Time in Tight Range (TITR)

There have been discussions on whether the concept and targets of TIR need revising [85], and that’s where TITR comes in. TITR represents the time spent in a narrower glycaemic range (70-140 mg/dL or 3.9-7.8 mmol/L), sometimes referred to as ‘normoglycaemia’ or ‘euglycaemic range’ as this is where people without diabetes spend most of their time. Several reasons have been suggested for this new and stricter target range.

First, the growing popularity of TITR aligns with the goal of T1D management: achieving an ambulatory glucose profile that is “Flat, Narrow, and In Range”. Second, advocating for TITR is based on the rationale that:

(a)     “It has become possible.” In other words, spending considerable time in this glucose range will become more and more realistic with further technological advancements. Automated insulin delivery (AID) systems will likely make it possible for more patients to achieve strict glucose target range goals.

(b)    “It will perhaps be needed.” TITR might be better related to the development of diabetes-related complications. Some researchers believe that focusing on TIR is insufficient to avoid complications.

However, the evidence on the association between TITR and diabetes-related complications is currently still limited, coming from one cross-sectional [86] and one retrospective longitudinal study [87]. Moreover, the studies have not demonstrated whether the association is independent of TIR, which is crucial before considering implementing TITR in clinical practice [88].

 

Glycaemic Variability

Glycaemic variability refers to fluctuations in glucose levels throughout the day and night. Frequent and excessive fluctuations can be clinically important [89]. In people with T1D, glycaemic variability is substantially higher than in people without diabetes [90], and higher levels of glycaemic variability are associated with more hypoglycaemic events [91-93], lower quality of life, and disrupted sleep [94, 95].

It remains unclear whether glycaemic fluctuations independently contribute to the development of vascular complications [89, 96-99]. The degree of variability might be significant, so it’s uncertain if frequent minor fluctuations are as important as more extreme ones.

The CGM consensus statement considers glycaemic variability an essential aspect and a clinically valuable marker of glucose management, which should be assessed, monitored, and treated [89, 100]. Currently, the coefficient of variation (CV%) is the primary measure used to evaluate glycaemic variability, with a target of less than 36% usually suggested for clinical management [73, 79].

 

Other CGM-Related Visuals and Parameters Related to Diabetes Management

The Ambulatory Glucose Profile, or AGP, has been widely implemented [101, 102] and continues to be refined with additional information [103]. In clinical practice, the Glucose Management Indicator (GMI) is increasingly being used as the ‘CGM-derived-HbA1c-equivalent’ [101, 104, 105]. CGM metrics are recognised for their ability to more adequately reflect an individual’s glucose management, but patients need to understand the meaning and use of these parameters.

It should be noted that CGM-derived metrics, such as Time Above Range, Time in Range, etc., are just numbers and do not necessarily explain the underlying cause of glucose management challenges. Therefore, the parameters should always be interpreted together with the individual CGM profiles, nutritional intake, and physical activity levels.

The Final Word: Education is Key

One major benefit of CGM is that individuals with T1D can analyse their data alongside healthcare professionals. Increasing access to knowledge and insight into CGM metrics may enhance shared decision-making. Therefore, patients should be involved as much as possible in interpreting these parameters.

Since people with T1D can now immediately observe the impact of food choices, physical activity, sedentary behaviour [106, 107], stress levels, and other factors, they can better understand how they affect TIR, hypoglycaemia risk, and glycaemic variability. People living with T1D can (and should) monitor these parameters themselves to improve their glucose management, and, importantly, this may also help reduce barriers to physical activity [108].

In conclusion, both people living with T1D and all caregivers of people with T1D who use CGM should be educated on the meaning, interpretation, and clinical use of the different key CGM metrics.