHealthCare.

Figures

Figure 1.. Screening, Allocation, and Study Follow-up

BGM indicates blood glucose meter; CGM, continuous glucose monitoring; and HbA1c, hemoglobin A1c. aThree participants who wore CGM for less than 70% of the time during the 10-day prerandomization screening phase (≥70% was eligibility criterion) were randomized: 2 to the CGM group and 1 to the BGM group. bOne participant in each group was missing baseline data. cOne participant randomized to the CGM group who was determined after randomization to have type 1 diabetes was excluded from the analyses (participant had HbA1c level of 8.2% at baseline, 7.3% at month 3, and 6.8% at month 8).

Figure 2.. Hemoglobin A1c (HbA1c) Values at 8 Months

BGM indicates blood glucose meter; and CGM, continuous glucose monitoring. A, In this scatterplot, points below the diagonal line represent cases in which the 8-month HbA1c level was lower than the baseline level (80 [76%] in the CGM group vs 34 [67%] in the BGM group) and points above the diagonal line represent cases in which the 8-month HbA1c level was higher than the baseline level (23 [22%] in the CGM group vs 14 [27%] in the BGM group). Two participants in the CGM group and 3 in the BGM group had a baseline value equal to the 8-month value. B, For any given 8-month HbA1c level, the percentage of participants in each treatment group with a HbA1c value at that level or lower can be determined from the figure.