Continuous Glucose Monitoring (CGM) has become an essential tool for managing diabetes, particularly in 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 person’s glucose levels remain within a target range. Previous research has established that higher TIR is associated with lower HbA1c levels, a common measure of long-term glucose control.
This study, conducted by Johnson et al. (2026), investigates the relationship between TIR and HbA1c in relation to CGM wear-time. Specifically, it compares data from youth with T1D who have a CGM wear-time of 70% or more to those with less than 70% wear-time. The authors aimed to determine whether the correlation between TIR and HbA1c remains significant even when CGM wear-time is lower.
Methodology
The study involved 60 youth participants diagnosed with T1D. Participants were divided into two groups based on their CGM wear-time: those with ≥70% wear-time and those with <70% wear-time. The researchers calculated Pearson correlations between TIR and HbA1c for each group and compared these correlations using a Fisher r-to-z transformation.
Results
The findings revealed significant correlations between TIR and HbA1c in both groups. For the group with ≥70% wear-time, the correlation coefficient was r = -0.800 (p < .001), indicating a strong negative association. In contrast, the group with <70% wear-time exhibited a weaker correlation (r = -0.404, p < .001). The difference in strength of association between the two groups was statistically significant (z = 3.15, p = .0016).
Conclusion
The results suggest that while a higher CGM wear-time enhances the reliability of the TIR-HbA1c association, there remains a statistically significant correlation even with lower wear-time. This finding indicates that healthcare providers may still find utility in TIR data derived from patients with less than optimal CGM wear-time, although caution is warranted in interpreting these results.
What this study does not show
This study does not establish a causal relationship between CGM wear-time, TIR, and HbA1c levels, nor does it address the clinical outcomes resulting from varying CGM wear-time.
Evidence scorecard
- Analytic validity: Established
- Clinical validity: Established
- Clinical utility: Not established
The evidence is based on primary research involving human participants.