Dexcom G6 Continuous Glucose Monitors (CGM)
LOS ANGELES — Are metrics derived from continuous glucose monitoring more predictive of all-cause mortality in diabetes patients than standard blood tests such as hemoglobin A1C?
A new study has suggested that is the case. Researchers from UCLA and the Phoenix, AZ, VAMC and colleagues found that metrics derived from continuous glucose monitors (CGM) were associated with all-cause mortality in diabetes patients and might better capture long-term risk associated with glucose fluctuations and periods of hypo- and hyperglycemia than hemoglobin A1C.
The study sought to investigate the association between CGM-derived glucose metrics and all-cause mortality in patients with Type 1 or Type 2 diabetes (T1D or T2D). The results were published in Diabetes Care.1
Data was analyzed from 2,752 veterans who had diabetes—65% of them diagnosed with T2D—from the VHA. All of the participants, who received Dexcom CGM between 2015 and 2020, had 10 or more days of CGM data over landmark (LM) periods (14 days, 3 months and 6 months) merged with electronic health records.
The study team assessed all-cause mortality over 5 years from CGM initiation. Cox models evaluated associations between mortality and CGM metrics:
- mean glucose (MG, mg/dL),
- time in range (TIR, %),
- time above range (TAR, %),
- coefficient of variation (CV) and
- glycemic risk index (GRI, %).
The authors advised that the mean age at CGM initiation was 64 years, and median CGM use was nearly 3 years. Overall, 407 of the participants died.
“In separate multivariable Cox models (adjusting for mortality-related variables), higher MG, TAR, CV, and GRI and lower TIR during the 6-month LM were associated with 5-year mortality (hazard ratios: MG 1.18, TAR 1.20, GRI 1.23, CV 1.18, and TIR 0.83; all P ≤ 0.01) and those associations remained significant after adjusting for LM HbA1c,,” the authors reported. “Results were similar with shorter CGM LM observation windows.”
The researchers pointed out that the association between CV and mortality was independent of other CGM metrics and appeared strongest in those with lower HbA1c levels.
They concluded, “CGM-derived metrics were associated with all-cause mortality in patients with diabetes and may better capture long-term risk associated with glucose fluctuations and periods of hypo- and hyperglycemia than HbA1c.”
Overall Morality Effect
A study earlier this year with some of the same researchers was published in Diabetes Technology & Therapeutics and looked at the overall effect on mortality of CGM initiation.2
“Although use of continuous glucose monitoring (CGM) has been linked with improved glucose control, including reductions in hemoglobin A1c and episodes of hypoglycemia, there has been little investigation of its possible role in reducing other serious clinical events,” the authors wrote.
The cohort study compared mortality between propensity score-matched CGM users and non-CGM users over 18 months. Included were VHA patients receiving insulin who were identified as CGM users or non-CGM users between Jan. 1, 2015, and Dec. 31, 2020.
Defined as the primary outcomes were all-cause mortality; secondary outcomes of serious all-cause hospitalization, cardiovascular events and admissions related to hyperglycemia and hypoglycemia.
For the study, 12,729 patients with T2D (94% male with mean age 66) who were new CGM users were 1:1 matched with non-CGM users; total follow-up time was 17,676 and 17,034 person-years for CGM and non-CGM users.
The results indicated that the risk for mortality was lower in CGM users (hazard ratio or HR 0.79: 95% confidence interval or CI 0.73-0.86), as were risks for all-cause hospitalization (0.91: 0.86, 0.96), cardiovascular events (0.84: 0.73, 0.96) and admissions for hyperglycemia (0.88: 0.81, 0.95).
“Lower risk for mortality persisted after accounting for early deaths, COVID-19, recent onset of diabetes, subsequent use of insulin pumps or newer diabetes medications, or when stratifying by frequency of CGM use, frailty index or mortality risk (all HRs: 0.83 or less, range of CI: 0.60-0.94),” the authors explained. “No differences between CGM and non-CGM users were seen with negative control outcomes”
They cautioned, however, that unmeasured health factors, behaviors or other confounders might have existed in some of the participants.
“In a large national cohort, initiation of CGM was associated with lower mortality in T2D patients using insulin and indicates use of CGM may have benefits that extend beyond glucose lowering,” the study concluded.
- Okuno T, Macwan SA, Norman GJ, Miller DR, Reaven PD, Zhou JJ. Continuous Glucose Monitoring Metrics Predict All-Cause Mortality in Diabetes: A Real-world Long-term Study. Diabetes Care. 2025 Aug 6:dc250716. doi: 10.2337/dc25-0716. Epub ahead of print. PMID: 40768053.
- Reaven PD, Macwan S, Newell M, Arani G, Norman GJ, Miller DR, Zhou JJ. Initiation of Continuous Glucose Monitoring and Mortality in Type 2 Diabetes. Diabetes Technol Ther. 2025 May 28. doi: 10.1089/dia.2025.0227. Epub ahead of print. PMID: 40432529.
