CGM Use in Type 1 Diabetes Management May Mitigate Risk of Retinopathy

Risa M. Wolf, MD

Credit: Johns Hopkins University School of Medicine

Continuous glucose monitoring (CGM), an integral tool in diabetes care, was associated with a reduced likelihood of developing diabetic retinopathy and proliferative diabetic retinopathy (PDR) in adults with type 1 diabetes (T1D).¹

The retrospective cohort study involved a diverse population of adults with T1D who had consultations at an academic tertiary diabetes center and ophthalmology center between 2013 and 2021. The positive association with CGM use remained after adjustment for hemoglobin A1c (HbA1c) levels in this adult population.

“As the use of CGM in the management of T1D continues to increase, it may help mitigate the development of DR and vision loss related to diabetes, and thus should be encouraged in the management of diabetes,” wrote the investigative team led by Risa M. Wolf, MD, division of pediatric endocrinology, department of pediatrics, Johns Hopkins University School of Medicine.

Development of diabetic retinopathy, a global leading cause of irreversible blindness, is linked to higher hemoglobin levels and a longer duration of diabetes in patients with diabetes.² Adults with T1D often experience a significant risk for retinopathy complications, given the disease’s earlier onset and inherent glycemic variability, compared with those with type 2 diabetes.

Without the use of intensive insulin therapy, landmark results have found nearly half of patients with T1D developed DR during a mean timeline of 6.5 years.³ On the other hand, intensive insulin therapy combined with a reduction in HbA1c levels could significantly reduce the risk for retinopathy.

Emergence of diabetes technologies, including CGM and insulin pumps, has become the standard of care for modern diabetes management. However, a knowledge gap exists apparent on the potential for outcomes associated with diabetes-related complications, particularly for adults with T1D using CGM.¹

For this analysis, Wolf and colleagues examined whether CGM, insulin pump, or a combination of both was associated with a lower retinopathy risk, including PDR, in patients with T1D. Utilizing the Johns Hopkins Endocrine and Diabetes Center and the Wilmer Eye Institute, the study included 550 adults with T1D with a median duration of diabetes of 20 years and a median HbA1c of 7.8%.

During the study period, 345 (62.7%) patients used CGM, 320 (58.2%) patients used an insulin pump, and 261 (47.5%) used both CGM and an insulin pump. Among the study population, 44.4% of patients (n = 224) were diagnosed with diabetic retinopathy at any point.

Upon univariate analysis, the use of CGM was associated with a lower risk of retinopathy (odds ratio [OR], 0.53; 95% CI, 0.37 - 0.75; P <.001) and PDR (OR, 0.40; 95% C, 0.26 - 0.62; P <.001), compared with no CGM use. In addition, CGM and pump use together were associated with a lower likelihood of PDR (OR, 0.60; 95% CI, 0.38 - 0.94; P = .03).

Further multivariable logistic regression analysis, adjusted for age, sex, race and ethnicity, diabetes duration insurance type, mean HbA1c, and micro- and macrovascular complications revealed CGM use was significantly associated with a lower likelihood of retinopathy (OR, 0.52; 95% CI, 0.32 - 0.84; P = .008), as well as PDR (OR, 0.42; 95% CI, 0.23 - 0.75; P = .004), compared with no CGM use.

A longitudinal analysis of retinopathy progression included 418 individuals who had ≥2 separate ophthalmology visits—after 55 were excluded due to baseline PDR, 363 were left for analysis. Among this population, 79 (21.8%) exhibited progression of DR during the study period, while the remaining patients remained stable over the study period.

In an accompanying editorial, Estelle M. Everett, MD, David Geffen School of Medicine, University of California, Los Angeles, suggested the unique advantage of CGM in preventing retinopathy could be particularly beneficial for groups at high risk for retinal complications.⁴

“Given that individuals with similar HbA1c levels may have very different glucose profiles, the association of CGM use with reduced odds of retinopathy may be related to the ability of CGM to capture more detailed aspects of a patient’s glucose trends, including short-term glycemic variability,” Everett wrote.⁴

In a recent episode of HCPLive’s Diabetes Dialogue, guest Viral Shah, MD, a professor of medicine at Indiana University, described results from a recent retrospective analysis of CGM data from more than 160 adults with T1D.⁵ These results showed CGM metrics, including time-in-range, time-in-tighter-range, time-above-range, and mean glucose, were associated with an increased risk for incident diabetic retinopathy in T1D.

“Whether you use the HbA1c or you use the time-in-range, what it suggests is that both metrics are providing us a very similar information about an individual’s glycemic control, as well as the long-term in association with microvascular complications,” Shah explained.

References

1. _{Liu TYA, Shpigel J, Khan F, et al. Use of Diabetes Technologies and Retinopathy in Adults With Type 1 Diabetes. JAMA Netw Open. 2024;7(3):e240728. doi:10.1001/jamanetworkopen.2024.0728}
2. _{Foster NC, Beck RW, Miller KM, et al. State of Type 1 Diabetes Management and Outcomes from the T1D Exchange in 2016-2018 [published correction appears in Diabetes Technol Ther. 2019 Apr;21(4):230]. Diabetes Technol Ther. 2019;21(2):66-72. doi:10.1089/dia.2018.0384}
3. _{Diabetes Control and Complications Trial Research Group, Nathan DM, Genuth S, et al. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med. 1993;329(14):977-986. doi:10.1056/NEJM199309303291401}
4. _{Everett EM. Leveraging Continuous Glucose Monitors to Reduce the Risk of Diabetic Retinopathy. JAMA Netw Open. 2024;7(3):e240718. doi:10.1001/jamanetworkopen.2024.0718}
5. _{Diana Isaacs P, Natalie Bellini D. Diabetes dialogue: Time in range, CGM Metrics for predicting outcomes in diabetes. HCP Live. February 20, 2024. Accessed March 6, 2024. https://www.hcplive.com/view/diabetes-dialogue-time-in-range-cgm-metrics-for-predicting-outcomes-in-diabetes.}