Assessment of Glucagon-like Peptide-1 Receptor Agonists in Veterans Taking Basal/Bolus Insulin Regimens
Background: Clinical use of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) is well established as add-on therapy to oral medications and basal insulin. However, there is little published data regarding the use of GLP-1 RAs for longer than 12 months in patients taking basal/bolus insulin regimens. The primary goal of our study was to assess the long-term efficacy of GLP-1 RAs as add-on therapy to basal/bolus insulin regimens.
Methods: This study was a retrospective record review of all patients on basal/bolus insulin regimens who received additional therapy with a GLP-1 RA. The primary outcome was the change in glycosylated hemoglobin A 1c (HbA 1c ) at 3, 6, 12, 18, and 24 months after initiation of the GLP-1 RA. Secondary outcomes included change in weight and total daily dose (TDD) of insulin and incidence of hypoglycemia and other adverse effects (AEs).
Results: Ninety-two patient records were reviewed. Mean glycemic control changed from baseline −1.1% (95% CI, −1.3 to −0.8; P < .001) at 3 months; −1.0% (95% CI, −1.3 to −0.7; P < .001) at 6 months; −0.9% (95% CI, 1.3 to −0.6; P < .001) at 12 months; −0.9% (95% CI, −1.4 to −0.3; P = .002) at 18 months; and −0.7 (95% CI, −1.4 to 0.1; P = .07) at 24 months. A significant decrease in weight was also observed from baseline through 18 months, and a significant decrease in TDD of insulin was identified from baseline through 12 months. Hypoglycemia was documented in 29.8% of patients at any point during GLP-1 RA therapy, and gastrointestinal AEs were documented in 18.3% of patients.
Conclusions: Adding GLP-1 RAs to complex insulin regimens may help achieve glycemic control while decreasing insulin requirements and mitigating undesirable AEs, such as weight gain.
Limitations and Strengths
Limitations of this study include a small patient population and a gradual reduction in available data as time periods progressed, making even smaller sample sizes for subsequent time periods. A majority of participants were older, males and White race. This could have limited the determination of statistical significance and applicability of the results to other patient populations. Another potential limitation was the retrospective nature of the study design, which may have limited reporting of hypoglycemia and other AEs based on the documentation of the clinician.
Strengths included the study duration and the diversity of GLP-1 RAs used by participants, as the impact of many of these agents has not yet been assessed in the literature. In addition, the retrospective nature of the study allows for a more realistic representation of patient adherence, education, and motivation, which are likely different from those of patients included in prospective clinical trials.
There are no clear guidelines dictating the optimal duration of concomitant GLP-1 RA and insulin therapy; however, our study suggests that there may be continued benefits past short-term use. Also our study suggests that patients with T2DM treated with basal/bolus insulin regimens may glean additional benefit from adding GLP-1 RAs; however, further randomized, controlled studies are warranted, particularly in poorly controlled patients requiring even more aggressive treatment regimens, such as concentrated insulins.
Conclusions
In our study, adding GLP-1 RA to basal/bolus insulin was associated with a significant decrease in HbA1c from baseline through 18 months. An overall decrease in weight and TDD of insulin was observed through 24 months, but the change in weight was not significant past 18 months, and the change in insulin requirement was not significant past 12 months. Hypoglycemia was observed in almost one-third of patients, and gastrointestinal symptoms were the most common AE observed as a result of adding GLP-1 RAs. More studies are needed to better evaluate the durability and cost benefit of GLP-1 RAs, especially in patients with high insulin requirements.
Acknowledgments
This material is the result of work supported with resources and facilities at Veteran Health Indiana in Indianapolis. Study data were collected and managed using REDCap electronic data capture tools hosted at Veteran Health Indiana. The authors also acknowledge George Eckert for his assistance with data analysis.
