Initiation of Continuous Glucose Monitoring and Mortality in Type 2 Diabetes

Background: 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. Objective: To estimate the effect of starting CGM in patients with type 2 diabetes (T2D) on mortality. Research Design: A cohort study comparing mortality between propensity score-matched CGM users and non-CGM users over 18 months. Setting: Veterans Affairs Health Care System. Participants: Adult patients with T2D receiving insulin who were identified as CGM users or non-CGM users between January 1, 2015, and December 31, 2020. Measurements: Primary outcome of all-cause mortality; secondary outcomes of serious all-cause hospitalization, cardiovascular events, and admissions related to hyperglycemia and hypoglycemia. Results: A total of 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. 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). No differences between CGM and non-CGM users were seen with negative control outcomes. Limitations: Unmeasured health factors, behaviors, or other confounders may exist. Conclusion: 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.