Aims: To update and extend a previous cross-sectional international comparison of glycaemic control in people with type 1 diabetes. Methods: Data were obtained for 520,392 children and adults with type 1 diabetes from 17 population and five clinic-based data sources in countries or regions between 2016 and 2020. Median HbA1c(IQR) and proportions of individuals with HbA1c < 58mmol/mol (<7.5%), 58–74mmol/mol (7.5–8.9%) and ≥75mmol/mol (≥9.0%) were compared between populations for individuals aged <15, 15–24 and ≥25 years. Logistic regression was used to estimate the odds ratio (OR) of HbA1c < 58mmol/mol (<7.5%) relative to ≥58mmol/mol (≥7.5%), stratified and adjusted for sex, age and data source. Where possible, changes in the proportion of individuals in each HbA1c category compared to previous estimates were calculated. Results: Median HbA1c varied from 55 to 79mmol/mol (7.2 to 9.4%) across data sources and age groups so a pooled estimate was deemed inappropriate. OR (95% CI) for HbA1c< 58mmol/mol (<7.5%) were 0.91 (0.90–0.92) for women compared to men, 1.68 (1.65–1.71) for people aged <15years and 0.81 (0.79–0.82) aged15–24years compared to those aged ≥25years. Differences between populations persisted after adjusting for sex, age and data source. In general, compared to our previous analysis, the proportion of people with an HbA1c<58mmol/l (<7.5%) increased and proportions of people with HbA1c≥ 75mmol/mol (≥9.0%) decreased. Conclusions: Glycaemic control of type 1 diabetes continues to vary substantially between age groups and data sources. While some improvement over time has been observed, glycaemic control remains sub-optimal for most people with Type 1 diabetes.
