Association Between Time-Weighted Haemoglobin A1c and Longitudinal Changes in Growth Parameters Among Children With Type 1 Diabetes: A Retrospective Cohort Study

Background: Managing early-onset type 1 diabetes requires balancing glycaemic control with developmental milestones.The relationship between cumulative glycaemic exposure and auxological outcomes in children has not been well characterised using time-weighted haemoglobin A1c (HbA1c).Objective: This study explored the longitudinal association between time-weighted average HbA1c and changes in height-for-age, weight-for-age, and body mass index z-scores among children diagnosed with type 1 diabetes.Methods: A retrospective cohort study included children aged 2-14 years with type 1 diabetes and ≥18 months of follow-up (n=200).The primary exposure was time-weighted average HbA1c.Outcomes were changes in height-for-age z-score (HAZ), weight-for-age z-score (WAZ), and BMI z-score (BMI-z).Linear mixed-effects models adjusted for age, sex, diabetes duration, insulin regimen, and pubertal status.Results: Mean age was 9.5 ± 2.8 years, with 105 (52.5%) female subjects.Mean diabetes duration was 4.8 ± 3.2 years.A significant negative association was found between time-weighted average HbA1c and ΔHAZ (β = -0.15,95% CI: -0.26 to -0.04, p < 0.01).Positive associations were identified with ΔWAZ (β = 0.08, 95% CI: 0.01-0.15,p<0.05) and ΔBMI-z (β = 0.10, 95% CI: 0.03-0.17,p<0.01).At baseline, suboptimal glycaemic control (HbA1c > 7.5%) was present in 116 (58.0%) of participants.The negative effect on HAZ was most pronounced in children with a diabetes duration >5 years (β = -0.22,p = 0.003) and in those with a baseline HbA1c >9% (β = -0.28,p < 0.001).Conclusions: Lower time-weighted HbA1c, reflecting early and sustained glycaemic control, is associated with enhanced linear growth and a more favourable weight profile in children with type 1 diabetes.