Glycaemic control and adult height: a nationwide Swedish cohort study on childhood type 1 diabetes.

Aims: To assess adult height outcomes across levels of glycaemic control in children and adolescents with type 1 diabetes, as well as to investigate the impact of sex, age at disease onset, and timing of glycaemic control in relation to puberty.

Methods: In this population-based Swedish cohort study, we collected data on glycaemic control and height from specialist healthcare visits of all individuals with childhood-onset type 1 diabetes in the National Diabetes Register. Using linear and logistic regression, we compared suboptimal (HbA1c 53-75 mmol/mol [7.0-9.0%]) and poor (HbA1c >75 mmol/mol [>9.0%]) to optimal (HbA1c <53 mmol/mol [<7.0%]) glycaemic control in relation to final adult height and the risk of short stature.

Results: Poor glycaemic control was associated with lower final adult height (-2.91 cm [95% CI - 3.48, -2.33] for males, -1.83 cm [-2.42, -1.23] for females) as well as a higher risk of short stature in males (odds ratio 1.90 [1.07, 3.35]) but not in females (0.73 [0.36, 1.51]). For females, adult height was only lower among those with type 1 diabetes since before puberty and if the poor glycaemic control occurred before puberty. For males, adult height was lower irrespective of their age at diabetes onset, but only if they had poor glycaemic control during or after puberty.

Conclusions: Poor glycaemic control after the onset of type 1 diabetes, compared to optimal control, is associated with lower adult height in males and females. The prepubertal period seems to be more critical for females than males.