Time in Range: The New Gold Standard in Glucose Management
Time in range (TIR) is an actionable metric that captures the highs, lows and in-range glucose values that people with diabetes experience each day. Because TIR shows these daily fluctuations in glucose, the metric can be more useful and actionable than A1C.
Time in range (TIR) is an actionable metric that captures the percent of time that someone’s glucose is between 70 and 180 mg/dl. TIR, along with time below range (TBR) and time above range (TAR), as measured by a continuous glucose monitor (CGM), shows daily fluctuations in glucose and the amount of time spent high or low across several days. This information can be more useful and actionable than A1C, which only provides the average blood glucose and nothing about glucose variability. Knowing TIR and TBR helps to focus necessary action to improve glucose management.
TIR is strongly associated with HbA1C. As a result, it is also associated with diabetes complications. In other words, as a person with diabetes increases their TIR, they also lower their risk for complications.
Dr. Roy Beck, Jaeb Center for Research, further explained this relationship in his presentation at the 2022 American Diabetes Association (ADA) Scientific Sessions.
- “Since Time in Range is strongly associated with hemoglobin A1c and since hemoglobin HbA1C is clearly strongly associated with complications - then it follows that Time in Range must be associated with complications,” he said. And so far the data seems to back this up.
More specifically, time in range can effectively predict long-term diabetes complications, including eye disease (retinopathy), kidney disease, and a cardiovascular disease risk marker (carotid intima-media thickness).
Beck explained that the progression rate of retinopathy increases by 32% for each 0.5 percentage point increase in A1C and for each 6.2 percentage point decrease in TIR.
- Further, a person’s risk for having microalbuminuria (a risk factor for kidney disease) increases by 40% for each 10 percentage points lower TIR.
TIR is also associated with a better quality of life. One study demonstrated this relationship, showing that greater daily time in range is significantly associated with a more positive mood.
Limitations of Time in Range and HbA1C
“While TIR and HbA1C are both useful metrics for people with diabetes, they have limitations,” explained Dr. Grazia Aleppo of Northwestern University Feinberg School of Medicine.
“HbA1C has been known as the gold standard of diabetes management outcomes, but it does not provide information about hypoglycemia, hyperglycemia, or daily fluctuations in glucose levels,” she added. “Although TIR is an immediate, flexible way to view daily glucose patterns, many healthcare providers and people with T1DM diabetes aren’t familiar with the metric or how to use it.”
Acceptance of TIR by regulatory agencies in USA (like the FDA) and health insurance companies alike is currently low, whereas HbA1C has been accepted as a standard metric of glucose management for decades. It is better in Europe.
In addition to limited awareness and education, barriers preventing access to diabetes technology have limited the use of TIR. CGMs are needed to measure TIR.
Putting Time in Range into practice
To increase the awareness and use of TIR, clinicians should understand how they can put the metric into practice. If you believe a CGM and TIR could improve your diabetes management, but your healthcare team has never discussed these options with you, advocate for this technology at your next appointment and see if it could be an option for you.
According to Natalie Bellini, a diabetes nurse practitioner and certified diabetes educator at R&B Medical Group in Buffalo, New York, the DATAA Model can help healthcare professionals interpret CGM data and communicate with people about their TIR data – even for those providers who are less familiar.
The DATAA model is:
- Download Data: Look at how long a person with diabetes is wearing a CGM. Ideally, it should be at least 70% of the time.
- Assess for Safety: Review any occurrences of hypoglycemia - time below range (TBR).
- Time in Range: Focus on the positive – what worked well? Discuss TIR not as “good” or “bad” but as “high” or “not high” for those days.
- Areas to Improve: Address lows and then go back and review highs.
- Action plan with the individual with diabetes: This should be made in collaboration with the healthcare provider and person with diabetes. Changes to consider include:
- Lifestyle changes – Understand how physical activity and food affect glucose levels and make changes to increase TIR
- CGM optimization – customize alerts according to high and low glucose levels
- Medication adjustments – reduce basal insulin dose if snacking to avoid hypoglycemia overnight.
Perhaps most importantly, Bellini said, healthcare providers must create realistic expectations. “Don’t ask your patient to do what you can’t expect [them] to do,” she said.
Bellini emphasized that it’s important to address any episode of hypoglycemia first. After addressing the lows, it’s also important to focus on getting high glucose levels down.
The future of TIR
As we look to the
• future of TIR, more people continue to adopt the metric along with CGM. TIR,
• time below range (TBR) and
• time above range (TAR) should be used together with A1C to provide a complete picture of an individual’s diabetes management.
“Time in range alone is not enough,” said Dr. Irl Hirsch, Professor of Metabolism, Endocrinology and Nutrition at the University of Washington in Seattle.
- TBR must also be considered when discussing TIR in order to reduce the immediate risk from severe hypoglycemia episodes, while improving diabetes management.
- While TAR is also important and should be reduced if possible, hyperglycemia is more often associated with long-term complications. These metrics together help paint a clearer picture of a person’s glucose levels than TIR alone can provide.
Additionally, TIR goals are different for every person and may depend on medication, type of diabetes, diet, age, health, and risk of hypoglycemia. “What’s good for most people may not be good for everyone,” Hirsch cautioned.
“It’s important to recognize that no metric is absolutely perfect for diabetes management,” he said. With every new measurement comes the need to inform, increase access, and fully understand the effects on glucose management.
- As more people with diabetes continue to gain access to CGM and learn about TIR, this new metric may become the gold standard in glucose management.
www red DiabetologNytt