Use of continuous glucose monitoring and long-term diabetes outcomes within the Veteran Affairs Health Care System

Phoenix Va Health Care System, Phoenix AZ

Investigators

Abstract

Summary: Continuous glucose monitoring (CGM) is increasing rapidly in the Veterans Administration Health Care System (VAHCS). Experience with CGM is greatly modifying our concepts of glucose control and our understanding of how to define and achieve optimal glucose goals. Most available data on CGM has been derived from short-term small trials or observational studies conducted in classic early onset T1D patients and have illustrated the value of CGM in these patients with respect to glucose lowering and reduced hypoglycemia. However, much less is known about benefits of CGM in T1D that develops later in life nor in the far more frequent setting of T2D. There is also very little known about CGM related effects on the many serious, debilitating and costly diabetes complications that are so prevalent in both T1D and T2D. Because use of CGM has substantial financial costs and requires extensive time on the part of patients, physicians, nurses and other staff participating in diabetes care to implement and sustain CGM, we need to better understand how to best use CGM and what is gained from it. Our preliminary data demonstrate we can extract clinical and demographic information for T1D and T2D patients and evaluate the benefits of CGM initiation on short-term glucose control and several adverse outcomes. There is also a striking signal of potential benefits on major comorbidities such as renal disease, cardiovascular disease and even mortality. Now we propose to expand the years of data collection and follow-up time to directly focus on the benefits of CGM initiation on long-term clinically important outcomes. There will be three main aims for this project. In Aim 1, we will assess in T1D and T2D within the VAHCS the effect of CGM initiation (compared with matched nonCGM users) on the occurrence of ER or hospital admissions for hypoglycemia and hyperglycemia and all-cause hospital admissions over 4 years. In all three aims we will use overlap propensity score weighting to balance CGM users and nonusers and will conduct multiple sensitivity analyses to assess and adjust for potential bias in matching. As a secondary analyses we will compare the effects in T1D and T2D of initiating CGM on long-term glucose control. We will also examine baseline features, such as age, racial/ethnic identity, glycemic control, hypoglycemic risk, complication status, CGM type as well as patterns of CGM use to identify subgroups with differential long-term benefits of CGM on these outcomes. In Aim 2, we will assess in T1D and T2D the effects of CGM on development of renal disease and diabetes complications. To achieve this aim, we will compare the effects in T1D and T2D of initiating CGM (vs. nonCGM users) on development of a composite outcome indicating severe renal disease and assess change in a validated diabetes complication index score. As in Aim 1, we will also attempt to identify subgroups with differential benefits of CGM on these outcomes. We will also explore the contribution of improved HbA1c to CGM related improvements in outcomes. Aim 3 will build on promising preliminary data to examine the effects of CGM on a cardiovascular disease composite outcome (myocardial infarction, ischemic stroke and heart failure) and all- cause mortality. We will initially compare CGM users and nonusers in combined cohorts of T1D and T2D patients to ensure sufficient event numbers to detect small group differences, but will subsequently examine them in distinct groups. We will also conduct subgroup comparisons as described for Aims 1 and 2. To minimize differences in extent of follow-up between individuals we will initially limit follow-up time to 4 years, although secondary analyses will explore extending the follow-up time to 6 years where appropriate. This study will clarify the range of benefits that can be obtained with longer-term use of CGM, and determine if these extend well beyond improvements in glycemic control. These aims will determine whether CGM initiation may reduce multiple relevant outcomes and how to best identify these individuals. Results from this study could add prevention of serious clinical outcomes to the rationale for initiating CGM. Overall, the study will advance our ability to apply precision medicine in our application of CGM to both later-onset T1D and T2D patients.