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Time In Range Associated With Diabetic Retinopathy

Jan 5, 2019
Editor: Joy Pape, MSN, FNP-C, CDE, WOCN, CFCN, FAADE

Author: Angela Reyes, Pharm.D. Candidate, LECOM College of Pharmacy

By assessing time in target glucose range using a continuous glucose monitor, a person with type 2 diabetes can get a measure risk for diabetic retinopathy.

Continuous glucose monitoring is a way to keep track of glucose levels at any time of the day. It can keep a person who has diabetes in the know about when their glucose is going too high or too low which improves glycemic control. It also can detect the time in range (TIR), or the time an individual spends within the target glucose range. This can be beneficial in helping the person know which therapies are working for them, evaluate the duration of hypoglycemic or hyperglycemic events over time, and help discover any relation between TIR and complications.

Diabetic retinopathy is a microvascular complication of diabetes caused by long term damage usually from uncontrolled blood glucose levels. Diabetic retinopathy can lead to severe visual impairment. It is the most common cause of blindness in adults. A recent study just published examines the association between the TIR data of people who have type 2 diabetesand incidence of diabetic retinopathy.

The study looked at a total of 3,262 patients with type 2 diabetes. A continuous glucose monitor was inserted and collected 288 sensor values over 3 consecutive days. After 3 days the data was used to calculate the time in range value defined as time spent within the target glucose range of 3.9-10.0 mmol/L during a 24hour period. Diabetic retinopathy was classified based on severity as either non-DR, mild non-proliferative DR, moderate non-proliferative DR, and vision threatening DR. The continuous variables were assessed using ANOVA for normally distributed variables and Jonckheere-Terpstra test for non-normally distributed data. The Cochran-Armitage test was used to examine trends across groups and the Spearman correlation for association between severity of retinopathy and time in range.

Results found 23.9% of the enrolled participants were affected by diabetic retinopathy. Patients with longer duration of diabetes had the more severe cases of diabetic retinopathy. When subjects were stratified according to how much time they were in target range, those with time in range over 86% of the time had less prevalence of severe diabetic retinopathy. A multinomial logistic regression model showed associations between time in range and prevalence of retinopathy by severity with the group with most time in range being an independent factor for all stages of diabetic retinopathy even after adjusting for risk factors like HbA1c. Glucose variability also had an independent effect on time in range and retinopathy.

These finding show continuous glucose monitoring can be an effective way to gauge whether a patient is at risk of developing a complication from having diabetes like retinopathy. HbA1c is the now considered gold standard when it comes to judging a person’s glycemic control and risk for micro or macrovascular complications. However, HbA1c can vary among ethnic groups, or in patients with blood disorders like anemia. It also gives a 2-3 month range of how glucose levels were controlled and does not give the variations in range that could be taking place daily. The time in target range has an impact on risk of complications and therefore is an accurate data point when assessing a patient. This study showed measuring a patient’s time in range could potentially be an acceptable clinical measure to assess risk of complications in diabetes.

Practice Pearls

  • Continuous glucose monitoring is an accurate way to assess glycemic control among patients with diabetes.
  • Greater time in target glucose range was associated with less risk of severe diabetic retinopathy.
  • Continuous glucose monitoring can help assess risk of retinopathy and possibly other diabetes complications through assessment of time in range data.


Jingyi Lu, Xiaojing Ma, Jian Zhou, Lei Zhang, Yifei Mo, Lingwen Ying, Wei Lu, Wei Zhu, Yuqian Bao, Robert A. Vigersky, Weiping Jia. Association of Time in Range, as Assessed by Continuous Glucose Monitoring, With Diabetic Retinopathy in Type 2 Diabetes. Diabetes Care (Sep 2018) dc181131; DOI: 10.2337/dc18-113

Angela Reyes, Pharm.D. Candidate, LECOM College of Pharmacy