Glycemic Control and Adult Height: A Nationwide Swedish Cohort Study on Childhood Type 1 Diabetes

Context: Normal growth throughout childhood and adolescence is considered an indicator of adequate glycaemic control in patients with type 1 diabetes. While it has been suggested that growth in type 1 diabetes is reduced, the literature is conflicting and differences in final adult height and the risk of short stature depending on glycaemic control remain largely unexplored. Objective: This work aims to assess adult height outcomes across levels of glycemic control in children and adolescents with type 1 diabetes, as well as to investigate the effect of sex, age at disease onset, and timing of glycemic control in relation to puberty. Methods: In this population-based Swedish cohort study, we collected data on glycemic control and height from specialist health-care visits of all individuals with childhood-onset type 1 diabetes in the National Diabetes Register. Using linear and logistic regression, we compared suboptimal (glycated hemoglobin A(1c) [HbA(1c)] 53-75 mmol/mol [7.0-9.0%]) and poor (HbA(1c) > 75 mmol/mol [>9.0%]) to optimal (HbA(1c) < 53 mmol/mol [<7.0%]) glycemic control in relation to final adult height and the risk of short stature. Results: Poor glycemic control was associated with lower final adult height (-2.91 cm [95% CI, -3.48 to -2.33] for males, -1.83 cm [-2.42 to -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 lower only among those with type 1 diabetes since before puberty and if the poor glycemic control occurred before puberty. For males, adult height was lower irrespective of their age at diabetes onset, but only if they had poor glycemic control during or after puberty. Conclusion: Poor glycemic 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.