Continuous Glucose Monitoring (CGM) has become an essential tool for managing diabetes, particularly for youth with type 1 diabetes (T1D). One of the key metrics derived from CGM data is Time-in-Range (TIR), which reflects the percentage of time a patient spends within a target glucose range. Research has indicated that a higher TIR, specifically above 70%, is associated with lower HbA1c levels, a common measure of long-term glucose control.
This study, published in the Journal of Diabetes and Its Complications, investigates the relationship between TIR and HbA1c in relation to CGM wear-time. The authors aimed to determine whether the reliability of TIR as a predictor of HbA1c diminishes with shorter CGM wear-time.
Methodology
The research involved a sample of 60 youth with T1D, categorized based on their CGM wear-time into two groups: those with ≥70% wear-time and those with <70% wear-time. The authors calculated Pearson correlations between TIR and HbA1c for each group and compared the strength of these correlations using a Fisher r-to-z transformation.
Results
Findings revealed that the correlation between TIR and HbA1c was significant in both groups. For the ≥70% wear-time group, the correlation coefficient was r = -0.800 (p < .001), indicating a strong inverse relationship. In contrast, the <70% wear-time group exhibited a weaker correlation (r = -0.404, p < .001). The statistical analysis confirmed that the association was significantly stronger in the ≥70% wear-time group (z = 3.15, p = .0016).
Conclusion
The study concludes that while the correlation between TIR and HbA1c is weaker in individuals with <70% CGM wear-time, it remains statistically significant. This suggests that even with lower wear-time, TIR may still provide valuable insights into glycemic control when necessary.
What this study does not show
This study does not establish a causal relationship between TIR and HbA1c levels, nor does it provide evidence on the clinical outcomes of relying on TIR data from lower CGM wear-time.
Evidence scorecard
- Analytic validity: Established
- Clinical validity: Established
- Clinical utility: Not established